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September 1971

Prepared under Authority of Section 6, Public Law 83-566 (as amended) by the Soil Conservation Service and Forest Service representatives on the U. S. Department of Agriculture, River Basin Planning Staff, Berkeley, California.





The East Fork of Scott River Watershed is located in Southern Siskiyou County, approximately 25 air miles southwest of Yreka, California, the county seat. The principal streams of the watershed are the South and East Forks of Scott River which originate in the Scott Mountains in the south and southeastern part of the watershed. The East Fork flows in a southerly direction joining the South Fork of Scott River just above the community of Callahan, California, forming the Scott River which flows in a northerly direction through the watershed.

The rural community of Callahan with a population estimated at less than 100 is the only community within the watershed boundaries. State Route 3 passes through this community. A county maintained road traverses a portion of the watershed in a north-south direction and connects State Route 3 with State Route 99 and Interstate 5 near the community of Gazelle, California.

The drainage area of the watershed is approximately 267 square miles or 170,750 acres. Ground elevations vary from 2,720 feet above mean sea level at the northern part of the watershed to 8,542 feet mean sea level at China Mountain. The irrigable area in the watershed slopes toward the river and generally north and totals about 12,630 acres.

Present land use in the watershed is estimated as follows: Cropland 7 percent; Rangeland 41 percent; Woodland 47 percent; miscellaneous land use 5 percent.

The majority of the soils in the irrigable area belong to the Stoner, the Greenhorn, and the Serpa associations.

The soils of the Serpa association are poorly drained, over 60 inches deep and occupy low terrace and fan positions. They formed in mixed alluvium from metamorphosed igneous and sedimentary rock. The runoff is slow and the erosion hazard slight. These soils have dark gray, silty clay loam, moderately alkaline surface layers. The subsoils are dark gray to light olive gray, silty clay which are moderately alkaline and noncalcareous. The water table is normally within three feet of the surface. These soils are mainly used for hay and pasture.

The soils of the Greenhorn association are somewhat poorly or poorly drained, up to 60 inches deep and occupy alluvial plain or fan positions. They have formed in stratified sediments mostly from basic material of metamorphosed igneous and metamorphosed sedimentary rock. Runoff is slow and erosion hazard is slight. Low lying areas are subject to frequent flooding. These soils have dark brown loam that has hard, friable and slightly acid surface layers. The subsoils are stratified loams and clay loams over a stratum of layers of sand and gravels at depths of 36 inches or more. Free water usually occurs at 2 to 5 feet. These soils are used mainly for pasture and hay production.

The soils of the Stoner association are well drained, over 60 inches deep and occupy alluvial fans, terraces, and bottoms. They have formed in gravelly alluvium from metamorphosed rock. The runoff is slow to medium and erosion hazard is slight. These soils have very dark brown, gravelly loam surface layers that are granular and slightly acid. The subsoils are pale brown, gravelly clay loams that are medium acid. The substratum is stratified silty, sandy or clayey sediments. These soils are used mainly for the production of hay, pasture and small grains.

The soils of the upper watershed are described as follows. The predominant upland soils on the north portion of the watershed are in the KinkelBoomer-Duzel association. Soils on the east and south are in the KinkelBoomer association; the Chawanakee-Shaver-Tollhouse association; and the Dubakella-Ishi Pishi-Weitchpec association.

The Kinkel-Boomer-Duzel association is described in the "Siskiyou General Soil Report" as soils which are moderately deep to very deep, well drained and occupy hilly mountainous uplands between Scott and Shasta Valleys. They formed in place from metamorphosed igneous and sedimentary rock. They are generally gravelly throughout. The runoff is medium to very rapid and the erosion hazard is moderate to high. Vegetation consists of mixed coniferous forests on Kinkel and Boomer soils with an understory of shrubs and grasses. These soils have a grayish brown gravelly loam surface that is neutral to medium acid. Subsoils are gravelly clay loams that are medium acid to neutral. Bedrock underlies these soils at 20 or more inches. These soils are used mainly for timber production. The Duzel soils in this association are used for rangeland.

The soils of the Kinkel-Boomer association are 36 inches to over 60 inches deep, and well drained. They have formed in place from metamorphosed igneous and sedimentary rocks. The runoff is medium to very rapid and the erosion hazard is moderate to high. The vegetation consists of mixed coniferous forest, shrubs and grasses. These soils have thin, dark grayish brown gravelly loam surface layers that are granular and medium acid. The subsoils are reddish yellow, very gravelly clay loams that are medium acid. Highly fractured bedrock occurs at 20 inches or more. These soils are used mainly for timber production.

The soils of the Chawanakee-Shaver-Tollhouse association are shallow to very deep and somewhat excessively drained. They have formed in place from granitic rock. The runoff is medium to very rapid and the erosion hazard is moderate to very high. Severe erosion has occurred on a majority of these soils where they have been logged or burned. The vegetation is mixed coniferous forest and shrubs. These soils have a coarse sandy loam surface layer over subsoils that are coarse sandy loam which is largely weathered granite rock. Firm bedrock frequently is seen in outcrops but is generally 20 inches to 40 inches below the surface. These soils are used for timber production.

Average annual precipitation in the watershed area is about 38 inches per year. This varies from a low of 20 inches near Fort Jones to a high of 60+ inches per year in the higher elevations. Typical of California, the East Fork Scott River Watershed lies in a region of warm dry summers. Only about 10 percent of the precipitation falls during the summer months. The frost free season is 100 to 130 days.

The economy in the watershed is dependent almost entirely upon agriculture. The upper watershed has commercial and national forest. In the service area the typical farm unit is a livestock enterprise with a beef cow-calf operation. A few row crops such as corn silage have been grown in this area.




It is estimated that 24,482 acres would flood in Scott Valley at the one percent chance event, including 14,715 acres due to Scott River. The remaining 9,767 acres flooded is attributed to the tributaries within the valley.

To reduce flooding it is necessary to control major tributaries such as East Fork of Scott River. The East Fork of the Scott River accounts for $52,900 of the total average annual flood image of $337,900 within the entire Scott River drainage. This damage is composed primarily of damage to roads, bridges, existing channel improvements, crops and pasture. For detailed information regarding damages from floodwater see Table I.


Soils in the upland areas have a high to very high erosion hazard. Major erosion of the uplands is in the form of sheet and gully erosion, primarily caused by poor vegetal cover.

Streambank erosion occurs in isolated areas of the watershed. One major source of sediment is located downstream from Callahan. During periods of high flows in Scott River; steeply sloping sands and gravel form a portion of the streambank for a distance of 5 miles. These sand and gravel mounds whose origin can be attributed to the past gold dredging era make a substantial contribution to sediment problems.


To fully realize the agricultural potential of the watershed, additional irrigation water is needed. The potentially irrigable land in the East Fork watershed is 8,820 acres. At present 8,418 acres are being partially irrigated. The existing supply from the Scott River and its tributaries is inadequate. The flow diminishes by mid-July furnishing on An average about one-half the amount of water needed.

Preliminary estimates for alfalfa, grass pasture and potatoes show a seasonal consumptive use of 28, 27 and 22 inches, respectively. 0f this amount, seasonal precipitation supplies 7 inches for alfalfa, 6 inches for pasture and 2 inches for potatoes. Net irrigation water requirements for alfalfa and grass pasture is 21 inches and for potatoes is 20 inches. Assuming an overall field efficiency of 70 percent, the gross irrigation demands for alfalfa and grass pasture would approximate 2.5 acre feet per acre and potatoes would need 2.4 acre feet per acre.

Soils information available in this area indicates that drainage is presently a problem and that it will increase under full irrigation. Present USDA programs should be adequate to solve drainage problems.

An improved irrigation distribution system would reduce the drainage problem by minimizing seepage losses, which presently occur from existing irrigation canals.


Between 1958 and 1980 the recreational needs of Siskiyou County are expected to increase by more than 200 percent to an estimated use of over 3 million activity days (California Department of Water Resources, Bulletin No. 136, North Coast Area Investigation, Appendix C, Fish and Wildlife, April 1965 by Department of Fish and Game, Water Projects Branch, Contract Services Section). There is a need for recreational facilities for such activities as fishing, swimming, camping, hiking, horseback riding and picnicking.


According to the California Department of Fish and Game, the 800 square miles of the Scott River system supports an annual run of approximately 10,000 King salmon, 2000 silver salmon and 20,000 to 40,000 steelhead (California Department of Water Resources, Bulletin No. 136, North Coast Area Investigation, Appendix C, Fish and Wildlife, April 1965 by Department of Fish and Game, Water Projects Branch, Contract Services Section). The majority of King salmon spawn in the Scott River downstream to its confluence with the Klamath River. Deterioration of spawning areas by silt and sand from past mining operations covering streambed gravels appears to be a problem. Several miles of Scott River and many tributaries utilized by salmon and steelhead become dry both from natural causes and from irrigation diversions in the summer.

Present wildlife populations are limited by lack of suitable habitat and more small grain culture would benefit pheasant and quail.

The valley area and the lower slopes around the valley are important winter ranges for migratory deer. Suitable browse areas need to be developed adjacent to the valley to support deer population; however, an adequate harvest of antlerless deer is also needed to bring the deer herd into balance and to reduce their threat to valley crops.



The East Fork Scott River Watershed has an average annual rainfall that ranges from approximately 20 inches at the valley floor to over 60 inches at the mountain tops. Runoff from the watershed averages about 13.3 inches per year and appears to be adequate to supply the future foreseeable needs.

A preliminary investigation showed that a favorable dam and reservoir site exists on the East Fork of Scott River about 4 miles east of Callahan and just upstream from the mouth of Grouse Creek. The California Department of Water Resources previously investigated this site (referred to as "Grouse Creek Dam and Reservoir") and published its findings in DWR Bulletin No. 83, "Klamath River Basin Investigation," July 1964. The drainage area at the site is 57.4 square miles with an average annual precipitation of 33 inches. The mean annual runoff is approximately 34,600 acre feet with a firm yield (80% chance) of 24,800 acre feet.

A flood retarding structure on the East Fork of Scott River could control runoff from 57.4 square miles. This structure could provide complete protection for the 10 percent chance event on 780 acres of agricultural lands.

Opportunities for satisfying some of the recreational needs of the County with this project are excellent. Sides of the reservoir are easily accessible and on gentle slopes, ideal for swimming, fishing, camping, horseback riding and picnicking facilities. The scenic beauty of East Fork Scott River Watershed and Scott Valley creates opportunities for developing vista points, roadside parks and picnic areas. Improved roads around the proposed lake and trails leading into the higher country with its beautiful mountain lakes would provide outdoor recreation to fishermen, hikers and campers.

Drainage from the underground water supply 1s another means of meeting future demands for water. The estimated ground water storage capacity of the entire Scott Valley is 400,000 acre feet (1/ United States Department of Interior, Geological Survey, Water Supply Paper 1462, Geology and Groundwater Features of Scott Valley, Siskiyou County, California, 1958). There are wells in use in Scott Valley which yield from 1,200 to 2,500 gallons per minute at depths of 75 to 120 feet. Sufficient ground water is available at a reasonable depth beneath the service area to supply the 28,052 acre feet required to meet the irrigation needs.

Water quality of both ground water and surface water is excellent for irrigation within the East Fork Scott River Watershed.

The construction of a reservoir on East Fork Scott River will block steelhead runs, and prevent them from reaching spawning areas in the headwaters, such as Kangaroo Creek and other smaller streams. However, releases from the reservoir will have beneficial effects on the Scott River fishery.

Flood flows will be stored in the East Fork Scott River reservoir to be used in the summer for irrigation as natural flows in the river begin to subside. Planned delivery of irrigation water via the river from the damsite to the point of diversion will allow for a larger escapement of juvenile steelhead spawned in tributary streams below the dam, and provide a productive summer brooding area benefiting the salmon population on the Scott River system. Therefore, fish habitat will be improved in seven miles of stream below the dam. The reservoir would also afford an opportunity to establish both a cold and warm water fishery.

The proposed water development will inundate approximately 475 acres of which a portion is considered to be winter range used by migratory deer. This loss can be mitigated by improving rangeland and bottom land adjacent to the reservoir area.

Present fire protection facilities are adequate. However, temporary improvements and precautionary measures will be necessary during the construction period. Firebreaks and other fire protection facilities w111 be needed as recreation activities expand. Storage assigned to recreation could safely be used for fire fighting in case of emergency.



This project is in the Siskiyou Soil Conservation District. The Soil Conservation District and the Siskiyou County Board of Supervisors are interested in sponsoring watershed projects. The Soil Conservation District is willing and able to accelerate the needed land treatment that would be required in a watershed project. Local interest is developing in the two organized groups, the Scott Valley Irrigation District and Farmer Ditch Group, who deliver irrigation water to lands in the service area. At present, local interest in a watershed project appears to be moderately high.



The California Department of Water Resources investigated the Scott Valley for both ground water and surface water development and are described in Bulletin No. 83, Klamath River Basin Investigation July 1964. Their Grouse Creek Dam and Reservoir with a capacity 50,000 acre feet, would have a safe yield of 20,000 acre feet annually for irrigation downstream. Capital costs of the "Grouse Creek Dam and Reservoir" was estimated at $4,130,000 (price base 1956) with an annual cost of $200,000. This represents a cost of about $10 per acre foot at the dam. DWR Bulletin No. 83 also proposes serving this area by tapping the ground water. This ground water development plan assumes the establishment of well fields in the higher yielding alluvium and improving the existing conveyance system in the service area. Costs of project are expected to vary from $3 to $11 per acre foot. DWR Bulletin 83 further states that, "however, further engineering and economic studies may show a combination of surface and ground water development to be the most desirable" (DWR Bulletin 83, Klamath River Basin Investigation, July 1964 page 125).

DWR Bulletin 83 describes the Callahan Dam which would provide flood control on the main stem Scott River but not on the tributaries. Capital cost of Callahan Dam was estimated to be $10,900,000 with annual costs of $522,000 based on 1956 prices.

A "Report on Comprehensive Planning Study," was prepared in March 1967 by McCreary-Koretsky Engineers. The report contains information on the Scott Valley area, problems of interest in comprehensive planning, a program for development, and recommendations for its implementation.



Land treatment measures will be necessary to minimize erosion in the upper watershed and fully realize the benefits from the structural works of improvement. About 28,400 linear feet of streambank protection at critical locations will be needed to minimize bank erosion and protect irrigable cropland. The installation of 60 to 70 irrigation systems and some land smoothing and grading will be necessary to prepare the land for proper irrigation. A few acres of subsurface drainage will be needed. A follow-up practice of irrigation water management will be needed to insure efficient use of irrigation water minimizing drainage problems. Conservation cropping systems will maintain cropland tilth and fertility. Costs for irrigation and drainage measures have been subtracted from the benefits as associated costs necessary for land improvement. Pasture management practices will be needed for more intensive use of the land.

Fencing of gullied and eroded areas to improve the vegetal cover will help control erosion and enhance wildlife habitat. Sound timber management and a planned program of brush manipulation, reforestation, proper grazing and wildlife management, timber stand improvement, browse propagation and browse regeneration on suitable soils would improve range forage, wildlife habitat and timber production as well as reduce the fire hazard.


A multi-purpose flood prevention-irrigation-recreation storage structure is proposed on the East Fork of Scott River approximately 4 miles upstream to its confluence with the South Fork. An earthfill dam approximately 140 feet high would provide 23,800 acre feet of beneficial use storage allocated to the following: Irrigation storage - 20,000 acre feet including 5,000 acre feet used jointly for flood prevention and recreation storage - 2,000 acre feet. An additional 1,800 acre feet of storage capacity is required for the 100 year sediment accumulation. The earthfill volume approximates 1,050,000 cubic yards.

For the 10 percent chance event, this dam will eliminate flooding on Scott River flood plain by 780 acres. For events as large as the 1 percent chance this dam would reduce the number of acres flooded by 547 acres.

About 30 miles of concrete lined canal will deliver irrigation water to 8,820 acres of irrigable land. Utilizing the existing distribution systems of the Scott Valley Irrigation District and the Farmers Ditch Group would help reduce the cost of constructing the irrigation distribution facilities. Turnouts will be provided for an estimated 80 farms in the service area.

The recreation pool will have 155 acres of surface area and a depth of 13 feet above the sediment pool. This pool will extend about 2.5 miles in length along the East Fork Scott River and will provide 7 miles of shoreline.

To utilize the full recreational potential of the reservoir several basic facilities are proposed. They include picnic, camping and sanitation facilities. A boat launch, dock, and parking area for 20 or more vehicles are planned.

To mitigate the loss of fish habitat from construction of the dam, adult salmon and/or steelhead will be trapped below the dam and released above the dam to spawn. Traps will also be placed above the reservoir to catch the young fingerling, so they can be released downstream of the dam. An alternative would be to trap the adult fish below the dam for transportation to a nearby hatchery to spawn, and subsequently release fingerlings below the dam.

See Tables II, III, and IV for detail information.



Cost estimates for the multipurpose storage reservoir were based upon data developed from USGS quadrangle maps and from recent Public Law-566 work plans in California. Stage, storage, surface area, and dam centerline profile data were taken from California Department of Water Resources Bulletin 83, Klamath River Basin Investigation, July 1964 and supplemented by field data obtained by the SCS staff. From the recent Public Law 566 work plans, unit costs were developed and included all construction costs for placing the fill and providing the necessary outlet works.

The sediment storage requirements were based upon information gathered during the North Coastal River Basin Study (Type IV) in the Klamath River Basin. Flood prevention storage requirements were determined by using procedures outlined in SCS Technical Release No. 10 and a regional stream study for the Klamath River Basin. The effects of the proposed structure on the Scott River Flood plain was determined by a computer study. The computer programs (water surface profiles - FW -HD1-1130F and hydrology TR-20 - FW-HYI-1130F) were used to evaluate the effects of several dams including East Fork Scott River dam within the Scott River drainage. Procedures outlined in SCS Technical Release No. 21 were used to estimate the net irrigation requirements.

Construction costs for the irrigation distribution system were based upon unit cost estimates used in similar watershed investigations in Scott Valley. A unit cost per acre was derived and then applied to the East Fork Scott River Watershed.

Costs for engineering services were estimated to be 23 percent of the total construction cost. Project administration was estimated at 1 percent of the total construction cost.

Land easements and rights-of-way were based on estimates secured from local SCS personnel. Costs for relocation of utilities were developed from existing PL-566 Work Plans and are based on a percentage of the construction cost of the distribution system. Unit prices for road relocation are based upon a recent cost study by the SCS State Office Design Unit.

Operation and maintenance costs for East Fork Scott River dam and irrigation distribution system are based on factors developed in California and used in PL-566 watershed planning. An annual lump sum was included to cover maintenance personnel and equipment and necessary secretarial help.

See Tables V, VI and VII for detailed information.



Under present conditions, Scott River will inundate about 11,580 acres of flood plain in Scott Valley from a 10 percent chance event. By controlling the runoff from East Fork Scott River, the effect of this project on the Scott River will be to reduce flooding by 780 acres for the 10 percent event. The flooding will be reduced for events greater than the 10 percent chance, but to a lesser degree. The reduction in flooding along the Scott River from a 1 percent chance event would be about 547 acres.

Average annual flood damage reduction benefits occurring primarily to agricultural crops, roads, bridges and sediment in the flood plain total $20,600 annually. In addition, $31,200 of agricultural enhancement type benefits were allocated to flood prevention and included in Table VII.

With adequate water available for the irrigation season and protection from flooding of the lower lands, farm operators will be able to increase their net income on 8,820 acres of farmland. The difference in net income with and without the project, less the associated cost for irrigation, allowing for a 5 year straight-line lag in accrual, total $623,400 annually. Of this amount, $592,200 was allocated to irrigation.

Recreation benefits accruing to the 156 acre recreation pool at the multiple-purpose reservoir will amount to $53,000 annually, assuming a 5 year straight-line delay in accrual and a recreation day value of $1.50. An annual total of 39,000 visitor days was the estimated full use at this site.

Secondary benefits were estimated to be ten percent of primary flood prevention, recreation and irrigation benefits. These secondary benefits total $69,700 annually and were local in nature. Secondary benefits from a national viewpoint were not considered.

The benefit-cost ratio is 2.4:1.0 for the overall project not considering secondary benefits. A summary of benefits and costs is given in Table VII.



Combining this watershed and French Creek watershed into one project would have many advantages. By controlling the runoff from a greater portion of the Scott River watershed the computer study revealed a reduction in flooded acres on the flood plain would be 1,180 acres from a 10 percent occurrence. An adequate supply of irrigation water could be distributed to 11,320 acres from a combined development of these watersheds. Such a project would have a federal cost of less than $4,500,000. The combined watershed would be 199,250 acres which would permit development under Public Law 566

Consideration should be given to the development of a flood control plan for the entire Scott Valley area. At the present time there are four other watersheds in Scott Valley - French, Etna, Kidder, and Moffett Creeks - that are under preliminary investigation as potential PL-566 projects. Channel improvement on the main stem Scott River was investigated briefly with the assumption that 5 multi-purpose dams, controlling 30 percent of the drainage area and having a combined flood control storage of 17,500 acre feet, would be installed. Complete flood protection could be provided at the 10 percent chance event with a reduction in flooding of 9,600 acres on the main stem Scott River because of channel improvements alone. Five dams would reduce flooding by 5,000 acres on the tributaries and 2,000 acres on the main stem Scott River. Capital cost of channel improvement on Scott River was estimated at $2,102,000 with an annual cost of $138,100.

If the valley is planned as one unit, additional storage and releases should be considered at all potential reservoirs for fisheries enhancement. Also adequate planning would be needed to guide the type of development which would take place on the flood plain in Scott Valley. Although a 10 percent chance event is considered adequate for agricultural purposes in this valley it is not intended to provide sufficient protection for residential types of improvements.

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Table 1. Estimated Average Annual Flood Damage - East Fork Scott River Watershed, Klamath River Basin


Damage (Dollars)



Crop and Pasture


Other Agricultural




Road Bridge and Channel






Table 2. Structural Data - East Fork Scott River Watershed, Klamath River Basin

Dam Site

Grouse Creek

Drainage Area

57.4 sqmi

Estimated Height of Dam

140 feet

Estimated Volume of Fill

1,050,000 cubic yards

Emergency Spillway Type


Max. Surface Area Emergency Spillway Level

475 acres

Concrete lined irrigation distribution system

8,820 acres

Recreation Facilities

Boat launch and parking area

1 each

20 acre parking area

1 each



475 acres


1 facility

Table 3. Planned Reservoir Storage Capacity (in acre feet) - East Fork Scott River Watershed, Klamath River Basin

Reservoir site

Drainage Area

in sq miles

Sediment Storage

Recreation Storage

Flood Prevention and Irrigation



Grouse Creek







Table 4. Estimated Structural Cost - East Fork Scott River Watershed, Klamath River Basin, in 1970 price base dollars

Structural Measures

Amount Planned

Estimated Total Cost in Dollars


Multipurpose dam

1 each


Irrigation Distribution System

8820 acres


Recreation Facilities

lump sum


Fish and Deer Mitigation Measures

lump sum


Sub total construction


Engineering services


Land, easements, and rights-o-way


Project Administration


Total Structural Measures


Table 5. Distribution of Structural Cost - East Fork Scott River Watershed, Klamath River Basin, Installation Cost in Dollars (price base 1970)


Engineering Services

Land Rights

Project Administration

Installation Costs

Multipurpose Reservoir

Flood Prevention






Agricultural Water






Recreation Storage






Sub totals






Irrigation Distribution System





Recreation Facilities






Fish and Deer Mitigation Measures












Table 6. Annual Cost - East Fork Scott River Watershed, Klamath River Basin, in 1970 price base dollars


Amortizaiton of Installlation Cost (100 yrs @ 53/8% int)

Operation, Maintenance and Replacement Cost






Irrigation Deliver Sys.




Recreation Facilities




Mitigation Measures








Table 7. Comparison of Benefits and Costs for Structural Measures - East Fork Scott River Watershed, Klamath River Basin in price base 1970 dollars, benefits and o & m adjusted normalized prices

------------------ Average Annual Benefit -----------------


Damage Reduction





Average Annual Cost

Benefit Cost Ratio

Multipurpose Reservoir








Table 8. Cost Allocation And Cost Sharing Summary - East Fork Scott River Watershed, Klamath River Basin, in 1970 price base dollars

Cost Allocation

Cost Sharing





Flood Prevention