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...

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Wetlands are often vital physical and social components of a country’s natural capital, as well as providers of ecosystem services to local and national communities. We performed a network analysis to prioritize Sustainable Development Goal (SDG) targets for sustainable development in iconic wetlands and wetlandscapes around the world. The analysis was based on the information and perceptions on 45 wetlandscapes worldwide by 49 wetland researchers of the Global Wetland Ecohydrological Network (GWEN). We identified three 2030 Agenda targets of high priority across the wetlandscapes needed to achieve sustainable development: Target 6.3—“Improve water quality”; 2.4—“Sustainable food production”; and 12.2—“Sustainable management of resources”. Moreover, we found specific feedback mechanisms and synergies between SDG targets in the context of wetlands. The most consistent reinforcing interactions were the influence of Target 12.2 on 8.4—“Efficient resource consumption”; and that of Target 6.3 on 12.2. The wetlandscapes could be differentiated in four bundles of distinctive priority SDG-targets: “Basic human needs”, “Sustainable tourism”, “Environmental impact in urban wetlands”, and “Improving and conserving environment”. In general, we find that the SDG groups, targets, and interactions stress that maintaining good water quality and a “wise use” of wetlandscapes are vital to attaining sustainable development within these sensitive ecosystems.