Modeling of Climate Change Impact on Water Availability in Metropolitan Mamminasata, Indonesia

Abstract

Metropolitan Mamminasata is a National Strategic Area in South Sulawesi Province, Indonesia enacted based on Presidential Regulation Number 55 of 2011 on the spatial plan of Makassar, Maros, Sungguminasa, and Takalar urban areas. The development of these areas as central urban areas makes these areas are very prone to issues of water resilient. Eleven watersheds are affecting the water system in these areas: Jeneberang, Tallo, Maros, Bonelengga, Tabaringan, Lepa-Lepa, Paleko, Saro, Galesong, Pamukkulu, and Cikoang watersheds. The impact of climate change coincides with the change of land use affecting the availability of water in the area. Therefore, this study was conducted to find out the impact of climate change and land use on the availability of water at watersheds affecting the Metropolitan Mamminasata areas. The analysis was done by using Soil model and Water Assessment Tools (SWAT software). The data on climate was analyzed by using data on global weather climate of the 1987-1996 period (past condition) and 2004-2013 period (actual condition) and climate change projection of the 2035s period using RCP 4.5 Model CSIRO Mk3.6.0. Moreover, the data on land use analyzed was of 1996 and 2015. The results of the study indicate that land use in the study area had changed a lot from 1996 to 2015. This change decreased total forest area in watersheds in Metropolitan Mamminasata around 2,000 hectares (42,803.02 ha become 40,815.85 ha) and improved established areas such as settlement, agriculture, mining, and paddy field to 84,79% of the total watershed areas. The change of land cover has an interesting interaction with the climate change condition especially related to the availability of water in the study area. The SWAT model results explain the availability of water in 1987-1996 period as much as 1,682.55 million m3/year and in the 2004-2013 period decreased as much as 11.2% that is 1,485.30 million m3/year. The results of future water availability in the period of 2035s projected total potential water increased, but the potential increased in the wet month and decreased significantly in dry months, comparing to the actual condition of availability of water. This condition illustrates the change of land use, and climate contributes to the level of the quantity of water availability in several watersheds in Metropolitan Mamminasata. The planning of land use in the spatial plan is necessary to be applied so that the continuity of water availability is sustained every year to satisfy the need for water to fellow the increasing number of community.