Waduk Tilong merupakan satu-satunya waduk di Nusa Tenggara Timur yang baru selesai dibangun tahun 2001, sehingga peranannya sangat menentukan keberhasilan pemenfaatan sumberdaya air khususnya di Kabupaten Kupang. Oleh karena itu agar Waduk Tilong dapat berfungsi sesuai rencana maka perlu disusun suatu pedoman operasi waduk. Untuk dapat menyusun pedoman operasi Waduk Tilong khususnya untuk pemanfaatan dan alokasi air yang optimal, maka dilakukan analisis dengan metode optimasi dan simulasi. Perhitungan optimasi dilakukan dengan program linier untuk mencari keandalan waduk terhadap tiga jenis tahun yaitu tahun kering (Q80), tahun rerata (Q50) dan tahun basah (Q20). Perhitungan simulasi dilakukan untuk mencari rule curve Waduk Tilong yang mengacu kepada Standard Operating Rule, dengan persamaan dasar adalah keseimbangan air di waduk. Perhitungan simulasi dilakukan dengan dua skenario sesuai dengan pola tanam dan variasi luas lahan yaitu : pertama pola tanam padi-padi-padi (3 kali tanam) dan kedua pola tanam padi-padi (2 kali tanam). Hasil penelitian menunjukkan bahwa dengan aliran andalan (dependable flow) 50% menunjukkan kecukupan air untuk pemenuhan kebutuhan irigasi dengan intensitas tanam 270% dan air baku 150 l/detik. Intensitas tanam 270% tersebut berupa pola tanam padi-padi-padi dengan rincian luas lahan tiap musim tanam : MT I = 1.000 ha, MT II = 1.000 ha dan MT III = 700 ha.

The Tilong reservoir is the only reservoir in the Nusa Tenggara Timur province which was completely built in 2001. Its function is very important for success of water-resource utilization especially in the Kupang Regency. Therefore in order to obtain the optimal benefit through water utilization, a reservoir operating rule should be developed. In order to establish the operating rule of the Tilong reservoir especially for optimal water utilization and allocation, analysis by using optimization and simulation method were carried out. Optimization calculation was carried out by using linear programming model for observing the reliability of reservoir operation toward three types of year; dry year (Q80), normal year (Q50) and wet year (Q20). A simulation procedure was done to establish rule curve as a visualization of the Tilong reservoir operating policy referring to Standard Operating Rule method. The simulation calculation was performed by two scenarios which fit to cropping pattern and cultivated area variation including the first pattern of rice-rice-rice (3 times cultivation) and the second pattern of rice-rice (2 times cultivation). The research results showed that dependable flow of Q50 gave water sufficiency for irrigation requirements with crop intensity of 270% and domestic water demand of 150 lt/sec. The optimal crop intensity can be obtained for the cropping pattern of rice-rice-rice with the cultivated area in each planting season of 1,000 ha, 1,000 ha and 700 ha, respectively.

Kata Kunci : Waduk,Alokasi Air,Optimasi Operasi, optimization, reservoir, simulation, operating rule, rule curve