ANALYZING RUNOFF DYNAMICS THROUGH PARAMETERIZING A HYDROLOGICAL MODEL IN A WATERSHED A Case Study in Upper Part of Serayu Watershed, Central Java Province, Indonesia

• Main Authors: , Adhi Nurul Hadi, , Prof. Dr. H.A. Sudibyakto, M.S.
• Format: Theses and Dissertations NonPeerReviewed
• Published: [Yogyakarta] : Universitas Gadjah Mada 2011
• Subjects: ETD
• Online Access: https://repository.ugm.ac.id/39107/; http://etd.ugm.ac.id/index.php?mod=penelitian_detail&sub=PenelitianDetail&act=view&typ=html&buku_id=50506
• Institution: Universitas Gadjah Mada

A hydrological model can represent processes of precipitation, interception, evapotranspiration, and infiltration, as hydrological components, in an upper part of a watershed. The hydrological components determine runoff dynamic on the upper part of watershed itself and on the low land area. Upper part of Serayu Hulu Watershed, as the study area, contributed to the occurrences of flooding on next lower area, Banjarnegara District. 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 landcover 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 landcover change. The model resulted that during research period, the highest runoff occurred on built up area and the lowest occurred on cultivation area. The strongest correlation coefficient was shown by infiltration-runoff positive correlations. It shows that infiltration and runoff have the strongest linear relationship and have the same responses to rainfall, the factor mostly determining values of hydrological components. Infiltration was also the hydrological component that mostly influenced runoff. When infiltration was added by half of its original value, runoff decreased more than 20 %, and the decreasing raised up to 35 % as infiltration was increased two times of its original value. Replacing forest, shrub, and plantation by cultivation greatly reduced runoff up to 49 %. Changing cultivation, forest, and shrub to plantation gave different effects to two Sub Watersheds. It increased runoff on integrated Serayu Hulu Sub Watershed about 16 %, meanwhile it decreased runoff on Merawu Sub Watershed about 24 %. Enlarging forest area increased runoff on the study area 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.