Spatial Analysis of Drought and Water Carrying Capacity in The Dynamic Development Area of Aceh Besar Regency Based on Remote Sensing
Abstract
Drought is conventionally diagnosed through rainfall deficit, yet in humid tropical regions the land surface can be under severe moisture stress while precipitation remains close to its long-term average. This study analyzes that divergences and its consequences for water carrying capacity across Lhoknga, Peukan Bada, and Darul Imarah Districts, Aceh Besar Regency, covering 14,613.97 hectares. Landsat 8 OLI imagery and CHIRPS precipitation data were processed in Google Earth Engine and ArcGIS. Metereological drought was assessed using the Standardized Precipitation Index (SPI) and vegetation drought was using the Normalized Difference Drought Index (NDDI) , while water carrying capacity was derived from the balance between water availability and demand against a threshold of 1,600 m³/capita/year. The two indices diverge sharply. SPI indicates near-normal precipitation across 14,604.67 ha, or almost the entire study area, where NDDI classifies 13,613.74 hectares (93%) experiencing the least moderate drought (NDDI > 0.3). Water deficit affects2,454.68 hectares (17%), concentrated in densely populated areas such as Darul Imarah. Geographically Weighted Regression (GWR) revealed Local R² values ranging from 0.02 to 0.304, with the highest concentration in southern Darul Imarah but falling below 0.15 across most of Lhoknga and Peukan Bada. Surface drought therefore accounts for at most one third of the spatial variation in water carrying capacity, and substantially less in most locations. The residual variation points to mechanism that index cannot observe: karst hydrology with high infiltration but negligible storage and the horizontal expansion of built-up area long Banda Aceh boundary. This finding carries a pratical implication for spatial planning, namely that rainfall-based drought monitoring will systematically underestimate water stress in karst-dominated peri-urban territory.