PENGARUH PERSENTASE PENUTUPAN HUTAN TERHADAP DEBIT PUNCAK DI SUB DAERAH ALIRAN SUNGAI HUTAN ALAM KABUPATEN TANAH LAUT (The effect of forest coverage percentage on peak discharge in the natural forest sub watershed, Tanah Laut Regency)

The percentage of forest coverage holds an important role in regulating water in watersheds. This paper studies the influence of forest coverage percentage on peak discharge in sub watersheds with various percentage of natural forest areas. The study took place in Bakar, Tanjung, Iwakan, and Langsat Sub Watersheds, Tanah Laut Regency, South Kalimantan Province in 2017. The percentage of natural forest varied from 9,7 to 98% of the the sub watershed areas. This research was conducted by direct measurement of rainfall and stream water levels that were converted into peak discharge. The p eak discharges between sub watersheds were compared to the rainfall and the percentage of forest. The r esults showed that in general the percentage of natural forest coverage affect the peak discharge. The forest coverage showed a positive response in lowering the peak discharge when the rainfall was below 115 mm/day. Bakar and Tanjung Sub Watersheds that had low percentage of natural forest c overage had higher peak discharge than Langsat and Iwakan Sub Watersheds, which had higher percentage of forest coverage. The relationship between the percentages of natural forest coverage with peak discharge marked by the coefficient of   determination value of 5 3 . 3 %. Since the existence of forest is very important as the hydrological controller, forest conservation efforts and reforestation should be conducted in the upper sub watersheds.