Groundwater Inputs to an Alpine Hydroelectric System

Authors: Brailey, David E., Brailey Hydrologic

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Abstract

The Juniper Creek hydroelectric system displaces 2 million pounds of carbon dioxide annually and meets the annual energy demand for 200 homes. With 370 feet of head and a design flow of 13.3 ft3/s, the system delivers a constant 300 kW baseload from June through October, declining toward an annual low in May. Up to half of the winter flow consists of groundwater sourced from a series of springs. The spring water increases annual power production by about 15 percent and prevents ice formation on the intake screen. For year-round operation, a 50 percent increase in minimum generation capacity allows a corresponding increase in the maximum design flow.

Juniper Creek flows through an underfit gorge cut by receding glacial meltwaters. An upstream tarn limits bedload to weathering of the armored streambed, resulting in minimal sediment accumulation in the spillway pool. Providing groundwater freeze-protection, sediment control, and by eliminating woody debris, the alpine environment results in a nearly maintenance-free intake. After initial balancing of control parameters, the system has been 100 percent reliable for its first 18 months of operation.

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