Fossil water: Last resort to resolve long-standing water scarcity?

Abstract

Sistan is a drought-affected region in the southeast of Iran, dependent on the variable surface water inflow from the Helmand River basin in Afghanistan. The river flow has recently experienced sharp annual fluctuations in Afghanistan, resulting in a collapse of the agriculture and ecosystem in Sistan. Therefore, the authorities have recently decided to rely on non-renewable groundwater (fossil water aquifers) resources to support the current developments in Sistan. The current study aims to assess the adequacy of fossil water aquifers to back the water demand in scarcity. A system dynamics model for the Sistan Water Resources System (SWRS) is developed to analyze the complicated water management system in the basin, which considers major hydrological, socioeconomic, agricultural, and, specifically, environmental aspects. The results show that the water resources in Sistan are incredibly unreliable and vulnerable due to their dependence on the surface water inflow from Afghanistan. Fossil aquifer withdrawal can address the current water problems in Sistan. However, fossil water over withdrawal without considering the critical level of aquifers can eventually lead the project to fail. Unmanaged use of fossil aquifers in Sistan has the characteristics of a "Limits to Growth Archetype" system, with negative and dangerous effects in the long run. In the environmental subsystem, meeting the minimum environmental demand is demonstrated as the effective way to stabilize the soil of the lake and considerably reduce dusty days. Further, fossil aquifer exploitation and demand management by increasing irrigation efficiency and reducing wastage of reservoirs have a great impact on the sustainability of the agricultural sector.