Representative synthetic unit hydrograph due to the rainfall station network

Samiran watershed is instead of Semajid River and its affluents. This watershed is located in Pamekasan Regency, Madura Island of Indonesia. There is 5 (five) rainfall stations which are spreaded in this watershed. This paper intended to analyze the representative synthetic unit hydrograph. In depth analysis this research would investigate this analysis due to the effectiveness on distribution of rainfall station network. Synthetic Unit Hydrograph could become as the source of some important informations that is nacessary for the reliable of hydraulic structures. The methodologies consisted of hydrological analysis on rainfall stations density and hydrograph. Analysis of rainfall stations density used the method of Kagan-Rodda and Krigging. Synthetic Unit Hydrograph of Gama I and Limantara were used for hydrograph analysis. Both of the Synthetic Unit Hydrographs were established by two researchers from Indonesia and were recommended to apply for watersheds which had similar characteristic as observed watershed (Indonesia). Results showed that the effective amount of rainfall stations due to Kagan Rodda Method was 3 units and Krigging Method was 5 units with relative error of design rainfall each of 13.63% and 23.02%. Analysis hydrograph based on the result of rainfall station density indicated that there were small difference on time to peak and peak discharge between Gama I and Limantara Synthetic Hydrograph due to the observed hydrograph. However, results of Limantara Synthetic Unit Hydrograph was more closely to the observed one.