Optimasi pemanfaatan sumberdaya air danau dibawah Kabupaten Solok Sumatera Barat
SYOFYAN Z, Dr.Ir. Rachmad Jayadi, M.Eng
2003 | Tesis | S2 Teknik SipilDaerah Pengaliran Sungai (DPS) Batang Lembang adalah salah satu DPS yang terletak di Kabupaten Solok. Perkembangan penduduk mengakibatkan meningkatnya kebutuhan air di berbagai kebutuhan. Kekurangan air pada daerah irigasi Bandar Ubo dan Kinari, pengelolaan yang kurang baik, maka Danau Dibawah sebagai sumber air irigasi untuk daerah irigasi Bandar Ubo, Salayo Tanang, Koto Anau dan Kinari perlu di optimalkan. Dalam penelitian ini, model Mock untuk pengalihragaman hujan menjadi aliran digunakan untuk perhitungan potensi ketersediaan air. Untuk kebutuhan air irigasi, air baku/air bersih dan air penggelontoran sungai dikawasan daerah yang dilayani sekaligus merupakan keluaran model. Sedangkan masukan dalam model simulasi adalah tampungan awal, inflow, kebutuhan air irigasi, kebutuhan air baku/air bersih dan kebutuhan air penggelontoran sungai. Metode model simulasi operasi danau dipilih untuk mendapatkan keseimbangan ketersediaan dan kebutuhan air. Analisa imbangan air dilakukan tiap periode setengah bulanan antara ketersediaan dan kebutuhan air berdasarkan pola tanam padi-padi-palawija dengan 3 (tiga) alternatif jadwal tanam, jika kebutuhan air tidak terpenuhi maka dilakukan simulasi. Hasil penelitian menunjukkan bahwa hasil perhitungan potensi ketersediaan air periode setengah bulanan dengan debit rerata yang terjadi cukup bervariasi yaitu pada bulan Januari sampai bulan April debit berkisar antara 1,422 m3/dt – 2,353 m3/dt, sedangkan pada bulan Mei sampai bulan Agustus debit berkisar antara 1,351 m3/dt – 1,654 m3/dt serta pada bulan September sampai bulan Desember debit berkisar antara 1,570 m3/dt – 2,260 m3 /dt. Berdasarkan perhitungan simulasi, keseimbangan air dan kebutuhan air untuk irigasi diperoleh pola tanam terpilih yaitu pola tanam Padi-Padi-Palawija, jadwal tanam awal bulan Oktober. Kebutuhan air irigasi, air baku dan penggelontoran sungai dalam kurun waktu sebelas tahun terpenuhi seratus persen, dengan variasi kebutuhan 100%, 80% dan 60% dengan reliabilitas 100%. Untuk ketersediaan air sepanjang tahun dengan luas areal irigasi 1754 hektar kebutuhan optimal ketersediaan air adalah 60%, untuk kebutuhan air baku terpenuhi 100%.
Catchment area of Batang Lembang is one of the Catchment areas located in Solok Regency. Population development increases water need for various purposes. Due to water insufficiency in Bandar Ubo and Kinary irrigation area, and poor management, the Dibawah lake as the irrigation water resource for Bandar Ubo, Salayo Tanang, Koto Anau and Kinari required tobe optimized. In the research, Mock’s model for transferability of rain becomes stream used to calculate the water available potential. To the water need of irrigation, standard water/clean water and river mainstream in the served area all at once was as the model output. While the input in the simulation model was the first reservoir, inflow, water need of irrigation, water need of standard/clean water and water need of river upstream. The simulation model method of lake operation was chosen to get the availability balance and water need. The analysis on water balance was conducted for the period of a half month among the availability and water need based on the planting pattern of rice-rice-crop with 3 (three) alternatives of planting schedules, of the need of water was not fulfilled, so it was necessary to have a simulation. The research result shows that the calculation result of the water availability potential in half-monthly period with average volume happening vary enough, that is, in January to April the volume was about 1,422 m3/sec.-2,353 m3/sec., while in May to August the volume was around 1,351 m3 /sec.-1,654 m3/sec. and in the September to December the volume was around 1,570 m3/sec.- 2,260 m3/sec. Based on the simulation calculation, the water balance and need for irrigation provide preferable planting pattern, that is, rice-rice-crop, planting schedule in the beginning of October. Based on the simulation calculation, water balance and water need for the irrigation were obtained the chosen planting pattern, that is planting pattern of rice-rice-crop, early planting schedule of October. The water need of irrigation, standard water and river main-stream during the period of eleven years was fulfilled one hundred percents, with the need variation of 100%, 80% and 60% with the rehabilitation 100%. For the water availability along the year with the irrigation area of 1754 hectare the optimum need of water availability was 60%, for the standard water need was fulfilled 100%.
Kata Kunci : Sumberdaya Air, Danau, Irigasi, Water demand, water supply, simulation.
