The severity of ill effects (SEV) index is based on the limited meta-analysis of previous peer reviewed reports and consultations, and described as a function of duration of exposure to turbid conditions in fisheries or fish life stages by fish adapted to life in clear water ecosystems. In this study, the performance of classification by SEV index was investigated using the K-Means clustering algorithm. This study is based on 303 tests undertaken on aquatic ecosystem quality over a wide range of sediment concentrations (1–50,000 mg SS/L) and durations of exposure (1–35,000 h). Training and testing data includes concentration of suspended sediment, duration of exposure, species and life stages as the input variables and the SEV index for fish as the output variable. Results indicate that the K-Means clustering algorithm, as an efficient novel approach with an acceptable range of error, can be used successfully for improving the performance of classification by SEV index.

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Environmentally friendly flushing aims to send only the concentrations of the sediment that the environment can withstand. In this study, the time required for environmentally friendly flushing in Dez dam reservoir was estimated. For this purpose, the relationship between the concentration, duration, and scale of the severity of ill-effect for fish was considered. A study was conducted on Dez dam reservoir in Iran, where the average historical outflow from the dam, and the volume of sediment flushing was evaluated. According to this study, the dam is facing a serious sedimentation problem. Its dead volume is presumed to be quite full in the coming 10 years. Performing flushing operations through the three irrigation gates of the dam has received much more attention in recent years as compared to the past. The results from this study help us to determine the appropriate hydraulic conditions to decrease the negative environmental effects of Dez dam flushing operations on the downstream ecosystem.

Repeated games, an important mathematical formalism, open attractive perspectives in the modeling and studying of interactions between multiple self-interested parties (individuals or groups). The main conceptual difference between static, and repeated and dynamic games is that the former have a preset, finite number of turns, while the latter can potentially last forever and end only with a decision by a player, or by chance. Unlike previous surveys of repeated games, which originated mainly from the economics research community, the performances of repeated games were investigated in this study for evaluating the time required to flush a reservoir, taking account of water quantity and quality. A sediment-flushing model was developed to estimate the flushed sediment and water volumes, and operating period of flushing, to be taken into account in the reservoir simulation model. Dez Hydropower Reservoir in Iran was chosen as the case study for applying the proposed methodology. The results show that the methodology provides an effective and useful tool for reservoir operation.