Arizona republican., 1919-06-08

irrigation would nave on the ground waters of the project. Aided by these studies the Water Users association aas timely forwarned of the approach ing danger of water logging the lands of the valley due to the rising water plane. Wishing to forestall this men Rce the board of governors Of the Water Users association ordered an investigation and report be made by the Board of Engineers consisting of W. R. Elliott, V. w. Murphy and w. H. Code. A brief review of this report fol: lows. The complete report is now in the hands of the printer and will be ready for general distribution within the following two or three days. Copies can be secured by applying at the of flee of the Water Users association:
 Attention is called to the rapid rate at which water has been rising on DOT tions of the project during the past year. and the large area over which the ground waters are now sufficiently high to threaten the soils. We regard if of especial importance that consider alton be given to relieving this condi ton at as early date as is practicable.
 The deep water bearing strata of gravel and boulders, which are found over the greater portion of the area, give free movement of underground water. Drainage, as a result of this. becomes a general problem involving large areas rather than local one that may be applied to individual tracts. The fine textured soils which are found over a large part of the area have a high capillary power and result in bringing up water from considerable depths m sufficient quantities to dam age surface soils through Waterlogging and concentration of harmful alkali salts in them. This condition makes it necessary that the ground water be kept, at all times. below the surface.
 The results of observations since 1913 on 97 wells show the rise for the entire project to be 66 feet and for the North and South sides separately 10 feet and 4. feet.
 During the present year extensive observations have been made to de termine the rise of ground water and it's average depth over the entire pro- ject. The results of observations made on 462 wells in May and October, 1918, are matter of record. A summary of these results shows an average rise of Is feet on the North side and an aver age fall of 0.9 feet on the South side of the river. The fall was confined en- tirely to the eastern portion of the south side lands. In townships 1 North and 1 South and 1 to East, an area of approximately 73,000 acres, the av- craze fall was 1.9 feet.
 The minimum depth to ground water that must be maintained to protect the tilth and irrigability of soil and pre- vent their becoming alkaline through capillary action and evaporation, var ies for different types of soils. It also depends in a large degree upon the character of crops grown and the treatment which the soil receives. Gull tlvation tends to break upon the soils and reduces capillary action through them. A higher ground water table, consequently, may be maintained upon thoroughly cultivated soils than upon non-cultiVated ones, without increas ing the danger due to alkali accumula- tions.
 From observations in the valley it has been found in some instances, that capillary action, from depths of from 6 to feet is sufficient to bring percep- tible quantities of alkai to the surface. In other instances, due 10 different character of soils and methods of cul- tivation, little or no surface accumula- tion of alkah is noted with ths water table feet or less below the surface. From a study of these various condi- tions it is believed, for complete protec- tion of the soils, that a depth of not less than about s feet to ground water should be maintained. Areas where ground water is now 10 feet or less be- low the surface and still rising, are re- Sarded as threatened and consideration should be given to their drainage in order to prevent a further rise beyond the danger limit. The area over which ground water was 10 feet deep or less in October, 1918, is estimated at about 67,o00 acres.
 There are four principal sources which contribute to the filling up ot the subsoils of the valley as follows:
 Railfall on the irrigable area;
 Underground flow from streams;
 Canal losses;
 Irrigation.
 The first two, rainfall and under ground percolation from streams. are natural sources which have always ex- isted. Waters falling as rain upon the valley which sink below the limit ot capillary action and evaporation, and also waters which. percolate from streams or that reach the valley as un- derground flow from the adjacent mountains, become a part of the un- derground supply. A series of wei years contributes more water to the valley than a series of dry years, and tends to cause a rise of ground water A seriee of dry years, on the other hand, contributes a smaller amount tc the underground storage and permits 8 portion of that already in the subsoils 10 be carried out by natural drainage and causes a lowering of the water table. Such @hanges, however, do nof affect the aN age elevation of ground water taken over a long period O years, and it is probable that tho amount of underground water contrib uted by these natural sources is prac. ticaIly the same now as before irriga- tion was begun. The water contrib uted to the subsoils through these na, tural sources is less than the natura drainage capacity. The result of thi; is that before irrigation ground wate1 was generally well below the surfac, except on a few low lying areas inlrne diately adjacent to the river.
 During the past few months mea surements have been made of losse hy seepage and evaporation from sec tions of three of the main canals ana on four main laterals. Some of tn measurements were made above area of high ground water for which it wa believed the leakage from canals wa largely the cause, the results shoV comparatively low losses.
 Considering the amount of wate that is lost from the canals. it is no believed that a general system of linin; is feasible from an economic view point. The cost of saving water il this manner is excessive, and it is no certain if the entire canal system 0 the project were concrete lined, tha the drainage problem would be solved Underground losses from irrigation