Dampak Perubahan Iklim Terhadap Indeks Erosivitas Hujan Pada Daerah Tangkapan Air Waduk Saguling

The Effect of Climate Change on Rain Erosivity Index in the Saguling Reservoir Catchment Area

Abstract

Climate change is a global phenomenon that become a concern. Climate change affects the hydrological conditions of a watershed, including rainfall. Saguling Reservoir has a high erosion rate on the watershed. One factor that affects erosion based on USLE is the rain erosivity index which has a relation with rainfall amount. So the climate change effect of rainfall on erosivity factor in Saguling Reservoir watershed needs to be investigated because it will affect the erosion rate which is useful to determine the sedimentation rate of the reservoir. The purpose of this study was to analyze the effect of climate change on the erosivity index. Climate change (rainfall) was analyzed using GCM CanESM2 Model in the RCP scenario through a downscaling process. Downscaling has been done with SDSM. The rain erosivity index was analyzed using Lenvain’s formula. Downscaling with the SDSM method was able to give good results based on the coefficient of determination and it was found that there was a change of monthly rainfall in the short, medium, and long term periods, as well as an increase in annual rainfall up to 34.3%. The annual rainfall erosivity index changes along with changes in rainfall due to climate change and there is an increase of up to 44.1%.

ABSTRAK

Perubahan iklim merupakan fenomena global yang kini menjadi perhatian. Perubahan iklim mempengaruhi kondisi hidrologi suatu DTA (Daerah Tangkapan Air) antara lain terjadinya perubahan curah hujan. Waduk Saguling memiliki laju erosi tinggi pada DTA. Salah satu faktor yang mempengaruhi erosi berdasarkan Persamaan USLE adalah indeks erosivitas hujan yang terkait erat dengan besarnya curah hujan. Sehingga Pengaruh perubahan iklim terhadap faktor erosivitas hujan di DTA Waduk Saguling perlu diteliti karena akan mempengaruhi laju erosi yang berguna untuk menentukan laju sedimentasi waduk. Tujuan penelitian ini adalah menganalisis pengaruh perubahan iklim terhadap indeks erosivitas hujan. Analisis perubahan iklim (curah hujan) dilakukan dengan Model GCM CanESM2 skenario RCP melalui proses downscaling. Downscaling dilakukan dengan metode SDSM. Indeks erosivitas hujan dianalisis berdasarkan rumus Lenvain. Downscaling dengan metode SDSM mampu memberikan hasil yang baik berdasarkan koefisien determinasi dan didapatkan perubahan curah hujan bulanan pada periode jangka pendek, menengah dan panjang, serta untuk curah hujan tahunan terdapat peningkatan hingga 34,3%. Indeks erosivitas hujan tahunan di DTA Waduk Saguling mengalami perubahan seiring dengan berubahnya curah hujan akibat perubahan iklim dan terdapat peningkatan hingga 44,1%.