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<br />~-,,,,'-" <br />..,. <br /> <br />:"- <br /> <br />ro <br />'''-I <br /> <br />_~~" l <br />,:":l <br /> <br />THE SAN LUIS VALLEY <br />GROUNDWATER DISPUTE <br /> <br />1. <br /> <br />INTRODUCTION <br /> <br />A. The San Luis Valley Situation <br /> <br />1. The San Luis Valley in Colorado is a high elevation <br />flat plain about 50 miles across in an east and west <br />direction and 90 miles in a north and south <br />direction, filled with unconsolidated and <br />consolidated alluvial materials to a depth of <br />several thousand feet. See Attachment 1, map of San <br />Luis Valley. <br /> <br />2. It is generally quite permeable and filled with <br />water in amounts estimated at approximately 2 <br />billion acre-feet. <br /> <br />3. This system of groundwater is separated to a degree <br />into two components: the unconfined aquifer in the <br />upper one to two hundred feet; and, below a series <br />of clay confining layers, the confined aquifer. <br /> <br />4. The unconfined aquifer is under free water table <br />conditions and is in tributary hydraulic connection <br />to the streams in the areas where they flow. The <br />major portion of the San Luis Valley north of the <br />Rio Grande drains into a closed sump area where the <br />only outflows are to evapotranspirative losses. It <br />is generally conceded that this water in the <br />unconfined aquifer of the closed basin is not <br />presently tributary to the Rio Grande stream system. <br /> <br />5. The confined aquifer throughout the entire San Luis <br />Valley tends to be under artesian pressure and since <br />early in the history of the San Luis Valley has been <br />the source for many, many small-capacity domestic <br />and stock-watering wells. It is generally believed <br />to be in hydraulic connection to the surface stream <br />system (1) by receiving recharge from them in the <br />recharge gone around the periphery of the confining <br />layer along the rim of the valley floor; and (2) by <br />interruption in the confining layer allowing <br />artesian spring flow upward into the streams, <br />particularly the Conejos. <br /> <br />B. The Rules and Regulations Case <br /> <br />1. The effect on the stream flows of the Conejos River <br />and the Rio Grande of pumping in both the unconfined <br />and confined aquifers throughout the San Luis Valley <br /> <br />-1- <br />