Laserfiche WebLink
<br />Mancos Formation shale underlies most of the Uncompahgre Valley. The <br />Mancos is a calcareous marine shale and is fractured and jointed near the <br />surface. During the weathering process, salts in the shale were dissolved <br />and redeposited in the joints and bedding planes of the weathered shale. <br />Residual soils formed during the weathering process and prior to leaching <br />contained the same minerals. Adobe soils contribute about 5.8 tons of <br />salt per acre. <br /> <br />Ground water movement takes place within two distinct aquifers; <br />however, evidence suggests the two aquifers interact freely, with the <br />overall water table being dependent upon both systems. <br /> <br />The build-up of ground water is accompanied by an increase in salts <br />within the soil profile. Many of these areas are clearly evidenced in <br />parts of the study area by a white encrustation of salts on the soil <br />surface. (During the irrigation season, enough water is added to the soil <br />to keep these salts flushed.) <br /> <br />Reduction of canal and lateral seepage by implementation of any of <br />the lining alternatives would lower the water table and capillary action <br />would be reduced. Rain and properly applied irrigation water could then <br />leach salt from the topsoil resulting in better vegetation growth. <br /> <br />For Lower Gunnison Basin Unit studies, samples of water and salt <br />flows were collected in the lower Uncompahgre Valley from 1976 through <br />1979. The 4 year average for these measurements and the associated <br />salinity concentrations are shown on the following table. <br />