Shrinking streamflows in the Redwood RegionAuthor(s): Randy. D. Klein; Tasha McKee; Katrina Nystrom
Source: Gen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 187-197
Publication Series: General Technical Report (GTR)
Station: Pacific Southwest Research Station
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The ongoing, severe drought in the redwood ecosystem has many ramifications, including loss of summer rearing habitat for juvenile salmonids. Many ‘perennial’ streams now cease to flow during parts of the summer and fall, either drying up completely or disconnecting pools as riffles go dry, subjecting fish to increased predation, high water temperatures, and desiccation. Numerous factors have contributed to this hydrologic impairment, including natural hydrologic cycles, legacy land use effects, human consumptive uses, and climate change. The search for solutions is now in full swing, and will be most effective if based on site-specific monitoring to identify controllable causes and a non-confrontational approach to changing water usage in time and space.
Monitoring of low flows in the region has been ramping up in recent years, led by the program pioneered by Sanctuary Forest, a non-profit group located in the Upper Mattole River. Their data collection program has run from 2004 through the present and consists of measuring low summer/fall stream discharge at a network of key locations in the watershed. The primary goals of hydrologic monitoring are to identify locations of extreme flow impairment and to guide efforts for water conservation.
A crucial element of Sanctuary Forest’s program has been to heighten the awareness of landowners of the low flow problem and involve those willing in a forbearance program that offers increased water storage capacity in exchange for cessation of water withdrawals during drought conditions. The date of water withdrawal cessation varies each year, but this date is important for landowners involved with the program: it determines when their water sources switch from the creeks to their storage tanks. Correlations with online-accessible, real time streamflow and precipitation data have provided convenient means to determine, and even forecast, the date when pumps must be turned off.
Recent data show that Sanctuary Forest’s forbearance program is having a positive effect on low flows. Measurable increases in low flows in the Upper Mattole River have been observed since 2009, elevating extreme low flows and reducing the number of days when flows fall below minimums needed for juvenile salmonid migration. With growing participation in the program, benefits to summer low flows will continue to accrue and improve conditions for fish in the Upper Mattole River.
Because of the success of Sanctuary Forest’s monitoring and forbearance program, it is now being replicated in nearby watersheds. If the recent trend of worsening droughts proves to be the new ‘normal’, maintaining and augmenting forbearance in the Upper Mattole River, and indeed the entire redwood region, will become increasingly important for juvenile salmonids.
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CitationKlein, Randy. D.; McKee, Tasha; Nystrom, Katrina. 2017. Shrinking streamflows in the Redwood Region. In: Standiford, Richard B.; Valachovic, Yana, tech cords. Coast redwood science symposium—2016: Past successes and future direction. Proceedings of a workshop. Gen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 187-197.
Keywordsdrought, forbearance, low flow, streamflow, water withdrawal
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