86 BULLETIN 1358, U. S. DEPARTMENT OF AGRICULTURE 
Where storm-water reservoirs furnish the only livestock water, 
important ones may have dams containing from 5,000 to 10 000 
cubic yards or more of material. Many valuable reservoirs, how- 
ever, have been formed by dams that clo not contain more than from _ 
2,000 to 3,000 cubic yards. Yardage is not fixed by length, height, 
and width alone; pronounced variations result from differences in | 
shape of the ground upon which the dam is built and the cross | 
section of the dam necessitated by the kind of available material. 
A recent survey by the Forest Service (5), based on 592 surface 
reservoirs on the ranges of 10 national forests in Arizona and New | 
Mexico, shows an average cost of $695, with extremes of $20 and — 
215, 000. On the Jornada Range Reserve, near Las Cruces, N. Mex., 
5 small reservoirs used to supplement deep wells during wet seasons | 
were built in 1916 at an average cost of $157 each, with extremes of © 
G53 and $309 (16, p. 12). 
Many owners of large ranches handle their own “tank work.” On 
most ranches there are certain parts of the year when slack time of 
employees may be so_ utilized, although extra work animals and 
equipment may be needed. The necessary equipment may be a heavy 
investment where only one reservoir is to be built, but is a compara- 
tively small item per reservoir on large ranches where each year’s 
schedule includes maintenance or new construction. The outfit 
shown in Plate XVIII, Figure 1, represented an investment in work 
animals, harness, plows, scrapers, wagons, and camp equipment of 
approximately $3,000, and was used in repair or construction work 
on reservoirs scattered over a large cattle range. Although deprecia- 
tion on such equipment is heavy. only a portion of it is a proper 
charge against water development, since wagons, teams, and harness 
are used in other ranch activities. 
A statement of work units necessary to move given quantities of 
dirt will serve as a working basis for cost estimates at any time, 
regardless of fluctuation in cost of provisions, labor, and other items, 
whereas costs expressed in dollars and cents may soon be unreliable. 
The earth moved by a well-organized crew, using a 4-horse scraper, 
varies between 25 and 50 cubic yards a scraper a day. There is 
always much variation due to kind of earth, size of scraper, and par- 
ticularly to length of haul and time lost in moving camp from one 
reservoir to another. For estimate purposes from 35 to 40 yards per 
4-horse scraper a day should not be far off under average conditions. 
RESERVOIR MAINTENANCE 
Upkeep charges, resulting from silting, spillway cutting, under- 
cutting of end or lower base of dam, overflow, or complete ‘breaking 
of dam, frequently reach high figures in comparison with construc. 
tion costs. Where storm waters are heavily charged with silt, up- 
keep is of more concern than original cost, and every practicable 
effort should be made to minimize silting and injury to the dam. 
Seventeen representative reservoirs from 2 to 20 years old had an 
average annual upkeep of approximately 10 per cent of original 
cost. Maintenance cost is influenced by the amount of silting, dam- 
age from washouts, and prevailing costs of labor and materials. 
An annual upkeep of 15 per cent is not uncommon. One large dam 
included in the above average washed out twice in 19 years and the 
