Bibliography Background About KRIS
Hypothesis #6: Reduced surface flows are limiting salmon and steelhead production in the Gualala River.
The California Department of Water Resources (CDWR) in the Gualala River Watershed Synthesis Report (CA RA, in Review) acknowledged that "stream flow can be a limiting factor for anadromous fisheries affecting migration and the quantity and quality of spawning, rearing and refugia habitats." The California Department of Fish and Game (Hunter, 1996) expressed concern about the diversion of the North Fork Gualala by the North Gualala Water Company, citing reduction in fish habitat if minimum stream flows were not retained. The State Water Resources Control Board (1999) prohibited diversion of surface water when the North Fork dropped below four cubic feet per second (cfs), then in August 2000, ruled that this order applied to two NGWC groundwater wells (SWRCB, 2000). This decision recognizes the importance of North Fork flows to the lower mainstem Gualala as well. See note from Higgins (1997) on the history of water extraction and particular problems with water rights permits.
CDWR indicated that aggradation had decreased water supply in the Gualala River basin, particularly the lower Gualala River and estuary (CA RA, in press). CDFG 2001 habitat typing surveys found that extensive reaches of the Gualala River and its tributaries lacked surface flows, including the mainstem South Fork Gualala below Big Pepperwood Creek (Figure 1). CDFG found flows of 12.5 cfs in this reach in 1977, during an extreme drought (Boccone and Rowser, 1977). The Wheatfield and upper South Fork contributed three cfs, the North Fork 4.3 cfs, and five cfs came from Buckeye, Rockpile and Big Pepperwood creeks. In 2001, the Wheatfield Fork (Figure 2-3), upper South Fork and Rockpile were subsurface at, or near, their mouths. This difference is surprising, given that rainfall records at nearby Ft. Ross indicate that only 16.01 inches of rain fell in 1977 while 24.56 fell in 2001.
Figure 1. The South Fork Gualala River below Big Pepperwood Creek ran underground for extensive reaches in 2001 as shown by the CDFG habitat typing data at left. Lower Rockpile Creek also lost surface flows in more than a quarter mile extending up from the mouth of the lower South Fork. In the North Fork drainage, McGann, Robinson and Dry creeks all had extensive reaches that lacked surface flow.
Figure 2. The Wheatfield Fork of the Gualala was dry above its confluence with the South Fork and in patches for the entire distance below Fuller Creek. Spacek (1997) noted that this reach had surface flows and deep swimming holes prior to 1955.
Figure 3. The Wheatfield Fork, just upstream of its convergence with the South Fork, ran underground in 2001, as evidenced at left. Although the aggradation of the Wheatfield Fork is a factor contributing to lack of surface flows, water diversion may also play some role.
Figure 4. This chart shows rainfall records at Ft. Ross from 1872-2002. This gauge allows comparison of rainfall that is representative of the Gualala Basin, although the gauge is just outside the southeast boundary of the watershed. Records show that rainfall in 1977 was just 16.01, the record low for the entire period, while rainfall in 2001 was 24.56 inches. The fact that there was less surface flow in 2001 shows a loss of fish habitat between 1975 and 2001.
The extensive dry reaches of the Gualala River and its tributaries impair salmonid carrying capacity. Whether the loss of surface flow is in response to aggradation, flow diversion, or a combination of both is unknown. Sommarstrom (1992) thought that small diversions would not significantly decrease Gualala River flows because of the terrain and low population density. In recent years, conversion of land to vineyards has increased concerns about flow diversion and water supply in the Gualala River basin (Higgins, 1997).
The following is a listing of topics and maps from the KRIS Gualala database and the KRIS Gualala Map project that are used in the arguments above. Viewing them in context allows access to data, Metadata and associated Info Links. The large-case letters in parentheses indicate KRIS Gualala sub-basins.
Both Figures 1-2 from Fish and Aquatic Habitat View: KRIS Gualala Map project
(WF) Tour: CDFG Wheatfield Fork #1 CDFG Photos 2001
(MG) Climate: Annual Rainfall in Fort Ross 1878-2002
Alternative Hypothesis
Flow conditions in the Gualala River are not impairing salmonids.
Salmonids have adapted, through long term evolution, to the Gualala River and its natural flow variability. CDFG did not survey all reaches in 2001 and extensive segments of healthy habitat and high salmonid abundance exist in the watershed in areas not surveyed.
Monitoring Trends to Support or Refute the Hypothesis
As sources of erosion are abated through natural watershed healing and restoration efforts, surface flows may recover in some reaches. Long term water temperature monitoring could help discern if water conservation measures decrease water temperature as well as increase flows.
References
Boccone, V and W. Rowser. 1977. Field Note: Gualala River Stream Flow Measurements Taken with Pygmy Flow Meter Using 6-Tenths Depth Method To Determine Mean Velocity At Ten Stations. Includes Stations from the South Fork, North Fork, Wheatfield Fork, and Mainstem GualaIa River (maps, data sheets). California Department of Fish and Game, Region 3, Yountville, CA. 2 pp.
California Resources Agency. In press. Gualala River Watershed Synthesis Report. CA Dept. of Fish and Game, State Water Res. Control Bd., CA Dept. of Water Resources, CA Div. on Mines and Geology and CA Dept. of Forestry. Sacramento, CA. Draft released January 16, 2001.
Higgins, P.T. 1997. Gualala River Watershed Literature Search and Assimilation. Funded by the Coastal Conservancy under contract to Redwood Coast Land Conservancy. Gualala, CA. 59 pp.
Hunter, B. 1996. Response to CDU 1 l-96; Applicant North Gualala Water Company, Proposed Upgrade of Water Pumping, Storage and Conveyance System; Affecting the North Fork Gualala River Watershed, Mendocino County. Memo to Charles Hudson, Mendocino County Planning and Building Services. California Department of Fish and Game, Region 3, Yountville, CA. 4 pp.
Sommarstrom, S. 1992. Final Report, An Inventory of Water Use And Future Needs In The Coastal Basins Of Mendocino County. Prepared for Mendocino County Water Agency. August, 1992.
Spacek, K. 1997. Letter to Pat Higgins re: Gualala River Watershed Literature Search and Assimilation. Resident of Annapolis, CA and life long Gualala River angler. 6 p.
State Water Resources Control Board, Division of Water Rights. 1999. Order WR 99-011. Sacramento, CA. November, 1999.
State Water Resources Control Board, Division of Water Rights. 2000. Letter to John Bower, President, North Gualala Water Company. Sacramento, CA. August 23, 2000.
