Manitoba and North Dakota and determine what plan or plans of cooperative development would be practical, economically feasible and to the mutual advantage of both countries, having in mind domestic water supply and sanitation, control of floods, irrigation and other beneficial uses.

The Commission was asked specifically to recommend what plan or plans would best meet the above purposes and requirements, to estimate the costs, benefits and any adverse effects of carrying out such plan or plans, to recommend how the available water should be apportioned in order to achieve the above benefits, and to recommend how the cost of carrying out such plan or plans might be apportioned between Canada and the United States.

The text of the Reference from the two Governments is quoted in full in the Appendix.

SECTION II

CONDUCT OF THE INQUIRY

In accordance with its usual procedure in such investigations, the Commission appointed three senior officials from appropriate agencies in each of the two countries to its International Pembina River Engineering Board. They were experienced engineers from the Canadian Departments of Agriculture, and of Energy, Mines and Resources and the United States Departments of the Interior and of the Army. A list of the members of the Board, its Committee and participating agencies is set out in the Appendix.

The Board was directed to carry out, through appropriate agencies in the two countries, the necessary technical investigations and studies, and, to avoid duplication of effort and unnecessary expense, make use of the information and technical data acquired by the International Souris-Red Rivers Engineering Board and technical agencies in both countries.

Over the course of the next three years, as its work progressed the Board submitted five semi-annual progress reports. At the conclusion of its study the Board presented a report dated December 1964 supported by twelve comprehensive appendices. In October 1965 the Commission, after reviewing the report, asked the Board to re-examine two of the proposed plans, which called for construction of a dam in each country, and to indicate the extent to which the construction schedule might be varied in order to meet the immediate needs of each country; and to ascertain the advantages and disadvantages to each country of implementing construction in stages. The Board indicated in March 1966 that construction in stages would not be advantageous as compared to construction in three consecutive years.

The Commission inspected the Pembina River Basin, the proposed dam sites, the irrigable areas and communities that would benefit on August 12, 1962.

The Commission made the Board's report available to the public and then held public hearings at Manitou, Manitoba and Walhalla, North Dakota on June 9 and 10, 1965.

After deliberating on the Board's report and representations made at public hearings, the Commission undertook additional studies to determine the modifications required in the proposed plans in order to best meet the

purposes and requirements set forth in the Reference from the two Governments. Throughout these studies the Commission's major objectives were to:

Formulate a plan for cooperative development that would achieve a high degree of optimization of net benefits for the entire Pembina River Basin, considering all potentials for the management of its water resources;

Devise arrangements under which participation in the cooperative development would provide a net advantage to each country as compared with the advantages of any alternative courses of action available to it and under which the net advantages to each country would be reasonably equivalent; and

Determine what apportionment of water would be equitable in the light of all pertinent considerations and at the same time practicable for the accomplishment of the cooperative development.

SECTION III

THE RIVER AND ITS BASIN

The Pembina River Basin is approximately 80 miles southwest of Winnipeg, Manitoba and 160 miles north of Bismarck, North Dakota. It lies astride the international boundary between the Red River (known in the United States as Red River of the North) and the eastern edge of the Souris River Basin. See Figure 1.

Physical Features

The Pembina River Basin is approximately 130 miles long and varies in width from 18 to 52 miles. The area of the watershed west of Walhalla is 3330 square miles of which 1990 are in Canada and 1340 in the United States.

Between the Red River and the Pembina Escarpment, a distance of 35 miles, is an unusually smooth plain with regular slopes gently varying from nearly flat to 10 feet per mile. In this reach the Pembina River has cut a meandering channel 10 to 30 feet below the featureless plain which was once the bed of an ancient glacial lake.

Immediately west of Walhalla the Pembina Escarpment abruptly rises 500 feet to a drift prairie plateau interspersed with irregular hills, undulating plain, flat areas, poorly drained depressions, and the Pembina Valley.

For about 130 miles below Pelican Lake the Pembina Valley is terraced, approximately 200 feet deep and 2 miles wide. In this reach alluvial and sedimentary deposits from deep coulees have formed natural dams creating at series of shallow lakes. For the next 40 miles to Walhalla, the "V" shaped valley is characterized by slump blocks and soil creep and is about a mile wide and 400 feet deep. East of Walhalla the valley rapidly decreases in size and within 15 miles disappears. Further downstream, the river banks are at the same or slightly above the elevation of the adjacent broad flat plain.

The main stem of the Pembina River rises in Canada, flows in an easterly direction in a deeply incised glacial valley for 200 miles through southern Manitoba before crossing into North Dakota. It then winds gently to the east for a further 110 miles to its mouth on the Red River, two miles south of the

Pembina River west of Walhalla with the Pembina Escarpment in the background international boundary. It drops from elevation 2000 feet at its source to elevation 750 feet at its mouth.

Above Walhalla, the principal tributaries of the Pembina River are Badger Creek, Long River and the Little Pembina River. Below Walhalla, the Tongue River joins the Pembina a few miles above its confluence with the Red.

Climate

The climate in the Basin is characterized by wide variations in temperature and rainfall. Average monthly temperatures vary from 67°F in July to 2°F in January. Extreme temperatures of 112°F and -54°F have been recorded. The mean effective growing season is about 155 days. The average frost free period is 124 days.

The average annual precipitation is about 18 inches. Average monthly precipitation ranges from 3.2 inches in June to 0.6 inches in February. Rainfall during the growing season is rarely more than 13 inches. Severe drought conditions were experienced during the 1930's and more recently in