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(Q. € t>) Q;l (,y ( (. SAN JUAN RIVER SEVEN YEAR FISHERIES RESEARCH PLAN (Year 2 - Fiscal Year 1992) INTRODUCTION Water resources in the western United States are being increasingly subjected to potentially conflicting uses. Water supply. and power production needs have been considered the primary beneficial uses of water in the west during much of this century. In recent years, as a result of changing public attitudes and legislation, including the Endangered Species Act and the National Environmental Policy Act, maintenance of fish and wildlife both sport and native, and particularly endangered species has placed competing demands on water resources and has become an important issue in water development projects. BACKGROUND. The San Juan River is a major tributary of the Colorado River in the upper basin of the Colorado River drainage. The river arises in the mountains of southwestern Colorado and exhibits several distinct geomorphic reaches as it traverses northwestern New Mexico and southeastern Utah before entering Lake Powell on the Colorado River. In its upper reaches in Colorado and the northern New Mexico, the river passes through rugged terrain, exhibits relatively high gradient with the flow generally restricted to a single channel. Approximately 50 kilometers of this section is inundated by Navajo reservoir. Near Archeluta, New Mexico, the river emerges from a canyon to meander across a broad floodplain. Between Archeluta and Shiprock, New Mexico, river gradient is relatively low and flow is generally restricted to one channel. Downstream of Shiprock, gradient remains relatively low but the river is frequently divided into several channels and permanent islands are common. This network of one or two main channels carrying the majority of flow and several smaller channels containing the remainder persists to Bluff, Utah. Downstream of Bluff, flow is generally restricted to a single channel and islands are less common. Near Mexican Hat, Utah, the river again enters canyon bound reaches and assumes a single channel with higher gradient until it reaches Lake Powell. Major tributaries in the upper basin above Navajo reservoir include the Pinos, Piedras, and Navajo Rivers. Comparatively few tributaries enter the San Juan below the reservoir. The primary tributaries present in the. 400 kilometers downstream of Navajo reservoir are the Animas, La Plata, and Mancos Rivers and McElmo, Montezuma and Chinle creeks. Numerous washes and arroyos also empty into the river, but none have permanent flow. The Animas River contributes more flow to the lower river than any other tributary. Prior to construction of Navajo reservoir, peak flows in the Animas river were almost equal in magnitude to San Juan River flows. Since the construction of Navajo reservoir which stores much of the spring runoff in the upper San Juan River, the 1