Struggling over water, losing it through evaporation: The case of Afghanistan and Iran

Prolonged droughts and rising water demand have worsened water disputes in the transboundary Helmand basin, shared by Afghanistan and Iran. While both countries have built water storage reservoirs to mitigate water shortages, evaporative losses from these reservoirs reduce their effectiveness. This issue intensifies challenges over water shortages in the region without reliable monitoring data. In this study, reanalysis and remote sensing data was used to calculate the rate of water evaporation from the major water reservoirs located in Helmand basin. Additionally, globally available moisture trajectory datasets were used to analyze where the evaporated water from these major storage reservoirs eventually falls as precipitation. Our main focus was on quantifying how much of this water precipitates outside the Helmand Basin. Our results indicate that evaporative losses of blue water from reservoirs in this transboundary river basin have reached to 284 million cubic meters in 2023. Additionally, our results indicate the presence of a teleconnection, whereby a significant portion of the water evaporated from these reservoirs is transported and then precipitates outside the Helmand Basin, reaching up to an annual average of 92%. The largest portion of this evaporated water was received as precipitation by India, Pakistan, Afghanistan and China, accounting for 25%, 19%, 16% and 6%, respectively. This study provides a real-world example of how improved water intelligence and transparency, achieved through remote sensing data and modelling, can support water diplomacy and conflict resolution in transboundary basins.