| Summary: | Ngrancah Sub Watershed is a Watershed located above Sermo Reservoir,
Kulonprogo Regency. The Sermo Reservoir utilized as a source of water by the
Regional Water Company (PDAM) and also iirigation water to irrigate rice fields in
the surrounding area and Wates District. However, basically the availability of water
in Sermo Reservoir from year to year is declining. This happens because of the
environmental damage cause erosion, and then the result of erosion as sediment is
being accumulated in the river. The more sediments transported and settled in
reservoir causing siltation and can reduce the age of reservoir. This research aims of
predicting discharge using Mock methods and predict sediment into the Sermo
Reservoir from Ngrancah River
In this research, the sediment was calculated using the method of Meyer-Peter
and Muller's. Ngrancah Sub Watershed model parameters are sub-watershed area =
20.56 km2, infiltration coefficients wet season (WIC) = 0.67, coefficient of
infiltration dry season (DIC) = 0.78, initial soil moisture (ISM) = 100 mm, soil
moisture capacity (SMC) = 170 mm, initial groundwater storage (IGWS) = 700 mm
and groundwater recession constanti (K) = 0.49 . The prediction of sediment
transported to the Sermo Reservoir for 10 years (2002-2011) amounted to
5,579,927.18 m3.
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