STUDY HUBUNGAN KUANTITAS DAN KUALITAS AIR WADUK SERMO SERTA PENELUSURAN KONSERVASI LAHAN GREEN BELT WADUK SERMO

YOSEP BAHARI, Prof. Dr. Ir. Bambang Triatmodjo, CES., DEA ; Prof. Ir. Sudjarwadi, M.Eng., Ph.D.

2015 | Tesis | S2 Teknik Sipil

Waduk Sermo adalah waduk yang terletak di Desa Hargowilis, Kecamatan Kokap, Kabupaten Kulonprogo, Propinsi Yogyakarta. Fungsi Waduk Sermo adalah untuk pertanian, air minum, air baku, pengendalian banjir dan pariwisata. Dalam usaha melestarikan fungsi waduk agar berkesinambungan dan berkelanjutan, maka pemerintah secara berkala melakukan maintenance waduk diantaranya adalah: pengukuran debit air, pengecekan kualitas air dan perawatan tanaman maupun lahan green belt. Berkaitan dengan maintenance yang dilakukan pemerintah tersebut, maka tujuan dari penelitian ini adalah untuk menentukan Indek Pencemaran air Waduk Sermo, mengkaji hubungan antara kuantitas dan kualitas air Waduk Sermo, mengetahui praktek konservasi lahan yang telah dilakukan di area sabuk hijau Waduk Sermo sejauh ini, mengetahui segala permasalahan dan memperoleh solusi yang lebih baik mengenai konservasi lahan di area sabuk hijau Waduk Sermo, dan mengetahui nilai ekonomi tanaman konservatif di area sabuk hijau Waduk Sermo. Bagi pemerintah, informasi dasar ini dapat digunakan sebagai masukan atau bahan pertimbangan dalam memformulasi kebijakan Waduk Sermo. Metode untuk menentukan status mutu air yaitu dengan cara menghitung nilai Indek Pencemaran (IP) disesuaikan dengan fungsi waduk dalam PP No. 82 tahun 2001. Metode untuk menentukan hubungan antara kuantitas dan kualitas air dilakukan dengan menghubungkan keduanya dan melihat nilai rho (r) yang dihasilkan. Untuk mengetahui praktek konservasi lahan green belt dilakukan dengan dokumentasi penelusuran menggunakan alat kamera dan GPS. Dan untuk mengetahui nilai ekonomi tanaman green belt dilakukan dengan wawancara penduduk sekitar. Berdasarkan perhitungan nilai IP diperoleh status mutu air Waduk Sermo pada tahun 2010, 2011, 2012 telah tercemar ringan, maka pemerintah hendaknya memperhatikan asal sumber-sumber polutan agar tidak mencemari air waduk lebih banyak lagi. Dari grafik hubungan kuantitas air (Q) dan kualitas air (TDS, turbudity, Ph, DO, COD, BOD, Fe, TSS, NH4) diperoleh nilai r > 0, maka hubungan antara kuantitas dan kualitas air menunjukan korelasi positif, antara besarnya kuantitas air dan banyaknya polutan menunjukan hubungan berbanding lurus. Penelusuran konservasi lahan green belt menemukan adanya permasalahan yaitu: erosi lahan, pengolahan yang salah oleh masyarakat, longsor, sedimentasi cek dam dan lahan tidur. Erosi lahan diatasi dengan perbaikan mekanik dan vegetatif, longsor diatasi dengan pembangunan DPT, sedimentasi cek dam diatasi dengan pengerukan, dan lahan tidur dimanfaatkan dengan ditanami tanaman produktif seperti: kelengkeng, kelapa, pisang dll. Berikut adalah nilai ekonomi tanaman konservatif di lahan green belt Waduk Sermo: 1 pohon kelapa menghasilkan Rp. 414.000,00/th, 1 pohon kakao menghasilkan Rp. 1.296.000,00/th, 1 pohon kelengkeng menghasilkan Rp. 3.150.000,00/th, 1 pohon durian menghasilkan Rp.750.000,00/th, 1 pohon rambutan menghasilkan Rp. 500.000,00/th, 1 pohon petai menghasilakan Rp. 500.000,00/th, 1 pohon salak pondoh menghasilkanRp. 75.000,00/th, 1 pohon bambu apus menghasilkan Rp. 20.000,00/3th, 1 pohon pisang ambon menghasilkan Rp. 150.000,00/th, dan 1 pohon ketela menghasilkan Rp. 8.000,00/th.

Sermo Reservoir is a reservoir located in Hargowilis Village, Kokap District, Kulon Progo Regency, Yogyakarta Province. Sermo Reservoir functions for agriculture, drinking water, raw water, flood controlling and tourism. In an effort to preserve the functions of the reservoir to make it ongoing and sustainable, the government should perform reservoir maintenance in a regular basis, among others: the measurement of water flow, water quality checking, and the treatment of plants and green belt land. In relation to the maintenance conducted by the government, the objectives of this research were to determine the Water Pollution Index of Sermo Reservoir, to examine the relationship between the water quantity and quality of Sermo Reservoir, to determine land conservation practice done in the green belt area of Sermo Reservoir to date, to find out all problems and obtain better solutions related to land conservation in the green belt area of Sermo Reservoir, and to find out the economic values of conservative plants in the green belt area of Sermo Reservoir. For the government, such basic information can be used as an input or consideration in formulating the policy of Sermo Reservoir. The method to determine the water quality status was by calculating the value of Pollution Index (IP) adjusted to the reservoir functions in Government Regulation Number 82 of 2001. The method to determine the relationship between the quantity and quality of water was by connecting both and view the R2 value generated. To find out the green belt land conservation practice, it was performed by using a search documentation employing camera and GPS. Interviews with surrounding residents were done to determine the economic values of green belt plants. The water quality of Sermo Reservoir in 2010, 2011, 2012 which has been lightly polluted is found based on the calculation of IP value. Thus the government should consider the origin of pollutant sources in order not to contaminate the reservoir water even more. From the chart of water quantity (Q) and water quality (DHL, TDS, turbidity, Ph, DO, COD, BOD, Fe, TSS, NH4), the r > 0 value is obtained, then the relationship between the water quantity and water quality shows a positive correlation, between the amount of water quantity and the number of pollutants showing a directly proportional relationship. The investigation of green belt land conservation finds the existing problems, namely: soil erosion, incorrect cultivation by the community, erosion, sedimentation check dams and uncultivated land. The soil erosion is handled by mechanical and vegetative improvement. The landslides are handled by the development of DPT. The sedimentation check dams are handled by dredging. And uncultivated land is utilized by planting with productive plants, such as longan, coconut, bananas etc. The following are the economic values of conservative plants in green belt land of Sermo Reservoir: 1 coconut tree generates 414,000.00/ year; 1 cocoa tree generates IDR 1,296,000.00/ year; 1 longan tree generates IDR 3,150,000.00/ year; 1 durian tree generates IDR 75,000.00/ year; 1 rambutan tree generates IDR 500,000.00/ year; 1 petai tree generates IDR 500,000.00/ year; one salak pondoh tree generates IDR 75,000.00/ year; 1 bamboo apus tree generates IDR 20,000.00/ 3 year; 1 Ambon banana tree generates IDR 150,000.00/ year, and 1 cassava tree generates IDR 8,000.00/ year.

Kata Kunci : water quantity, water quality, green belt, cocervation, economic