12 
Colorado Experiment Station 
increased only from 54 to 8.9 grains per imperial gallon though farms 
and pastured meadows border a large portion of its course and the 
three towns of Del Norte, Monte Vista and Alamosa are located on 
its banks. In addition to these factors, which usually cause radical 
changes in the character of our river waters, the Rio Grande may re¬ 
ceive waters from the Alamosa, La Jara, Conejos and other streams. 
I cannot state from what streams the river received water at the time 
the sample was taken at the State Bridge. There was some water 
flowing into the Rio Grande from the Conejos but how much I do not 
know, neither do I know whether this flow was continuous or only 
accidental. 
ANALYSES SEEM TO INDICATE THAT NO RETURN WATER FLOWS 
INTO RIVER 
The analyses of the six samples taken at different points in the 
river, the extreme points being about 100 miles apart, show no differ¬ 
ences in the character of the total solids held in solution and no dif¬ 
ferences in the quantity of solids held in solution that might not be 
accounted for by evaporation. These results are wholly different from 
those obtained in our study of the Poudre, the Arkansas and other 
streams. These results are, however, in harmony with the inferences 
to be drawn from the topography of the valley, i. e., from the fact that 
the bed of the river is higher than the valley and further that the vol¬ 
ume of the flow is decidedly less as we go down the river, at least, as 
far as the State Bridge. At this point the flow of the river during the 
months of August, September and October is usually very small, in 
fact, is never large, except during the months of flood, which are May 
and June, and, exceptionally, a part of Julv. The range of the flow for 
the other months of the year, given for the eight years of which I find 
records, is from 17 second feet in August, 1902, to 196 second feet in 
September, 1904. The usual flow is considerably under 75 second 
feet. The flow at Del Norte for the same months and years was 152 
second feet in August, 1902, and 689 second feet in September, 1904.* 
The irrigating canals take out, at times, nearly all of the water by the 
time it passes a little way beyond Monte Vista. 
If any volume of return waters finds its way into the river, it 
would follow from our results, that these waters have the same char¬ 
acteristics and composition as the river water before it is used for ir¬ 
rigating the land or while it is still within the mountain section of its 
course. This is very improbable, or, judging from our knowledge of 
the changes which take place in the waters of other streams, impos¬ 
sible. 
*These data are taken from U. S. Geo. Survey Water Supply Paper No. 240. 
C. E. Siebenthal. 
