40-years of Lake Urmia restoration research: Review, synthesis and next steps.

Public concern over environmental issues such as ecosystem degradation is high. However, restoring coupled human-natural systems requires integration across many science, technology, engineering, management, and governance topics that are presently fragmented. Here, we synthesized 544 peer-reviewed articles published through September 2020 on the desiccation and nascent recovery of Lake Urmia in northwest Iran. We answered nine questions of scientific and popular interest about causes, impacts, stabilization, recovery, and next steps. We find: (1) Expansion of irrigated agriculture, dam construction, and mismanagement impacted the lake more than temperature increases and precipitation decreases. (2) Aerosols from Lake Urmia's exposed lakebed are negatively impacting human health. (3) Researchers disagree on how a new causeway breach will impact salinity, evaporation, and ecosystems in the lake's north and south arms. (4) Most researchers tried to restore to a single, uniform, government specified lake level of 1274.1 m intended to recover Artemia. (5) The Iranian government motivated and funded a large and growing body of lake research. (6) Ecological and limnological studies mostly focused on salinity, Artemia, and Flamingos. (7) Few studies shared data, and only three studies reported engagement with stakeholders or managers. (8) Researchers focused on an integration pathway of climate downscaling, reservoirs, agricultural water releases, and lake level. (9) Numerous suggestions to improve farmer livelihoods and governance require implementation. We see an overarching next step for lake recovery is to couple human and natural system components. Examples include: (a) describe and monitor the system food webs, hydrologic, and human components; (b) adapt management to monitored conditions such as lake level, lake evaporation, lake salinity, and migratory bird populations; (c) improve livelihoods for poor, chronically stressed farmers beyond agriculture; (d) manage for diverse ecosystem services and lake levels; (e) engage all segments of society; (f) integrate across restoration topics while building capacity to share data, models, and code; and (g) cultivate longer-term two-way exchanges and public support. These restoration steps apply in different degrees to other Iranian ecosystems and lakes worldwide.

Quantifying streamflow response to climate variability, wastewater inflow, and sprawling urbanization in a heavily modified river basin.

Considering the growing recognition that human activity and climate variability are critical stressors influencing river regimes, there is an urgent need to identify the contribution of these fundamental factors. Here we examine the runoff changes of a wastewater-effluent dominated river flowing in a heavily modified urban environment. The study concerns the Utrata River basin (727 km2), central Poland, a challenging human-natural system for investigating changes in hydrological processes. The new insights into the present-day functioning of a system are provided through the quantification of runoff changes resulting from the following factors operating simultaneously: climate, wastewater, and urbanization. We adopted and applied the water balance and elasticity-based methods to assess the contribution of particular factors. Climatic data were provided by the gridded observational dataset, while runoff comes from observed daily streamflow values at the stream gauging station. Satellite-derived estimates of evapotranspiration acquired from Operational Simplified Surface Energy Balance (SSEBop) were assimilated into the conceptual framework to provide a robust representation of the system. To determine the changes in urban water budget components, two distinct periods were determined: the baseline period (1951-1960), with a relatively low level of urbanization (9.8%), and the change period (2007-2016), with controlled wastewater inflow and urbanization reaching almost 20%. The results show that in the change period, the mean annual runoff increment attributed to climate variability amounted to 68 mm; the contribution of wastewater inflow - 36 mm; and the contribution attributed to urban-induced changes - -43 mm. Thus, the relative contributions of human activity and climate were estimated as 54% and 46%, respectively. The results demonstrate that in a heavily modified environment, the hydrological effects of human activity can exceed those caused by climate variability. Moreover, wastewater inflow and climate impact can mask decreases in the streamflow induced by urban land fragmentation and land management practices.

Finding water scarcity amid abundance using human-natural system models.

Water scarcity afflicts societies worldwide. Anticipating water shortages is vital because of water's indispensable role in social-ecological systems. But the challenge is daunting due to heterogeneity, feedbacks, and water's spatial-temporal sequencing throughout such systems. Regional system models with sufficient detail can help address this challenge. In our study, a detailed coupled human-natural system model of one such region identifies how climate change and socioeconomic growth will alter the availability and use of water in coming decades. Results demonstrate how water scarcity varies greatly across small distances and brief time periods, even in basins where water may be relatively abundant overall. Some of these results were unexpected and may appear counterintuitive to some observers. Key determinants of water scarcity are found to be the cost of transporting and storing water, society's institutions that circumscribe human choices, and the opportunity cost of water when alternative uses compete.