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Vulnerability and Use of Ground and Surface Waters in the Southern Mississippi Valley Region

Duration: September 1, 1996 to September 30, 1997

Federal Funds Requested: $110,190

Non-Federal Funds Pledged: $301,415

Principal Investigator(s): H. Don Scott, Hangsheng Lin, Terry L. Lavy, Eric J. Wailes and Kenneth Young, University of Arkansas, Fayetteville, AR,


Alton B. Johnson, Alcorn State University, Lorman, MS, MWRRI

David R. Shaw, T. M. Kaminski, and S. H. Schoenholtz,

Mississippi State University, Starkville, MS, MWRRI

Congressional Districts: Arkansas: District 3

Mississippi: Districts 2 and 3

Statement of Critical Regional or State Water Problems:

There is a major concern in the Southern Mississippi River Valley of the United States about non-point source pollution of ground and surface waters resulting from activities associated with agricultural production. This region consists of two major land resource areas (MLRAs): Southern Mississippi Valley Silty Uplands (MLRA 134) and the Southern Mississippi Valley Alluvium (MLRA 131). Both MLRAs have level to undulating and rolling topography, relatively fertile soils and a climate particularly conducive for row crop production. The region is a major agricultural production area in the US with crops and on-farm fish production that use extensive amounts of water. In 1994, Arkansas ranked first in the US in the production of rice, fourth in cotton, fifth in grain sorghum, eight in soybeans and third in fish production. During the same year, Mississippi ranked third in cotton , fifth in rice, eleventh in soybeans, twelfth in grain sorghum and first in fish production. Irrigation is a major input to crop production with well over 4 million acres of cropland irrigated annually in these two states. Extensive use of pesticides for control of diseases, weeds and insects coupled with nitrogen fertilizers are potential sources of non-point pollution in the region. Essentially, all of the crops receive fertilizers and pesticides susceptible to vertical movement through the profile an as runoff through both the aqueous and sediment phases.

Contamination of ground and surface waters involves transport from the sites of application. This movement is caused by water percolating through the soil profile and vadose zone over the land surface to drainage ditches, bayous and small ponds. Prominent features of the landscape also include wooded areas that often are designated as wetlands. These is strong interest in examining the factors involved in quantifying the movement and fate of contaminants such as pesticides in the Southern Mississippi River Valley region. Protection and enhancement of the region's surface and ground water resources, while sustaining agricultural production has been the general goal of all Federal and state agencies concerned with water resource protection and especially the Water Resources Research Centers of Arkansas and Mississippi. The proposed project addresses the research priorities of the Southeastern and Island Region and the Water Resources Centers of Arkansas and Mississippi related to water quality, water management, and water quantity. Specifically, we will concentrate our research on contaminant transport in selected dominant soils as well as on water quality and use of surface and ground waters in rice production.

Statements of Results Benefits and Information Gained:

This coordinated regional research will result in additional insights in the movement of water and contaminants in the Southern Mississippi River Valley. The regional research is divided into two groups, with each group having three projects. In the first group, tow studies (UA and ASU) will quantify and simulate the subsurface movement of a conservative tracer (bromide) and selected pesticides in several of the dominant soils of the region. The deterministic computer models to be used in the study vary in complexity but require considerable physical and chemical characteristics of the soils and vadose zone porous materials in the region. Both principal investigators are actively developing databases on those important physical and chemical properties of the dominant soils in the region that are needed as inputs to the models. This is important because there is little quantitative information available on contaminant transport to the ground waters in Arkansas and Mississippi. These studies also serve as a model for enhanced assessment of ground water vulnerability for the Mississippi River Valley alluvial aquifer region and will aid in implementing the Agricultural Chemical Ground Water Management Plans for Arkansas and Mississippi. The third project (MSU) in this group quantifies the impact of vegetative filter strips on reductions in sediment and herbicide-contaminated runoff from fields of soybeans. This field-oriented project will examine the impact of varying widths of tall fesuce filter strips below soybean fields on the loss of sediment and off-site movement of herbicides in runoff.

Three studies (UA, MSU, and UA) relate water quality and water quantity issues associated with rice production. More than 50% of the rice produced in the US is grown in the region. Rice requires water ponded on the soil surface for 60+ days during growing season. It is not uncommon in this region to find that more than 60 cm of water is required during a rice growing season. One research project (UA) in this group will examine waters from commercial rice production fields for residual pesticide concentration and calculations of pesticide degradation rates. Another project (MSU) will examine ponding of water in rice fields during the winter months for use as potential wildlife and water quality management areas. Winter flooding is believed to have non-point source pollution control and agronomic benefits, such as increased sediment and nutrient retention, increased crop residue decomposition, increased soil water content and tilth, decreased winter weed coverage and decreased weed seed density. The quality and quantity of the runoff water and sediments will be related to the characteristics of the soils and surface residue management in the fields. The third project (UA) in this group focuses on the economics of the utilization of surface and ground waters for irrigation. The level of the Alluvial aquifer in some areas of the region has declined due to the greater rates of extraction than rates of replenishment. Depletion of ground water is particularly evident in areas with extensive rice and fish production. This research will examine the economics related to the use of on-farm surface water storage reservoirs to supplement and more efficiently utilize available ground water for irrigation.

U.S. Department of the Interior, U.S. Geological Survey
Maintained by: John Schefter
Last Updated: Wednesday March 23, 2005 9:17 AM
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