IRRIGATION 



In the semi-arid regions west of the 100th meridiau, 

 ■with a. rainfall of from 20 to 30 inches, crops are liable 

 to be entire failures three or four years out of five; 

 while with an Irrigation plant there should not be a 

 failure one year in five. In the arid regions with less 

 than 15 or 20 inches of rain, Irrigation is a necessity on 

 most soils. Here the work has been highly organized 

 and systematized, so that the cost of water delivered at 

 the field amounts from $2 to $5 per acre per annum. 

 Under skilful management the most abundant yields 

 are secured. The most careful management is required 

 in the application of water to prevent serious injury to 

 the land and to avoid actual injury to the crop in ren- 

 dering the plants tender and liable to disease, and in 

 maintaining the quality and flavor, both of which are 

 liable to depreciate unless good judgment is displayed 

 in supplying water. 



Sources of Water Suppli/.— The principal sources of 

 water supply are streams, surface wells, artesian wells, 

 and the storage of storm waters. For small irrigated 

 tracts near cities the city water supply may often be 

 used to advantage. In other localities the nature of the 

 conditions will determine the most economical source 

 from which to obtain the water. Perpetually flowing 

 streams, if situated in such a way that water can be 

 carried to the land by gravity, have the advantage of 

 cheapness of construction and maintenance. On the 

 other hand, if the stream supplies others in the com- 

 munity, there is liable to be trouble and expense in es- 

 tablishing and maintaining water-right claims and in 

 securing water when needed for the crop. Questions 

 arising out of the water rights on streams and rivers in 

 the western states, with the various state laws, the 

 multiplicity of court decisions on the most intricate 

 legal questions— both in different states and different 

 counties along the line of the stream — the absence in 

 most states of adequate police or judicial powers vested 

 in the Irrigation commissioner, have led to the most 

 perplexing and bewildering state of affairs, and have in- 

 volved the states and individuals in enormous costs for 

 law suits, resulting in many cases in the apportionment 

 of many times the volume of the stream to the settlers 

 along its bank. 



The large planter must seek some perennial and 

 abundant supply of water, as is furnished by streams, 

 but it is safe to say that all streams of any size iu the 

 western part of the United States are already appropri- 

 ated to their fullest extent, although the water so appro- 

 priated is not all in present use. Smaller planters are 

 much more independent with some of the other sources 

 of supply mentioned above. Wells from 10 to 20 feet 

 deep, with pumps operated by windmills, or wells of a 

 maximum depth of 50 feet operated by many forms of 

 gasoline, hot air or portable engines, attached to direct 

 acting pumps or centrifugal pumps, form in general a 

 very satisfactory means of irrigating small areas. 



Over limited areas artesian wells have been very suc- 

 cessfully used. If they are flowing wells delivering a 

 considerable stream, they can be used over small areas 

 without storage reservoirs, or over much larger areas 

 with reservoirs. They should be capped in all cases, 

 where possible, so that the flow can be stopped when 

 not actually needed. 



In many places it is possible, at a comparatively small 

 expense, to construct a dam to collect the storm waters. 

 The magnitude and expense of such work will depend 

 entirely on the configuration of the surface, the area 

 of the watershed, the volume of the water to be handled 

 as well as the nature of the soil, and the material out of 

 which the dam is to be constructed. 



Methods of Raising irn^er.- Various methods are 



reservoirs which may lie below the general level of the 

 land to be irrigated. H5'draulic rams are sometimes 

 used for small areas, but these are not economical when 

 a small volume of water is at hand, as only about one- 

 seventh of the water can be collected. Open buckets 

 carried on an endless belt, operated by eitlier wind- 

 mills, steam power or even horse-power, are used with 

 success and offer the advantage of cheap construction. 

 The ordinary cylinder or plunger pumps are usually 

 employed when the water has little or no sediment, and 

 are operated by windmills or by steam or other form 



IRRIGATION 



833 



of engine. When the water carries considerable sedi- 

 ment such pumps are liable to wear away rapidly, and 

 the centrifugal pump is the most economical form to 

 use. The relative first cost of equipment for pumping 

 with windmills or with gasoline or hot air engines of 

 approximately equal horse-power is about the same. 

 The windmill, however, is dependent upon a mean ve- 

 locity of wind of about eight miles per hour, while the 

 engine may be operated at any time, and is thus more 

 reliable when either form of motive power is taxed to 

 nearly the extreme limit. There are many kinds of 

 windmills ou the market, and many forms of home-made 

 construction are in use. 



Storing and Conducting Il'd/e)-.- Storage reservoirs 

 for streams and for storm waters vary in size and in 

 cost as well as in mode of construction, according to the 

 character of the land, size of area, volume of water, na- 

 ture of the material of construction, and demand for the 

 water. The construction of such reservoirs sometimes 

 involves engineering problems of the most difEicultkind, 

 demanding the expenditure of immense sums of money. 



In the use of windmills it is necessary to have small 

 distributing ponds or tanks, as the direct fiow from the 

 pump is usually so small and varies so much with the 

 velocity of the wind that it cannot be depended on to 

 water any considerable area. Where it is stored it can 

 be turned out onto the land in large volumes, so that it 

 spreads over the surface and waters the whole area uni- 

 formly. For an ordinary windmill the ponds are from 

 50 to 100 feet square. They can be stocked with fish and 

 thus be a source of some revenue and variety in the 

 family supplies. Unless the pond is situated on a slight 

 elevation, the earth for the embankment must be taken 

 from the outside. The banks are usually made with a 

 slope of IH to 1 foot. For a bank 5 feet high and 2 feet 

 across the top, the side would be about 7^ feet and the 

 base about 17 feet wide. If the ground is at all pervious 

 to water, the bottom of the pond should be protected 

 from undue seepage and loss of water by puddling. This 

 should be done with clay, if this is obtainable. This 

 puddling is often done by driving horses or cattle 

 in the ])ond while the surface is wet. A pond of the size 

 indicated above, operated by a windmill where the mean 

 wind velocity is about 8 miles per hour, will irrigate 

 from 3 to 5 acres of land in the semi-arid regions. Such 

 a pond could be counted upon to irrigate from 5 to 10 

 acres where, as in the East, only one or two irrigations 

 would be required during the season. The size of the 

 reservoirs and the area they will irrigate, when supplied 

 by steam or other kind of engine, will depend upon the 

 available water supply and upon the size of pump and 

 power used. 



Ditches and Flumes. — The water is usually carried 

 from the stream or storage reservoir by gravity in open 

 ditches. This Involves loss by evaporation from the sur- 

 face and by seepage through the soil. When the water 

 supply is limited and its value is consequently great, 

 terra -cotta pipes, iron pipes, cement or %vooden pipes 

 may be used. When the surface of the country is uneven 

 and ravines have to be crossed, flumes are used to carry 

 the water on an even grade across the depression. 

 These flumes may be iron pipes, open wooden troughs, 

 or wooden pipes held together with substantial hoops. 

 If the depression is not too great the ditch may be built 

 up on an earth embankment. When the water has to 

 pass through a gravelly soil, or when for other reasons 

 the soil is very pervious, special precautions should be 

 taken to prevent seepage by using pipes, cementing the 

 sides of the open ditch, or puddling the ditch with clay 

 or similar material. 



Application of Water.— The water is usually applied 

 to the ground by flooding over the whole surface. For 

 this purpose the surface must be perfectly level and the 

 ground carefully prepared, so that the water will fiow 

 uniformly and quickly over the entire area and be of 

 uniform depth throughout. Where crops are cultivated 

 in rows or on beds the water is allowed to fiow down in 

 the troughs between the rows, and there must be a suf- 

 ficient head of water to reach the end of the rows in a 

 reasonably short time, so that the whole width of the 

 field will be properly watered. 



Where the surface of the ground is so uneven that 

 surface flooding cannot be used, basins are formed by 



