In this research, the impact of climate change in the next 15 years (2036–2022) in the (LarDam) area has been investigated. The results showed that in the case of climate change under scenarios RCP2.6, RCP4.5, RCP8.5, the maximum temperature and the minimum temperature have increased by5, 5.23, 6.2% and 3.5, 5.6, 5.17%, respectively, and the amount of precipitation increased by 8.55, 9.5, 13%, respectively. Also, the highest rainfall will be in 2031 and the lowest will be in 2036. Then, based on the intermediate state of the scenarios, i.e. RCP4.5 scenario, the amount of runoff was obtained and the reliability index was calculated according to the upstream runoff of Lar Dam and downstream needs for drinking, agriculture, and environment. The simulation was also performed in the WEAP model. The obtained reliability showed that the highest reliability was 86.60% of the agriculture needs in the WEAP model, and by using the optimization of a honey badger and harmonic search algorithms, it was found that the reliability is approximately 5.06 and 1.73% higher than the reliability of the simulation, respectively. Moreover, in comparison with the optimization algorithms, due to the smaller value of the objective function of the honey badger algorithm and the greater reliability of this algorithm in optimizing downstream needs, it can be concluded that the performance of this algorithm was better than the harmonic search algorithm. The honey badger algorithm has a faster calculation speed than the harmony search algorithm with less execution time.
These methods have been used for the first time. Forecasts are based on the impact of climatic parameters on the future situation and the latest algorithm. The predicted data have been generated based on real daily data, and using validation and re-calibration of the model, the results have been obtained. Optimization was done using several meta-heuristic algorithms and the definition of the objective function.