COLORADO IRRIGATION WATERS AND THEIR CHANGES. 59 
and these return waters, for, as already clearly stated, the return 
water taken near the month of the Pondre must have come in 
within the last six miles of its course. Still it seems that the 
drain waters and these return waters are representative of the end 
results produced by water applied to onr soils, and passing through 
it to a depth of say four and one-half feet, and then finding a free 
channel of escape. These similarities are clearly shown by the 
analyses, the average percentages of which are as follows: Calcic 
sulfate in return water, 44.2; in drain water, 43.9; magnesic sul- 
sulfate in return water, 25.2; drain water, 22.4; sodic sulfate, re¬ 
turn water, 3.3; drain water, 4.3 per cent. The reason for the 
omission of the Arkansas river water at Rockyford from these 
averages is evident from what has been previously said. 
THE WATERS OF SOME OTHER STREAMS. 
§ 114. The streams of this section of Colorado including the 
Laramie, Poudre, Big Thompson, St. Vrain, Boulder, Clear Creek, 
South Platte and Arkansas, have collecting grounds of essentially 
the same character. Some of them, it is true, receive drainage 
from large parks, but these are surrounded by mountains of the 
same character as those forming the collecting areas of the other 
streams. The South Platte, for instance, receives drainage from 
South Park, but this water, springs excepted, some of which in 
this case are very rich in mineral matter and others are brines 
which at one time were used as a source of salt, comes from the 
mountains. Some of the tributaries of the South Platte carry as 
pure water as is to be found within the state. 
§ 115. The analyses of these waters will be given without 
comment, except such as is necessary to a reasonable understand¬ 
ing of the samples, some of which, like the water served to the 
town of Fort Collins, fail to represent the true character of the 
water, but represent it after the stream has become a plains 
stream and has already received enough seepage to perceptibly 
modify its composition. This applies to all the following samples 
with the exception of the Boulder and Clear Creek samples. The 
sample of Platte river water was taken from a tap in the City of 
Denver, but inquiry of the Denver Union Water Company elicited 
the fact that the water obtained was not pure Platte river water, 
but was a mixture of this with water from some other sources of 
su Pply* Tor analyses of Poudre river water see table II. 
