Interaction Model of Rainfall, Lake, and Ground Waters

Abstract

This research intends to build an interaction model between rainfall, lake water, and ground water. The location of research is in the Sentani Lake where is placed in the Jayapura Regency-Papua-Indonesia. Sentani Lake is a lake in the Sentani Watershed. Sentani Lake is located between Jayapura City and Jayapura Regency-Papua Province. The area of Sentani Lake is 9,630 ha with the depth is 75 m over the sea. In the northern of this lake are the Cyclops Mountains (Dafonsero) that separate the Sentani Lake and the Pacific Sea. The Sentani Lake functions as the track of transportation, food source, drinking water source, and tourism. Based on the bathymetry analysis result which is obtained from the River Region Institution of Papua, the Sentani Lake has the smallest elevation from 13.05 mdpl until 71.5 mdpl with a maximum storage capacity of 4.8 milliard m3. The methodology of this research consists of 1) To set and to simulate of Hydrology Model; 2) Analysis of water balance; 3) To set up the hydro-geology model; 4) To simulate the integration of rainfall-lake water- ground water. The interaction model between rainfall and lake waters is built based on the relation between the outlet discharge and the rainfall at 10 points and then is validated at the 5 points of observation data. This model produces the formulation as follows: inflow to the lake from rainfall = 0.067 x rainfall – 5. The interaction model between the lake water level and the ground water level is built based on the value of ground water-level fluctuation and the lake water level at the 10 points, and it is validated at the 6 points of observation data. This model produces the following formulation: fluctuation of ground water level = 0.1529 x fluctuation of lake water level. By combining the ground water and run-off in the Sentani Watershed, it is known as follows: inflow total of lake = base-flow + 0.067 x rainfall – 5.