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These quantities do not include Lower Colorado River water used in the California Region. In 1965 approximately 5.1 million acrefeet of Lower Colorado River water was used in the California Region by the Metropolitan Water District of Southern California, the Palo Verde Irrigation District, the Imperial Irrigation District, the Coachella Valley County Water District, the Reservation Division of the Yuma Project and miscellaneous users. By 1980 that quantity is expected to be reduced to 4.4 million acre-feet and is expected to remain at that level of use unless or until adequate water supplies are imported into the Colorado River system to enable an increase in use in the California Region.

Table 44.--Present and Future Consumptive Water Use

Columbia-North Pacific Region

Use in Acre Feet per Year

More than 60 per cent of the average annual natural runoff from the 11 western states originates on the public lands. Of that quantity, about 90 per cent is from Forest Service lands. Watershed programs on the public lands, therefore, can influence to a great extent the volume and quality of water yield from those lands.

In this section there will be described the measures taken to improve watershed conditions on the public lands, the amounts invested in watershed programs on the public lands and on similar non-federal lands, a summary of lands acquired by the United States for watershed protection and the potential productivity of the public lands.

Measures Taken to Improve Watershed Conditions on Public Lands.

The primary measures taken to improve watershed conditions on Forest Service lands in the 11 western states are generally categorized under the following items: gully stabilization, sheet erosion control, stabilization of dunes and blowouts, streambank and lakeshore stabilization, rehabilitation of abandoned roads and trails, and mine restoration.

The improvements under gully stabilization include special erosion and drainage measures required to stop gully formation. The measures consist of check dams and other structures or means necessary for stabilization of side slopes. From 1958, through 1966 more than 1000 miles of side slopes on Forest Service lands were treated to prevent gully developments.

Sheet erosion control is designed to reduce erosion caused by overland flow and to reduce flood hazards. The control measures include special planting procedures using extra large stocks of trees, close spacing of trees, sodding, mulching, seeding, countour trenching, contour furrowing, and others. From 1958 through 1966, about 322, 000 acres of Forest Service lands were treated to control sheet erosion.

Light soil areas on the forest lands subject to wind erosion are stabilized by constructing wind barriers, mulching sodding, planting grass clumps, and planting closely spaced, rapidly growing trees. About 3,000 acres of such areas were treated on Forest Service lands during the period from 1958 through 1966.