FARM RESERVOIRS. 



T. S. VAN DYKE. 



The following paper was read at the Pomological Society meeting 

 in Riverside, CaL, on May 4. 



' ; Many small reservoirs have been built in the last twelve years, 

 and all that I have seen or heard of have been practical failures, 

 where intended to give safe storage for water enough to irrigate 

 any considerable area of fruit trees in full bearing. Small reservoirs 

 differ from large ones only as small fish do from large ones. Both 

 demand genuine water and decline to work on wind. Most of the 

 mistakes have arisen from not considering the difference between a 

 pond that you may fill several times in the growing season from sum- 

 mer rains, or flowing streams, artesian wells or some pumping system, 

 and those that receive little or no water during the irrigating season, 

 but must depend upon the winter floods. The latter will almost al- 

 ways be failures, unless built on a scale entirely too expensive for an 

 ordinary ranch. Much money and time have been wasted on them, 

 and many trees planted to be of no use. With the return of the usual 

 rainfall and a series of good years this experiment will again be pop- 

 ular, and in time be almost certain failure, even in years of fair rain- 

 fall. As a rule, water can be reservoired most cheaply on the largest 

 scale. The small scale is both expensive and unreliable. 



Consider first, that it takes an acre a little over fourteen feet deep 

 to hold an inch of water that is, for a year, or 365 twenty-four-hour 

 inches. It takes a very good basin with a fairly flat floor to hold an 

 average depth of water equal to one-third the height of the dam. 

 Such basins as you are likely to find for farm use will not hold over 

 one-fourth of the heights of the dam, and in many the average depth 

 of the water back of the dam will not be over one-fifth, as where there 

 are many sloping points jutting into it, with mounds or ridges in the 

 bottom. 



Taking the mean of these, or one-fourth for the average depth of 

 the flowage back of the dam, it would require a dam fifty-six feet high 

 te hold an inch if the water surface were one acre; twenty- eight feet 

 high if the surface w r ere two acres, and fourteen feet high if the sur- 

 face were four acres. 



You see at once this is quite a pond, and yet we have not allowed 

 for evaporation. This is about four feet for the year on an average 

 throughout the country, of which nearly three feet will be in the dry 

 season. If this came off the bottom it would be trifling, but it comes 

 off the top layers, and amounts to 15 or 20 per cent, of the supply. In 

 this way you can easily judge of the value of a res3rvoir if you know 



