Analysis Of Land Use Changes Effect For Hydrological Citarik Sub-Basin In 2000 And 2007

Abstract

Upstream has a protective function for the entire watershed. Citarik sub-basin is one of the Citarum upstream watershed. Watershed condition can be seen from land cover index (LCI), runoff coefficient (C,) rivers regim coefficient (RRC), baseflow, and maximum discharge. This research aims to examine land use changes and its effects on hydrological conditions of Citarik sub-basin. ArcGIS 9.3 used in the spatial data processing to obtain land use changes. Occurring increase in plantation and settlement areas of 5854.51 Ha and 260.87 Ha, and the decrease in forests, fields, rice fields, and a body-water areas of 2606.95 Ha, 5588.05 Ha, 2400.75 Ha, and 18.24 Ha. It brings also a decrease in the LCI from well category (77.60%) to medium category (59.11%). LCI impairment indicates that there has been a decrease in vegetated area which could increasing runoff and the maximum discharge. Hydrological data processing using Microsoft Excel and the USGS Thornthwaite Monthly Water Balance. Primarily used data are precipitation data, debit, and Bandung temperature year 2000-2007. All data used in this research was sourced from TA 7189-INO. According to analysis result, rainfall increases 749.95 mm in 2000-2007. During the rainy season, C increases from 0.22 in 2000 to 0.42 in 2007, with and an annual increases from 0,22 to 0,46. Maximum discharge increasing in 2004-2007 periode. The minimum discharge has a uniform values in period 2000-2007. RRC values during this period was increased by 8.44. Out of all the calculation results, can be said that the land use change in sub-basins Citarik in 2000-2007 lead to a decrease in the watershed hydrological conditions.

Daerah aliran sungai (DAS) terbagi atas tiga daerah yaitu hulu, tengah, dan hilir. DAS bagian hulu mempunyai peranan penting sebagai fungsi perlindungan terhadap seluruh bagian DAS tersebut. Sub-DAS Citarik merupakan salah satu bagian dari DAS Citarum hulu. Salah satu karakteristik DAS yang memiliki hubungan erat dengan sistem hidrologinya ialah tataguna lahan. Perubahan penggunaan lahan yang tidak tepat pada DAS hulu akan mengakibatkan penurunan kualitas DAS tersebut. Penurunan kualitas DAS dapat dilihat dari penurunan kelas indeks penutupan lahan (IPL), peningkatan koefisien limpasan (C), peningkatan koefisien regim sungai (KRS), penurunan debit minimum, dan peningkatan debit maksimum. Penelitian ini bertujuan untuk mengkaji perubahan penggunaan lahan dan pengaruhnya terhadap kondisi hidrologis sub-DAS Citarik. Metode yang digunakan dalam penelitian ini dibagi dalam dua tahap, yaitu pengolahan data spasial dan pengolahan data hidrologis. Pengolahan data spasial menggunakan software ArcGIS 9.3. Pada pengolahan spasial digunakan data peta penutupan lahan DAS Citarum tahun 2000 dan 2007 (.shp), peta sub-DAS Citarik, dan peta lokasi stasiun curah hujan DAS Citarum (.shp) dengan output berupa peta penggunaan lahan sub-DAS Citarik tahun 2000 dan 2007 dan luasan polygon tiap stasiun curah hujan.