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Applications of long-term watershed research to forest management in California: 50 Years of Learning from the Caspar Creek Watershed Study

Informally Refereed

Abstract

For over 50 years, the Caspar Creek Experimental Watersheds, located in western Mendocino County, California, have been the site of long-term cooperative watershed research carried out by the U.S. Forest Service Pacific Southwest Research Station (PSW) and the California Department of Forestry and Fire Protection (CAL FIRE). Preliminary stream flow, suspended sediment, and rainfall measurements began on October 1, 1961. Monitoring has continued nearly uninterrupted since then, making the research site one of the few in the United States with hydrologic records spanning this length of time. This report summarizes results of the first 50 years of studies at Caspar Creek.

Two major watershed experiments have been carried out at Caspar Creek to study the hydrologic effects of second-growth harvesting of coast redwood and Douglas-fir forests. The first experiment focused on the 424-ha (1,048-ac) South Fork Caspar Creek watershed. After five years of pre-treatment monitoring to establish calibrations to the North Fork control watershed, a riparian road was constructed along the South Fork channel in 1967. The effects of road construction were monitored for four years before the watershed was selection logged and tractor-yarded during the early 1970’s. The practices used were typical for that time, which was just before implementation of the modern California Forest Practice Rules.

The second experiment employed a different silvicultural strategy and a different experimental design. In this study, sub-watersheds within the 473 ha (1,169 ac) North Fork Caspar Creek watershed provided the controls, and pre-treatment monitoring was carried out between 1985 and 1989 at 13 gaging stations. Sub-watersheds in the North Fork were then clearcut from 1985 to 1992, predominantly using skyline cable yarding from roads located high on ridges.

Key findings from the South Fork and North Fork experiments address topics often of concern to California resource professionals, including the effects of logging on peak flows, summer low flows, annual water yields, sediment yields, surface erosion, channel erosion, gullies, landslides, hillslope hydrology, stream temperature, fog drip, nutrient cycling, and biological responses. Study results have quantified the effects of forest management activities on these watershed characteristics, and have allowed the influences of clearcutting and selection logging to be compared for many of them. Results have also shown how different kinds of influences can interact and contribute to cumulative watershed effects on downstream habitats. As a by-product, the studies have led to significant advances in monitoring technology, and turbidity monitoring procedures developed at Caspar Creek are now being used at sites throughout the world.

Keywords

climate, stream flow, forest management, erosion, logging

Citation

Cafferata, P.H.; Reid, L.M. 2013. Applications of long-term watershed research to forest management in California: 50 years of learning from the Caspar Creek Watershed study. California Forestry Report No. 5. Sacramento: State of California, The Natural Resources Agency, Department of Forestry & Fire Protection. 114 p.
https://www.fs.usda.gov/research/treesearch/52182