Laserfiche WebLink
i <br />14 <br />1 These minimum flows are of special interest because of the reduced capacity <br />for dilution of effluents to the stream. <br />Notwithstanding occasional large flood discharges and substantial spring <br />snowmelt, the 550 sq. mi. catchment above the Madrid gaging station would <br />be classified as a low yield watershed. The 6 year mean annual runoff volume <br />measured at Madrid is 23,980 ac-ft and represents an average yield of 1 in. <br />I over the entire watershed. <br />f The width of the valley ranges from a few hundred to a few thousand <br />feet. Where the geometry of the valley permits, limited flood irrigation <br />is practiced. It is estimated that approximately 6000 ac-ft are diverted <br />from the stream for irrigation above the Madrid station. Irrigated lands <br />are, for the most part, located on the strath terraces. Irrigation on the <br />lower alluvial terraces is also practiced but, apparently, the small size <br />often precludes viable irrigated agriculture. Much more extensive irri- <br />gation occurs in the valley downstream of Trinidad. The stream discharge <br />in this reach is heavily influenced by the Trinidad Dam and Lake located <br />C immediately upstream from Trinidad. . <br />In addition to irrigation, water is used along the valley for domestic, <br />stock, and municipal purposes. Numerous wells are known to exist in the <br />vicinity of the study area. Powell (1952) characterizes the water bearing <br />capacity of the Raton formation as poor and suggests that, even where an <br />adequate discharge can be realized, the quality is likely to limit its <br />usefulness. Measurements of the hydraulic properties and water quality in <br />both the bedrock and alluvial terraces, conducted as a part of this study, <br />are in agreement with Powell's conclusions. Amore detailed discussion of <br />the ground-water hydrology is contained in a subsequent section. <br />GROUND WATER <br />The specific objectives of the ground-water investigation ~.vere to <br />quantify the hydraulic properties of both bedrock and alluvial water-bearing <br />materials and to characterize the quality of waters encountered. These <br />are the necessary first steps toward projecting the potential consequences <br />of mining. Of particular interest was the extent and recovery time of the <br />