Tour the Site:  «-  page 2 of 28   -»

Watershed Background > Hydrology

Hydrology

The Russian River drains an area of 1,485 square miles that is approximately 100 miles long and from 12 to 32 miles wide. From its source, about 16 miles north of Ukiah, the river flows southward for 90 miles through Redwood, Ukiah, Hopland, and Alexander Valleys, and through the northwestern part of the Santa Rosa Plains. The river then turns abruptly westward at Mirabel Park and flows for 22 miles through a canyon in the mountains before entering the Pacific Ocean at Jenner. The several alluvial valleys through which the river flows are separated by mountain gorges. Altitudes in the basin range from 4,480 feet to sea level. The principal tributaries of the Russian River are East Fork, Sulphur Creek, Maacama Creek, Dry Creek, and Mark West Creek. The principal tributary of Mark West Creek is Laguna de Santa Rosa, which drains a large flat marshy area and enters Mark West Creek about 5 miles upstream from its mouth. The flow in the lower reaches of Mark West Creek reverses during periods of medium and high stage on the Russian River. At those times Russian River water enters Mark West Creek, flows into Laguna de Santa Rosa, and spreads over the surrounding lowlands. These lowlands, when inundated, act as a natural detention basin and thereby reduce peak discharges on the lower reaches of the Russian River. (Rantz and Thompson, 1967)

The principal use of water in the basin is for the irrigation of agricultural land; water is also used for municipal, domestic, and industrial purposes, notably in the communities of Ukiah, Cloverdale, Healdsburg, Santa Rosa, and Sebastopol. Evapotranspiration from the irrigated areas accounts for most of the water actually consumed. (Rantz and Thompson, 1967)

Several major water developments have been made in the Russian River basin. The Pacific Gas and Electric Co. annually diverts about 150,000 acre-feet of Eel River water into the East Fork Russian River through its Potter Valley diversion tunnel and powerplant, northeast of Ukiah. This diversion, which began in 1908, is now regulated by storage in Lake Mendocino, a flood-control and water conservation reservoir that was built in 1959 on the East Fork Russian. Lake Mendocino has a capacity of 122,500 acre-feet. Its releases maintain runoff on the main stem of the Russian River during the dry season to satisfy irrigation and water-supply requirements downstream. This is done by maintaining a minimum flow of 125 cfs (cubic feet per second) at the Geological Survey gage near Guerneville, 74 miles downstream from the mouth of the East Fork (Rantz and Thompson, 1967)

The Sonoma County Water Agency (SCWA) diverts water from the Russian River, just upstream from the mouth of Mark West Creek, for municipal use in the cities within the Russian River basin and for other towns outside the basin. This diversion, which began in 1959, increased from 6,600 acre-feet in 1959 to 18,000 acre-feet in 1969. Water for this diversion is pumped from a gallery 60 feet beneath the streambed. Lake Sonoma, a flood-control and water-conservation reservoir on Dry Creek, was completed in 1983. Lake Sonoma was designed to provide 212,000 acre-feet of water supply storage and 130,000 acre-feet of flood control storage (SCWA website).

SCWA water-right permits are described in Section 1.4.3. Currently, SCWA is permitted to divert water to storage at Lake Mendocino and Lake Sonoma and to divert and redivert water from the Russian River at the Wohler and Mirabel pumping facilities. In water year 2001/2002, SCWA diverted and rediverted approximately 65,000 AF of water from the Russian River, including both SCWA diversions and water diverted under SCWA water rights. The total amount of water that may be diverted and rediverted under SCWA permits is 75,000 AFY, at a maximum rate of 180 cfs. (SCWA Final Biological Assessment)

It is estimated that there are presently over 600 diversions by various entities along the mainstem of the Russian River and approximately 800 other diversions along the tributaries of the Russian River (SCWA 1996b). The uses of diverted water include municipal, domestic, agricultural, and industrial. SWRCB records list a total of over 1,500 water rights filings for the Russian River watershed. SCWA estimates that the present total-diversion demand on the Russian River and its tributaries by all users, including agriculture and urban, is 110,000 to 120,000 AFY, depending on the amount of rainfall per year. Approximately 41,000 to 49,000 AFY of this demand occurs on the Russian River upstream from Dry Creek, where agricultural uses account for most of the total. Diversions along Dry Creek below Warm Springs Dam and along the Russian River downstream of the confluence with Dry Creek total approximately 70,000 AFY, including SCWA’s diversions. Municipalities and agricultural interests are the primary diverters. (SCWA Final Biological Assessment)

Precipitation in the Russian River is distinctly seasonal, about 80 percent of the total occurs during the 5 months November through March. The bulk of the precipitation occurs during moderately intense general storms of several days duration. Snow falls in moderate amounts at altitudes above 2,000 feet, but it seldom remains on the ground for more than a few days. Hourly precipitation in excess of inch uncommon (Rantz and Thompson, 1967). However, 24-hour rainfall totals may be sufficient to initiate widespread debris flows have a return period of about 15 years in the Maacama Creek watershed (Jackson, 2004). Given the similarity of mountainous tributaries of the Russian River the return-period of widespread debris flows is probably about 15-years in other tributary watersheds.

Mean annual precipitation, for the 1931-1963 water-years, above the USGS Russian River near Guerneville, CA stream gauge is about 45 inches. The mean annual natural runoff, adjusted for the transfer from the Eel River, for the 1931-1963 water-years, at the Guerneville stream gauge is 19.1 inches (1,367,000 acre-feet) which is 42% of the mean annual precipitation. Subtracting the mean annual natural runoff from the mean annual precipitation gives a ean annual amount of water lost to evapotranspiration and percolation to deep groundwater above the Guerneville gauge of about 25.9 inches or 58% of mean annual rainfall for the 1931-1963 water-years (Rantz and Thompson, 1967).

The average of the highest discharge reported each water-year at a gauging station is called the mean annual flood. The mean annual flood has a return-period of 2 years when the flood series is fit to the normal distribution. So, the mean annual flood is a rough approximation of the bankfull discharge. A review of the flood records for 23 USGS gauging stations on tributaries of the Russian River and nearby streams reveals that the unit mean-annual-flood (average peak discharge/watershed area) is roughly 100 cubic-feet-per-second/square-mile, for watersheds larger than 1.0 square-miles.

References

Jackson, Dennis. Hydrology of the Maacama Creek Watershed. Unpublished report. November 2004.

Rantz, S. E., and T. H. Thompson. 1967. Surface-Water Hydrology of California Coastal Basins Between San Francisco Bay and Eel River. 1851, U.S. Geological Survey. http://www.scwa.ca.gov/history.html

SCWA, Final Biological Assessment, Section 3, Environmental Baseline, September 29, 2004. http://www2.scwa.ca.gov/docushare/dsweb/Get/Document-1185/Sec+3+Final+BA_environmental_baseline.pdf