Abstract

ARES, María Guadalupe; CHAGAS, Celio  and  VARNI, Marcelo. Runoff prediction and antecedent moisture estimation in a gauged basin. Cienc. suelo [online]. 2012, vol.30, n.2, pp.151-160. ISSN 1850-2067.

Soil moisture is one of the major factors affecting rainfall-runoff response. The objectives of this paper are to discuss the effect of antecedent moisture condition on surface runoff calculated by Curve Number (CN) method on a gauged basin of Tandilia hills, Buenos Aires province, and to estimate this moisture condition by an alternative method employing a soil water balance calibrated for the study area. The limit set between antecedent moisture conditions I and II was 87,5 mm of soil water reserve at the rainfall previous day. This variable was estimated by water balance adjustment. The relationship between observed and estimated runoff by CN method and 5-day antecedent rainfall had a coefficient of determination that only explained 28% of the variability and overestimated predicted values. The same relationship but adjusting antecedent moisture using soil water reserve at the rainfall previous day showed an R2 of 0.48, with less overestimation of runoff depths than the first method. It follows that new runoff estimations were improved compared to those obtained by the original Soil Conservation Service CN method. This shows that the water balance procedure can be useful to evaluate antecedent moisture conditions for the study region. According to the present results and others from local and international sources, initial moisture condition proved to be a highly sensitive variable for runoff estimation. This highlights the need to carry on further studies to improve the prediction of this soil water variable.

Keywords : 5-day antecedent rainfall; Soil water reserve; Curve Number.

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