R:eSERVOIRS AND PONDS. I07 



wasted, but could be diverted below for purposes of 

 irrigation. 



Such works and methods would, of course, be 

 expensive, but on the other hand their eife(5liveness is 

 unquestionable and it is believed to be by far the most 

 feasible method yet proposed for cleaning a large 

 reservoir. The tendency of an economical use of this 

 method would be to keep the reservoir open in its 

 lower part, where it is deepest, and allow the shallow 

 portions along the edges and at the upper end to 

 remain filled. This would contradl the relative area of 

 water surface and diminish evaporation, which would 

 in a measure compensate for the destru(ftion of storage 

 capacity. The use of the three methods — first, the 

 employment of one or more large scouring sluices; 

 second, the enlargement of the reservoir to the prac- 

 ticable limit; and, third, the construcftion of works and 

 the adoption of hydraulic operations — would in many 

 cases insure the perpetuity of great storage reservoirs 

 in this country within practicable limits of expense. 

 Certain it is that some efficient method or methods 

 for this purpose must be employed. Where feasible, 

 storage reservoirs can be construdled in side cartons or 

 other basins having no considerable natural drainage 

 tributary to them, the water being carried through 

 artificial conduits from the streams, the waters of which 

 it is desired to store. Where this can be done the 

 danger of filling the reservoir with silt can be easily 

 averted. Sand boxes can be construc5led along the 

 supply ditch and be easily operated in such manner as 

 to effe(5lually clear the waters of the load of solid 

 matter. Inasmuch as the surplus waters are discharged 



