48 
of reservoirs. The seepage of the district is probably not equal to 
the 25 claims for 132.83 cubic feet per second. 
Seepage measurements on the river show that the return waters arc 
probably close to 50 cubic feet per second, but much water does not 
reach the river, being taken up and diverted from the small draws and 
depressions where it first appears. As will he seen on the map, the 
seepage ditches, represented by the broken lines, do not head near the 
river, hut under and near some of the large canals. This water does 
notappear in the measurement of the river, and its quantity can not 
be determined. It probably equals the amount which does reach the 
river, and the two should then equal 100 cubic feet per second. With 
an average How, as shown heretofore, of 237 cubic feet per second, 
the seepage water would equal -12 per cent of the flow, and that 
returning to the river would be 21 per cent. On the Cache la 
Poudre River the return water, according to the investigations of 
Professor Carpenter, of the agricultural experiment station, is 30 per 
cent. Sufficient measurements of seepage have not been made on the 
Big Thompson to give more than approximate figures, but from data 
at hand 21 per cent seems at least a conservative estimate. In prac- 
tice it is found that the Hill and Brush, the Hillsboro, and the Evans 
Town ditches are supplied largely during the latter part of the season 
with seepage water. The great value of seepage water is that its 
greatest flow occurs at the time of least flow in the river and supplies 
water when most needed. 
In the consolidation of ditches it will always be necessary to main- 
tain some on the lower river to take advantage of the return water. 
One large high line ditch on each side of the river with one or more 
seepage ditches below should be all that is necessary. The only objec- 
tion to the use of seepage water appears to be that it is often quite 
strongly impregnated with alkali, and on evaporating leaves alkali 
deposited on the land. On the Big Thompson there appears to be 
very little trouble from this, because of the small amount of alkali in 
the district and because much of it has already leached and passed 
away. It has been observed that lands ruined by alkali have in time 
recovered and the alkali has almost entirely disappeared, the water, 
surface and underflow, passing through the soil Inning carried away 
most of the surplus. Much of mineral matter that is required by plant 
growth is contained in alkali, and when not in too great quantities it 
is a benefit to the soil, so that the leaching done by the surplus water 
used in irrigating deprives the land in one place of beneficial ingre- 
dients, which, concentrated and deposited on other land, makes them 
worthless. There are few spots which in their natural state contain 
alkali in such quantities as to make it harmful. It is the disturbance 
of its natural and even distribution through the earth by water and 
consequent concentration in spots or on the surface that makes it 
harmful. 
