Applications of Long-Term Watershed Research to Forest Management in California:

1. Applications of Long-Term Watershed Research to Forest Management in California: 50 Years of Learning from the Caspar Creek Watershed Study Peter H. Cafferata California Department of Forestry and Fire Protection, Sacramento, California Leslie M. Reid USDA Forest Service Pacific Southwest Research Station, Arcata, California • Examples of Study Results and Their Application • Mid-winter peakflows increased after clearcutting • Prediction methods aid cumulative effects assessment and allow calculation of appropriate rates of harvest; used in Freshwater Creek and Elk River watersheds. • Data used 1) to predict changes for proposed harvesting in THPs and NTMPs by RPFs and CAL FIRE staff; 2) in THP Official Responses; 3) in aquatic HCPs (e.g., GDRCO, PALCO), 4) in JDSF management plan EIR, and 5) in vineyard conversion project EIRs. • Data used to validate watercourse crossing 100-yr flow prediction methods. • Low flows initially increase with selective harvest, then decrease • Low-flow data used to plan water drafting and instream flow requirements. • Data used in HCPs and vineyard conversion EIRs to evaluate potential impacts. • Input rates to streams, recruitment mechanisms, and source distances measured for large wood • Informs design and management of WLPZs and development of Anadromous Salmonid Protection Forest Practice Rules; data used for draft MRC aquatic HCP. • In-channel erosion produced more sediment than small to medium sized landslides after cable-yarded clearcut logging • Used to address rate of harvest issue in western Mendocino County THPs (WLPZs or buffer strips alone can’t prevent some kinds of riparian sediment increases). • Erosion data used in THP Official Responses, HCPs, EIRs, etc. • With WLPZs, water temperature increases were small and within tolerable ranges for salmonids • Used to validate a water temperature prediction model and to develop an RPF guidebook for water temperature prediction. • Water temperature data used in THP Official Responses, EIRs, etc. • Fog drip was not hydrologically important at this site • Used in THP reviews, the draft MRC aquatic HCP, JDSF management plan EIR, and vineyard conversion EIRs. • Nitrate concentrations increased in streams after clearcutting, but fluxes were relatively low • Used to address nutrient loss issue in JDSF management plan EIR. • Clearcutting with partially cut WLPZs produced increases in macroinvertebrate density and diversity and no dramatic short-term changes in aquatic vertebrate numbers • Used to address aquatic biological issues in the JDSF management plan EIR. • A turbidity monitoring method was developed to provide continuous suspended sediment records • The TTS method has been implemented from South Lake Tahoe to Okinawa. Introduction Initial stream discharge, suspended sediment, and rainfall measurement began in the Caspar Creek watershed, located in western Mendocino County, on October 1, 1961. During the following 50 years, this basin has been the site of a long-term cooperative study between the U.S. Forest Service Pacific Southwest Research Station (PSW) and the California Department of Forestry and Fire Protection (CAL FIRE). The Caspar Creek watershed is one of only a small number of watersheds in the United States with a continuous record of streamflow and sediment for this length of time. 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. Lessons learned from these studies have been applied to address numerous forestry-related issues in the Coast Ranges of California. Four kinds of information from the study are regularly applied. First, long-term monitoring provides data that can be used to characterize flow, sediment, and temperature conditions in the region, facilitating such things as design of instream flow requirements or sediment mitigations. Second, results of the watershed-scale experiments demonstrated the effects of tractor-yarded selective logging and cable-yarded clearcutting on a watershed’s sediment yield and runoff, providing the kinds of data useful in designing and modifying forest practice rules and BMPs. Third, process-based studies provide topical information that can be used to resolve particular problems or to understand the basis for certain kinds of environmental responses. Finally, monitoring technology designed and tested during the Caspar Creek study has now been implemented at variety of other sites, reducing sediment monitoring costs and improving data quality. Ziemer (1998) describes results of Caspar Creek studies, and a full bibliography and access to Caspar Creek data are available at: http://www.fs.fed.us/psw/topics/water/caspar/. North Fork Caspar Creek, NFC weir, summer low flow Example of Calculating a Change in Peak Flow in the Santa Cruz Mountains for THP 1-01-170 SCR (Lompico THP) Changes in peak flows can be predicted based on the Caspar Creek data with the following equation (Lewis et al. 2001, Lisle et al. 2000): E(r) = exp{[1+B2(t-1)]c[B4+B5ln(yc)+B6ln(w)]} Where: r ratio between the observed peak flow and the expected flow without a logging effect in a watershed as the result of a storm B2 logging recovery coefficient (-0.0771) t number of summers since logging c proportion of the watershed logged B4 constant (1.1030) B5 storm size coefficient (-0.0963) yc expected mean peak discharge of control watersheds in Caspar Creek to a storm having the return period of the storm being estimated (m3s-1ha-1) B6 watershed wetness coefficient (-0.2343) w watershed wetness index Freshwater Creek and Elk River Watersheds Class II Watercourse and WLPZ in the Lompico THP The Timber Harvesting Plan proposed to selectively harvest 204 acres in the 1,791 acre Lompico Creek watershed, with an average canopy reduction of 30% in the main harvest units (estimate provided by the RPF), and about 10% in the WLPZs. This can be considered the equivalent of clearcutting 55.1 acres. References Lewis, J., Mori, S.R., Keppeler, E.T., Ziemer, R.R. 2001. Impacts of logging on storm peak flows, flow volumes and suspended sediment loads in Caspar Creek, California, in: Wigmosta, M.S., Burges, S.J. (Eds.), Land Use and Watersheds: Human Influence on Hydrology and Geomorphology in Urban and Forest Areas. Water Science and Application Volume 2, American Geophysical Union, Washington, D.C., pp. 85-125. Lisle, T.E.; Reid, L.M., and Ziemer, R.R. 2000. Addendum: Review of Freshwater flooding analysis summary. Unpublished report submitted to the California Department of Forestry and Fire Protection. USFS Pacific Southwest Research Station, Redwood Sciences Laboratory, Arcata, CA. 16 p. Ziemer, R.R., (technical coordinator). 1998. Proceedings of the Conference on Coastal Watersheds: the Caspar Creek Story. General Technical Report PSW GTR-168, U.S. Forest Service, Pacific Southwest Research Station, Albany, CA. Excel Spreadsheet to Calculate Changes in Peak Flows using the Caspar Creek Regression Equation The Caspar Creek peak flow prediction equation was used for predicting the 2-year peak flow increase expected from the proposed harvest unit in the Lompico Creek basin. The first year after harvest with 70% residual canopy cover remaining following harvest for the selection area/WLPZs, estimated peak flow increases for a 2-year return interval storm are: 0.8% for average wetness (wetness index of 304) 0.3% for very wet soil wetness (wetness index of 600) 2.2% for very dry soil wetness (wetness index of 50)