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Figure 8 displays the downstream water temperature regime for a natural flow and the optimal regime based on the output of the optimization model. The performance of the optimization model is robust in terms of optimizing the downstream water temperature regime as the optimal and natural temperatures are similar for most time steps. Figure 9 displays the storage time series in the simulated period. The performance of the minimum storage penalty function is not robust but is generally acceptable. The reservoir storage is more than the minimum operational storage for most time steps. Moreover, the performance of the maximum storage penalty function is robust. Due to changes in the reservoir inflow, the available storage at some time steps is critically low. The performance indices for the water supply, storage, and temperature regime are given in Table 2. Interestingly, the reliability index of 10.1% demonstrates that the optimization model is unable to supply more than 90% of the water demand. In other words, managers will pay a high price to satisfy environmental requirements. Values of the VI and RMSE for the storage loss indicate that it is considerable but not as great as the water supply loss. As a challenging period with respect to reservoir inflow is currently occurring, a reduction in storage benefits is expected. The NSE and RMSE of the downstream water temperature regime indicate that the optimization model is robust in this regard, i.e., the optimal regime is close to the natural regime.
Table 2

Measurement indices of the optimization model

Model factorPerformance indexValue
Water supply  10.1% 
Storage loss VI 82% 
RMSE 39.9 MCM 
Downstream water temperature regime NSE 0.971 
RMSE 1.1 °C 
Model factorPerformance indexValue
Water supply  10.1% 
Storage loss VI 82% 
RMSE 39.9 MCM 
Downstream water temperature regime NSE 0.971 
RMSE 1.1 °C 
Figure 8

Optimal downstream water temperature regime and natural temperature regime.

Figure 8

Optimal downstream water temperature regime and natural temperature regime.

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Figure 9

Optimal storage in the reservoir in the simulated period (blue line: minimum operational storage, yellow line: capacity, grey line: optimum storage, black line: optimal storage time series in the simulated period). Please refer to the online version of this paper to see this figure in color: http://dx.doi.org/10.2166/wqrj.2022.018.

Figure 9

Optimal storage in the reservoir in the simulated period (blue line: minimum operational storage, yellow line: capacity, grey line: optimum storage, black line: optimal storage time series in the simulated period). Please refer to the online version of this paper to see this figure in color: http://dx.doi.org/10.2166/wqrj.2022.018.

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