Seasonal rainfall-runoff relationships in a lowland forested watershed in the southeastern USA

  • Author(s): La Torre Torres, Ileana ; Amatya, Devendra ; Sun, Ge; Callahan, Timothy ;
  • Date: 2011
  • Source: Hydrological Processes 25:2032-2045


Hydrological processes of lowland watersheds of the southern USA are not well understood compared to a hilly landscape due to their unique topography, soil compositions, and climate. This study describes the seasonal relationships between rainfall patterns and runoff (sum of storm flow and base flow) using 13 years (1964–1976) of rainfall and stream flow data for a low-gradient, third-order forested watershed. It was hypothesized that runoff–rainfall ratios (R/P) are smaller during the dry periods (summer and fall) and greater during the wet periods (winter and spring). We found a large seasonal variability in event R/P potentially due to differences in forest evapotranspiration that affected seasonal soil moisture conditions. Linear regression analysis results revealed a significant relationship between rainfall and runoff for wet (r2 = 0.68; p < 0.01) and dry (r2 = 0.19; p = 0.02) periods. Rainfall-runoff relationships based on a 5-day antecedent precipitation index (API) showed significant (r2 = 0.39; p < 0.01) correspondence for wet but not (r2 = 0.02; p = 0.56) for dry conditions. The same was true for rainfall-runoff relationships based on 30-day API (r2 =0.39; p < 0.01 for wet and r2 = 0.00; p = 0.79 for dry). Stepwise regression analyses suggested that runoff was controlled mainly by rainfall amount and initial soil moisture conditions as represented by the initial flow rate of a storm event. Mean event R/P were higher for the wet period (R/P = 0.33), and the wet antecedent soil moisture condition based on 5-day (R/P = 0.25) and 30-day (R/P = 0.26) prior API than those for the dry period conditions. This study suggests that soil water status, i.e. antecedent soil moisture and groundwater table level, is important besides the rainfall to seasonal runoff generation in the coastal plain region with shallow soil argillic horizons.

  • Citation: La Torre Torres, Ileana B.; Amatya, Devendra M.; Sun, Ge; Callahan, Timothy J. 2011. Seasonal rainfall-runoff relationships in a lowland forested watershed in the southeastern USA. Hydrological Processes 25:2032-2045.

Requesting Publications

You can order print copies of our publications through our publication ordering system. Make a note of the publication you wish to request, and visit our Publication Order Site.

Publication Notes

  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
  • Our on-line publications are scanned and captured using Adobe Acrobat. During the capture process some typographical errors may occur. Please contact the SRS webmaster if you notice any errors which make this publication unuseable.
  • To view this article, download the latest version of Adobe Acrobat Reader.