Least Cost Optimization in Middle Sakarya River Basin with the focus on Water-Energy Nexus

Water-energy systems have an interconnected relationship. While water is needed to generate energy, energy is required for water extraction, treatment, and distribution. It is important to understand this relationship since a demand failure in one of the systems can cause a breakdown in the other one. Ensuring energy security actually depends on ensuring water security and vice-versa. This relationship between water and energy is called as water-energy nexus. Increase in water and energy demand, growing population, and climate change are significant threats for this reslationship. Achieving sustainable water-energy relationship is especially important for semi-arid regions where water availability is low.

In light of this information, this study aims to evaluate the water-energy nexus in the Middle Sakarya River Basin and to determine the least cost electricity generation options for this basin. For this purpose, two separate modelling tools are integrated so that the feedbacks between the water management and energy management sectors are captured. These tools are the Water Evaluation and Planning (WEAP) system and the Long-range Energy Alternatives Planning (LEAP) system. The hydropower plants are modelled in WEAP and LEAP responds to the total electricity demand by dispatching the thermal and hydropower mix including the WEAP's estimate of available hydropower. The models are calibrated for the 2005-2008 simulation period. Within this simulation period, there are three active hydroelectric power plants and one lignite fired thermal power plant in the watershed. The total installed capacities of the power plants is 1096 MW. The least cost optimization scenario results show that the electricity generation in the hydroelectric power plants should be increased by 23% while the generation in the thermal power plant is decreased by 4% on average to meet the electricity demand based on least cost electricity generation. This also means that the capacity factors of the hydroelectric power plants is increased from 13% to 19%, and that of the thermal power plant is decreased from 79% to 76%. These are the initial findings of the study. As a future study, the model will be verified for a different simulation period, i.e. for wetter years, and the impacts of the climate change on water and energy systems will be analyzed.