LONG-TERM RAINFALL-RUNOFF CHARACTERISTICS OF A SMALL SOUTHERN PIEDMONT WATERSHED

Authors: Endale, Dinku; Fisher, Dwight; Steiner, Jean

Submitted to: First Interagency Conference on Research in the Watersheds
Publication Type: Proceedings
Publication Acceptance Date: 9/2/2003
Publication Date: 10/27/2003
Citation: Endale, D.M., Fisher, D.S., Steiner, J.L. Long-term rainfall-runoff characteristics of a small southern piedmont watershed. First Interagency Conference on Research in the Watersheds. 2003. p. 497-502

Interpretive Summary: Runoff-induced soil erosion is a serious and costly problem in the Southern Piedmont, a 41.2 million acres region that extends from Virginia to Alabama. The effectiveness of various farming practices and land uses for reducing runoff and, therefore, erosion needs to be determined at field and watershed scales to identify management practices that protect the land and its resources. The USDA Agricultural Research Service, J. Phil Campbell Sr. Natural Resource Conservation Center has been monitoring rainfall and runoff from a 19.2 acres watershed since 1940 near Watkinsville, GA, in the Southern Piedmont. Four different land uses were evaluated: row cropping, kudzu, grazed kudzu mixed with rescuegrass, and grazed coastal bermudagrass. The data from 45 years of research showed that row cropping produced the greatest runoff and peak flows. The other land uses provided the soil protective cover throughout the year and reduced runoff and peak flows significantly, especially from highly intense spring and summer storms. These long-term data demonstrate that the best way to protect Southern Piedmont farmlands is to have vegetative cover all year around. The information is useful for landowners, local, state and federal resource conservation agents, and for citizens concerned about degradation of our natural resources.

Technical Abstract: The long-term hydrologic responses of a small (7.8 ha) zero-order Southern Piedmont watershed were analyzed from 1940-1984. Four land use phases occurred during this period: row cropping (5-yr), kudzu [Pueraria thunbergiana (S.&Z.) Benth] (5-yr), grazed kudzu mixed with rescuegrass [Bromus wildenowii Kunth] (7-yr), and grazed coastal bermudagrass [Cynodon dactylon L. Pers.](28-yr). Land use and rainfall variability influenced runoff characteristics. Row cropping produced the greatest runoff, percentage runoff, and peak flows. Kudzu reduced spring runoff and almost eliminated summer runoff, as did a mixture of kudzu and rescuegrass; however, rainfall was reduced during these two phases. Peak flows were also reduced during these two phases. Bermudagrass reduced runoff more than row cropping but not as much as kudzu or kudzu mixed with rescuegrass. Peak flows increased during grazing of bermudagrass but stayed below those during the cropping phase. Monthly rainfall-runoff regression relationships were developed and R2 greater than 0.60 were found for: cropping phase - summer, spring and winter; kudzu phase - spring and winter; kudzu-rescuegrass phase ¿ summer, spring, winter; and bermudagrass phase - summer and spring. Despite the relatively short records for some of the land uses, it is clear that relatively subtle differences in land use have significant hydrologic ramifications at the small watershed scale.