The Supply of water in Bua District based on spatial planning of Luwu Regency at the 2030s

Abstract

Land cover in a watershed area has an impact on the infiltration capacity related to the water supply. Water needed for irrigation of rice fields in Bua District, especially in the Bua, Malenggang, and Salu Beroa watersheds are experiencing drought each year. This means that water needs are not in accordance with the existing water supply, so research needs to be done related to water supply and rice field irrigation water needs. This study aims to determine the water supply of Bua, Malenggang, and Salu Beroa watersheds based on the existing land cover and the spatial pattern of the Luwu Regency in 2030 and the need for water for rice fields in this area. Data was used in this study include existing land cover maps, Luwu Regency spatial pattern maps in 2030, soil type maps, Digital Elevation Model (DEM) data, and daily climate data analyzed by using the SWAT model. The results of SWAT model analysis based on existing land cover found that water supply in Bua watershed is 40.291.452 m3/year, Malenggang watershed is 19.467.893 m3/year, and Salu Beroa watershed is 2.685.224 m3 / year. Meanwhile, based on the spatial pattern in 2030 found that water supply in Bua watershed is 40.076.558 m3/year, Malenggang watershed is 19.396.958 m3/year, and Salu Beroa watershed is 2.689.116 m3/year. The amount of water needed for irrigating in these watersheds is 50.848.015,7 m3/year or 81% out of the total water supply of existing land cover and 82% out of the total of spatial pattern water supply in 2030. It is showed that if the spatial pattern plan is implemented and simulated by using a watershed-based SWAT model, the water supply in the study area will be reduced or lower than 281.937 m3 at the end of the planning year, which are the total water supply based on existing land cover is 62.444.569 m3 while the water supply based on the spatial pattern is 62.162.632 m3. Therefore, an evaluation of the implementation of the Luwu Regency spatial plan is needed. The monthly demand of rice fields is 4.237.335 m3 while water supply in August is 3.377.597 m3, September is 3.340.444 m3, and October is 3.484.457 m3. It means that the demand for rice fields is not fulfilled in August, September, and October. Thus, in that month, Drought occurs.