Estimation model of basin water yield of five main rivers in Aceh Province

Abstract

The design of hydrologic model may vary depend on some influencing factors, such as size, slope, river network and land use of the watershed. All these factors will affect the water yield. This research will study the estimation model of water yield of five main rivers in Aceh. The objectives of this research are : (1) present the characteristic of watershed of five main rivers in Aceh (2) present the variation of water yield estimates of the different watersheds and what are the influences of the different factors, (3) present water yield analysis and simulate the effect of rehabilitation and land use conservation for water yield in five watershed in Aceh Province with three subsequent models: H2U (Hydrogramme Unitaire Universel) model, Integration models between NRCS (Natural Resources Conservation Service) and baseflow and Mock Model. H2U model interpreted the Unit Hydrograph as the travel time probability density function (pdf) to the watershed outlet. Each flow path is characterized by the probability that a water drop follows it, its length and the pdf of its travel time. NRCS-TR 55 uses the runoff curve number (CN) method to estimate runoff from storm rainfall. Determination of CN depends on the watershed’s soil and cover conditions, which the model represents as hydrologic soil group, cover type, treatment, and hydrologic condition. Mock Model aims at a preliminary assessment of the available water resources in three main forms: precipitation; surface water and ground water. H2U model is able to simulate flood discharge at watershed in Aceh Province with efficiency coeficient 92 % compared to discharge measured. Integration models between NRCS and baseflow, capable to simulate water yield in Aceh Province with Nash-Sutcliffe efficiency coeficient 79.05 % compared to discharge measured. Mock model that used in this research capable to estimate of monthly discharge with efficiency coeficient 86.8 percentage, average yearly water yield in Aceh Province is 62.9 x 109 m3/year. Rehabilitation and land use conservation by reforestation at five watersheds in Aceh to result in stable water yield in a whole year and capable to lower runoff and increase baseflow.