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



These conditions, stated imperfectly and in general terms, 

 raise the question of a general underground flow out of the 

 valley. 



We have, in the case of these brown waters, an artesian 

 basin of approximately 420 square miles. The water, finding 

 its way into this area, must be brought into the valley by the 

 streams descending from the surrounding mountains which 

 carry only snow and rain water. In the other portions of the 

 valley the artesian waters are not only pure, but have the 

 characteristics of the water which we find in mountain streams; 

 in this area we find them characterized by a decided color, the 

 presence of hydrogen sulphide, accompanied in some cases by 

 marked quantities of combustible gases, probably marsh gas, 

 and containing sodium carbonate. Further, these waters are not. 

 confined to one or more horizons within this area, but all flows, 

 from the most shallow to the deepest, bear the same character- 

 istics, and the area itself has quite sharply defined limits. If 

 there be any general movement of these waters, it must be to 

 the southward, for the valley is completely enclosed by moun- 

 tains except on the south. The pressure shown by these wells 

 is in no case great. The Denver and Rio Grande R. R. had a 

 well put down at Alamosa to a depth of about 1,000 feet. 

 The flow is excellent, but the pressure is not sufficient to force 

 the water into the tank for supplying the engines, so it is prob- 

 ably less than 25 feet. Such a pressure with a head of 360 

 feet, this being the approximate difference of level between 

 iUamosa and the western portion of the valley, is not incom- 

 patible with an outflow to the southward, perhaps a hundred 

 or more miles away. 



As the characteristics of these brown waters may aid in the 

 solution of these general questions, I have paid some attention 

 to their study. 



If these waters were to pass through strata very different 

 from those of the section in which they occur, the brown color 

 would in all probability be removed, but not so with the sodium 

 carbonate, for even clayey soils have but a limited power to 

 retain sodium carbonate, as is shown by the fact that it passes 

 quite freely into drain waters from soils which contain but 

 little of this salt. 



The sanitary analysis of the brown water presented some 

 difficulty due to the organic matter present, but less than the 

 water from the San Luis lake. In the former case the 

 organic matter is probably humus, in the latter it is entirely 

 different, as it is without color and at most imparts a slight 

 milkiness to the water. The question of a possible connection 

 of the San Luis lake with the reservoir of artesian water is a 

 proximate one ; indeed it is said that the water has been seen 



