Water resources/reservoir management in developing countries attracts considerable attention due to growing human requirements and environmental concerns. The Seimare–Karkheh hydropower reservoir cascade, in the Karkheh River basin southwest of Iran, was studied. The impacts of changing reservoir operating water levels on hydropower generation and downstream environmental requirements were evaluated under different climate change conditions. For several years, the operating water level of Seimare reservoir was 704.5–720.0 metres above sea level (masl) (H1). Decision makers then adopted a different policy, with the operating range changed to 704.5–723.0 masl (H2). More recently, decision makers reduced the normal and minimum water levels so the reservoir now operates at 695.0–704.5 masl (H3). It was found that, for the period 2006–2050, based on H3, hydropower production would be reduced by 2.3–12.1% and 2.4–12.6% compared with policies H1 and H2, respectively. In 2051–2100, these reductions were found to be 5.8–11.2% and 7.7–11.3%, respectively. Furthermore, the results demonstrated that the current policy would substantially affect downstream hydrological alteration: 60–72% in Seimare River and 48–66% in Karkheh River for the period 2006–2050. The issue was found to be more pronounced in 2051–2100, with hydrological alteration of 68–73% in Seimare River and 59–66% in Karkheh River.
In this study, the artificial neural network (ANN) method was applied to investigate the impacts of climate change on the water quantity and quality of the Qu'Appelle River in Saskatchewan, Canada. First, the second-generation Canadian earth system model (CanESM2) was adopted to predict future climate conditions. The Statistical DownScaling Model (SDSM) was then applied to downscale the generated data. To analyze the water quality of the river, concentrations of dissolved oxygen (DO) and total dissolved solids (TDSs) from the river were collected. Using the collected climate and hydrometric data, the ANNs were trained to simulate (i) the ratio of snowfall-to-total precipitation based on the temperature, (ii) the river flow rate based on the temperature and precipitation; and (iii) DO and TDS concentrations based on the river flow and temperature. Finally, the generated climate change data were used as inputs to the ANN model to investigate the climate change impacts on the river flow as well as DO and TDS concentrations within the selected region. Hydrologic alteration of the river was evaluated via the Range of Variability Approach (RVA) under historical and climate change scenarios. The results under climate change scenarios were compared with those under historical scenarios and indicated that climate change would lead to a heterogeneous change in precipitation and temperature patterns. These changes would have serious degrading impacts on the river discharge as well as DO and TDS concentration levels, causing deterioration in the sustainability of the river system and ecological health of the region.
In this paper, alternative reservoir operation models under different environmental operating conditions were developed to analyze the impacts of applying different policies in a multi-reservoir system in order to balance human and environmental requirements. Three scenarios/models were developed under four sub-scenarios/operating conditions. The scenarios were: (1) an optimization model to maximize the hydropower production, (2) an optimization model to minimize the squared of the difference between the release and need, (3) a simulation model under the Hydropower Standard Operating Policy. The sub-scenarios were developed as follows: (i) no environmental flow, (ii) minimum environmental flow, (iii) environmental flow bounded by the minimum and maximum flow, and (iv) maximum environmental flow. Hydropower production and system performance criteria were calculated and compared in all cases. Moreover, the Range of Variability Approach was used to assess the hydrological alterations of each of the 12 cases. The results in a two reservoir cascade of Seimare-Karkheh, located within the Karkheh River Basin in Iran, showed that sub-scenario 3 performed best in all three scenarios. Further comparison indicated that scenario 1, under sub-scenario 3, was a good compromise solution, as it provided adequate hydropower production and performance criteria and the least hydrological alterations.
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