Location: Water Quality and Ecology Research2008 Annual Report
1a. Objectives (from AD-416)
Develop and refine conservation technologies for implementation within agricultural watersheds that improve water quality and ecosystem function, contribute to TMDL and nutrient criteria development, and conserve natural resources by (1) evaluating farm and land management systems in Beasley Lake Conservation Effects Assessment Project (CEAP) watershed that are intended to reduce erosion, conserve soil, improve receiving water quality, and protect ecological resources; (2) determining the effectiveness of conservation practices for improving water and soil quality within the Yazoo River Basin to meet Total Maximum Daily Load criteria; (3) developing a database for Beasley Lake CEAP watershed that contains water, soil, ecological, and land management results from research conducted at field, farm, and watershed scales for assessment of conservation practices applicable to the Yazoo River Basin; (4) validating and quantifying uncertainties of model predictions for Beasley Lake CEAP watershed; (5) determining essential abiotic and biotic relationships required to effectively restore streams impaired by physical habitat degradation as defined by Total Maximum Daily Load criteria; and (6) assessing effects of conservation practices on off-site water quality for improved TMDL and nutrient criteria decision-making in agricultural watersheds impaired by non-point source pollution.
1b. Approach (from AD-416)
There is extensive literature on agricultural conservation practices aimed at protecting water quality and ecological integrity. Most of this work, however, is based on small-scale studies, and findings often are not easily scaled up due to complex interactions at the whole-farm, watershed, and landscape scales. Therefore, effects of widespread implementation of conservation measures (i.e. BMPs) have not been demonstrated. Continued work is needed on assessing individual innovative BMPs. Furthermore, realistic ecological restoration experiments require additional work at the prototype scale. To address these issues, natural resource (water, soil, and biological quality) responses to conventional and innovative conservation measures will be studied across a range of scales to provide support for the goals of the Clean Water Act of 1972 (and its amendments) and the Farm Security and Rural Investment Act of 2002. This research will focus on quantifying and assessing impacts associated with conservation practice implementations in an economically efficient manner to reduce nutrient, pesticide, and sediment loadings to the nation's surface waters necessary to produce sustainable ecosystems. This plan calls for a set of complementary experiments dealing with physical, chemical, and ecological processes at a range of scales from the laboratory bench to the watershed.
3. Progress Report
This project is staffed by ten SYs representing five disciplines in collaboration with five other research institutions. Data collection, including data for sediment quality, water quality, meteorology, hydrology, fish, or invertebrates occurred at more than ten field sites. Topics investigated were very diverse, but directly addressed four of the six problem areas in the National Action Plan for Program 201. National program problem area 1—Effectiveness of conservation practices. Progress continues in assembling a comprehensive data set to describe soils, cropping patterns, cultural practices, topography, climate, stream flows and water quality in the watershed of Beasley Lake, a natural oxbow lake in the Mississippi Delta and one of the watersheds selected for concentrated analysis within the Conservation Effects Assessment Program. These data have been transferred to the national repository. The data have also been used in validation of the AnnAGNPS computer model. Monitoring of lake water quality and fish resources and evaluation of runoff from CRP areas and buffer strips continues. Cotton production areas were monitored to determine effects of within-field residue management and edge-of-field best management practices on soil herbicide concentrations and runoff quality. Runoff was also sampled from fields with continuous corn and winter cover crop systems and from fields with reduced-till and no-till corn with and without grass hedges. Field studies were conducted to measure the effects of soil amendment using industrial byproducts (gypsum and ferrihydrite) on soil quality, runoff quality, and crop production. National program problem area 4—Integrated soil erosion and sedimentation technologies. Soil and sediment sample collection and analyses were performed to support a study relating soil erodibility to geomorphology. National program problem area 5—Watershed management, water availability, ecosystem restoration. An artificial stream has been constructed, and initial survival tests using fish and invertebrates are underway. Fish and habitat data were collected from the Big Sunflower and Coldwater Rivers, which drain the intensively cultivated Mississippi Delta region. Big Sunflower studies assess potential to address habitat deficiencies in channelized rivers using weirs or artificial riffle structures. Coldwater River studies are targeted at effects of backwater rehabilitation. National program problem area 6—Water quality protection systems. A set of laboratory toxicology studies using a common invertebrate, Hyallela azteca, and sediments from river backwaters were completed. Results are being compared with fish collections from the study backwaters. The efficacy of using rice fields for mitigating pesticide contamination of runoff was studied by collecting and analyzing samples of water, sediment and plant tissue. Studies examining use of vegetated drainage ditches to mitigate runoff contamination continued. Resilience of native herbaceous plant species in harsh drainage ditch environments was evaluated, while additional work sampled runoff quality in ditch systems with and without vegetation.
1. Rice fields may serve as pollution controls. In late fall and early winter, pesticides in runoff from fields may contaminate downstream waterbodies. An experiment was conducted to determine the degradation of an organophosphate insecticide added to simulated storm runoff into winter rice fields. Samples of plant materials in decomposition bags over the study duration indicated rice plants were effective at adsorbing the insecticide and preventing it from leaching back out to the water for possible contamination. Results suggest possible use of harvested rice fields as treatment units for pesticide-contaminated runoff. NP 201, Problem area 6, product 6.
2. Erosion controls quantitatively evaluated. More than $300 million in federal funds was spent for erosion control in 16 watersheds in northern Mississippi between 1985 and 2003, but effects on sediment yield have not been fully quantified. All available records of stream flow and suspended sediment concentration for seven of the larger watersheds were analyzed using statistical procedures designed to detect increasing or decreasing trends with time. A trend was found for only one of the seven gages, showing declining sediment concentration over the period 1986-1997. Real reductions in sediment concentrations may be hard to achieve with the orthodox types of channel erosion controls (grade controls and streambank protection) applied in these watersheds. NP 201, Problem area 1, product 2.
3. Natural river wetlands for pollution control. Natural wetlands occurring in the flood plain near rivers can be modified and used as best management practices to improve and sustain river water quality. An 8-week study was done in a modified natural wetland near the Coldwater River in northern Mississippi to improve our understanding of how efficiently this wetland could trap three commonly used agricultural pesticides, atrazine, metolachlor and fipronil. The study showed the wetland was capable of efficiently trapping all three pesticides and preventing them from entering the Coldwater River. These results are of interest to regulatory and other agencies and the pesticide industry as an additional tool to improve and sustain river water quality and overall environmental quality. NP 201, Problem area 6, product 6.
4. No-till safe for groundwater. Cropping systems such as no-till or conservation tillage can reduce erosion and production cost but may pose a risk to groundwater quality due to enhanced infiltration. This study in north Mississippi from 1991 to 1996 showed that conservation tillage practices for corn did not significantly increase chemical contamination of the shallow groundwater; however, increased infiltration contributed to briefly increased herbicide levels following rainfall events early in the growing season. The research points to using pre emergence rotating herbicides, and post emergence glyphosate in resistant corn to effectively control weeds in conservation tillage systems. These research results are important because they show that distribution and varying amounts of rainfall throughout the different seasons of the year may alter the effects tillage practices have on groundwater contamination. Information from this study provides the National Resource Conservation Service (NRCS) and extension personnel with additional guidance for making pesticide management recommendations to farmers. NP 201, problem area 4, product 5.
5. Stream restoration experiment yields valuable lessons. Stream ecosystems in the southeastern U.S. harbor large numbers of species and represent significant ecological resources, but have experienced widespread degradation due to factors driven by land use and channel modifications. Few scientific reports describe attempts to rehabilitate these ecosystems, and technical guidance for standard practices is often absent. A group of multidisciplinary studies were conducted for five years associated with rehabilitation of a 2-km-long reach of a severely eroded sand bed stream in central Mississippi. Restoration practices featured the use of native living and dead plant materials. Although the project was initially successful in producing improved aquatic habitat, it ultimately failed to stabilize the eroding channel and produce long-term ecological benefits due to processes of channel instability operating at the landscape scale. Insights gained from this experiment will guide future research and demonstration efforts. NP 201, problem area 5, product 2.
6. River restoration measures evaluated. River ecologists have found that floodplain lakes and sloughs that are attached to the river during higher flows (backwaters) are extremely valuable habitats, but these areas are undergoing rapid degradation due to sedimentation and pollution. Several techniques have been proposed and demonstrated for restoring the ecological quality of these areas, but methods for evaluating the effectiveness of the techniques are lacking. An approach for restoration evaluation developed river channels was applied to a backwater restoration project using a computer model that simulated backwater levels for a given set of river conditions. This method will assist others in planning, design and evaluation of river backwater restoration projects. NP 201, problem area 5, product 2.
7. Soil and sediment characterization suggests pollution control strategy. Mercury concentrations in fish in Grenada Lake in Mississippi exceed Food and Drug Administration standards for human consumption, and the primary source of mercury is sediment transported from the upland soils and stream channels. Watershed soils, stream sediment, and reservoir sediment were characterized for several physical and chemical properties that influence the transport of chemical pollutants. Mercury was most concentrated in the surface watershed soils where it is more susceptible to runoff and erosion processes, and it is not closely associated with soil clay and organic matter components responsible for most chemical transport. However, reservoir and stream sediment data showed that mercury was picked up by the clay portion of sediment. Evidently, during transport and deposition, dissolved mercury is picked up by suspended sediment clay and organic matter and is carried into Grenada Lake primarily on fine clay particles. This information can be used to select best management practices to reduce the content of particulates in runoff from upland soils and mercury concentrations in sediment for improved water quality. NP 201, problem area 6, product 6.
8. Sources of elevated nutrients identified. Plant nutrients such as nitrogen and phosphorus are entering coastal marine systems from rivers at greatly elevated rates, causing excessive growth of algae, triggering episodes of oxygen depletion when the algae die and decay. Available data regarding the concentrations of nitrogen and phosphorus in streams draining the Yazoo River basin of Mississippi were compiled and summarized. Although processes that govern transport of nitrogen and phosphorus are very different, levels of both nutrients tend to be much higher in the Delta portion of the Yazoo River basin than in the Hills, particularly in Spring, and reflect higher levels of row crop agriculture in the Delta. The Yazoo River basin retains most of the nutrients that are input to it, and water leaving the basin generally carries lower concentrations of nutrients than the receiving stream, the Mississippi River. However, nutrient concentrations are several times higher than water quality criteria set by the U.S. Environmental Protection Agency (EPA) for this region. This information is useful to land managers seeking to develop strategies for controlling nutrient pollution at the landscape scale. NP 201, problem area 6, product 1.
9. Slope position indicates erosion potential. Runoff and erosion losses from soils formed in the loess deposits of the lower Mississippi River Valley are the highest in the United States due to generally low concentrations of cementing agents that bind soil aggregates into water stable units. The distributions of these cementing agents vary along slope positions due to differences in soil wetness, and a soil erodibility index was developed based on total clay and water dispersible clay contents. It was shown that as the soils became wetter in the lower slope positions, an increase occurred in their susceptibility to erosion losses due to the loss of iron, aluminum, and silica oxide cementing agents. These results facilitate the determination of erodibility as a function of slope position when predicting runoff and erosion losses at watershed scales, and thus aid individuals and agencies involved in soil conservation and pollution control. NP 201, problem area 4, product 4.
Yuan, Y., Bingner, R.L., Theurer, F.D., Kolian, S.R. 2007. Water Quality Simulation of Rice/Crawfish Within Annualized AGNPS. Applied Engineering in Agriculture, Vol. 23(5): 585-595.