PERMODELAN PERSEBARAN KONSENTRASI NITRAT DALAM AIR SUNGAI DENGAN SOIL AND WATER ASSESSMENT TOOL

Modelling approaches is widely used to get best watershed management because it’s possibility to forecast the impact of human activities on watershed. Soil and Water Assessment Tool (SWAT) model has been used extensively to study run off, sediment yield, and nutrient load. This research was take place at Kali Gede, Ci Putat, Kali Caringin, and Kali Angsana located in Bojongsari and Sawangan Sub-district, Depok City. The purposes of this research were to know accuracy of SWAT modeling making simulation nitrate concentration in river related with homegeneous slope and soil, and heterogeneous landuse and to forecast tthe impact of the residential area expansion to the nitrate consentration. Model simulation is validated using observe nitrate concentration data which was taken from river in April 2013. The conclusion of this research are SWAT model can be used to make acurate simulation of nitrate concentration whichare shown by Normalized Objective Function (NOF) values which 0.21 at Kali Gede, 0.11 at Ci Putat, 0.09 at Kali Caringin, and 0.05 at Kali Angsana. NOF value indicated how accurate model's simulation which is allowed from 0-1 and 0 indicated perfect simulation. The expansion of residential area in Bojongsari and Sawangan Sub-district will cause nitrate concentration in these rivers increase.