Effects of precipitation changes and human activities on surface flow in an arid region of Southern Iran

Abstract

The management of water resources within basins has become increasingly complex as a result of the dual pressures of escalating drought conditions and human activities. The Minab River Basin, situated in southern Iran, is acknowledged as one of the most extensive basins in the area. Water resources in the area have been reduced significantly as a result of decreases in the flow of the river. Besides drought, human activities were a key factor in decreasing the river discharge. The main object of this research is to assess the effects of various drought-related factors alongside human activities on the water resources surface in from 1995 to 2021. It used statistical analysis to investigate changes in aquifer water and surface flow. Also, meteorological and hydrological drought data were measured by the Standard Precipitation Index (SPI) and Stream Drought Index (SDI). The results show that surface flow decreased by 73% with 32% attributed to climate conditions and the remaining 68 % resulting from human activities. The results obtained also suggest that water levels in the Rudan, Mosafarabad, and Jaghin Tu Kahur aquifers had decreased by 9.47, 8.30, and 16.63 m, respectively, which means the river can no longer receive water from the aquifers. The existence of unauthorized farm dams numbering about 84, the diversion of rivers for floodplain agriculture, and the presence of pits resulting from sand extraction, especially in the Rudan sub-basin are some factors leading to the reduction in water flow into the dam. The presence of dams within river branches during flood events results in a decrease in the volume of water flowing through the rivers. Results show that the effects of water withdrawals on water stress in the basin compared to the climate variability, in which anthropogenic water demand, has increased substantially due to different factors.