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A climate-driven model to serve as a predictive tool for management of l groundwater use from the Mississippi Delta shallow alluvial aquifer
Final Project Report

Year: 2011 Authors: Wax C.L., Pote J.

The objective of this research was to develop a model that can be used as a management tool to find ways to meet the needs for water use while conserving groundwater. This is the third phase of the project to meet these objectives. In phase one of the project, the growing season precipitation was used to develop a relationship that estimated irrigation use, and this was the driving mechanism of the model that simulated water use to the year 2056. Phase two added the use of surface water when growing season precipitation was 30% or more above normal. In this third phase, a new climatological input was introduced into the model—irrigation demand. Irrigation demand was calculated using daily precipitation, evaporation, and a crop coefficient to estimate daily water needs by crop type. Daily values were summed to one week segments which were added to derive the total growing season irrigation demand. Weekly summations increased temporal resolution, improving model efficiency in accounting for excess daily rainfall, allowing the model to apply excess rainfall in subsequent days.

Coles Creek Watershed Assessment and Education
Final Project Report, Project #2008MS82B

Year: 2011 Authors: Silitonga M., Johnson A.

The Coles Creek Watershed, located in the southwestern quadrant of the state of Mississippi, is listed under the US EPA impaired water section 303(d). Degradation of the ponds/lakes and streams/creeks in this watershed is caused mostly by biological impairment, followed by nutrients, organic enrichment or Low Dissolved Oxygen, sediment/siltation, pesticides, and pathogens (US EPA, 2007). These impairments cause the degradation of water quality thus causing euthrophication or algal bloom that can lead to fish kills and can also adversely affect human health. The causes of algal blooms have not been studied; therefore, data is needed to evaluate the quality of water and soil in the surrounding areas of the watershed. The data obtained will be used to analyze and determine the situation and find effective methods to solve the problem. Community participation in the area is much needed to improve, maintain, and restore the quality of water. Thus, educational materials are necessary to engage the community in protecting the quality of water in this area.

Each water body is unique depending upon its geological characteristics such as natural landscape features and human activities related different land uses and landmanagement practices. In the Coles Creek Watershed, several identified water bodies have been heavily impaired.

Poor water quality can harm fish, wildlife, and their habitats. Many things are known to cause poor water quality including: sedimentation, runoff, erosion, dissolved oxygen, pH, temperature, decayed organic materials, pesticides, and toxic and hazardous substances. Therefore, identifying the cause of degradation and finding the best management practice(s) (BMPs) as well as protection strategies have to be developed for each lake, pond, or river, individually.

The purpose of the study is to investigate, assess, and find solutions to improve the quality of surface water bodies that can be adopted and implemented in the watershed.

Influences of Land Surface/Land Use Characteristics on Precipitation Patterns Over the Lower Mississippi Alluvial Plain
Final Project Report, Project #2009MS85B

Year: 2011 Authors: Dyer J.

The lower Mississippi River alluvial valley in southeast Arkansas, northeast Louisiana, and northwest Mississippi is characterized by widespread agriculture with few urban areas. Land use is predominantly cultivated cropland with minimal topographic variation; however, the eastern edge of the alluvial valley is defined by a rapid, though small, change in elevation into a heavily forested landscape. This change in land use / land cover has been shown to potentially enhance precipitation through generation of a weak mesoscale convective boundary. This project defines the causes and influence of the land surface on associated precipitation processes by simulating a convective rainfall event that was influenced by regional surface features. Analysis was conducted using a high-resolution simulated dataset generated by the Weather Research and Forecasting (WRF) model. Results show that the strongest uplift coincides with an abrupt low-level thermal boundary, developed primarily by a rapid change from sensible to latent heat flux relative to the agricultural and forested areas, respectively. Additionally, surface heating over the cultivated landscape appears to destabilize the boundary layer, with precipitation occurring as air is advected across the land cover boundary and the associated thermal gradient. This information can be used to define and predict surface-influenced convective precipitation along agricultural boundaries in other regions where the synoptic environment is weak.

Sources, sinks, and yield of organic constituents in managed headwaters of the Upper Gulf Coastal Plain of Mississippi
Final Project Report

Year: 2011 Authors: Hatten J.A., Dewey J.C., Ezell A.W.

Sediment, organic matter, and nutrients (particularly nitrogen) are the constituents that most often lead to the impaired designation for rivers in Mississippi (E.P.A. 2000). Headwater streams are very important contributors of water, sediment and nutrients to the downstream fluvial environment. Many studies of non-mountainous systems have focused on the quantity of particulate or dissolved forms of material (e.g. suspended solids, organic matter, and nitrogen); few have examined the source of this material. The relationships among origin, storage, consumption and export of organic matter (OM) with stream discharge and subsurface interflow represent significant gaps in our understanding of headwater processes. This study is part of a larger-scale study investigating the effects of silvicultural best management practices in ephemeral and intermittent drains on hydrologic function in small-scale headwaters. A 30 ha watershed located approximately 8 miles west of Eupora in Webster County, MS has been continuously monitored for water table elevation, precipitation intensity and duration, in-stream TSS, and chemical composition of water and particulates. Data were used to elucidate the transport and source/sink behavior of sediment, and dissolved and particulate forms of organic matter, in the form of nitrogen (N) and organic carbon (OC), over a broad range of hydrographic conditions. Results indicate that particulates in perennial and ephemeral-intermittent stream segments are derived from surface mineral soil horizons as a result of downcutting. The source of water in the perennial stream is dominated by ephemeral stream contributions rather than groundwater during dry periods. During the wet winter months perennial streamwater chemically resembles groundwater whereas ephemeral-perennial segments chemically resemble canopy throughfall waters. Ephemeral drains are significant contributors to downstream perennial streams, especially during dry periods; therefore it is important to consider ephemeral basins within an overall basin management plan.

Water-Conserving Irrigation Systems for Furrow & Flood Irrigated Crops in the Mississippi Delta
Final Project Report

Year: 2011 Authors: Massey J.H.

The goal of this project was to improve irrigation water- and energy-use efficiency for one of the most economically important cropping rotations practiced in the Mississippi delta, the soybean-rice rotation. Combined economic activity for the two crops in the delta exceeds $600 million annually while combined irrigation water use approaches 2 million A-ft per season. As a result, a modest reduction in the amount of irrigation water used in the soybean-rice rotation could help reduce the current overdraft of the alluvial aquifer. Results from these 2010 on-farm trials indicate soybean irrigation savings using NRCS Phaucet optimization software ranged from 6 to 18% compared to non-optimized furrow irrigation while associated energy use reductions ranged from 32 to 20%, respectively. (It is important to note that in order to foster comparison, the soybean fields used in these studies were rectangular in shape; water savings are expected to be greater for more irregular (i.e., hard to irrigate) soybean fields.) Irrigation water used in rice grown using straight-levees with multiple inlets and intermittent flood management averaged 23.1 ± 2.4 A-in/A as compared to 32.4 A-in/A for straight-levee rice using multiple inlets without intermittent flood management. These results indicate that by overlaying an intermittent flood regime on practices that are already familiar to rice producers in Mississippi, rainfall capture is increased and over-pumping is decreased such that overall water use is reduced by ~40% over the standard rice irrigation practices. Field trials comparing rough rice yield and milling quality for 15 rice varieties grown on two soil series indicated that commercial rice varieties, grown using standard fertility and pest control programs, well-tolerated a carefully-controlled intermittent flooding regime. Each inch of water not pumped from the Alluvial aquifer onto an acre of rice or soybean saves the energy equivalent of ~0.7 gallon diesel fuel (with concomitant reduction in CO2 emissions by ~200 lbs/A). Assuming a current off-road diesel price of $3.20/gallon, a 9 acre-inch (40%) reduction in rice irrigation translates to a savings of ~$20 per acre while a 1.5 acre-inch (18%) reduction in soybean irrigation represents a savings of ~$3 per acre. By reducing irrigation water and associated energy inputs in soybean and rice production, the producer reduces input costs while reliving pressure on the Alluvial aquifer and also reduces carbon emissions.

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