306 Headden — Brown Artesian Waters of Costilla Co., Colo. 



The supply of water is furnished by the streams descending 

 from the surrounding mountains. The artesian basin has a 

 length of about 75 miles and a width from 40 to 45 miles. 

 The Rio Grande del Norte enters the valley at a point about 

 the middle of its western side and then flows easterly and 

 southerly out of the valley by way of its canyon. All of the 

 streams which enter the valley north of the Rio Grande are 

 wholly lost in the sands of the valley, their waters do not at 

 any time join those of the Rio Grande by overground courses 

 and it is a question whether they do so, at least within the 

 limits of the valley, by underground circulation. So complete 

 is the disappearance of the waters of these northern streams 

 that it is only very rarely that the united waters of the 

 Saguache river and the San Luis creek have been known to 

 reach so far south as the San Luis lake, 14 miles north and 7 

 miles east of the town of Alamosa. The Rio Grande loses 

 from 75 to 100 second feet of water on its entrance to the val- 

 ley. The streams to the south also lose large quantities of 

 w T ater as they enter the valley or daring their course through 

 it. These sources are probably quite sufficient to supply all 

 the artesian waters of this basin. 



In the eastern part of the northern half of this basin we 

 find a water wholly different from any of the springs or wells 

 previously mentioned. The water heretofore described has 

 been a colorless, tasteless water, carrying but small amounts of 

 mineral matter in solution and the chief constituent of these 

 mineral matters is silica. In this area, which begins about eight 

 miles north of Alamosa, and extends almost to the town of 

 Moffat, a distance of 25 to 30 miles from north to south and 

 extending from 5 or 6 miles west of the town of Mosca 

 almost to the San Luis lake on the east, a distance of about 

 14 miles east and west, the water has a decidedly " red " or 

 brown color, generally smells of hydrogen sulphide, is often 

 accompanied by marsh gas, has an alkaline reaction and is rich 

 in sodium carbonate. The wells sunk in this area show these 

 characteristics throughout. The flows struck at about 200 feet 

 are slightly brown, taste of hydrogen sulphide, and contain 

 about 22*0 grains of solid matter per imperial gallon, which is 

 wholly sodium carbonate. The intensity of \\iq color deepens 

 with the depth of the wells till at about 500 feet it attains its 

 maximum ; from this point the color diminishes till at about 880 

 feet it has become somewhat fainter but still decidedly colored. 

 The mineral matter, in this case sodium carbonate, increases with 

 the depth ; at 200 feet it is 22*0 grains, at 500 feet 76'0 grains, 

 and at 800 feet 103 4- grains in each imperial gallon. No 

 well sunk in this section has passed through this zone of red 

 or brown water and obtained white or colorless water beneath 



