Alamosa River Restoration Project

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Land use along the river is predominately agricultural, and most of the lands through which the river passes are privately owned. Principal crops include alfalfa, small grains, and potatoes. A small fringe of land near Terrace Reservoir is owned by the U.S. Forest Service (USFS) and the U.S. Bureau of Land Management (BLM). Flood irrigation and center pivot sprinkler systems are used to water crops. Cattle and sheep are pastured in meadows and in the riparian areas, many of which have been grazed excessively. Woody species have not regenerated due to overgrazing of seedlings and saplings. Many of the old growth cottonwoods are dying from age and young growth is often lacking or absent. During the winter months of the year, the river below Terrace reservoir is completely dry. Terrace Irrigation Company has storage rights upstream and stores all water entering the reservoir during the winter months. Spring and summer discharges from Terrace Reservoir are limited to approximately 950 cubic feet per second (cfs) by the capacity of the principal outlet gates. Data from the USGS stream gauge below Terrace Reservoir indicates that the 1.5 yr return frequency flow is 605 cfs. This return frequency flow is often equivalent to the "Bankfull" discharge for unregulated watersheds. A total of twenty seven ditch companies withdraw water for irrigation from the Alamosa River starting at Terrace Reservoir and ending at US Hwy. 285. All of the water in the river has been appropriated. This leads to the stream being managed, in great part, as an irrigation canal rather than as a natural river. Although water is being diverted and the system is dewatered as it goes downstream, a significant amount still arrives at the end point of the river system to serve a senior right that exists in this geographic area during spring runoff and into the middle of summer. Regardless of how it is managed, the river still behaves as a natural stream, with sediment and precipitation being transported from the mountains to the valley floor. The water diversions and the dewatering of the system create a unique set of problems which add to the already unstable condition of the river. The origina15.5 mile project area included 19 ditch companies and 23 individual landowners. The completed 2.5 miles involved 9 of the 19 ditch companies and 11 landowners. The ditch companies that are part of the project vary in size of ownership, with the average being around 7 individual water users. The farms irrigated by these ditches are located anywhere from near the river to 15 miles away. Water Quality Problems There are two primary water quality problems in the Alamosa River: sediment loading and metals contamination. The primary sources of sedimentation in the project area are unstable and eroding streambanks. Sedimentation from erosion was identified as a pollution issue in the 1989 Colorado Non-point Assessment Report (page 115). Chemical contamination (high metals, acidic pH) comes from the Summitville Superfund site and other abandoned mines in the upper reaches of the Alamosa River. Between Terrace Reservoir and US Highway 285, the Alamosa River is on Colorado's 303-D list of water quality limited segments. The impairments to this stream segment are metals-related 6