The Water Quality Control Plan for the North Coast Region (Basin Plan) (NCRWQCB 1989) identifies the designated beneficial uses of water within the Shasta Valley. These include: municipal, domestic, and agricultural supply, freshwater replenishment, cold freshwater habitat, warm freshwater habitat, wildlife habitat, fish migration, and spawning habitat. Numeric water quality objectives have been adopted by the Regional Water Quality Control Board (Regional Board) for some parameters. Narrative objectives have been adopted for other water quality parameters, nutrients, for example.

This office was contacted in writing by the California Department of Fish and Game (CDFG) with regards to observed water quality and fish survival problems in the Shasta River (CDFG 1985; 1987; 1988). At that time, Regional Board staff had already fostered concerns with respect to these issues. There was not a large amount of historical water quality data, anadromous spawning/escapement was declining, and existing water quality data indicated problems (U.S. Department of the Interior:USDI 1985; CDFG 1960s, misc. data). Recent reports of juvenile fish mortality have preserved a high level of concern in the area.

In mid 1985, CDFG stated in a memo (CDFG 1985) that: 1) the Shasta River is the most important spawning and nursery area for the King chinook salmon population of the upper Klamath River; 2) the Shasta River is warm and enriched with nutrients and organic materials, resulting in the occurrence of dissolved oxygen concentrations of less than five mg/L during the late spring and early summer period; 3) there have been documented instances of anadromous fish kills during the end of the out-migration period; 4) the existing (1985) Water Quality Control Plan does not fully describe the extent of water quality problems in the Shasta River; 5) there is concern that water quality problems in the Shasta River will interfere with maintenance and restoration of the fishery; 6) corrective actions are recommended to be sought for the water quality problems on the Shasta River.

Review of the 1985 U.S. Department of the Interior report (USDI 1985) revealed that: 1) water temperatures adverse to salmon and steelhead use of the lower Shasta River have been a problem since at least 1961. Water temperatures up to 85 F (29.4 C) were reported between 1961 and 1970. As of 1985, high water temperatures were still a problem along the lower Shasta; 2) the principal constraints to salmon and steelhead production in the Shasta sub-basin were (in order of importance): low flows and high summer water temperatures; unscreened water diversions; degraded spawning gravel; and possible hydroelectric projects. Relatively rapid in-stream flow reductions at the start of the irrigation season were seen as a possible contribution to juvenile fall chinook, coho, and steelhead losses by stranding them in pools and side channels.

A 1987 CDFG memo to this office (CDFG 1987) discussed the problem of depressed dissolved oxygen levels possibly resulting from high biological oxygen demand and high temperatures. It further stated that more information is needed on water quality problems to establish funding priorities and management strategies for efforts to improve the physical habitat on the Shasta River. Internal communications here, in the summer of 1987, discussed the feasibility of addressing these concerns with Regional Board staff studies.

Another memorandum from CDFG to the Regional Water Quality Control Board Executive Officer, in the spring of 1988 (CDFG 1988), stated that: 1) the Department had documented critical conditions due to low dissolved oxygen concentrations, high nutrient concentrations, and high temperatures, especially during poor water years; 2) a great deal of emphasis had been placed upon restoration of salmon and steelhead in the Klamath River system. Rehabilitation on the Shasta River would be critical to the success of current major efforts of various state and federal agencies to restore anadromous fish runs in the Klamath River; 3) CDF&G officially asked for cooperation from Regional Board staff in conducting a joint water quality monitoring program on the Shasta River to "identify potential solutions for these significant water quality problems."

In May of 1988, the North Coast Region Surveillance, Monitoring and Planning Unit (SMP) prepared a "Proposal for a Water Quality Investigation of the Lower Shasta River", with the stated objective "to determine the extent to which changes in water quality are affecting the beneficial uses of the Shasta River downstream of Dwinnell Reservoir, by distinguishing between the multiple actual/possible dissolved oxygen consumers in the system. The final result of this study will be a report detailing the findings and making recommendations regarding solution of the problem." Funding was subsequently made available to the Regional Board staff for a water quality study during FY '91-92 and FY '92-93.

In October of 1989, staff of the Regional Board SMP Unit attended a meeting of the Shasta Valley Resource Conservation District (RCD). At that meeting staff of the California Department of Water Resources (DWR) announced their intent to perform a three pronged study of the Shasta River: 1) water quality characterization; 2) water budget; and 3) land use. In March of 1990, DWR published the Shasta Valley Water Quality Literature Review (DWR 1990). Budgetary constraints have prevented further progress toward the completion of this study by DWR.

Staff of the Regional Board collected field data from selected stations in July and August of 1986. No data were collected in 1987. Again, in 1988, field data were collected on two occasions, in May and September, and one set of samples was submitted for laboratory analysis. In 1989, data were collected in April, June, and October. On three of these dates, samples were submitted for laboratory analysis. No sampling was performed in 1990.

In April, 1991, laboratory contract funds and staff resources were committed to an intensive two year study of the water quality conditions in the Shasta River. Frequent sampling episodes focused on daily changes in water quality parameters, mainly during the irrigation season, from April 1 through October 1. Sampling during this study period has typically included morning, midday, and evening field measurements of pH, temperature, specific conductance, and dissolved oxygen. Additional water samples were collected at various times throughout the day and submitted for laboratory analysis. Laboratory parameters typically included nutrients, general chemistry, and minerals. The results of these sampling efforts, through June 1992, are the subject of this report.

The Shasta Valley is in central Siskiyou County (Figure 1). It is elliptical in shape with the major axis lying in a north-south direction. The valley is 36 miles long and 30 miles wide at its widest point. In 1964, California Department of Water Resources estimated that of the 507,000 acres within the Shasta Valley, 141,000 are irrigable lands (DWR 1964).

Glacial melting on Mount Shasta and mountain precipitation are the principal sources of recharge for the Shasta River. Much of this recharge reaches the river through underground flow (DWR 1961). The Shasta River originates in the higher elevations of the Eddy Mountains southwest of the Shasta Valley and flows northward to join with springs from underground flow from Mount Shasta which surface in the vicinity of Big Springs and elsewhere in the valley (Figure 1). The river continues north through the Shasta Valley to Yreka before entering a steep seven mile long canyon leading to the Klamath River. The Little Shasta River, a major tributary within the valley, originates in the Cascade Range near Goosenest and flows westward to join the Shasta River about two miles south of Montague. The Little Shasta River is heavily diverted for irrigation prior to its confluence with the Shasta River. Several minor tributaries originate in the mountains along the west side of the Shasta Valley. These streams are generally short and steep, and drain areas of impervious rock. Most of these tributaries are ephemeral (DWR 1990).

A single large storage reservoir, Lake Shastina (Dwinnell Reservoir), with a storage capacity of about 50,000 acre-feet, has been in operation on the Shasta River since 1928. Dwinnell Reservoir is filled with the flows of the Shasta River, Beaughton Creek, and a major ditch diversion from Parks Creek at the south west extreme of the valley. There is heavy agricultural usage of the waters of Beaughton Creek and the Shasta River above Dwinnell Reservoir. This reservoir supplies water through a 20-mile long canal to Little Shasta Valley and the northeastern portion of the Shasta Valley. Several other instream diversions are accomplished through in-stream control structures or pumps. Water diverted in this way is used through the remainder of the valley.

Groundwaters in the valley are heavily influenced by local geology, and are best described as bicarbonate in nature, with a dominant cation (DWR 1976). Waters derived from serpentine areas have been found to contain magnesium as the dominant cation with a high percent of silica. Waters derived from limestone were found to contain calcium as the dominant cation. Waters derived from volcanic formations were found to contain high salinity, sodium, silica, and boron (USGS 1960). Boron is a micronutrient, but in higher concentrations becomes toxic to plants. Most groundwater mineral problems within the Shasta Valley have been found to be quite localized, stemming from natural sources. Areas which have been found to contain poor quality ground water due to mineralized conditions include: 1) along Oregon Slough and the Little Shasta River; 2) in the vicinity of Montague; 3) between Grenada and Big Springs; 4) in the Willow Creek/Julian Creek drainages (DWR 1951, 1959, 1964, 1990). The Willow Creek and Julian Creek areas contain highly mineralized groundwater of deep origin which is high in boron, dissolved solids and sodium. Consequently, irrigation water derived from these sources (from pumped wells) can have the potential of adding a proportionately high load of dissolved solids through agricultural return flows. The Table Rock area contains springs which are high in boron, chloride and sodium (DWR 1959). These springs feed into both Oregon Slough and the Little Shasta River and are deemed to be largely responsible for high boron levels found in the lower Shasta River during low flow periods (DWR 1990).

Agriculture is the major land use within the valley. However, local springtime flooding in typical years and a short growing season restrict the type of crops produced to pasture, alfalfa, small grains and a very limited selection of field crops (DWR 1990). Cattle production is a prominent feature of the valley landscape, with livestock frequently exercising unlimited access within the river channel. The lower river and tributaries from Yreka Creek down contain massive evidence of gravel spoils from early mining activities.