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) - Esa Bagus Nugrahanto; Rahardyan Nugroho Adi; Agung Budi Supangat; Nunung Puji Nugroho (Center for Implementation of Standards for Environmental and Forestry Instruments Solo, 2018)
ABSTRACTThe 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 peak discharges between sub watersheds were compared to the rainfall and the percentage of forest. The results 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 coverage 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 53.3%. 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.Keywords: peak discharge; natural forest coverage; rainfall; sub watershedsABSTRAKPersentase penutupan hutan memegang peran penting dalam mengatur tata air Daerah Aliran Sungai (DAS). Hutan dengan fungsi hidrologisnya berpengaruh terhadap debit sungai. Penelitian ini bertujuan untuk mempelajari pengaruh persentase penutupan hutan terhadap debit puncak di sub DAS hutan alam. Penelitian ini dilakukan pada tahun 2017 di Sub DAS Bakar, Sub DAS Tanjung, Sub DAS Iwakan, dan Sub DAS Langsat, Kabupaten Tanah Laut Provinsi Kalimantan Selatan. Persentase hutan alam bervariasi dari 9,7 sampai 98% dari uas sub DAS. Penelitian dilakukan dengan pengkuran langsung data curah hujan dan tinggi muka air (TMA) yang dikonversi menjadi debit puncak. Data debit puncak antar sub DAS dibandingkan menurut curah hujan dan persentase penutupan hutan alam. Hasil penelitian menunjukkan secara umum persentase penutupan hutan berpengaruh terhadap debit puncak. Penutupan hutan memberikan respon yang positif dalam menurunkan debit puncak ketika curah hujan dibawah 115 mm/hari. Sub DAS Bakar dan Tanjung yang memiliki persentase penutupan hutan alam yang rendah memiliki debit puncak yang lebih tinggi dibandingkan dengan Sub DAS Langsat dan Iwakan yang memiliki persentase penutupan hutan yang tinggi. Pengaruh persentase penutupan hutan alam terhadap debit puncak ditandai oleh koefisien determinasi sebesar 53,3%. Keberadaan hutan sangat penting sebagai pengatur hidrologi sehingga sangat penting untuk dilakukannya upaya konservasi dan penghijauan di hulu sub DAS yang diamati.Kata kunci: debit puncak; penutupan hutan alam; curah hujan; sub DAS