The Gotvand dam was built on the most important Iranian river to support a number of populated cities with freshwater, provide irrigation water for million hectares of fertile farmlands, and meet water demand for the country’s hub industrial zones. This dam is known as one of the worst engineering failures in Iran’s history because its impoundment submerged the enormous salty unit of Gachsaran evaporite formation (GEF) outcropped in the reservoir, leading to reservoir water salinization in deep layers up to several times greater than that of in the high-seas. Given the failed practical application of direct intervention strategies to control the salinity crisis, we suggested a low-cost salinity management strategy based on the reservoir operation to mitigate the dam outlet salinity and preserve the downstream environment from the salinity hazards. The three-dimensional MIKE3 model, was run to calculate the GEF dissolution rate, accumulated salt in the reservoir, and the dam outlet salinity. Then, we ran the model considering different outlet salinity levels to explore the best reservoir operation strategy to prohibit the accumulated salt in the reservoir and keep the safe salinity for downstream irrigation-use. Simulation results suggested that the GEF dissolution rate varied from 0.5 to 7 cm/hr, mainly due to incremental submergence of the GEF during multi-stage impoundment of the reservoir. Considering the final dissolution rate of 0.5 cm/hr and inlet salinity from the upstreams, salt accumulation inside the reservoir can be gradually prevented by setting the outlet salinity to its maximum historical downstream level, i.e., 1400 µmhos/cm.

The majority of lake temperature studies have investigated climate-induced changes occurring at the lake surface, primarily by analyzing detailed satellite images of surface water temperature. Whilst essential to observe long-term change, satellite images do not provide information on the thermal environment at depth, thus limiting our understanding of lake thermal responses to a warming world. Long-term in-situ observational data can fill some of the information gap, with depth-resolved field measurements providing a detailed view of thermal change throughout the water column. However, previous studies that have investigated multi-decadal changes in lake temperature, both at the surface and at depth, have typically focused on north temperate lakes. Relatively few studies have investigated temperature variations in lakes situated north of the Arctic circle, which is one of the most rapidly warming regions globally. Here, using a sixty-year (1961-2020) observational dataset of summer water temperature from Lake Inari (Finland), we investigate changes in the thermal environment of this pristine lake. Our analysis suggests a significant summer warming trend at the lake surface (+0.247 °C decade-1) and a marginal cooling trend (–0.027 °C decade-1) at depth. The contrasting thermal response of surface and bottom water temperatures to climatic warming has likewise resulted in a strengthening of summer stratification in this high latitude lake. Implications of the observed change in both temperature and stratification on the lake ecosystem will likely be extensive, including impacts on aquatic organisms in which this lake supports. Our work builds on ever-growing literature regarding lake thermal responses to climate change.