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

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.