7 
The Waters oe the Rio Grande 
BED OF RIVER HIGHER THAN VALLEY 
The river has built up its. bed till it is higher than the valley. It 
does not matter to us when or how this has been done; the important 
fact is, that the present bed is higher than the adjacent territory. Un¬ 
der such condtions it may seem a perfectly simple matter that a river 
flowing O'ver a pervious bottom should lose a considerable portion of 
its water and that none could flow into it, if these conditions prevail 
in all sections of its course. The annual discharge of the Rio Grande 
at the State Bridge, is about two-thirds of its discharge at Del Norte; 
or, in flowing about 60 miles, it loses one-third of its annual flow. 
There is no other visible outlet for the waters of the valley. The dis¬ 
charge at Embudo in New Mexico, however, is much greater than at 
the State Bridge, though the river receives no considerable visible 
streams in the intervening section. This last statement is made to 
avoid the plainly legitimate inference from the preceding statement 
that the valley is being filled with water by the Rio Grande. While 
the facts to be presented may appear at times to approach very near to 
this problem, it remains entirely beyond our purpose to discuss it. As 
stated, our problem would seem very simple, if its solution depended 
wholly upon the Rio Grande waters, \rhich flow over a pervious bed 
higher than the surrounding country. Such waters should flow, as 
they actually do, for about 60 miles, oveff such a bed with small, al¬ 
most insignificant changes in their composition. 
In the'beginning of this work we proposed to treat it as an exten¬ 
sion of the work presented in Bulletin 82. This included ground and 
return-waters and had been preceded by a presentation of the compo¬ 
sition of the soil, its water-soluble portion and of the ground-waters. 
While the water-soluble portion of the soil is not necessarily identical 
with our alkalis, it is so closely related to them that it seems useless to 
insist on the difference. While I disclaim any intention to discuss the 
water-supply questions of the valley and its drainage, the smaller 
questions suggested above cannot be avoided. It is true that these 
questions are subordinate to the geological question of the drainage of 
the valley, but they involve the questions pertaining to the river and 
well waters used for irrigation, the ground waters and the alkalis. 
The waters used for irrigation in the San Luis Valley are, as in 
the Poudre Valley, essentially mountain waters, and I shall take the 
Rio Grande waters as typical of them, but I have no proper return- 
waters to present, and but few ground-waters. 
The Rio Grande has no tributary entering it from the north, 
though the valley receives the waters from a very large mountain area 
at this end. I am credibly informed that the water flowing into the 
