Instantaneous runoff coefficients for Tutuvén river basin, Maule Region, Chile

Abstract

In Tutuvén river basin, central Chile, instantaneous runoff coefficient (C), defined as the rate between runoff and rainfall, and its influence on different vegetation cover considering previous soil moisture were studied. Coefficients were calculated for intervals of 1, 2 and 4 hours in three different vegetation covers and three different moistures soil conditions, defined by the Curve Number method. 30 storms were used for the period 1982-1997. Results showed that the highest runoff coefficient values were obtained for one hour, with high moisture in soil and thin cover vegetation. On the other hand, the lowest runoff coefficient values were observed in sites of high cover vegetation and dry soils. It is concluded that rainfall intensity is the main factor influencing runoff coefficient values. Good estimates of C were obtained through a regression analysis between daily rainfall amount and C, with a R2 ranging from 0.84 to 0.97.