ANALYZING RUNOFF DYNAMICS THROUGH PARAMETERIZING A HYDROLOGICAL MODEL IN A WATERSHED: A CASE STUDY IN UPPER SERAYU BASIN, CENTRAL JAVA PROVINCE, INDONESIA

Abstract

This research constructed a hydrological model by means of available data,
hydrological equations, and GIS program to find out the runoff dynamic on the
study area. The runoff dynamic was analyzed by describing runoff on different land
cover types, figuring the correlation between hydrological component and runoff,
calculating the sensitivities of the hydrological components to runoff, and
identifying the response of runoff to possible land cover change. The model
resulted that the highest runoff occurred on built up area and the lowest occurred
on cultivation area. Infiltration was also the hydrological component that mostly
influenced runoff. Replacing forest, shrub, and plantation by cultivation greatly
reduced runoff up to 49 %. Enlarging forest area increased runoff about 12 %.
Based on those findings, the hydrological component having the strongest
correlation with runoff gave the most influence to runoff change, and enlarging
forest area does not always decrease runoff.