Variability and change in the hydro-climate and water resources of Iran over a recent 30-year period

Abstract

Comprehensive assessment of hydro-climatic variations and change trends is essential for understanding, mitigating, and adapting to key water resource changes in different parts of the world. We performed such an assessment on Iran, as representative of an arid/semi-arid and geopolitically important world region. We acquired and calculated data time series of surface temperature (T), precipitation (P), runoff (R), evapotranspiration (ET), and water storage change (DS), to determine their status and changes in and among the 30 main hydrological basins in Iran over the period 1986-2016. From 1986-2000 to 2001-2016, the country warmed, P mostly decreased and R even more so, while water storage was depleted (DS < 0) and ET increased in some basins. Overall, the extra water provided from primarily groundwater depletion has fed and kept ET at levels beyond those sustained by the annually renewable water input from P. This indicates unsustainable use of water for maintaining and expanding human activities, such as irrigated agriculture, in this part of the world. Climate change and human activities can alter large-scale patterns of hydrological fluxes (precipitation, runoff, evapotranspiration) 1,2 and deplete groundwater 3 and surface waters 4,5 , with feedbacks to climate 6. For example, the dramatic decline in Lake Urmia in Iran is a well-known destructive impact of hydrological change in this arid/ semi-arid part of the world 5,7,8. Other surface waters in Iran have also changed in recent decades, including Lake Maharloo-Bakhteghan in central Iran 9 , Lake Hamoon in the east 10 , and Lakes Shadegan and Hoor-Al-Azim in the south and southwest 11,12. Moreover, hydrological changes in Iran are not limited to surface waters, but also extend to groundwater resources, with substantial decreases in groundwater level reported for different parts of the country 13. Surface and subsurface hydrological changes in Iran have previously been estimated for six major hydrological basins over a period of 11 years, based on general availability of remote sensing data for both surface water and groundwater 14. Effects of surface water withdrawals on long-term average surface water storage have been estimated on finer spatial resolution (for 30 main hydrological basins in Iran), but without accounting for related groundwater changes 15. Considering the extent and magnitude of water changes in Iran, and their impacts and consequences in such a dry and geopolitically important part of the world 13,16 , there remains a need for more long-term, comprehensive, but still relatively fine-resolution assessments of hydro-climatic variability and change in the country and the region. Such assessments are essential for understanding, mitigating, and adapting to key water resource changes. This study aims to address this need by determining annual conditions and changes in both surface and subsurface water resources in and across Iran's 30 main hydrological basins over the recent 30-year period with relevant available data (1986-2016). With this a...

Socioeconomic benefits of conserving Iran’s water resources through modifying agricultural practices and water management strategies

“…The spatial variation of the unsustainable and inefficient blue WFs is partly due to the spatial variation of crops’ ET, which depends on seasonal and inter-annual climatic status change (Khazaei et al 2019 ). Iran has a large geographic diversity of hydro-climatic regimes due to having a spatial difference of 16.65 °C for its annual average temperature, and 1107 mm y −1 for its annual precipitation (Madani 2014 ; Moshir Panahi et al 2020 ). The site-specific behavior of unsustainable and inefficient blue WFs in Iran is also caused by the regional differences of cropping patterns.…”

“…Over the past decades, Iran became warmer, its annual precipitation and surface runoff experienced a decreasing trend, and faced with severe droughts in 1990 and 2008 (Karandish et al 2017 ; Moshir-Panahi et al 2020 ). For instance, annual precipitation in the western basins, which are the backbone of crop production in Iran (Karandish et al 2017 ), decreased by 65 mm year −1 over the period 1986–2016 (Moshir-Panahi et al 2020 ). Continuing agriculture production under such condition entailed exacerbating unsustainable exploitation of the limited blue water resources.…”

Effects of Water Level Decline in Lake Urmia, Iran, on Local Climate Conditions

“…1a). The basin is endorheic (closed), with mean annual precipitation of 400 mm (most of which falls in winter and spring), mean annual temperature of 20 °C (Moshir Panahi et al, 2020), and mean annual relative humidity ranging between 52 and 64 %. More than five million people live in the Urmia basin and agriculture plays a significant role in the livelihoods of these people (Delju, Ceylan, Piguet, & Rebetez, 2013).…”

“…The reasons for the decreases in the area and level of Lake Urmia, and management strategies to restore the lake, have been addressed by many researchers over recent years. Most of this research has emphasized the role of human activities, drought, and climate change in drying out the lake (e.g., Dehghanipour et al, 2019;Hosseini-Moghari et al, 2018;Moshir Panahi et al, 2020;Schulz et al, 2020). The different management scenarios proposed to save Lake Urmia are based on reducing water consumption in the agriculture sector and on adaptation to drought and climate change (e.g., Chaudhari et al, 2018;Dehghanipour et al, 2020;Tourian et al, 2015).…”

Iran's Groundwater Hydrochemistry

“…Also, according to the official reports issued by the Iranian Parliament Research Center (IPRC, 2017), about 5 km 3 out of the 50 km 3 of groundwater extracted annually comes from non-renewable groundwater sources. Such over extractions have led to: a) An alarming pressure on Iran's groundwater resources (IGWR), causing a severe and widespread decline in water levels across the country of about 50 cm yr -1 during the last two decades (Noori et al, 2021), b) Socio-physical crises such as population displacement (Madani et al, 2016;Danaei et al, 2019;Panahi et al, 2020) and unprecedented/extensive land subsidence (Motagh et al, 2008), c) Fundamental environmental challenges such as saltwater intrusion and groundwater quality deterioration (Ebrahimi et al, 2016;Madani et al, 2016;Kardan Moghaddam et al, 2017;Motevalli et al, 2018;Vesali Naseh et al, 2018;Noori et al, 2019a).…”