FLOOD10483 - Laserfiche WebLink

Home Browse Search

source on the eastern side of the Rocky Mountains in south-central Colorado, the Rio Grande flows eastward for approximately 150 miles to Alamosa, and then southward to the Colorado-New Mexico state line. It flows through New Mexico to El Paso, Texas, where it becomes the international boundary between the United States and Mexico. The river originates along the Continental Divide in the San Juan Mountain Range at elevations generally above 10,000 feet. Along the Continental Divide, the river is fed by perpetual snowfields and springs. From its source until it reaches the Alamosa stream gaging station, the Rio Grande drains an area of approximately 1710 square miles. The Rio Grande meanders through the San Luis Valley, a gently sloped plain surrounded by high mountain ranges. It is a flat, open, almost treeless plain. The valley varies in width from approximately 20 to 60 miles and is approximately 100 miles in length. It is surrounded by the Sangre de Cristo Mountains on the east, the San Juan Mountains on the west, and the La Garita Mountains on the north. Rock Creek originates in the southeastern corner of Rio Grande County, which is west of Alamosa County. It flows in a southeasterly direction to join the Rio Grande south of the City of Alamosa. Zapata Creek has its source on the western slopes of the Sangre de Cristo Mountains in the northeastern corner of Alamosa County and flows southwesterly to the Dry Lakes, northeast of the county. Gato Creek is not a well-defined channel, but overland sheet flow from it flows northeasterly from the southwestern corner of Alamosa County into the area of approximate study along u.s. Highway 285. The parent materials for soils of the area come from the volcanic San Juan Mountains, with only slight amounts from the Sangre de Cristo Mountains. Soils north of Alamosa are generally poor, with the texture variation ranging from sand to clay. Adobe and heavy alkali are common. Soils along the Rio Grande are quite variable and are dissected into small areas with numerous gravel bars and old channels. The extensive alluvial fans have soil that is very per- vious and underlain with gravel. Along Rock Creek, the soils are dark, loamy, relatively deep, and have varying amounts of alkali. Natural vegetation consists of only a limited number of dominant species. The open pinon and juniper stands of the surrounding foothills give way to a sagebrush association around the well- drained margins of the region. On large portions of the valley floor, the greasewood association, dominated by the black grease- wood and rabbit bush, is found. The groves of trees that line the streams are dominated by cottonwoods and willows. The Rio Grande Basin lies in a transitional zone between the Gulf and Pacific rainfall provinces, with attendent complex meteorological 4