AGRICULTURE. 19 



in economy in water, as only enough need be applied to moisten that 

 part of the soil within the root zone of crops, and it would, if gener- 

 ally practiced, be followed by improvement in the condition of the 

 lower lands now rendered worthless by seepage waters and alkali. 

 In the areas of gravelly porous soils heavy losses of water take place 

 through seepage from the canals and ditches. This condition can be 

 overcome by the use of temporary canvas lining, the installation of 

 permanent cement-lined ditches, or wooden or metal pipes. Such ex- 

 pensive methods will be found profitable only where the lands served 

 may be used in the cultivation of intensively farmed crops of high 

 market value. 



An extensive underground supply of water has been partially 

 developed. Pumping of seepage water from wells sunk in dry stream 

 beds has been successfully tested and is capable of considerable exten- 

 sion, but the most widely utilized source consists of the artesian water. 

 Artesian wells may be secured in almost all portions of the valley 

 except the upper margins, where the pressure becomes insufficient to 

 produce a flow in quantities suitable for irrigation without pumping. 

 More than 3,000 wells have already been driven, the most of which 

 occur in the southwestern and western parts of the valley. But few 

 occur east of the valley trough, and these are confined to occasional 

 stock ranches. 



The wells range in depth from 100 to 800 feet and in temperature 

 from 40 to 75 . 1 The wells of relatively high temperatures are con- 

 fined principally to the Swede Corners district and should prove of 

 distinct advantage in the irrigation of early vegetables. The water- 

 bearing strata consist of bluish or dark gray sand, alternating with 

 impervious clay. The usual well has a 3-inch casing, while larger 

 wells are of 4, 5, and 6 inch bore. The water is of good quality, except 

 in the lower part of the valley basin, where it is more or less stained 

 with organic matter and frequently charged with gas and alkali 

 salts. Here frequently the water is unfit for domestic use, although 

 usually satisfactory for stock and irrigation. In most cases the 

 wells are cased only to the depth of the first clay stratum occurring 

 below the superficial gravelly soil material, at a depth usually from 

 10 to 75 feet, the cost, including high freight charges, restricting 

 the use of pipe to that absolutely necessary. It is reported to be 

 unsafe to attempt to cap the partially cased wells so that the flow 

 may be controlled, as this tends to cause caving in of the lower 

 part of the bore. Consequently, the wells are usually allowed to 

 flow continuously, resulting in waste of water, a permanent high 

 water table, and saturation of adjacent areas. Increase in the num- 

 ber of wells, the only available source of supply for irrigation in 



1 See Water Supply Paper No. 240, U. S. Geological Survey, Geology and Water Re- 

 sources of the San Luis Valley, Colo. 



