APPLICATION OF THE SWAT (SOIL AND WATER ASSESSMENT TOOL) MODEL TO ANALYZE THE HYDROLOGICAL CONDITIONS OF THE CIKERUH ZONE 4 SUB-WATERSHED

• Main Author: Luhut Fortune Nababan, Dicko
• Format: Final Project
• Language: Indonesia
• Subjects: Bagian spesifik dan sistem fisiologi pada tumbuhan
• Online Access: https://digilib.itb.ac.id/gdl/view/76001
• Institution: Institut Teknologi Bandung

Water resources are one of the elements which existence has an important role for living things on earth. However, currently there are many water resources that do not have the ability to meet water needs and do not support a resilient biodiversity ecosystem. Every year the number of critical watersheds in Indonesia is increasing and the condition is getting worse, marked by an increase in priority watersheds in Indonesia every year. The Cikeruh Sub-Watershed (DAS) Zone 4 is part of the Upper Citarum watershed which is located in the Bandung basin area which is currently experiencing serious hydrological problems, mainly due to land conversion. In fixing the problems contained in a watershed, it is necessary to characterize a sub-watershed so that it is found how forest control and management techniques can be applied. Soil and Water Assessment Tools (SWAT) is a model that can be used to identify the hydrological characteristics of a watershed and to simulate management actions that can be implemented in a watershed in the long term. In this study, identification of the biophysical characteristics of the Cikeruh Sub-watershed Zone 4 was carried out using the SWAT (Soil and Water Assessment Tools) hydrological model by combining modified watershed ecosystem health indicators according to the Minister of Forestry Regulation P.61/Menhut-II/2014. The biophysical characteristics of the sub-watershed analyzed are land characteristics (percentage of critical land, percentage of vegetation cover, and erosion index), hydrology (KRA, KAT, sediment load, flooding, and IPA), and spatial use (protected areas and cultivation areas). . From the results of the SWAT simulation, the area of the Cikeruh sub-watershed zone 4 is 810.52Ha consisting of 7 subbasins and 96 HRUs with outlets in the seventh subbasin. After performing the statistical test results from the model, the Nash- Sutcliffe Efficiency (NSE) coefficient value is 0.47 and the coefficient of determination (R2) is 0.47 where the value is included in the satisfactory category. In order to obtain a better value and obtain evidence that the output of the resulting v model describes the actual watershed conditions, a calibration and validation process was carried out using SUFI2.SWAT-CUP. After the calibration process, the results of the NSE value of 0.55 and R2 of 0.59 are still included in the satisfactory category but with a better value; and the validation results obtained NSE values of 0.46 and R2 of 0.51 which were included in the satisfactory category. After calibration and validation, identification of the biophysical character of the Cikeruh Sub-watershed zone 4 was carried out and the results obtained were relatively very low critical land characteristics, relatively very poor vegetation cover, very high erosion index, relatively high KRA, very high KAT, moderate sediment load, flooding relatively high, IPA is poor, protected areas are very good, and cultivated areas are very low. Based on the results of the characteristic analysis, the carrying capacity of the watershed is calculated, where the Cikeruh Zone 2 subwatershed is generally included in the moderate category in all sub-basins, but in the second sub-basin it is in the poor category. So that a land use change skenario is carried out to obtain optimum or better land use model results, which consist of 20% land change from rice fields to forests and 30% plantations to forests. From the two skenarios carried out the best and effective results in fixing problems in the Cikeruh Sub-watershed Zone 4 are rice fields to forest as much as 20%, where in subbasins 1,3,4, and 7 the carrying capacity of the watershed changes from the medium category to good and at subbasin 2 the carrying capacity of the watershed changed from poor to moderate category.