SECTION OF IRRIGATION AND METEOROLOGY. 
11 
water coming through the supply ditches, or from the water sheds. 
The three lakes, Rigden lake, Loomis lake and No Name lake, where 
the loss is most evident, are cases where the water sheds are small. 
In the other cases, it was not thought that water could have come 
from the water shed, hut it may be possible. 
’ § 12. The loss from seepage during the months the lakes were 
measured, is evidently small. During the remainder of the year the 
loss will not be much more rapid, but the greater depth of water 
usually in spring increases the rate. When the lakes are nearly full, 
the water then covers some ground less completely protected by silt, 
but in the course of repeated fillings the whole lake bottom will 
reach much the same condition. 
§ 13. In the Rigden lake, the loss from seepage appears to be 
about 2 feet per year ; in the case of the No Name lake not quite so 
much ; in reservoir No. 2, during the period when gain was not 
noticed, at the rate of 13 feet per year. The loss from the last lake 
is looked upon with doubt, but no cause other than seepage has been 
established. 
§ 14. As a whole, the losses from the lakes under observation 
have been small ; less than the evaporation, and less than expected. 
In some other places that have not been subjected to careful obser- 
vations, the loss has been much greater than found in these reser- 
voirs. Numerous small reservoirs known to the writer have been 
abandoned for storage purposes, because the loss was so great. In 
the southern part of the state, one instance was found where a depth 
of 27 feet is reported to have disappeared between October and the 
following March. Yet in these cases much of the loss has doubtless 
been due to filling the adjacent subsoil, as well as to seepage proper. 
§ 15. In most of such cases, though the loss is so large at first, 
it may grow less with succeeding years after the adjacent subsoil is 
once filled. This may be expected to be the case where there are 
extensive beds of sand under and surrounding the reservoir. These 
beds absorb about one third of their volume of water, and continue 
to absorb as long as there are connected bodies of sand into which it 
can flow, or other outlets. Where the reservoir is small and the 
sand bed is large, the amount of water taken up in this way may be 
large and cause the loss from the lake to be excessive. When, how- 
ever, the sand is filled, the draft on the lake is much less, the loss is 
reduced, and the sand holds water with success, as is shown by the 
lakes in sand hills, or by the holding power of sand embankments. 
§ 16. In these and other cases the losses may be lessened. For 
since clay or fine material offers great resistance to the passage of 
water, only a thin layer of clay or fine sediment ‘is required to greatly 
diminish the loss of water. One of the most efficient means, there- 
