Small reservoir reliability under cropping pattern scenarios: a case study of embung ponggong in Lombok

A primary direct use of water's small reservoir in West Nusa Tenggara is irrigation. Analysing irrigated agriculture's performances is a valuable way to measure the impact of small reservoirs on the food security and livelihoods of local communities. Embung Ponggong is a small dam in West Nusa Tenggara with a limited capacity for irrigation purposes. The limited capacity of the reservoir and a large amount of water demand causes an imbalance between water availability and demand. This study aims to obtain information about reservoir behaviour by applying many alternative cropping pattern scenarios to meet the most profitable water allocation decisions. This study conducted a reservoir simulation to obtain the best alternative cropping pattern and the highest cropping intensity. The results showed that the potential water availability in the Ponggong Reservoir is 5,057,076.18 m3/year and could meet irrigation water needs of Paddy-Soybean-Soybean cropping pattern that produced a high cropping intensity about 300% and reservoir reliability of  84.72%. The second best cropping pattern is Paddy-Maize-Maize resulted in a cropping intensity of 300% and reservoir reliability of 82.18%. Another suitable cropping pattern is Paddy-Paddy–Maize resulted in a cropping intensity of 245% and reservoir reliability of 80.09%.