Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Wei Z., Jia Y.

Coastal wave is one of major forces that dominate coastal hydronydamics, sediment transport, morphology and threaten coastal infrastructures. In recent years, the non-hydrostatic technique for solving Reynolds-averaged Navier-Stokes equations has been developed for wave propagation study. It has been shown that this method has a comparable accuracy for wave simulation to Boussinesq-type approaches and a better computing efficiency.

In this paper, a one-dimensional depth-integrated non-hydrostatic pressure wave model for wave propagation, breaking and run-up is developed based on the numerical method proposed by Stelling and Duinmeijer. In this numerical method, the non-conservative form of Navier-Stokes equation is solved for either momentum conservation or energy head conservation by applying different advection approximation methods. The method is, therefore, able to handle rapidly varied water flows (such as wave breaking) in wide range of Froude numbers. When wave run-up is concerned, wetting and drying treatment plays a key role for many numerical models. The wet & dry handling approach in the method is simple, efficient and capable of reserving positive water depth.

In this non-hydrostatic wave model development, the fractional time step method is adopted. The shallow water equations without non-hydrostatic pressure terms are solved for approximation of velocity; a tri-diagonal equation for non-hydrostatic pressure terms is then solved, and the approximate velocity is corrected by non-hydrostatic pressure terms. The free surface elevation is calculated by the depth-averaged continuity equation to satisfy global mass conservation. This model will be validated by an analytical solution and several benchmark wave dynamics test cases; it is anticipated the model can predict wave breaking and run-up processes effectively.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Barrett J.

The majority of Mississippians enjoy access to one of the 1200 public water systems in Mississippi. Having access to a public water system provides the citizens with safety and quality of water through the regulatory enforcement of the Mississippi State Department of Health-Bureau of Public Water Supply (MSDH). Mississippi citizens on private wells do not have the luxury of knowing the quality and/or quantity of their water on a regular basis. In this presentation, by comparison of United States Census Data and MSDH data, the areas of Mississippi that have the highest concentrations of citizens on private wells will be derived. Data will be gathered to determine the likely contaminants to private wells in each particular county. This information will highlight the areas that could benefit the greatest from avenues in which private well owners can check the quality of their water as well as inform the surrounding water systems of their capacity to expand.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Dakhlalla A.O., Parajuli P.B.

Future climate changes, such as precipitation, temperature, and carbon dioxide (CO2) can have dramatic impacts on the hydrological cycle. These climatic changes can also increase the intensity and occurrence of peak flow events, which cause significant damage to agriculture and infrastructure. This study was conducted in the Lower Pearl River Watershed (LPRW) in southern Mississippi, which is dominated by forests and is characterized by its high peak flows. The Soil and Water Assessment Tool (SWAT) was utilized to assess the impact of future climate change scenarios on peak flow frequency and magnitude.

The SWAT model was calibrated and validated for streamflow at five United States Geological Survey (USGS) gage stations (Bogalusa, Columbia, Monticello, Hanging Moss Creek, and Jackson) with good model performance based on the coefficient of determination, Nash-Sutcliffe Efficiency index, and root mean square error statistics. Future climate change scenarios were based on adjusting precipitation, temperature, and CO2 values. Observed daily precipitation and temperature data for the years 1981 to 2010 were used as inputs in a stochastic weather generator model to generate future climate data with the same statistical characteristics as the observed data. The occurrences and magnitudes of extreme peak flow events in the LPRW were analyzed under each climate scenario by developing flood hydrographs. Employing climate scenarios will aid in determining which climatic parameters have the most and least influence on peak flow magnitude and frequency. This study is expected to help in implementing best management practices (BMPs) more effectively in the LPRW that serve to attenuate peak flows.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Thornton R.F., Sassenrath G.F., Schneider J.M., Corbitt J.Q., Schmidt A.M., Crumpton J., Rice B., van Riessen H.

The goal of this research is to determine how reliable National Weather Service (NWS) spatially gridded radar precipitation estimates are in Mississippi. If results are good, the plan is to incorporate this source of rainfall information into the Mississippi Irrigation Scheduling Tool (MIST). Several rain gauge sources are included in the analysis in order to increase the spatial resolution of precipitation across the state of Mississippi. These sources include The Community Collaborative Rain, Snow and Hail Network (CoCoRahs), National Weather Service Cooperative Observers (COOP) and one DREC station. These rain gauge values were obtained for July 1-31 2012. Each rain gauge location is referenced by latitude and longitude, so it can be compared to NWS radar precipitation estimates at the same coordinates.

Summertime precipitation in Mississippi demonstrates a high degree of spatial variability through pop-up afternoon showers and thunderstorms. This research will determine the usefulness of radar-estimated precipitation, the spatial context of which could eliminate the variability problem inherit in point-source measurements. Actual rain gauge values are compared to radar-estimated values through the use of ARCGIS. If it is determined that radar-estimated precipitation is comparable to actual rain gauge data, then this will be incorporated into a tool to aid the Mississippi agricultural community in knowing when to most efficiently irrigate. The analysis will also attempt to find any spatial bias present between the two measurements, resulting in the discovery of any consistent correction coefficients. This, along with other conservation efforts already in place, will potentially help Mississippi farmers to conserve groundwater by supporting recharge of the Mississippi River Shallow Alluvial Aquifer over time.

Final Project Report

Year: 2013 Authors: Prewitt M.L., Borazjani H., Willeford K.

Results from this research are expected to reveal which of 3 consortiums of bioaugmented PCP degrading bacteria will increase PCP degradation in contaminated groundwater. The information that will be gained from this research should lead to customizing remediation methods based on the indigenous microbial community at a contaminated site. Not only could bacterial consortiums be used for PCP degradation, they could also be used to address other water quality issues such as high Biological Oxygen Demand (BOD) that impacts wastewater discharge from industries in Mississippi and nationwide such as the pulp and paper mills, oil spills in the Gulf Coast and excess nitrogen in agriculture runoff.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Alford A.B., Grado S.C., Kaminski R.M.

Harvest of crayfish (Procambarus spp.) for human consumption in the United States and beyond is considerable, amounting to an annual value of $150-170 million annually in the southern United States alone. Most crayfish harvested for human consumption are cultivated in rice fields in southern Louisiana. Management of emergent vegetation in moist-soil wetlands is similar to cultivation of rice where the seasonal wet-dry cycle of these wetlands encourages the growth of annual plants that produce abundant seeds and tubers for waterfowl forage. Recent aquatic invertebrate studies in moist-soil wetlands suggest that populations of crayfish in these habitats may be large enough to warrant a harvest for human consumption. To estimate the economic potential of crayfish harvests in moist-soil wetlands, crayfish yield was estimated from moist-soil wetlands on public and private lands in the MAV in Arkansas, Louisiana, Mississippi, and Missouri in spring-summer 2009-2011 using typical crayfish harvest strategies practiced in commercial rice-crayfish fields of Louisiana. Average daily yields of crayfish from moist-soil wetlands ranged from 0.08 kg/ha to 23 kg/ha with an overall mean yield of 2.73 kg/ha (n = 42, CV = 21%). Whereas the mean daily yield of crayfish from moist-soil wetlands was >3 times less than the yield expected from a high production rice-crayfish culture system (e.g., 8-10 kg/ha), estimated cost associated with harvest of crayfish from moist-soil wetlands were $529/ha and were lower compared to costs associated rice-crayfish harvest practices which were estimated to be $1,856/ha. However, the estimated break-even selling price for crayfish harvested from moist-soil wetlands was $4.90/kg compared to $2.75/kg estimated for rice-crayfish practices. The estimates of break-even selling prices for crayfish harvested from moist-soil wetlands were higher than the 2012 estimate of $2.75/kg price for single crop production of crayfish in Louisiana. However, in areas where crayfish markets are sparse, such as the North Mississippi Delta, landowners may still realize economic potential from this fishery. Harvesting crayfish from moist-soil wetlands may provide a small profit to landowners but will likely provide additional recreational opportunities and can serve as additional extension vehicles to encourage wetlands conservation throughout the MAV.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Linhoss A.C., Kiker G.A., Aiello-Lammens M.E., Chu-Agor M.L., Convertino M., Munoz-Carpena R., Fischer R., Linkov I.

Sea-level rise is expected to dramatically alter low-lying coastal and intertidal areas, which provide important habitat for shoreline-dependent species. The Snowy Plover (Charadrius nivosus) is a threatened shorebird that relies on Gulf Coast sandy beaches for nesting and breeding. Selecting a management strategy for the conservation of this species under sea-level rise is a complex task that entails the consideration of multiple streams of information, stakeholder preferences, value judgments, and uncertainty. We use a spatially explicit linked modeling process that incorporates geomorphological (SLAMM), habitat (MaxEnt), and metapopulation (RAMAS GIS) models to simulate the effect of sea-level rise on Snowy Plover populations. We then apply multi-criteria decision analysis to identify preferred management strategies for the conservation of the species. Two decision analysis techniques are compared: Multiple Attribute Utility Theory and Stochastic Multi-criteria Acceptability Analysis. We investigate four conservation strategies including no action, beach nourishment, nest exclosures, and predator management. Results show that predator management and nest exclosures are the most promising conservation strategies. This is an innovative method for planning for sea-level rise through pairing a linked modeling system with decision analysis to provide management focused results in an inherently uncertain future.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Maurer B.J.

Alluvial deposits (Holocen) have made the harvest of sand and gravel profitable in the Buttahatchie River watershed. Historically, excavations in and adjacent to the river have altered the location and stability of the channel. Many inactive, pre-regulation quarries are still found concentrated along the lower 20 km of the main channel. Construction of the Tennessee-Tombigbee Watershed, of which the Buttahatchie River is a tributary, and the resultant head-cutting, have further exacerbated the process of "quarry capture", whereby the river channel changes course into a quarry.

With partners from Mississippi State University, and with support from the US Fish & Wildlife Service, The Nature Conservancy has undertaken a project to develop and implement stabilization BMPs to prevent further quarry capture on the Buttahatchie River. Utilizing LiDAR mapping of the area and modeling of flow patterns, this project will identify points vulnerable to quarry capture, and design and construct appropriate stabilization techniques. Techniques are expected to be both specific to the individual characteristics of each site, and exportable to vulnerable channels in other watersheds.

Construction on the first stabilization project will be completed in the winter of 2013 in Monroe County, Mississippi, and will stabilize 1300 feet of river bank to prevent the river from changing course into several inactive gravel quarries adjacent to the river. This presentation will detail the project design, the selection of BMPs, the construction, and the outcome of the project. The BMPs will include bendway weirs, locked logs, and customized planting installed under very difficult conditions.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Dash P.

Cyanobacteria represent the major harmful algal group in fresh to brackish water environments. Cyanobacterial blooms are aesthetically undesirable since they discolor the water, cause turbidity in recreational facilities and synthesize a large number of low molecular weight compounds which cause taste and odor problems. Of particular concern are a diverse range of toxins produced by cyanobacteria, termed cyanotoxins, which are hazardous to human, animal and aquatic ecosystem health. Recently, a procedure was developed to estimate cyanobacterial concentrations by quantifying chlorophyll a (Chl a) and the primary cyanobacterial pigment phycocyanin (PC) using OCM satellite data over a small lake- Lac des Allemands in Louisiana, USA. This required the development of an atmospheric correction and vicarious calibration methodology for satellite data. Empirical inversion algorithms were developed to convert the OCM Rrs at bands centered at 510.6 and 556.4 nm to concentrations of PC. For the algorithms to be uniformly valid over all areas (or all bio-optical regimes) of the lake, a holistic approach was developed to minimize the influence of other optically active constituents. Similarly, empirical algorithms to estimate Chl a concentrations were developed using OCM bands centered at 556.4 and 669 nm. The best PC algorithm (R²=0.7450, p<0.0001, n=72) yielded a root mean square error (RMSE) of 36.92 µ g/L (PC from 2.75 to 363.5 µg/L, n=48). The best algorithm for Chl a (R²=0.7510, p<0.0001) produced an RMSE of 31.19 µ g/L (Chl a from 9.46 to 212.7 µ g/L, n=48). The results demonstrated the preliminary success of using OCM satellite data to map cyanobacterial blooms in a small lake in Louisiana. In the summer of 2012, five field campaigns were undertaken to four large Mississippi lakes- Lakes Sardis, Enid, Grenada, and the Ross Barnett reservoir in order to obtain a database of photosynthetic pigment concentrations and phytoplankton composition. The objective of this project is to combine multiple satellite data from several sensors such as VIIRS, MODIS AQUA and OCM-2, and developed techniques to quantify cyanobacteria in these four large Mississippi lakes and make the mapped images available through a website for use by water quality managers and general public to rapidly obtain synoptic information on cyanobacterial blooms. Time-series of true color satellite images clearly show the presence of algal blooms. Preliminary analyses of the field data analyzed thus far demonstrate the presence of numerous toxic species of cyanobacteria in these lakes. Preliminary results from this project will be presented.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Chao X., Zhu T., Jia Y., Altinakar M.

Frequent natural and human activity induced disasters are influencing and degrading our water resources. To prevent and mitigate the damages that these disasters bring to our society in terms of water resources and eco-environmental quality, social and human welfare, life and property losses, and economic development, more effective and robust water resource management plans are necessary. The efforts of developing better research design and management tools have led to rapid advances in numerical modeling and computational simulation methodologies in parallel to the rapidly advancing computer technology. Computational models are effective and efficient tools that can be applied to study surface water flows, contaminant transport and environment impacts. Numerical models, CCHE2D and CCHE3D, developed at the National Center for Computational Hydroscience and Engineering of the University of Mississippi, have been applied to simulate the flow, sediment transport, pollutant distribution and water quality in natural water bodies. This paper briefly describes the CCHE2D & 3D models and demonstrate their capabilities by presenting the results of several study cases, including an oxbow lake in Mississippi, where water quality was degraded by excessive agro-chemicals, a hypothetical chemical spill case in a large lake in Mississippi, a salinity intrusion case in Lake Pontchartrain, LA, and hypothetical impact of radioactive chemicals to water quality in Kerr Reservoir and Lake Gaston, VA. The simulation results were validated using field measurements.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Sassenrath G.F., Schmidt A.M., Schneider J., Tagert M.L., van Riessen H., Corbitt J.Q., Rice B., Thornton R.

Increasingly variable and uncertain rainfall patterns together with higher production input costs have led farmers to rely on supplemental irrigation to enhance production. While many irrigation methods have been developed for dry climates, few tools are available for humid, high rainfall areas. Moreover, most scheduling tools require extensive data collection, entry and simulation runs, limiting their practical utility during the production season. We have designed the Mississippi Irrigation Scheduling Tool (MIST) as a web-based, easy to use management tool for crop producers. An estimate of crop water use is made using the modified Penman Monteith to calculate daily evapotranspiration. The "checkbook" water balance method sums the water balance of the soil, plus water from rainfall or irrigation, minus water used by the crop or evaporated from the soil. This method indicates the need for irrigation when the soil water available to the plant falls below that which is readily available for crop growth. To enhance utility, the MIST has been implemented in a web interface, allowing producers to access the information from anywhere through tablet computers or smart phones. To reduce the data entry requirements, the system relies on national databases for automated integration with a water balance model. The system was tested at multiple production sites during the 2011, and 2012 growing seasons. This presentation will give details on the development of input parameters for the water balance calculation, including crop water use and soil moisture, and water balance during the growing season for corn and soybeans. Additional presentations in this session will describe the implementation of the user interface (Rice et al.), calibration and validation of the model (Prabhu et al.), and spatial accuracy of national databases (Thornton et al.). The MIST will provide producers, consultants and other professional colleagues with a reliable, accurate, and easy to use tool for improved water management.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Kröger R., Hicks M., Prevost D., Thornton K.

There is a significant impetus within the Mississippi River Basin, at both federal and state levels, to determine the possibility and attainability of nutrient reductions. These questions are being asked at several spatial scales, but ultimately are driven toward the largest spatial scale - Gulf of Mexico hypoxia. The Mississippi approach has been to utilize inter-agency collaboration to identify watersheds where BMP nutrient reductions can be demonstrated and to discern the effectiveness of those BMPs. Harris and Porters Bayous are two HUC 10 watersheds where BMPs have been installed on the landscape, and where tiered water quality monitoring with identical sampling frequencies provides a means for quantifying both reductions in nutrient concentrations and loads. Water quality data is being collected at three tiers. The first Tier (edge of field) is being collected by MSU, while Tiers 2 and 3 are being collected by USGS. Nutrient reductions in concentration, 1-year post BMP implementation are discernible at the Tier 1 scale, but are not yet known at Tiers 2 or 3 due to continued data analysis. Monitoring of multiple watersheds provides environmental variables and landscape characteristics that suggest reasons for the observed reductions. These initial answers provide previously unknown information towards improving in state aquatic ecosystem health as well as critically important BMP attainability estimates to inform Gulf of Mexico restoration recommendations.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Kaminski R.

Science should guide conservation of natural resources to promote effectiveness, efficiency, and economy of management actions and policy development. Following the Deepwater Horizon Oil Spill in the Gulf of Mexico in April 2010, the Natural Resources Conservation Service (NRCS) established the Migratory Bird Habitat Initiative (MBHI). Working with owners and managers of private croplands, aquaculture ponds, and Wetland Reserve Program easements, NRCS and conservation partners managed thousands of acres of wetlands and agricultural lands in the Mississippi Alluvial Valley (MAV) and Gulf Coast regions to provide wetland and upland habitat inland from potentially oil-impacted coastal wetlands. In fall 2010, scientists and graduate students from Mississippi State University, Arkansas Tech University, and University of Missouri began designing and implementing local and landscape scale surveys to (1) estimate use of MBHI managed wetlands and comparable non-MBHI wetlands by shorebirds, waterfowl, and other waterbirds, and (2) assess relative effectiveness of different MBHI practices for providing habitat and food resources for migrating, resident, and wintering waterbirds. Currently, researchers are working in the MAV in Arkansas, Louisiana, Mississippi, and Missouri and the Gulf Coast Prairies in Louisiana and Texas. Our presentation will summarize estimated bird use and food abundance on MBHI and compared study areas and report future directions for completing the MBHI assessment by 2013. Generally, avian abundance and diversity have been greater on MBHI-managed than other areas, although complexes of managed and other wetlands are providing wetland habitat for waterbirds among seasons. For example, when managed wetlands are dewatered in spring-summer to promote emergent vegetation, wetlands lacking such hydrological management provide habitat for waterbirds. Our study will aid future habitat conservation and adaptive management on private and public lands inland from the Gulf, which is a proactive need considering continued decline of continentally important coastal wetlands.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Ramirez-Avila J.J., Poganski B., Kröger R.

Drainage ditches are an essential component of the agricultural landscape. Ditches mediate the flow of pollutants from agroecosystems to downstream water bodies. Low-grade weirs established along drainage ditches, as an agricultural best management practice, have been evaluated as an effective measure to mitigate nutrient and sediment loads to downstream aquatic systems. A study was performed to estimate sediment and nutrient loading reductions and to determine the cost-effectiveness curve of implementing low grade weirs in agricultural drainage ditches systems in the Mississippi Delta. The study goals were addressed by combining field data collection and computational modeling techniques. Runoff volumes flowing downstream of low grade weirs along different drainage ditch systems during stormflow and irrigation events were estimated by using the Hydrologic Engineering Center - River Analysis System (HEC-RAS 4.1) model. Monitored sediment and nutrient concentrations and the generated runoff flows were used to develop representative rating curves for each low grade weir on each drainage ditch system. Runoff hydrograph flows on each event were routed through the generated rating curves to estimate instantaneous and total sediment and nutrient loads at each location. Loads were compared to determine low grade weirs efficiency inside each drainage ditch and between drainage ditch systems. A second part of the study used the System for Urban Stormwater Treatment and Analysis Integration (SUSTAIN 1.2) to determine the most cost-effective solutions for meeting proposed agricultural runoff water quality conditions. Results from this study will provide more insights to further enhance the nutrient reduction strategy within the Mississippi Delta region.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Goetz D., Kröger R., Miranda L.E.

The smallmouth buffalo (SMB) (Ictiobus bubalus), a large bodied benthivore commonly considered a rough fish, is native to Mississippi. Smallmouth buffalos frequently access floodplain lakes during periods of high water level, and remain isolated within them for extended periods of time after the water recedes. Based on evidence from other benthivore studies we hypothesized that high densities of SMB may contribute to poor water quality conditions. We tested this hypothesis in 0.05 hectare, shallow (<1.5 m) earthen ponds at three stocking densities. Nine ponds were randomly stocked with either a low (15 kg/ha), moderate 85 (kg/ha), and high (315 kg/ha) density and measured for water quality parameters over a ten-week period during the summer of 2012. Results from repeated measures ANOVA suggest SMB at high and moderate densities significantly (p < 0.05) increased chlorophyll, turbidity, total suspended solids, volatile suspended solids, temperature, total inorganic phosphorus, while decreasing dissolved oxygen, and Secchi depth, both through time and across treatments. Several previous studies also attribute high benthivorous fish density to enhanced productivity through feedback mechanisms that keep nutrients and sediments in constant suspension. However, most studies have looked at densities much greater than 315 kg/ha (500 +kg/ha). Our results suggest that effects of SMB even at moderate densities may contribute to degraded water quality conditions in natural habitats such as shallow floodplain lakes.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Brison A., Poganski B., Kröger R.

Agricultural best management practices, in the form of low-grade weirs, have demonstrated the ability to mitigate nutrient and sediment loads to downstream aquatic systems. In a recent study, investigations of impacts of artificial low-grade weirs implemented in drainage ditches reported increased hydraulic residence times, an essential component to enhance nutrient reduction. However, research on the success of weirs is currently limited to controlled experiments rather than naturally occurring storm event conditions. This research investigated the effect of low-grade weirs on hydraulic residence time in several agricultural drainage ditches in the Mississippi Delta. Effects of low-grade weirs was assessed by comparing means of storm events and precipitation totals of varying magnitude within drainage ditches between pre- and post- weir implementation. Preliminary results suggest significantly shorter time to peak values between storm events pre- and post-weir implementation (K=11.522; p<0.05; Kruskal-Wallis) and longer time to base (K=18.566; p<0.05). No significant difference was found between pre-and post- weir time to maximum peak height (K=9.334; p>0.05; Kruskal-Wallis). Further research should account for variable physical dimensions, drainage area of each drainage ditch, and the number and spatial arrangement of weirs implemented to understand how weirs impact hydraulic patterns of drainage.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Shoemaker C., Kröger R., Pierce S.

Oxidation-reduction potential (Eh) is an important parameter in predicting biogeochemical reactions occurring in waterlogged soils, including nutrient reduction. Specifically, soil Eh can be used to classify the potential of a system for nitrate reduction, providing a convenient and inexpensive tool for assessing the capacity of primary water bodies for denitrification potential. Continuous automated data loggers were developed, tested, and confirmed for accuracy and precision of Eh measurements. These units were then used to test a vegetated agricultural ditch with weirs in order to assess the influence of hydrology and vegetation on Eh. Six two week testing periods were conducted around two weirs from May-September 2012, with plots above each weir undergoing controlled drainage while plots below each weir functioned as controls subjected to conventional drainage. No differences were observed in the median Eh between vegetated and non-vegetated plots or the median Eh of the location of plot about the weir; however hydrologic changes influenced the range of Eh values regardless of vegetation status. The high levels of temporal and spatial Eh variation inherent in soils make it difficult to determine bulk soil Eh shifts over space and time. A one dimensional moving split window analysis was run to elucidate Eh boundaries by reduction potential. Results of this analysis showed marked shifts of Eh on specific probes, but no overall trends. The standard deviation of probes shifted over time, suggesting the use of controlled drainage coupled with vegetation could increase electrochemical heterogeneity in waterlogged soils. This increase in soil electrochemical heterogeneity may indicate increased denitrification potential as a result of controlled drainage in vegetated ditches.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Omer A., Kröger R.

The Mississippi Alluvial Valley is the center for agricultural crop production in the Southeast United States. The necessity for irrigation to maintain maximum yields has led to increased pressure placed on the Mississippi Alluvial Aquifer resulting in a negative balance. As a method of water management, surface water capture and irrigation re-use systems are being implemented into agriculture systems in Mississippi. However, the environmental and economic benefits of these systems have yet to be described and quantified. The main objective of this research is to describe and quantify the potential benefits of surface water capture and irrigation re-use systems for water resource conservation. Four sites located in the Mississippi Delta Region which utilize water capture and irrigation re-use systems will be assessed by monitoring: pumping schedules of re-lift stations, water level of on-farm storage reservoirs and flows of surface water irrigation pumps through irrigation meters. This data will be compared to systems using strictly ground water to understand water saving differences. Three years of data will be used to quantify a water savings budget and assess at a regional scale the contributions of surface water capture to decrease ground water withdrawals. The water savings budget in addition to the potential energy savings will be combined to provide an economic analysis of water capture and irrigation re-use systems. The results of this research will be used to create an economic analysis to provide valuable outreach material for dissemination to Mississippi producers. This potentially will lead to further implementation of water capture and irrigation re-use systems throughout Mississippi.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Guzman S., Salazar G., Diaz-Ramirez J., Schauwecker T.J.

Excess nutrients are known as a primary problem facing Gulf of Mexico estuaries and coastal waters, leading to nuisance algal blooms, depletion of dissolved oxygen, and other water quality impairments. Soil and nutrient losses encourage siltation and eutrophication in Gulf of Mexico waters. Soil and nutrient exported from agricultural fields into water bodies in Mississippi is a major environmental concern by local, state, and federal agencies. This poster presents runoff and sediment & nutrient loads from two fields in north Mississippi: a 8.4-ha cattle drainage area located on the agricultural research property of the Mississippi Agriculture and Forestry Experiment Station (MAFES), adjacent to Mississippi State University (MSU); and a 11.3-ha crop drainage area located in Leflore County. The cattle field is monitored since 2011 by researchers from MSU Departments of Civil & Environmental Engineering and Landscape Architecture. At the outlet of the cattle field, MSU researchers are using a pressure transducer and automatic sampler to monitoring water depth and water quality, respectively. Field data (discharge and sediments & nutrient concentrations) from the crop drainage area were collected by the U.S Geological Survey from 1996 to 1999. The goal of this research is quantify sediment and nutrient loads by storm events yielded from fields managed with crops (soybeans and cotton) and beef production grazing pasture. Currently, we are computing and analyzing sediment and nutrient loads by storm events and planning to show results at the conference.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Lizotte Jr. R.E., Shields Jr. F.D., Locke M.A., Murdock J.N., Knight S.S.

Streams in watersheds supporting intensive row-crop agriculture are vulnerable to ecological degradation due to non-point source discharge of pollutants such as nutrients. Low gradient streams such as bayous are especially susceptible due to increased water residence time, and often result in poor water quality and chronic low dissolved oxygen (DO) concentrations (hypoxia). The goal of the current study was to assess physical, chemical, and biological components affecting low DO during summer of 2011 in three Mississippi Delta bayous. Three sites were selected within each bayou: upstream channel, lake or open water in the water body mid-section, and downstream channel. Dissolved oxygen was monitored at 40 cm depth every 15 minutes for 6-7 days on alternate weeks. Stream surface water samples collected biweekly were analyzed for nutrient and chlorophyll a concentrations. Minimum daily DO levels were frequently below the State instantaneous minimum DO standard of 4 mg/L. Diel DO fluctuation (the difference between daily maximum and minimum DO concentrations) reflected large 24-h DO ranges (=10 mg/L) across all three bayous. Pearson product moment correlations showed minimum DO concentrations to be negatively correlated with total phosphorus (TP) concentrations across all habitats. Total nitrogen (TN) concentrations and dissolved organic carbon (DOC) concentrations were negatively correlated with minimum DO concentrations only in lake habitats. Diel DO fluctuation was positively correlated with water column chlorophyll a concentrations across all habitats. Upstream diel DO fluctuation was also positively correlated with water depth and TP concentrations while downstream diel DO fluctuation was positively correlated with TP but not water depth. Low summer DO concentrations and changes in diel DO fluctuations were affected by both nitrogen and phosphorus driving summer algal blooms (eutrophic to hypereutrophic conditions) in Mississippi Delta bayous. Organic carbon inputs may exacerbate DO minimums in these nutrient-rich systems. As a result, nutrient reduction in all habitats in conjunction with increased water depth in upstream habitats is necessary to improve summer DO concentrations in Mississippi Delta bayous.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Faust D.R., Kröger R.

The overall objective of this study is to examine factors that may affect the fate and cycling of nitrogen species in agricultural drainage ditches with low-grade weirs installed. Emphasis will be on factors and processes that remove nitrogen from these ecosystems. Particular attention will be paid to factors that have been demonstrated to affect denitrification, as this process results in permanent removal of nitrogen from ecosystems. Three factors that have consistently been implicated in affecting denitrification are nitrate concentration, organic carbon availability, and oxidation-reduction potential. These three factors are the focus under of three specific objective to evaluate effects of these factors on nitrate removal and denitrification potential in sediment pore and overlying water in agricultural drainage ditches. Specific objectives are: 1) Water and sediment samples obtained from ditches at Spruill Farm (Belzoni, MS) will be used in laboratory experiments to determine if organic carbon availability is limiting denitrification potential and whether dissolved or particulate organic carbon is more suitable for denitrification; 2) Results from laboratory experiments will inform conditions used for simulated storm events in experimental v-ditch systems at Mississippi State University's South Farm Aquaculture Facility; 3) Effects of nitrate concentrations, organic carbon availability, and oxidation-reduction potential of sediment pore water and overlying water on nitrogen removal in agricultural drainage ditches at Spruill Farm will then be examined. In addition to best management practices already in use, results from these studies will allow for recommendations to enhance nitrogen removal in agricultural drainage ditch systems.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Rice B., Sassenrath G.F., van Riessen H., Schmidt A.M., Tagert M.L.

The Mississippi Irrigation Scheduling Tool (MIST) has been developed to provide a daily calculation of water balance for row crop production. This daily calculation incorporates field specific data on soil type, tillage depth, row spacing, and crop type to make a recommendation on crop water needs. Weather data is automatically downloaded from national and regional databases and used to calculate daily evapotranspiration rate using the Modified Penman-Monteith equations. The first goal of MIST was to make it more accessible to the users. To do this, MIST was implemented as a web application, developed with Java and HTML. Using a web application eliminates the need for the user to download, install and update software. The main difficulty with a web application is making sure that every browser is displaying the web pages correctly since each web browser can interpret code differently. Incompatibilities between web browsers were observed a few times; one of these occurrences was with the font that was being used. Potential incompatibilities are determined by testing the system on multiple web browsers and platforms, though updates in these systems may present problems in the future. All the data is stored within a MySQL database, which currently contains twenty tables each having between three to twenty data columns depending on the data stored. Database security is maintained by restricting server connections to local only. One of the more common SQL attacks is done through SQL injection. Prepared statements are used to prevent these types of attacks. Most of the data are stored in plain English text with a table's data column. Passwords are converted to a MD5 checksum. MD5 checksum is a cryptography based algorithm that allows the storage of data without knowing what the data actually is. This provides security in the event someone is able to obtain access to the database—sensitive information will not be accessible. There are a few different types of user ranks within the interface: admin, manager, consultant, company, and farmer, with each user rank assigned different permissions. To assist in the tedious task of setting up each field within the farm, farmers are allowed to select the border of their field with Google maps. Implementing MIST has been full of challenges and decisions that will be discussed in this paper. Given the widespread adoption of tablets and smartphones, a web application provides equal access to any device that has access to a web browser.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Gallo W.C., Overbey E.

The underlying theory behind green infrastructure or sustainable stormwater design is that the cumulative impact of many small facilities is greater than that of a few large facilities. This concept depends on the design, installation and management of many more facilities than a traditional pipe and detain ordinance would have created. Instead, a collection of small-scale, vegetated, best management practices are designed to fit seamlessly into the urban fabric to manage smaller storm events close to the source, mitigate nearly every new impervious area, and promote as much infiltration or bio-retention as possible.

For a municipality to move toward a green infrastructure approach requires major changes to how their stormwater ordinance is organized and administered. More facilities, potentially means more submittals, more calculations to check, and more designs to approve. A few municipalities have been grappling with this paradigm shift for the last decade. Their experience indicates that the shift toward green infrastructure requires new tools, which simplify the administrative and design process, and new policies, which ensure the goals of green infrastructure are implemented effectively.

This presentation will explore a few of the specific policies and tools, which have been developed to implement green infrastructure including:

• a pre-development definition which ensures policies will improve watershed protection over time;
• a low application trigger which is central to the concept of managing stormwater at the source;
• a detention requirement, which when combined with a low application trigger, does not impede urban development and also provides a high level of overall flood protection;
• an almost wholesale embrace of small-scale vegetated best management practices (BMPs), which focus on infiltration; and
• a collection of tools specifically designed to facilitate the design, approval, and implementation of small-scale BMPs.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Dyer J., Mercer A.

Water resources in the lower Mississippi River alluvial valley play a critical role in agricultural productivity due to the widespread use of irrigation during the growing season. Although the region receives abundant precipitation throughout the year, the unknown specifics of meteorological modifications in the region, along with continually changing anthropogenic needs on the groundwater system, makes it difficult for water resource managers to make sound decisions for future water sustainability. Additionally, agriculture in this region is under considerable strain due to diminishing groundwater availability and the non-sustainable trend in irrigation draws from the alluvial aquifer. As a result, it is crucial to correlate local rainfall patterns with aquifer water levels to better determine the spatial and temporal influence of precipitation on regional groundwater levels. This project will address water availability in the lower Mississippi River alluvial aquifer (LMRAA) over northwest Mississippi through an assessment of historical precipitation variability using high-resolution radar-derived precipitation estimates. This information will be used to estimate current and future precipitation availability over the region, which will be compared with regional groundwater observations to determine the level of interaction between rainfall and sub-surface water levels. Results of this project will aid in determining the natural limits to water resource availability, as well as the relationship between regional precipitation and groundwater variability.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Kokabian B., Blair M.F., Gude V.G.

Water, energy and environment play a vital role in the sustainability of mankind. Environmental degradation associated with water and energy production/supply processes is the immediate concern faced by many parts of the world. Utilizing wastewater and produced waters as resources to provide for potable water and energy needs could serve as a sustainable alternative to mitigate environmental degradation. Towards this goal, microbial desalination cells allow for efficient wastewater treatment combined with electricity generation and desalination of saline waters. The premise for this research is based on the principles that the bio-electrochemical (BES) systems convert wastewaters into treated effluents while producing electricity and ionic species migration within the system facilitates desalination. A microbial desalination cell (MDC) can be constructed by including an additional saline water chamber in a microbial fuel cell using anode and cathode exchange membranes. Domestic wastewater can serve as a substrate provider while air cathodes can provide oxygen to accept electrons. A new concept to provide in-situ oxygen generation in the cathode section by algae to increase electron mobility (i.e. electric current) in microbial desalination cells is presented in this paper. Treated wastewater in the anode chamber will be allowed to pass through the cathode chamber to serve as CO2 and nutrient rich medium for algal biomass growth and in-situ oxygen generation. This process eliminates current issues encountered in microbial desalination cells such as salt accumulation in treated wastewater, pH drop and rise in anode and cathode chambers and provision of strong electron acceptors such as oxygen. This paper presents the results from experimental studies and energy analysis on the feasibility of algal microbial desalination cells.
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Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Bathi J.R., Rhoads S.

A recent regulatory trend is to base storm water control requirements on the total volume of storm water runoff from a site rather than on runoff rates or a specific pollutant removal rate. This trend is based on a growing body of research which has concluded that volume-based controls accomplish the concurrent benefits of pollutant reduction, peak flow reduction, and base flow protection. The focus on runoff volume as the common currency for best management practices evaluation is gaining wider acceptance across the country. Current regulations in the region demand a high level of stormwater infrastructure to meet the total volume of detention storage required. Instead, the evolving volume based controls have been proving to be less cost intensive with distributed green technologies at the source level. The purpose of this paper is to provide an overview of new volume based standards and rainfall frequency analysis procedures for selecting the appropriate control matrix for an area. In addition, we have summarized commonly used green infrastructure practices, and outlined available computer models for designing and evaluating site level green infrastructure techniques.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Johnson D.R.

The determination of the minimum flow needed to support aquatic life and meet the needs of the Clean Water Act is a complex issue that has generally been answered with quick and meaningless statistical flows. This paper will examine a number of different methods used to establish low flow, and will compare them to observed flows several rivers in the Mississippi Delta.
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Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Sigsby N., Myers D.

Created in 1978, the Mississippi Dam Safety program began the task of identifying dams that were High Hazard and working to get those dams repaired. In 1994, Dam Safety Regulations were defined to classify the hazard potential of dams, establish minimum design and construction criteria, to require regular inspections and to have an emergency action plan for all high hazard dams. These regulations were again revised in 2005 and are currently used today.

Created in 1978, the Mississippi Dam Safety program began the task of identifying dams that were High Hazard and working to get those dams repaired. In 1994, Dam Safety Regulations were defined to classify the hazard potential of dams, establish minimum design and construction criteria, to require regular inspections and to have an emergency action plan for all high hazard dams. These regulations were again revised in 2005 and are currently used today.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Shirmeen T., Jia Y.

Torrential storms often trigger flooding that causes damage in properties and loss of life. In this study a numerical simulation module is developed to enhance the capability of a 2D surface flow model, CCHE2D. Following the procedure for numerical model verification and validation of ASCE, the developed module is tested using both analytical solutions and experiment data.

The analytical solutions of kinematic wave equation for runoff occurring on a sloping plane subject to a constant rainfall of indefinite duration and finite duration were used to compare to the results of the numerical model with good agreements. Runoff processes measured in laboratory experiments were also simulated in this study using the 2D model. The simulated runoff processes and the observed physical processes again showed excellent agreements. These tests indicate that the CCHE2D model is capable of modeling rainfall-runoff and kinematic overland flows.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Diaz-Ramirez J., Martin J., McAnally W., Rebich R.A.

The impact of excess nutrient loads on eutrophication of waterbodies, including the increasingly frequent occurrences of harmful algal blooms and hypoxia, is well known and well documented. The Mississippi River/Gulf of Mexico Hypoxia is also a major environmental issue, and a key component of the Gulf Hypoxia Action Plan is the development and implementation of state nutrient reduction strategies. Effective implementation of nutrient load reductions requires that analytical tools be available to accurately estimate loads from watersheds and waterbodies as a function of hydrologic conditions. Hydrologic models have widely been used to accurately estimate outflows from watersheds, and to a lesser degree sediment and nutrient loads. Factors impacting runoff of nutrients are not well understood and as a consequence predictions of nutrient loads are highly uncertain. This research evaluated the ability of the Hydrological Simulation Program—FORTRAN (HSPF) to simulate storm, seasonal, and long-term runoff, sediment, and phosphorus transport at the farm scale in the Deep Hollow drainage area, Mississippi. The main goal was to demonstrate the usefulness of HSPF as a computer tool for future environmental management and planning in the Mississippi Delta region. When analyzing the datasets developed by U.S. Geological Survey, 69 events were selected to setup and evaluate the HSPF model. Model evaluation consisted in splitting the available data in two different time periods, calibration from 1997 to 1998 and validation in 1999. Runoff processes were evaluated using 45 events for calibration and 24 events for validation. In evaluating sediment export processes, 29 and 11 storm events were utilized in calibration and validation periods, respectively. Phosphorus simulations (dissolved and total) were evaluated using 19 and four storm events in calibration and validation periods, respectively. The HSPF model was setup to evaluate runoff, soil erosion, dissolved & total phosphorus to storm, monthly, and annual time scales.

This study concluded that the HSPF runoff model's simulations of storm-by-storm, long term monthly, and annual intervals were very good. In simulating suspended sediment loads, HSPF performance was poor for storm-by-storm analysis. However, long term monthly, and annual suspended sediment load simulations were tracked fair and good, respectively. Simulations of dissolved phosphorus of storm-by-storm and long term monthly intervals were good. Simulated annual dissolved phosphorus loads correlated very good with observed data. Similarly, HSPF performed good in simulating long term monthly total phosphorus loads and showed very good results in modeling annual total phosphorus loads exported from Deep Hollow drainage area.
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Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Pote J.W., Wax C.L., Tagert M.L.

The daily volume of water in a 5200 acre lake with a full capacity of 104,000 A-F in a coastal Mississippi location is simulated from 1961-2010. The lake basin is 17,550 acres, a runoff coefficient of 0.7 is used, base flow is set at 3 A-F/d, infiltration rate is set at 12 A-F/d, and outflow is set at 3 A-F/d. Inputs from the present climate regime are precipitation (P) minus potential evaporation (PE). Positive daily P-PE adds water to the lake and daily negative P-PE subtracts water from the lake. Climate change is projected by reducing daily P by 1.57% and increasing daily PE by 9.73%.

Cumulative P-PE for the average of all 50 years, the wettest year (1961), the median year (1993), and the driest year (2000), with and without climate change, is calculated. Factoring in the daily interaction between P and PE and comparing the present and changed climate by graphing the cumulative effect through the year shows that the annual pattern stays relatively the same day-by-day through each of the years and that the modeled climate change does reduce the end result in each of the years. For example, the average curves in both graphs show that under present climate the year ends at 19.77" but with climate change it ends at 13.85", a reduction of 5.32" or about 28% of the extra water. The median year curves show that without climate change the year ends at 24.55" but with climate change it ends at 19.75", a reduction of 4.8" or about 20% of excess water. The wettest year curves show the year ending at 54.65" but with climate change it ends at 48.40", a reduction of 6.55" or about 12% of extra water. The driest year curves show the year ending at -10.93" but with climate change it ends at -15.97, an increase in the year's deficit of 5.04" or about 46%.

Even in light of these potential changes in the average and extreme years, a 50-year daily analysis shows that both without and with climate change, the lake's volume drops no lower than about 97,000 A-F at any point in the period. The conclusion is that the climate of coastal Mississippi will sustain a surface water supply from a lake through known climate variability and proposed climate change in the future.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Parajuli P.B., Jayakody P., Brooks J.P.

Pathogens loading from the non-point sources of agricultural and non-agricultural activities contribute to water quality degradation. Developing Total Maximum Daily Loads (TMDLs) for the pathogens (e.g. fecal coliform bacteria, E. coli) require quantifying bacterial load contribution from potential sources. Quantifying bacterial loads from each source will help in developing pathogenic load reduction strategies to meet applicable water quality standards.

The objective of this research was to monitor fecal coliform bacteria concentrations and quantify bacteria loads from the Upper Pearl River Watershed (UPRW-7,885 km²) in the east-central Mississippi. Analysis of observed fecal coliform bacteria concentrations with stream flows from the watershed will be presented. Preliminary results from the model simulations with seasonal variability of bacteria concentrations will also be presented using appropriate statistics.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Kajdan T.A., Carpenter Jr. W.O., Chambers J.P., Goodwiller B.T., Surbeck C.Q.

This research focuses on a new device to measure fine suspended sediment particles in rivers and streams using acoustic signal attenuation measurements. The purpose of this device is to create a high frequency signal attenuation system that will be able to measure concentrations continuously without having to physically visit the site in order to obtain the samples. This system will be non-intrusive as well as relatively cost-effective in comparison with the methods that have previously been adopted. Two 20 MHz transducers will be aligned in a pitch-catch configuration at a distance based upon near field effects and noise level caused by the interaction between the transmitting and receiving transducers. The 20 MHz acoustic device will be able to measure particles ranging from 0.2 to 65 µm in size. A vast attenuation database has been created at the National Center for Physical Acoustics (NCPA), located in Oxford, Mississippi, to account for this range of particle sizes. The database includes acoustic signal attenuation measurements of bentonite, kaolinite, illite, and silt, which were used to broaden the sediment range. The database consists of peak-to-peak voltage data that was captured by the receiving transducer during the experiment and displayed and analyzed using LabView 2010. This voltage data corresponds to known particle concentrations. A digital signal processing (DSP) board will be used to process the data obtained from the 20 MHz transducers in the field. The attenuation signal that is measured in the field will be compared with the database so that a sediment concentration can be determined. The 20 MHz acoustic device will be calibrated at the NCPA using the attenuation database. Once the calibration is complete, the 20 MHz acoustic device will be deployed at Harris Bayou, located in Coahoma County, Mississippi. This particular bayou has relatively steady base flow, which is ideal for the acoustic device. The steady base flow of this bayou ensures that the signal produced by the transmitting transducer will not reflect off of the surface of the water causing inaccurate attenuation data. The digital signal processing board will be mounted in the gauging station housing that is currently being used by the United States Geological Survey (USGS). The results that are obtained from the field will be compared with concentrations that the USGS finds from its grab samples.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Chao X., Jia Y., Shields Jr. F.D.

Sediment is a major nonpoint source pollutant. It may be transported into surface water bodies from agricultural lands and watersheds through runoff. These sediments could be associated with nutrients, pesticides, and other pollutants, and greatly affect the surface water qualities. Therefore, sediment has been listed as the most common pollutant in rivers, streams, lakes, and reservoirs by the US Environmental Protection Agency (USEPA).

This paper presents the development and application of a three-dimensional water quality model for predicting the distributions of nutrients, phytoplankton, dissolved oxygen, etc., in natural lakes. Three major sediment-associated water quality processes were simulated, including the effect of sediment on the light intensity for the growth of phytoplankton, the adsorption-desorption of nutrients by sediment and the release of nutrients from bed sediment layer. This model was first verified using analytical solutions for the transport of non-conservative substances in open channel flow, and then calibrated and validated by the field measurements conducted in a natural oxbow lake in Mississippi. The simulated concentrations of water quality constituents were generally in good agreement with field observations. This study shows that there are strong interactions between sediment and water quality constituents.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Flora C., Kröger R.

Mississippi is the largest producer of channel catfish (Ictalurus punctatus) in the United States. Channel catfish ponds cover over 20,000 hectares of land, mainly concentrated in the Alluvial Valley of northwest Mississippi. Water management practices to reduce mass discharge from ponds are currently a major point of concern, especially in light of potential regulations through nutrient criteria development. A vegetated ditch fitted with consecutive low-grade weirs is anticipated to be a practical and effective option of reducing nutrients and suspended solids entering downstream receiving systems. This study assesses the effect of low-grade weirs on chemical retention and settling of aquaculture pond effluent in a single drainage ditch. Nine embankment ponds were discharged at 48 hour intervals into a single vegetated drainage ditch fitted with 3 low-grade weirs. Two additional embankment ponds were discharged into the ditch while boards were removed from weirs, thus acting as a conventional ditch. Data were analyzed to quantify the ability of the low-grade weir system to reduce the levels of ammonia, nitrate, nitrite, total inorganic phosphorus, particulate phosphorus, and dissolved inorganic phosphorus. The levels of total suspended solids and volatile suspended solids will be compared across the system. As water passes each weir the nutrient and suspended solid loads should decrease through the system, overall reducing the load entering the downstream receiving systems.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Tagert M.L., Paz J., Pote J., McCraven K., Kirmeyer R.L.

The Mississippi River Basin contains over 60% of the harvested cropland in the United States, and the Mississippi and Atchafalaya Rivers contribute more than three-fourths of the total nutrient load to the Gulf. Since the 1970's, groundwater levels in the Mississippi Alluvial Aquifer have decreased at a rate of approximately 100,000 acre-feet per year due to increased irrigated acres. Today, there are roughly 18,000 permitted irrigation wells dependent on water from the Mississippi Alluvial Aquifer, with an average addition of approximately 35,000 new irrigated acres per year for the past few years. Adequate supply of good quality water is important to sustaining agriculture, the primary industry in the economically depressed Mississippi Delta. Due to concerns over groundwater declines and increasing fuel costs to run irrigation pumps, farmers have begun implementing irrigation conservation measures, such as creating on farm storage areas to capture irrigation and surface water runoff from the field for later use. These systems offer farmers the dual benefit of providing water for irrigation and also capturing nutrient rich tailwater for on farm reuse. This project includes monitoring of two on farm water storage areas in the Porter Bayou Watershed, Mississippi and has two primary research objectives: a) determine the downstream nitrogen and phosphorous concentrations of effluent from water storage systems and b) quantify the effects of water storage systems on downstream flow levels through a watershed. Data collection began in February 2012, with water samples collected for analysis every three weeks throughout the growing season from March-October. Effluent nitrate and phosphorus levels were significantly lower than the inlet levels at both on farm storage systems.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Kwon J., Brown A., Rodriguez J.

Residues of pharmaceuticals and personal care products (PPCPs) have been detected in surface waters. It is well known that effluent from wastewater treatment plants (WWTPs) is a major source of contamination of PPCPs in surface waters. The most frequently detected and toxic PPCPs, according to peer-reviewed articles published in the USA, are carbamazepine, sulfamethoxazole, gemfibrozil, and galaxolide. Three wastewater treatment plants (A, B, and C) in Mississippi, with different treatment technologies, were selected. Influent (law water) and effluent (treated water) were sampled from the three WWTPs over the course of one year. Upstream and downstream samples of the WWTPs were also collected. All the four PPCPs were detected in all influents, with galaxolide and sulfamethoxazole showing the highest concentrations of 4,020 ng/L and 3,905 ng/L, respectively while carbamazepine was detected at the lowest levels (66-348 ng/L). All the PPCPs were detected in all effluents except sulfamethoxazole. Different PPCPs were removed to different extent in the WWTPs, varying from -99% to 100%. Carbamazepine showed the lowest removal (-99% to 30%) and gemfibrozil showed the highest (73% to 100%) in the WWTPs. WWTP A gave lower removal rates than WWTPs B and C for sulfamethoxazole. WWTP A showed higher removal rates than WWTPs B and C for galaxolide. Comparing the concentrations of upstream PPCPs to the downstream, there is an apparent increase in concentrations.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Ramirez-Avila J.J., Oldham J.L., Kingery W.L., Crouse K.K., Ortega-Achury S.L.

Phosphorus (P) enrichment of surface and ground water involves a combination of source factors such as high soil test phosphorus (STP) levels and site-specific soil and field characteristics that influence P transport by water flow overland and through the soils. Long-term applications of manure have generally increased STP levels to a greater degree than has fertilizer application because manure applied to meet the nitrogen (N) needs of crops provides more P than utilized by crops. Preliminary research found that subwatersheds within the poultry production counties in Mississippi have a high potential for soil and water degradation from manure P and N. An assessment was developed to increase understanding of STP levels in soils of the top 20 poultry production counties in Mississippi. The study performed a descriptive summary and analysis of temporal dynamics of STP in 15,057 soil samples, submitted for forage and pasture crop recommendations, after analysis by the Mississippi State University Extension Service Soil Testing Laboratory for 10 annual periods from 2002-2003 to 2011-2012. There were gradual annual changes in STP level ranges from the first (5 to 3780 lb ac^-1) to the last year (5 to 3980 lb ac^-1). Individual peak STP values of 5990 and 4840 lb ac^-1 were observed in the 2nd and 7th year, respectively. However, mean STP levels increased from 113 lb ac^-1 to 302 lb ac^-1 from the first to the last year with the highest mean STP level of 356 lb ac^-1 in the 7th year. The MSU Extension Service would not recommend additional external P for 69% of the soils sampled in the last year of the dataset; in the first year this value was 38%. These results indicate increased STP in these soils that could contribute P to runoff and leaching flows. Because of the susceptibility of these areas to manure source P leaching and runoff, Best Management Practices should be implemented that manage P source and off-field transport to minimize environmental impacts. Balancing P inputs with crop removal is an essential part of a sustainable practice to controlling P losses. Maintaining moderate STP levels or reducing high STP levels can reduce the potential for transport of P from both particulate and dissolved P. Comprehensive nutrient management plans should be developed and implemented for all poultry production operations for the optimal use of poultry manure.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: .

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Oldham J.L., Ramirez-Avila J.J., Kingery W.L., Jackson W.

Nutrient Management develops blueprints for using the right amount of the right nutrient source at the right time in the right place. Using poultry litter as a nutrient source in pastures and forages results in increased soil test phosphorus (STP) levels when applications are based on crop nitrogen needs because more phosphorus (P) is provided in each unit of litter than the corresponding unit of grass removes. Increased STP in combination with site-specific soil and field characteristics may lead to P enrichment of surface and ground water. Phosphorus Indices (PI) are state-specific, site-specific algorithms to assess potential P loss that are used in the Nutrient Management Planning (NMP) process. These tools have been developed by individual state Natural Resource Conservation Service (NRCS) agencies under national policy guidance and integrated into the NRCS 590 Nutrient Management Conservation Standard since the late 1990's. Source factors such as STP, and nutrient source and management are used in combination with transport factors including soil characteristics, landscape characterization, and distance to nearest stream in various models to determine relative risk of P movement. Because of the leeway provided to the states, there are numerous versions of PI. Some are quantitative and predict P loss amounts; others, including Mississippi, are qualitative and assign relative risk. With higher risk of P movement to water as determined by PI categories, NMP preparation should assess potential mitigating Best Management Practices adoption. At issue are two recent published southern regional efforts that found differences in PI prediction capacity between state versions, including Mississippi. Individual state NRCS agencies, in cooperation with in-state partners, were asked to update their Nutrient Management Practice Standards in 2012, including reassessment of each state Phosphorus Index. In addition to the in-state standard revision with Mississippi NRCS, Mississippi State University is participating in a multistate effort under the national NRCS Conservation Innovation Grants to coordinate and advance P management in the southern region, ensuring that the PI have been tested based on new guidance in the NRCS 590 standard, and that tools produce more consistent results across physiographic regions in order to promote better consistency between southern state recommendations. This paper provides an overview of NMP, the factors used in the Mississippi Phosphorus Index, and additional efforts regarding NMP process in Mississippi.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Pappalardo G.

Environmental regeneration is not just a matter of natural science. Laypersons, different stakeholders, associations such as NGOs are crucial actors in managing ecosystems, at the grassroots level as well as at the institutional level. Gunderson, Holland et al (1995) describe the relationship between human organizational structures and nature, underlying how Sustainable Development is a process related to Social Learning. Even if the expressions Sustainable Development and Social Learning may have ambiguous meanings related to every different context, it is possible to find some similar issues at the global scale. The U.N. Rio Declaration on Environment and Development (1992) and its updated version Rio+20 show an arising awareness about the crucial role of local communities in taking care of the environment. Moreover, the Nobel Prize in Economic Science Elinor Ostrom (1991) proves the importance of collaborative practices and institutional reframing in order to overcome the Tragedy of the Commons (Hardin 1968).

This paper is aimed at describing and characterizing the process of Community Engagement in watershed management in Europe and USA. First, a critical review of the regulatory frameworks is examined, in order to explain similarities and differences between these two contexts. In Europe, the Convention on Access to Information, Public Participation in Decision-Making and Access to Justice in Environmental Matters (1998) is a milestone on the topic; then, the European Landscape Convention (2000) explains the strong relationship among physical heritage, cultural dimensions and inhabitants' perceptions. Furthermore, the specific Directive in matter of Water (2000/60/EC) is based on the same principles, i.e. broad involvement of the general public and different stakeholders, with different knowledge, values, interests and future perspectives. In U.S.A. the Environmental Protection Agency, with the Clean Water Act (1972) and 40 years of implementation phases, is moving the discussion toward a broader dissemination of participatory practices (Sirianni 2006).

After a comparative analysis of the aforementioned regulations, a multiple case-study research is discussed in order to understand in practice what is engagement, how is it related to watershed management, which are different paradigms and types of community involvement. The cases are selected according to the following characteristics: engagement as an opportunity to define a common vision for the future, starting from history and values of every context; engagement as a way to promote education and responsible behaviors in managing the water; engagement as a moment of dialogue amongst all community members. The outcome of the research is a typology that may operate as a guide in organizing communities that wish to manage ecosystems in a proactive and adaptive way.
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Final Project Report

Year: 2013 Authors: Kröger R., Gallo C., Overbey E.

Nutrient removal and volume reduction capabilities of a range of soil media mixtures in urban flow-through planters were investigated. Eighteen scaled flow-through mesocosms were evaluated for nitrogen and phosphorus removal rates and volume reduction by applying a synthetic stormwater solution over a simulated 2-inch, Type II storm hydrograph. Three replicates of six treatments were tested including four soil mixtures. Significant (p<0.05) reductions in volume for 100% sand, 75% sand, 50% sand content mesocosms compared to the controls, indicating bioretention mixes with higher sand content have greater water retention capabilities. For water quality results, both concentration and load reductions were calculated and compared, where load accounted for volume passing through the mesocosms and therefore more accurately represented water quality results. PO4 load reduction was greater in treatments with less sand (up to 41% reduction). NO₃-N load reduction varied greatly (7% removal to 53% loading). Significant phosphate loading was observed at the peak of the hydrograph (between minutes 60 and 120) compared to the controls, indicating greater flow rates decreased the nutrient removal capabilities of bioretention in the experiment. Preferential flow patterns were observed which potentially led to higher than expected infiltration rates and therefore no observable peak flow reduction.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Gunatilake S.R., Steelhammer S., Kwon J., Xia K., Armbrust K., Rodriguez J.M., Mlsna T.E.

An improved method for the analysis of estriol (E3), estrone (E1), 17α-estradiol (αE2), 17Β-estradiol (ΒE2), and 17α-ethinylestradiol (EE2) in wastewater is described. The method includes sample preparation using solid-phase extraction followed by a "QuEChERS" (Quick Easy Cheap Effective Rugged Safe) cleanup, and a LC-MS-MS detection. Solid phase extraction was carried out using Oasis HLB cartridges and a dispersive solid phase cleanup pack containing MgSO₄, PSA and C-18. The resulting extract was then derivatized with dansyl chloride. Separation was achieved on an Agilent Zorbex Extend C-18, Narrow Bore RR, (2.1 x 100mm, 3.5 µm) column and quantification was accomplished in the positive ion mode using multiple reaction monitoring. The cleanup method is quick, efficient, inexpensive, and requires only 200 ml of water. Reliable linearities were obtained for all the calibration curves (r₂ > 0.995). Calculated matrix effects were less than 12% for all the analytes and hence, matrix matched calibration curves were not needed. The recoveries for the estrogens ranged from 81–103% with a high repeatability (n=3, RSD = 9%) and low limits of quantification (0.6–0.9 ng/L). The method was used to analyze effluent and influent wastewaters in three Mississippi wastewater treatment plants but is broadly applicable for the determination of trace estrogens in any municipal wastewater samples.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Crawford J., Payne M.

Most of the 3,000 public water system (PWS) wells operating in Mississippi are screened in deep confined aquifers, often overlain with multiple confining layers. Due to this favorable hydrogeologic setting, incidences of groundwater contamination impacting PWSs have not been widely reported in Mississippi. State source water protection efforts have mainly focused on addressing abandoned wells identified in delineated protection areas that may serve as potential conduits for the introduction of contaminants. Unfortunately, the success of these past efforts has been limited due to the sizeable number of abandoned wells in need of plugging and the lack of available funding to help offset the prohibitive cost associated with meeting state regulations.

Most of the 3,000 public water system (PWS) wells operating in Mississippi are screened in deep confined aquifers, often overlain with multiple confining layers. Due to this favorable hydrogeologic setting, incidences of groundwater contamination impacting PWSs have not been widely reported in Mississippi. State source water protection efforts have mainly focused on addressing abandoned wells identified in delineated protection areas that may serve as potential conduits for the introduction of contaminants. Unfortunately, the success of these past efforts has been limited due to the sizeable number of abandoned wells in need of plugging and the lack of available funding to help offset the prohibitive cost associated with meeting state regulations.

The well decommissioning program process began with MSDH's selection of a licensed water well contractor to perform the actual plugging. Accompanying this phase was the decision to contract with MsRWA to coordinate the well abandonment procedure and to assist in prioritizing the plugging of over 200 wells identified thus far. Eleven wells considered moderate risks to contamination (as determined by SWAP) and 13 higher ranked wells have been properly decommissioned and fully funded by the program during 2012. Future plans are to maintain the well decommissioning program provided EPA continues to receive funding from Congress for the capitalization grant.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Jayakody P., Parajuli P.B., Cathcart T.P.

Deterioration of surface water quality is one of the most concern issues in the U.S. The knowledge of spatial and temporal variability of water quality parameters may help to formulate mitigation plans to improve water quality. This study was designed to investigate temporal and spatial variability of sediment, total nitrogen (TN), and total phosphate (TP) loadings to the surface water through a modeling approach. The Soil and Water Assessment Tool (SWAT) was applied for Upper Pearl River Watershed (UPRW) in central Mississippi. Water samples were collected from Burnside and Lena USGS gauging stations. The SWAT model was calibrated and validated for daily time steps using manual and automatic (SUFI-2) methods from Feb 2010 to May 2011. Preliminary results showed good to very good model performances with the coefficient of determination (R2) and Nash-Sutcliff Efficiency Index (NSE) from 0.6 to 0.8 (flow), 0.3 to 0.6 (sediment), 0.6 to 0.7 (TN), and 0.5 to 0.6 (TP) during both hydrologic and water quality model calibration and validation. Sub-watersheds were ranked based on water quality pollutants loading to prioritize land areas for watershed management operations.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Andrews C., Kröger R., Miranda L.E.

Shallow oxbow lakes carved in rich alluvial floodplains can support multiple microhabitats that maintain aquatic diversity. Oxbow lakes have a high shoreline to surface area ratio and are often connected to or surrounded by inundated wetlands such as cypress and tupelo brakes, creating within-lake structural habitat variability that may influence biotic composition. Furthermore, these microhabitats fundamentally function in different ways. We studied microhabitat oxygen dynamics of an oxbow lake in the Mississippi Alluvial Valley. Blue Lake has over 8 km of shoreline and is permanently connected to a tupelo brake (approximately 350 ha) inundated with 0.5-1 m of water during the spring, an important time for reproduction. Using hourly diel surface dissolved oxygen (DO) data collected in April-July 2012, we investigate several descriptors of DO dynamics including mean DO, daily DO peaks, rate of DO fall, time of DO peaks, and percent of time above minimum DO thresholds (2 and 5 mg/L). We test differences in spring oxygen dynamics between three habitat types (littoral, pelagic, and brake) using a MANCOVA (p<0.001) and explore the possibility of oxygen refugia in hypoxic systems. Mean temperature along with four DO metrics: mean, minimum, maximum, and range DO showed significant (p<0.05) difference in means and slope between sites. The observed differences promote habitat diversity likely to influence biotic composition and distribution.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Ramirez-Avila J.J., McAnally III W.H., Tagert M.L.

Researchers from Mississippi State University (MSU) are providing assistance to organize and draft a water management plan for selected northeast Mississippi counties, in the context of an overall basin plan, with the guidance and support of the Tennessee River Valley Water Management District (TRVWMD) and its stakeholders. Updating the MSU water budget for the Tombigbee River Basin developed by McKey and McAnally in 2008 is one of the main tasks included in the statement of work for the study in performance. Research activities to complete the proposed task involves the consecution of new information on withdrawals and discharges; the use of hydrologic calculations to fill in gaps of ungaged streams in the basin and identify potential extreme flows; and the statistical analysis of flow data for use in a risk analysis of extreme flows.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Mason P., Thompson D.

The water-bearing sands and gravels of the Mississippi River Valley alluvial aquifer (MRVA) underlying Mississippi's Delta region are very prolific and are important to agricultural interests. Significantly, the aquifer's overlying capping layer, or topstratum, is important in understanding the sustainability of this resource. This relatively thin topstratum is a primary controlling factor in determining how much direct recharge from precipitation passes from the surface to the aquifer. This process ultimately plays an important role in recharging this increasingly stressed and heavily utilized aquifer. Concepts and historical research vary regarding the permeability and character of the topstratum. Fisk (1944) described the topstratum as "various combinations of sand, silts, and clays" comprising a "relatively impervious topstratum". Little is known about specific locations in the Delta where direct recharge through the topstratum might be enhanced, restricted, or absent. As a result, previous efforts to simulate the groundwater flow system have postulated various schemes for assigning infiltration. These have included: 1) one uniform infiltration rate, 2) low rates in most areas with moderately low rates in zones controlled by topstratum geology, and 3) moderate to high rates in well-drained soils zones with no infiltration elsewhere. In an effort to clarify and illuminate the level of knowledge regarding this capping interval, systematic research and review of existing literature, surface geological mapping, soils mapping, and pertinent data sets is being undertaken. Some of the available data may be reprocessed or enhanced in order to better identify the various soil parameters, geomorphologic features, and depositional units which are thought to be useful tools in predicting and developing infiltration rates for the MRVA.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Brzuszek R.

The mission of the Crosby Arboretum, Mississippi State University Extension (located in Picayune, Miss.), is to preserve, protect and display plants and their communities native to the Pearl River Drainage Basin. The Crosby Arboretum's nationally award-winning master plan has designated a portion of its facility for the creation of a small stream swamp forest educational exhibit. Small stream swamp forests are wetlands situated on bottomlands of small streams that are predominated in species type and frequency by black gum (Nyssa biflora) and sweet bay magnolia (Magnolia virginiana). As specified in Mississippi's Comprehensive Wildlife Conservation Strategy by the Mississippi Department of Wildlife and Fisheries (MDWF), small stream swamp forests are considered vulnerable in the state of Mississippi. The proposed swamp forest exhibit will address MDWF priorities through the construction and management of the habitat type, as well as providing a venue for public education and experience in this vulnerable forest.

The Crosby Arboretum Foundation was awarded a grant to create a small stream forest educational exhibit. Graduate students in the Department of Landscape Architecture at Mississippi State University utilized a semester-long class project in spring 2011 to research and design the proposed exhibit. Students conducted a literature search on small streams and related wetlands and visited several in situ small stream swamps in Mississippi. Students recorded environmental data at the natural wetlands to inform the restoration design. Students also conducted an environmental inventory and analysis at the proposed exhibit site that recorded the site's hydrology patterns, plant species, soils and other data. A design charrette, or a collaborative session to determine solution to the design problem, was conducted with wetland specialists and landscape architects to develop the preliminary design. This paper will discuss the method used to develop the exhibit design and will exhibit the drawings for the proposed stream and associated wetland types. Long-term vegetation monitoring will be initiated after construction.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Feaga J., Kröger R.

Drainage ditches are an essential part to effective agricultural production by regulating water levels to control the inundation of production acreage. Drainage ditch construction in the Mississippi Delta, was merely a response to the need for access to more fertile soils, which previously was dominated by bottomland hardwood forests, oxbow lakes, and cypress swamps. Various ditches within the Mississippi Delta system contain weirs, which function to limit nutrient export into downstream habitats by reducing flow of water and increasing residence time. Until relatively recently, the biological significance of these agricultural structures to macroinvertebrate communities was not entirely understood. We investigated patterns of communal macroinvertebrate composition within seven agricultural drainage ditches with weirs near Belzoni, Mississippi. We examined macroinvertebrate abundance responses to weir age and distribution patterns with respect to distance from weirs. We then compared these results to results observed in 3 control ditches without weirs. Macroinvertebrates sampled from 7 ditch sites represented 11 distinct taxa with a total abundance of 3,948 individuals. The main contributors to total abundances were Chironomidae (48%), Physidae (30%), and Oligochaeta (20%) with Physidae (43%, n = 876) and Chironomidae (66%, n = 1905) representing the largest relative abundances in treatment and control ditches, respectively. Simple correlation tests showed macroinvertebrate abundances are not significantly influenced by either weir age or distance from weir. Our study suggests further investigation is needed to accurately assess the functional response of macroinvertebrate community composition to weirs. Our study was limited in both sample size and time. These limitations prohibited us from making significant conclusions about our results. We suggest a longitudinal study with a larger sample size across a wider pool of age classes may produce statistically significant results.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Shipes C., Kröger R.

Drainage ditches in the Mississippi Alluvial Delta are an essential part of the agricultural landscape of this region. These ditches vary greatly in size, location, and shape, but can aid in mitigation of contaminants from agricultural fields. Historically controlled drainage in the form of slotted or drop pipes, flash board risers, and vegetated drainage ditches have been used to effectively manage nutrients. More recently low-grade weirs have been used as an alternative to traditional controlled drainage structures. Low- grade weirs act to slow water flow, increase residence time, and allow sedimentation. Until recently the relationship between low-grade weirs and the vegetation communities present has not been evaluated. We selected 13 agricultural drainage ditches with weirs present in the Mississippi Alluvial Valley and investigated the vegetation community responses to weirs and weir age. We also selected 4 control ditches with no weirs present to compare our results. Vegetation assessment yielded 41 plant species ranging from obligate wetland plants to facultative upland plants. Simple correlation tests showed a strong positive relationship between weir age and species diversity, and also a positive correlation between total percent vegetative coverage and weir age. Linear regression also showed a positive relationship between weir age and the presence of facultative upland plants and a negative relationship between weir age and the presence of obligate wetland plants. This study shows some interesting trends, but we were limited in our sample size. Future studies should focus on a larger sample size with a wider range of age classes and should take other variables into account such as; vegetation communities upstream, slope of individual ditches, the spatial arrangement of weirs within the ditch system, and association with other weirs within the same ditch system.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Prabhu R., Lee N., Wadsworth M.C., Sassenrath G.F., Schmidt A.M., Crumpton J., Rice B., van Riessen H.

Implementation and use of a model requires an estimate of its accuracy. The Mississippi Irrigation Scheduling Tool (MIST) is an on-farm decision support tool to assist farmers in irrigating. The accuracy of the model is critical in designing good water management protocols. This research presents the results of the uncertainty analysis of the MIST model, showing the margin of error (uncertainty) of the irrigation advice. The basis for the verification and validation of the model is also given. The MIST calculates the daily soil water balance in a crop field from daily weather measurements, irrigation, and rainfall, accounting for crop type, planting date, soil type, tillage, and other field-specific information. The model output informs farmers of when irrigation is needed. The uncertainty analysis determines the margin of error in the irrigation decision and gives a range within which irrigation is feasible. The current uncertainty analysis also gives essential information on the influence of input parameters on the final irrigation recommendation calculated by the water balance.

The uncertainty calculations were based on Taylor's Series Method for the calculation of the total systematic uncertainty arising from measurement error of variables in the water balance calculation. The errors in measurement were one standard deviation in range, equivalent to an uncertainty with a confidence level of 68.2%. Because the current day's soil water balance depends on the previous day's water balance, the computations are iterative. As equations cascade to calculate the daily water balance, the uncertainties also propagate through the equations. Initially, uncertainty quantifications were performed for two sets of water balance calculations using local weather data. The final uncertainties for the water balance were of the order 3-6%, which is within the acceptable range for error.

The MIST water balance calculations were validated using local weather data consisting of rain days, and significant changes in the solar radiation, relative humidity and wind speed. The final water balance results showed values within acceptable ranges and comparable to in situ measurements of soil moisture. The final relative uncertainty in the water balance value was around 9%, which is in the normal range of margin of error. The current MIST web-based application and uncertainty quantification have been verified and validated for current parameters. The accuracy of the model was shown to be suitable for use by farmers in the Mississippi Delta area, and will help improve water management in crop production systems.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Overbey E., Gallo E., Kröger R.

An emerging practice for reducing the amount of nutrients and pollutants entering receiving waters is to filter urban stormwater runoff with infiltration based best management practices (BMPs). Small-scale BMPs for urban environments such as rain gardens, bioretention facilities, flow-through planters, and green roofs have been shown to slow peak flows and reduce the amount of nutrients that are washed from impervious surfaces during storm events. These BMP technologies are relatively new in design practice and all aspects of their structural design, potential for nutrient removal, and peak flow reduction is yet to be fully examined. The objective of this study is to provide understanding of different soil compositions in flow-through planters currently used in practice and determine their potential for water quality and quantity improvements. Eighteen 30"x18"x12" aquaria were modified to model flow-through facilities in a practical application using synthetic runoff which contained a 2ppm mixture of nitrogen and phosphorus. Soil mixtures varied across treatments and were composed of different percentages of sand, topsoil and compost. A hydrograph was used to simulate the most intense 4.5 hours of a 2-inch, Type II 24-hour rainfall event and was applied to the aquaria using manually controlled flow rate pumps. The outflow hydrograph was recorded to determine if peak flow was reduced and water quality samples were collected and analyzed to determine if nitrate and phosphate retention differed between soil treatments. Water quality data analyses indicate phosphate retention values ranged from (33-81%) and poor retention of nitrate (4- 23%). Nitrate values showed increases in concentration for some treatments. Preliminary results indicate the need for modification of the study design as higher infiltration rates in soil treatments reduced the residence time expected for the stormwater runoff in these facilities and as a result did not allow for the desired reduced peak flow. Further research is needed to test structural design modifications of flow-through facilities in order to increase their quantity reduction performance.

Proceedings of the 42nd Mississippi Water Resources Conference

Year: 2013 Authors: Poganski B., Kröger R., Pierce S.

The use of inorganic fertilizers in agricultural production is widely recognized as a source of nitrate contributing to annual hypoxic zones in the Gulf of Mexico. Ecosystem degradation and impacts on freshwater and marine biota from nutrient contamination of surface waters have motivated research efforts to develop and implement innovative nutrient management practices. Such efforts have become a major priority of many landowners, natural resource conservationists, scientists, and government agencies from a local to national scale. The current experiment investigates how frequency and variable spatial arrangements of best management practices (BMPs) within drainage systems impact water quality leaving the agricultural landscape over time. Preliminary water quality results highlight temporal nutrient trends in agricultural effluent, where concentration spikes were observed during seasons that experience heavy rainfalls and when fertilizer application occurs. Results also showed phosphorus concentrations to be higher in run-off during stormflows rather than during baseflows, while nitrate concentrations in run-off were found to be similar regardless of flow regime. Integrating nutrient reduction data, spatial and temporal variables of best management practices, drainage acreage, and fertilizer inputs will help determine factors that affect nutrient reduction efficiencies and drive the adaptation of management strategies to further enhance pollution mitigation. Investigations of nutrient reduction data and environmental factors highlight the short-term benefits of management practices, which include water conservation, pollution reduction, and ecosystem services. Recognizing that decreasing the loss of water resources and nutrients through BMPs may have additional long-term environmental and monetary benefits to all stakeholders from local to regional scales.