Flows that cannot be controlled by the mountain reservoirs, as well as winter releases through the powerplants, are diverted from Weber river at the Slaterville Diversion dam west of Ogden and carried eight miles north in the Willard Canal to Arthur V. Watkins Reservoir. The earth-lined canal has an initial capacity of 1,050 cubic feet per second. About five miles from the canal heading, a turnout diverts water into the Plain City Canal, a privately owned irrigation system.
Twelve miles northwest of Ogden on the shore of the Great Salt Lake, Arthur V. Watkins Dam is an offstream structure with a structural height of 36 feet. The dam is about 14.5 miles long in a rough rectangle, contains about 17 million cubic yards of material, and encloses a reservoir of 215,120 acre-foot capacity. Its siphon spillway has a capacity of 2,000 cubic feet per second. The 300-cubic-foot-per-second capacity outlet works functions only as a reservoir drain.
During the irrigation season, water can be pumped by Willard Pumping Plants No. 1 and No. 2 back through the Willard Canal from Arthur V. Watkins Reservoir to Slaterville Diversion Dam and on into the Layton Pumping Plant intake channel for irrigation of lands lying along the shores of Great Salt Lake.