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Indicators of Hydrologic Alteration for Hydroelectric Power Development in the Upper San Joaquin Basin, California, USA

Author(s): Brian Caruso

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Keywords: Hydrologic alteration; Hydroelectric power; Sierra Nevada Mountains

Abstract: Catchment and river management involving large-scale hydrologic alteration can have significant adverse impacts on natural river flow regimes and aquatic ecosystems. The Indicators of Hydrologic Alteration (IHA) methodology is a tool used to compare and quantify changes in 33 key hydrologic parameters considered important for ecosystem function before and after some type of water or river basin management scheme. Hydroelectric power (HEP) development is an example of water management that can cause considerable hydrologic alteration for which IHA has been widely used in river basins in the western United States. This study applied IHA to evaluate hydrologic alteration and impacts of the Big Creek HEP Project, an existing scheme in the Upper San Joaquin River Basin in the Sierra Nevada Mountains of California. The existing hydrology of the basin was evaluated using data from U. S. Geological Survey and Southern California Edison gages in the basin. The natural, unimpaired hydrology of the basin without HEP development was estimated using some flow data from unimpaired basins above diversions, and using water balance and area-based regression methods with flow data from nearby unimpaired basins. Quantitative comparison of the differences and changes between unimpaired and existing hydrologic statistics for the key parameters was performed using IHA. Mean annual flows ranged from 581cfs for the San Joaquin River (SJR) downstream of Dam 6. Mean annual low flows ranged from<1cfs in many of the small streams to 5.7 cfs at Bear Creek. IHA results for the river and stream gaging stations showed that for many locations large differences were observed between estimated or actual unimpaired flows and existing flows in the basin. The IHA indices reflected these differences. Bear Creek, a high-altitude catchment in the upper part of the basin, was used as an example to evaluate and discuss IHA results.

DOI:

Year: 2010

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