Optimally sizing small hydropower project under future projected flows

The global climate change trend is resulting in change in precipitation and temperature. This change is impacting water resources and flow patterns in rivers and streams world-wide. Due to this, it is becoming difficult to optimally size small hydropower plants and predict their performance during operations. This paper has endeavored to investigate a solution to this problem. Chitral River in the Kabul Basin in Upper Indus Region, Pakistan was selected as study area. Observed climatic data of Chitral for period 1984-2013 was obtained from Pakistan Meteorological Department (PMD), observed flow data of Chitral River for period 1989-2013 was obtained from Water and Power Development Authority (SWH-WAPDA) and future predicted climatic data (including temperature and precipitation) was downscaled from MEPH5 Global Circulation Model (GCM) using LARS WG 5 for period up to 2099 under A1B, A2 and B1 Emission Scenario. HEC-HMS was used to determine future river flow trends for periods 2014-30, 2046-65 and 2080-99. The historic and future river flows were used to size small hydropower plant using RETScreen 4.1 model. Multiple Objective Decision Making Methodology (MODM) was used to decide upon the most optimum size of the hydropower plant. This paper has determined that there will be 16.83% reduction in river flows simulated for 2011-30, 25.03% for 2046-65 and 22.02% for 2080-99 as compared to historical flows during 1989-2013. Consequently there will be 0.36% impact on yearly power generation due to river flow changes simulated for 2014-30, 6.25% for 2046-65 and 4.08% for 2080-99. It is concluded that optimal sizing of the small hydropower plants and better performance under variable flows due to climate changes can be ensured by taking into account the future river flows predicted through hydrological models in addition to historical flows. The results concluded that 49.64 MW will be the most optimal size of the small hydropower plant that will produce maximum electricity under future projected flows at the study area.