Arkansas Basin_Water Supply and Needs

Home Browse Search

I-I l ., .... , ~.............. r'L~'" _ J---- ....i. Section 3 Physical Environment of the Arkansas Basin ~~ ,Arkansas LB. aSln 3.1 Statewide Overview Evaluations conducted under SWSI followed CWCB's delineations of Colorado's eight major river basins, as shown in Figure 3-1. The basins include the Arkansas, Colorado, Dolores/San Juan/San Miguel, Gunnison, North Platte, Rio Grande, South Platte, and Yampa/ White/Green Basins. The purpose of this section is to provide a description of the Arkansas Basin that includes: . Geography . Climate . Topography . Land Use . Surface Geology . Surface Water . Groundwater . Water Quality . Areas of Environmental Concern, Special Attention Areas, and Threatened and Endangered Species . Energy and Mineral Resources Figure 3-1 Colorado's Eight Major River Basins Virtually all of these topics are interconnected or affect the state's water supplies and water quality - either through natural or man-made/induced factors. The topography of the Continental Divide, the backbone of Colorado's Rocky Mountains, dictates the direction of o :\SHAWN\ARKANSAS\S3 _ARKANSAS. DOC water flow either to the west or to the east for each of the river systems in the state. The Divide is also home to the headwaters of several major rivers and their tributaries that run throughout Colorado, including the Arkansas. I n contrast, over half of Colorado's land area and 85 percent of the state's population lies in the South Platte and Arkansas Basins, which contribute only about 5 percent of the flows leaving the state. These two river systems travel from the east side of the Continental Divide to the Mississippi River and ultimately the Gulf of Mexico. Groundwater resources also playa pivotal role in meeting Colorado's water needs. In 1995, groundwater withdrawals in Colorado were slightly more than 2.5 million acre-feet (AF), with agricultural users comprising about 90 percent of this amount. Overall, groundwater withdrawals by agricultural and M&I users in 1995 represented slig htly more than 20 percent of the state's total for these uses, with the remainder coming from surface water supplies. The median value for groundwater use as a percentage of total use for all counties in the state is 9 percent, with agricultural areas in the eastern plains and in the San Luis Valley in south central Colorado relying more substantially on groundwater over surface water sources (Colorado Geological Survey [CGS] 2003). The state's unique topography and climate are clearly intertwined with its water resources. Topography is an important component of water resources planning, in that it dictates the direction of natural flows within a watershed. Much of the state's precipitation is concentrated on its mountainous and western slope areas. Snowpack in the state's alpine headwaters areas provides the vast majority of water supplies, with spring runoff causing significant flow peaking in virtually all of the state's river systems. Groundwater storage and its recharge are also largely affected by the topog raphy and climatological patterns that characterize the state. Water quality can be affected by geography and various land uses including runoff from point and non-point discharge sources. For example, mining in the mountainous regions, urbanization along the Front CDIVI 3-1 a DEPAIUMENT OF NATURAL RESOURCES 11- f " .;, \r, OQ · (~, 'f ..