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<br />-13- <br /> <br />surface topography and as a deep ground water basin. We <br /> <br />wish to point out that, in our opinion, any ground water <br /> <br />closure which exists is confined to the shallow water zone <br /> <br />above the first confining layer and does not apply to the <br /> <br />deeper aquifers. Such geologic evidence, as is available, <br /> <br />indicates that the deep aquifers extend southward across the <br /> <br />State boundary into New Mexico where there are wells produc- <br /> <br />ing water from them for irrigation purposes. How far these <br /> <br />aquifers extend southward and how much water moves through <br /> <br />them into New Mexico and ultimately is drained away by <br /> <br />return flow to rivers or into other deeper formations, can <br /> <br />only be determined by extensive geological investigations <br /> <br />which are beyond the scope of this report. <br /> <br />Topography <br /> <br />The San Luis Valley, as a whole, is broad and long, <br /> <br />having a meniscus shaped profile from east to west, flat <br /> <br />across the center and sloping steeply upwards close to the <br /> <br />mountains on either side. From north to south the slope is <br /> <br />very gentle. It is traversed in a general northwest to <br /> <br />south line by the Rio Grande. <br /> <br />The Closed Basin lies in the northeast central part of <br /> <br />the valley and has the shape of a very flat, irregularly <br /> <br />oblong, shallow saucer, being enclosed and separated from <br /> <br />the Rio Grande by a low surface divide. The lowest portion <br /> <br />of the basin is referred to as the sump. In times of high <br /> <br />precipitation and runoff the water table may rise above the <br />000397 <br />