22 
BULLETIN 82. 
miles. The North Poudre canal was opened about 1884, and all 
the seepage and waste water arising from irrigation in this area 
has been washing out this tract for the past eighteen or nineteen 
years; and as Terry lake is emptied annually, and the water col¬ 
lected from the Dry creek will not average more than one-third of 
its contents when full, it is difficult to understand how it can 
furnish so very large an amount of alkali salts at the present time. 
To present this more clearly, we will give the actual quantities of 
the three salts constituting the principal part of our alkalies, 
which are calcic, magnesic and sodic sulfates. Terry lake con¬ 
tained, as the average for the two years, 1900 and 1902, 23,589.63 
tons of these salts, represented as follows: calcic sulfate, 5,859.43 
tons; magnesic sulfate, 10,616.42 tons; and sodic sulfate, 7,113.78 
tons; all calculated as anhydrous salts. The greatest amount that 
a like quantity of Poudre river water would have contained would 
have been 59.73 tons of calcic sulfate, and no magnesic or sodic 
sulfate; but we have estimated that two-thirds of the water filling 
the lake is taken directly from the river, and the amount of this 
salt would be 39.82 tons, leaving 5,819.61 tons to come from the 
Dry creek drainage area, together with all the magnesic and sodic 
sulfates. 
§ 41. I have spoken of the drainage area as though it ex¬ 
tended no further northward than the North Poudre canal; this is 
not strictly correct, but the land under the North Poudre canal is 
the most northerly irrigated land. I do not know what proportion 
of the Dry creek water is originally Poudre river water, coming 
from either the Poudre or the North Fork. 
LONG POND. 
§ 42. Dong pond lies east of Terry lake and within a mile. 
This reservoir is filled from the Larimer county ditch, and receives 
much less seepage than Terry lake. It contains about one-half as 
much water, or about 4,500 acre feet, but presents a proportion¬ 
ately smaller surface. The question, however, of concentration by 
evaporation, even in Terry lake, is one of a half-grain or less per 
gallon, and will be neglected. The changes in the water in this 
lake are much more nearly representative of those usually taking 
place than is the case with Terry lake. 
