Laserfiche WebLink
<br />WATER QUALITY <br /> <br />1. Surface Water <br /> <br />With the exception of Kerber, Willow, and Alamosa Creeks, which <br />are affected by mine drainage, the chemical quality of the stream <br />water is generally excellent as is typical of high mountain streams. <br />Specific-conductance measurements were made periodically on 32 <br />representative streams, and major chemical constituents were deter- <br />mined on water samples collected monthly from 14 of those 32 streams <br />during the 1967-68 water year. These data indicate the dissolved- <br />sol ids concentration ranged from 25 to 450 mg!1 (mi 11 igrams per <br />liter), and the water is a calcium bicarbonate type in streams <br />unaffected by mine drainage. Water in the streams affected by mine <br />drainage is calcium sulfate in composition. Specific-conductance <br />values exceeded 500 microhoms in only 4 of the 32 sampled streams. <br />Table D-I lists the specific-conductance values for each stream. <br /> <br />As water from the Rio Grande flows through the basin, its chemical <br />quality is influenced by many factors, such as: irrigation diver- <br />sions and return flow, tributary inflow, and ground-water inflow. <br />The water in the Rio Grande at Del Norte, where it enters the <br />basin, ranged from a calcium bicarbonate to a calcium magnesium <br />bicarbonate type, and the specific conductance ranged from 46 to <br />136 umhos/cm (micromhos per centimeter) during the I-year sampling <br />period. Above Del Norte, natural effects principally control the <br />water quality, whereas below Del Norte the use of the water for <br />agriculture, industry, and public supply, in addition to natural <br />effects, act collectively to increase dissolved solids in a down- <br />stream direction. <br /> <br />Water from various localities was sampled to determine the <br />relationship between discharge and dissolved-solids concentration. <br />In addition, historic data were employed to determine long-term <br />trends. Figure D-l shows the dissolved-solids load at various <br />locations along the Rio Grande at three different times. Generally, <br />the specific conductance increased downstream, with the greatest <br />increase occurring in the reach from Alamosa to the Mouth of <br />Trinchera Creek. The large dissolved-solids loads at Del Norte are <br />due to hi.gh discharges of relatively di lute water. As diversions <br />deplete the flow of the river, the load decreases proportionally as <br />shown. Near the Rio Grande-Alamosa County line, irrigation return <br />flow and ground-water inflow from approximately 243,000 acres . <br />(98,342 ha) cause an increase in the dissolved-sol ids load. The <br />largest increase, regardless of season, occurs in the reach between <br />Alamosa and the mouth of Trinchera Creek. From the mouth of <br />Trinchera Creek to the state line, both the dissolved-sol ids load <br />and the concentration remain relatively constant. <br /> <br />f' .... <br />1...' '.. <br /> <br />. <br />.,~'!:j; <br /> <br />D-1 <br />