34 Colorado Experiment Station 
we approach the question. The question between the states pertains 
to the waters collected within the water-shed by the Rio Grande—• 
whether the impounding of these waters will militate against the inter¬ 
ests of Mexico—and their comparisons of the flow of the Rio Grande 
at Embudo and at Del Norte are greatly to the advantafge of the citi¬ 
zens of Colorado and show that the discharge of the river at Embudo 
is largely dependent upon water which cannot be affected by the im¬ 
pounding of the head waters of the Rio Grande. 
RIVER ONLY DISCHARGE BUT NOT ONLY SOURCE 
It is not our purpose to discuss this question but to consider the 
discharge of the Rio Grande from another point of view. This dis¬ 
charge is the only one from the valley. We have seen that the dis¬ 
charge at the State Bridge shows a loss, two years out of five,* and 
at Embudo a loss three years out of four. The discharge during the 
year of maximum flow was over three and a half times that for the 
year of minimum flow, but this was also true of the discharge at Del 
Norte. The Rio Grande is the only visible discharge from the valley 
but it is not the only discharge into the valley. While it is perfectly 
legitimate to consider it in this light in discussing the interstate rela¬ 
tions of the Rio Grande waters it is misleading, as it appears to me, 
in discussing the water relations of the San Luis Valley. It confines 
our consideration to the fate of the water gathered within the water¬ 
shed of the Rio Grande as though there were no other water-shed 
around the valley, which is, as a fact, practically surrounded by high 
mountains from which waters descend into the valley. 
WHAT BECOMES OF EXCESS WATER? 
The discharge from the valley is, at best, probably no more than 
equal to the discharge of the Rio Grande into the valley. There are 
but two conclusions to be drawn in regard to what becomes of the 
excess of the discharge into the valley. It must flow out by unknown 
channels, or evaporate, or it is accumulating in the valley. The arte¬ 
sian waters do not constitute an addition to the waters of the valley, 
and all the irrigating water taken from the Rio Grande is already 
taken into consideration. 
The facts that the Rio Grande loses water instead of gaining, 
and that the composition remains practically unchanged through a 
course of 60 miles through an irrigated country are entirely compatible, 
and the latter fact excludes the accession of any return waters, for 
these, even in this valley, where they seem to be of exceptional com¬ 
position, would increase the amount of total solids in a materially 
greater degree than we find to be actually the case, and would increase 
the ratio of the sulfates. This is not true of the white, artesian waters, 
which differ mainly from the waters of mountain streams in their low 
content of carbonates of the alkaline earths. This difference between 
* See page 13. 
