Date of Award:

5-1956

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Department name when degree awarded

Irrigation and Drainage Engineering

Committee Chair(s)

C. H. Milligan

Committee

C. H. Milligan

Abstract

Accurate forecasts of stream flow produce direct benefits for the populace of a watershed which can be measured in terms of cash income. In 1946 in Deschutes and Crook counties of Oregon, the stream flow forecast based on snow surveys indicated appreciably greater than average runoff to be anticipated during the course of the subsequent irrigation season (10). Accordingly, some 6500 acres of agricultural land in the area, normally not cropped, were seeded and successfully irrigated. The cash value of crops, grown on this usually unproductive land, was estimated to be more than half a million dollars.

Conversely, when short water supplies are indicated appropriate steps in crop planning may be intelligently undertaken. Such steps may include a reduction in the acreage of irrigated land, development of alternate water supplies, or the production of early maturing crops which do not require late season irrigations. A successful forecast also allows time for adequate planning of reservoir operation and power production. Contemporary forecasts for the Bear River at Harer, Idaho, lack the inherent accuracy for complete realization of all of the benefits accruing from reliable streamflow predictions.

At the present time (1) more than half a million acres are irrigated from the Bear River and its tributaries, of which approximately 140,600 are located upstream from Harer (figure 1). During the three hundred mile journey of the river from the Uinta Mountains through Utah, Wyoming and Idaho to Great Salt Lake, the river crosses state boundaries five times. Immediately below Harer, Bear Lake has been utilized as a storage reservoir since 1902. An extensive network of reservoirs and power plants below Bear Lake have had a profound effect upon irrigation and power development.

The interstate nature of the river has caused problems of equitable distribution which have become more complex with the passage of time. In order to utilize the flow of the Bear River in the best possible interests of all concerned the Tri-State Investigations were instituted in 1943. The investigations were to be undertaken jointly by the United States Geological Survey, the Bureau of Reclamation, the states of Utah, Wyoming and Idaho together with other water users on the river (1). Intensified river development coupled with interstate appropriation difficulties indicate the necessity of an accurate estimate of stream flow in order to facilitate annual basin wide planning of crop requirements and stream regime.

An accurate forecast for the basin above Harer would provide additional information for the operation of the largest reservoir in the Bear River system, in addition to guiding cropping programs in the watershed. This thesis has such a prediction as its primary objective. Incidental to providing main stem forecasts, tributary predictions can be realized in the determination of their contribution to the total volumetric flow at Harer, Idaho.

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