Pendugaan Neraca Air, Erosi Dan Sedimentasi Menggunakan Aplikasi Tank Model Dan MUSLE Di Sub-sub DAS Cikadu, Kabupaten Bandung, Jawa Barat

Abstract

The difficulty in assuming flow characteristics of water in a watershed could be answered by Tank Model aplication, this model use the parameters of precipitation, evapotranspiration, and flow as input data to estimate characteristics of a watershed in the form water balance, presence of water and water level on each layer ground.The research was located at Cikadu Sub-Watersheds which is a part of Cisangkuy Sub-Watershed at Mangun Jaya Village, Arjasari Sub-District, Bandung District with water catchment area as much as 986.6 Ha. The research was held on November 2011 – January 2012. The objective of this research are : 1) Study of hydrology characteristics at Cikadu Sub-Watersheds using Tank Model with the basis of SPAS data, 2) Study of sedimentation and erosion rates at Cikadu Sub-Watersheds using MUSLE method with the input of runoff data generated by Tank Model application. Land cover in Cikadu Sub-Watersheds consist of 376.8 Ha (38.20%) shrubs, 199 Ha (20.17%) forest, 152.3 Ha (15.44%) plantations, 4.4 Ha (0.44%) residential area, 123.8 Ha (12.55%) irrigated rice field, 60.1 Ha (6.10%) rainfed rice field, and 69.8 Ha (7.08%) agricultural field. Result from the calibration of stream flow monitoring stations data shows a high correlation between water level and discharge which was Q = 50.82 TMA2,578, with R2 = 0.98. Correlation between discharge and sedimentation rate was Qs = 0.981 Q1, 897, with R2 = 0.70. The runoff rate can be predicted with Tank Model and the sediment rate by using MUSLE. The runoff coefficient is 37%, there is a strong correlation between sediment rate observed and sediment rate of calculated MUSLE with R2 = 0.75. Tank Model optimization results with parameter values R = 0.86. Total flow of Tank Model for 57 days in form of rainfall of 636.9 mm with the total ETP value 211.384 mm will be a total flow of 215.07 mm, the comparison of flow on each reservoir is surface flow of 71.98 mm (33.47%), Intermediate flow of 58.55 mm (27.22%), Sub-base flow of 2.05 mm (0.95%), and Base Flow of 82.47 mm (38.34%). Total sedimentation rate is 15.57 tons/ha/year, equivalent to a loss of soil as deep as 1.29 mm/year.