Perpustakaan Digital ITB

In many areas in Indonesia, flood from rivers and coastal zones is followed by drought at the same time in other places. Drought influences agricultural activities, especially in availability of irrigation water. Growing crops depend on the quantity of water that evaporates from the soil and plant through evapotranspiration. For each of the plant, the amount of water to do evapotranspiration is different. This can be measured from Crop Water Requirement. The water needed of a plant is linearly depended on evapotranspiration rate and is different from one place to the others. The total water balance depends on various components to stabilize total rainfall. The main components are evapotranspiration, run off, river discharges, and ground water levels. According to the weather station location, the data for parameters that give big influence to the evapotranspiration rate will be given. CLIMWAT (FAO, 2008) and Badan Meteorologi Klimatologi dan Geofisika (BMKG, 2008) give the climate data that is used in this study. Due to lack of the evapotranspiration rate data at most of Java area, it is suggested to interpolate the value of evapotranspiration rate at certain unknown coordinate points. In this study, it is shown how the robustness of interpolation method will be given.