What are the specific environmental concerns regarding the construction and operation of pumped storage hydroelectric facilities?

The construction and operation of pumped storage hydroelectric (PSH) facilities raise several environmental concerns. These concerns relate to habitat disruption, water quality, aquatic life impacts, and energy consumption. Construction of PSH facilities typically involves creating or modifying reservoirs, which can lead to habitat loss and fragmentation, impacting terrestrial and aquatic species. Building the dams, powerhouses, and transmission lines requires clearing vegetation and disturbing soil, which can increase erosion and sedimentation. Water quality can be affected by PSH operations due to changes in water temperature, dissolved oxygen levels, and nutrient cycling. The repeated filling and emptying of reservoirs can disrupt natural flow patterns and alter the physical and chemical properties of the water. Pumping water between the upper and lower reservoirs can also entrain and kill fish and other aquatic organisms. Fish can be injured or killed by the pumps and turbines, or they can be trapped in the reservoirs. PSH facilities also consume energy to pump water from the lower reservoir to the upper reservoir. If this energy is generated from fossil fuels, it can contribute to air pollution and greenhouse gas emissions. The ecological impacts of PSH depends on the site specific conditions. Closed loop systems, where water is only cycled between two reservoirs, generally have lower impacts than open loop systems, where water is drawn from and released into natural water bodies. Careful site selection, design, and operation are essential to minimize the environmental impacts of PSH facilities. Mitigation measures include habitat restoration, fish passage structures, and the use of renewable energy sources to power the pumping operations.