INFLUENCE OF THE OPERATION OF A PUMPED-STORAGE HYDROELECTRIC POWER PLANT ON THE RESERVOIR'S THERMAL STRUCTURE

Pumped-storage hydroelectric power plants are generally perceived as an environmentally respectful technology. Nevertheless, the pumping of water from a lower reservoir to an upper impoundment, and the return of that water during power generation can strongly affect the water quality of the reservoirs. In particular, plant operation can alter their thermal structure, deep water mixing and water circulation characteristics. The objective of this study is to quantify, through the use of 3-D hydrodynamic modeling, the potential impacts of a pumped-storage hydroelectric plant on the thermal stability and mixing of two reservoirs in Galicia, in the northwest of Spain. To this end, three-dimensional hydrodynamic simulations were conducted using Delft3D model. Two different coupled models, one for each reservoir, were constructed and subsequently tested for several stratification scenarios, according to measured temperature profiles during the spring and summer season. Several reservoir minimum and maximum operation water levels were also considered. Model simulations demonstrated a high level of mixing in the vicinity of the intake-outlet structures, in particular during startup of the power plant, regardless the water level in the reservoir. Beyond this area, the results showed a limited overall effect on stratification and mixing in the upper reservoir, and a more significant alteration of the thermal structure in the lower reservoir.