Effect of Land Use Changes of Upstream Komering Sub Watershed on Declining Water Availability

Potential water resources in the upstream part of the Komering sub-watershed, in March each year ranges from 645.49 m³/sec. With a debit of that size, it should be able to increase national agricultural production in South Sumatra, Indonesia. However, in August – September, the discharge of water availability in the upstream part of the Komering sub-watershed decreased to only 43.08 m³/sec. To analyze the reduced mainstay discharge of the Upstream Komering sub-watershed, due to poor land use practices in the upstream area and the effects of climate variability, it can be analyzed by analyzing land cover conditions, the value of rain variability, and the magnitude of evapotranspiration and validation of direct measurement of river discharge in the field. Changes in land use for the upstream part of the Komering sub-watershed, which are used mostly by residents as community plantation areas, have increased the critical condition of the upstream Komering sub-watershed area of 2,517,560 Km², or about 65.66% of the total upstream Komering sub-watershed. From the measurement of debit data at the Perjaya Dam in the last fifteen years (2005–2019), the largest main discharge value in 2 weeks to two months in April was 241.67 m³/sec, while the smallest mainstay discharge occurred in the first 2 weeks of October at 54.69 m³/sec. A large difference between the largest and smallest mainstay discharge, it is necessary to think of a way so that the availability of water is always maintained throughout the year (the difference between the mainstay discharge between the rainy season and the dry season so that it is not so extreme). Some ways that can be done to maintain the availability of water include making a reservoir that can be used during the dry season, or increasing storage in the soil by reforestation and harvesting rain.