SLV Groundwater Level Study 2007

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SAN LUIS VALLEY GROUNDWATER LEVEL STUDY O VERVIEW AND SCOPE OF WORK Davis Engineering Service, Inc. proposes to perform , as a subcontractor to CDM, a SLV Groundwater Level Study that includes two areas located near the Rio Grande in the San Luis Valley. This document is part of a request for HB140 0 funds to pay for the study. Study data collected will be of benefit to two subdistricts being formed under the authority of the Rio Grande Water Conservation District. O VERVIEW AND NEED H ydraulic Divide Study One study area encompasses the zone containing the shallow groundwater divide, commonly referred to as the “hydraulic divide ” that separates the Closed Basin in the San Luis Valley from the remainder of the Rio Grande Basin. Historically, the hydraul ic divide has been mapped as being nearly parallel to the Rio Grande lying about one to three miles north of the river between Del Norte and Alamosa. A low topographic divide also approximately paralle ls the hydraulic divide in the V alley and then follows definitive ridges to the Rio Grande Basin divide. The proposed area of study is a band parallel to the Rio Grande extending from the channel two to four miles northerly and extending from Del Norte to Alamosa as shown on the map identified as Figure 1 and included herewith . The study area is rural with areas of significant irrigation with water provided by wells, canals , and ditches . Most wells are used to supply center pivot irrigation systems. Other irrigation is accomplished largely by surface flo oding. The study area is within the floor of the San Luis Valley which is relatively level , sloping to the southeast. Davis Engineering proposes to undertake this study to aid Subdistrict No. 1 of the Rio Grande Water Conservation District (Subdistrict No. 1) in its development of a Plan for Water Management. Subdistrict No. 1 is charged with developing a court - approved Plan for Water Management that will reverse the pattern of declining aquifers and avoid the need for regulation of wells within the Sub district No. 1 by the State Engineer. A specific goal of Subdistrict No. 1 includes taking acreage in the Closed Basin out of agricultural production, thereby reducing consumption of water. Ultimately, the Subdistrict No. 1 hopes to reduce consumption of water to such an extent to halt the decline in the aquifer system underling the territory within Subdistrict No. 1 boundary . An additional goal of the draft Plan for Water Management is replacement of any depletion to senior surf ace water rights tha t result from well pumping within the Subdistrict No. 1 . There is significant legal and hydrologic importance attached to the location of the hydraulic divide. If the divide is located north of the Rio Grande, wells tapping the shallow unconfined aquifer and surface water are not administrated as being 1