Spatiotemporal changes in Iranian rivers’ discharge

Abstract

Trends in river flow at national scale in Iran remain largely unclear, despite good coverage of river flow at multiple monitoring stations. To address this gap, this study explores the changes in Iranian rivers’ discharge using regression and analysis of variance methods to historically rich data measured at hydrometric stations. Our assessment is performed for 139 selected hydrometric stations located in Iranian data-rich basins that cover around 97% of the country’s rivers with more than 30 years of observations. Our findings show that most of the studied Iran’s rivers (>56%) have undergone a downward trend (P value < 0.1) in mean annual flow that is 2.5 times bigger than that obtained for the large world’s rivers, resulting in a change from permanent to intermittent for around 20% of rivers in Iran’s subbasins. Given no significant change observed in the main natural drivers of Iranian rivers’ discharge, these findings reveal the country’s surface fresh-water shortage was caused dominantly by anthropogenic disturbances rather than variability in climate parameters. It may even indicate the development of new river regimes with deep implications for future surface fresh-water storage in the country. This research’s findings improve our understanding of changes in Iranian rivers’ discharge and provide beneficial insights for sustainable management of water resources in the country.

Decline in Iran’s Groundwater Recharge

“…Our results reveal the average amount of nationwide groundwater recharge is 39.6 mm/yr during the study period, which is more than the reported average annual runoff in Iran, i.e., ~32 mm/yr 16 , suggesting the national surface water resources are seeping into the groundwater basins. This conclusion is further supported by the studied conducted by Saemian et al 19 and Maghrebi et al 20 , who reported that Iran's surface water resources, as the main contributor of groundwater recharge, have largely declined during the last decades, mainly due to human interventions. Approximately 56% of Iranian rivers have undergone a decline in stream-flow, which is around 2.5 times higher than that reported for large world's rivers.…”

“…We also supposed that groundwater losses through aquifer discharge to surface waters are negligible due to severe decline in the countrywide groundwater table during the last five decades (> 20 m) 25 . This hypothesis is further supported once we notice both widespread decline in Iran's river flows 20 and drying out the national wetlands and inland lakes 8,26 .…”

“…Approximately 56% of Iranian rivers have undergone a decline in stream-flow, which is around 2.5 times higher than that reported for large world's rivers. Around 20% of the country's permanent rivers have transformed to seasonal rivers and former seasonal rivers have dried up and/or become narrow streams, leading to the development of new river regimes 20 . Anthropogenically dwindling renewable water has also resulted in shrinkage of almost all of national lakes, wetlands, marshes, and ponds 8,21 .…”

Water-related limits to growth for agriculture in Iran

“…Consequently, unsustainable agricultural land development at this level in Iran as an arid/semi-arid country caused two main challenges, including drying rivers and lakes [ [12] , [13] , [14] ] and severe groundwater (GW) drawdown [ 8 , [15] , [16] , [17] , [18] , [19] ]. Investigations of river flow changes in Iran over time and space showed that about 56% of stations have a decreasing trend in river flow (2.5 times the global average) [ 20 ].…”

Determining the Optimal Aquifer Exploitation under Artificial Recharge using the Combination of Numerical Models and Particle Swarm Optimization

“…Groundwater resources are the main and reliable water supplies in arid and semiarid regions, such as Iran, where groundwater recharge feeds aquifers supplying fresh water to a population over 80 million, a global hotspot for groundwater depletion [2]. At the other extreme, a severe decline in precipitation in the past few decades created an acute drought that negatively impacted around 90% of Iran [3]. Therefore, adoption of comprehensive plans to control the critical conditions of water shortage are vital [4,5].…”