Call Prefix : PR-T

Call Suffix : 1989

Call Cutter : D - FoRM 8

Location : SEARCA Library

Format : TD

Publisher : University of the Philippines Los Baños,

Publication Date : May 1989

Publication Place : Los Baños, Laguna, the Philippines :

Summary : A study of Padas and Wader watersheds located in Upper Solo watershed, Central Java, showed that the area was characterized by two distinct seasons, namely: dry season from May to October and Wet season from November to April. A deterministic, event, and lumped model was used to predict runoff from the two watersheds. The model consists of four parameters, namely: (1) maximum rate of seepage from the soil water zone in inches per day (S), (2) maximum soil moisture less readily available for evapotranspiration in inches (C), (3) fraction of seepage from the soil water zone that becomes runoff (F), and (4) maximum infiltration rate in inches per hour (Fmax). These parameters were optimized by minimizing the sum of squares of the difference between observed and simulated runoff. The model required as input the daily rainfall and the estimated potential evapotranspiration, which was computed using Penman method. Streamflow records for 10 years (1976-1977 and 1979-1986) of Padas watershed (3485 ha) and 11 years (1976-1977 and 1978-1986) of Wader subwatershed (202 ha) were used to test the validity of the model. Data of monthly flows for four years were used to estimate the optimal values of the parameters. The final test of the adequacy of the model lay in a comparison of observed and simulated runoff. Comparison showed that the observed and simulated runoff values are not significantly different. This was based on the results obtained from four statistical measures used to test the model. The model did a better simulation in Wader, the smaller watershed, than in Padas, the larger one.