8141A - Laserfiche WebLink

Home Browse Search

level in the northeast corner of the Great Basin that is covered by fertile sedimentary deposits of ancient Lake Bonneville. Tertiary rocks of the Salt Lake Formation are fairly well exposed in the foothill areas of the valley and Paleozoic rocks are found in the higher mountains bordering the valley (Williams 1962). Much of the sandstone is calcareous and about 95 percent of the rocks are of marine origin. Broad terraces of silt, clay, sand, and gravel were formed as ancient Lake Bonneville receded and these alluvial deposits are still conspicuous today between the canyons of the Blacksmith Fork and the Logan Rivers. At least 35 percent of the farmland is irrigated by canals in Cache Valley, and produces about 75 percent of the total crop value in the area (Williams 1962). The climate of this area is semi-arid with about 41 cm (16 in) of precipi- tation occurring annually. The average monthly air temperature for the year is 8.60C (47.30F) with a low in January of about -4.1oC {24.60F} and a high in July of 21.60C (71.20F) (Utah Department of Employment Security 1972). The dominant vegetation of the area depends upon the altitude (Johnson 1970). Douglas fir (Pseudotsuga menziesii), Engelmann spruce (Picea engel- mannii), and sub-alpine fir (Abies lasiocarpa) are common species found on the north slopes above 2286 meters (7,500 ft) in elevation. Quaking aspen (Populus tremuloides) is common on the cool moist mountain slopes and canyon bottoms. Rocky Mountain juniper (Juniperus scopulorum) and mountain mahogany (Cerocarpus ledifolius) are found on the shallow, drier soils with bedrock outcroppings on the south-facing slopes. In the canyon bottoms along the streams, the water birch (Betu~;Qccidentalis) is found in scattered clumps. Box elder (Acer ne undo), narrow leaf cottonwood (Po ulus angustifolia), red osier dogwood Corn us stolonifera), sandbar willow Salix exigua), velvet ash (Fraxinus velutina), and balsam poplar (Populus balsamifera) are trees that are character- istic to the floodplain areas at the study sites. Common plants found at the study sites are summarized in the Appendix. DESCRIPTION OF STREAMS Streamflows of the Blacksmith Fork and Logan Rivers are primarily governed by runoff from the snowpack as the air temperatures increase from mid-April to mid-July. The drainage area of t2e Blacks~ith Fork River at U.S. Geological Survey Station 10113500 is 694 km (268 mi). The average daily discharge for 62 years was 3.65 m3/sec (129 ft3/sec) with an annual production of 115 hm3/yr (93,460 acre-feet/yr) (U.S. Geological Survey 1976). The ~rainage for the Logan River at U.S. Geological Survey Station 10109000 is 554 km (214 mi). The average daily discharge for 62 years was 3.40 m3/sec (120 ft3/sec) with an annual production of 107 hm3/yr (87,000 acre-feet/yr). These values do not include the irrigation diversion that occurs in the canyon. The average combined daily discharge of the Logan River and the major canyon diversion~ the Logan, ~Yde Park, and Smithfield Irrigation CanalA for 79 years was 7.79 m /sec (275 ft /sec) with an annual production of 246 hm~/yr (199,200 acre-feet/yr). Hydrographs of the average daily discharge and maximum-minimum values were plotted for 1975-76 for a selected U.S. Geological Survey station on the Logan River (Figure 2) and on the Blacksmith Fork River (Figure 3). In general, 4