Kajian Neraca Air (Water Balance) Sub Daerah Aliran Sungai Karai

Abstract

The Karai sub-watershed is a part of the Ular watershed. The aim of this research is to obtain the value of the water balance components that occur in the Ular watershed, especially in the Karai sub-watershed. To determine the water balance in the Karai Sub-watershed, the equation is used: P−ETc—Q-In-Qd ±ΔS= 0 where P = amount of rainfall (mm), ETc = amount of plant evapotranspiration, Q = amount of surface runoff (mm) In = Number of interceptions (mm) Qd = Domestic Water Requirements (mm) and ΔS = change in water storage (mm). According to the findings of water balance research in the Karai sub-watershed, the source of water supply at the research location was 100% rainfall, or 2,811 mm/year, with a 19.24% interception rate, or 540.75 mm/year, from this rainfall, 49.176% of the water comes out as plant evapotranspiration of 1382.36 mm/year, 1.52% of the water comes out as surface runoff which is 42.82 mm/year, 0.816% of the water comes out as domestic water needs of 22.95 mm/year . In general, there is a surplus in changes in water storage of 822.14 mm/year with a percentage of 29.25%. The water surplus occurs because rainfall is quite high in the research area so that rainwater can supply water and maintain water availability in the soil to meet the water needs of plants in the Karai Sub-watershed area.