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United States Department of Agriculture

Agricultural Research Service

Title: A Modeling Approach to Assess the Water Balance of a Typical Southern Piedmont Catchment under Long-Term No-Tillage Usage

Authors
item Abrahamson Beese, Deborah
item Endale, Dinku
item Schomberg, Harry

Submitted to: Georgia Water Resources Conference
Publication Type: Proceedings
Publication Acceptance Date: April 1, 2003
Publication Date: April 15, 2003
Citation: Abrahamson Beese, D.A., Endale, D.M., Schomberg, H.H. 2003. A modeling approach to assess the water balance of a typical southern piedmont catchment under long-term no-tillage usage. Georgia Water Resources Conference. p. 884-887.

Interpretive Summary: Rainfall can run off the surface of a field or seep into the soil and move below the roots of a plant into deeper soil. If the rain runs off the surface, it can carry soil and minerals such as phosphorus with it. Minerals such as phosphorus eventually reach the rivers and streams with the runoff, and can cause more algae to grow in the streams. Alga uses the oxygen that fish need to survive. Soil that gets into the rivers and streams can also affect the fish and other life in the stream, and our drinking water. When we keep crop residues on the surface instead of tilling them in before we plant, this can help the rainfall seep into the soil instead of run off. We measured the runoff from a watershed at the USDA-ARS-J.Phil Campbell, Sr. Natural Resource Conservation Center in Watkinsville, Georgia. We compared the measured runoff to the runoff predicted by the Root Zone Water Quality Model. The watershed had been in no-till crop production since 1974. We also compared the predicted seepage of the rainfall into the soil to see how quickly it reached the water table below the root zone of the crop, which depends on the amount and intensity of rainfall. A tested model can help other agencies such as the USDA-Natural Resources Conservation Service predict runoff and advise farmers and land owners of the benefits of no-till practices which will improve crop production and prevent problems from runoff into our streams and rivers.

Technical Abstract: We used the Root Zone Water Quality Model to simulate runoff and seepage below the root zone from a 2.7 hectare watershed to look at rates of ground water recharge under long-term, no-till crop production systems in the Piedmont of Georgia. The watershed is located at the USDA-ARS-JPCNRCC (J. Phil Campbell Sr., Natural Resource Conservation Center) in Watkinsville, Georgia. It has been in crop production under no-till and winter cover cropping management practices since 1974. The model over predicted soil moisture and slightly over predicted runoff, however, the pattern of deep seepage to ground water was distinctly different for rainfall patterns that were small and consecutive versus large rain events. Ground water depth immediately responded when root zone soil moisture was at field capacity or greater. This indicates that under saturated or field capacity soil moisture conditions, larger rain events of short duration (> 15 cm and < 30 hours in this case) are recharging ground water rather than creating significant runoff. Simulations of watershed management practices such as long-term no-till and cover cropping can serve as a useful tool to show the effects of long-term management on potential surface water contamination.

Last Modified: 4/17/2014
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