IRRIGATION 



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

 with a rainfall of from 20 to 80 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 

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

 :nost soils. Here the work has been highly organized 

 ind systematized, so that the cost of water delivered at 

 ,he field amounts from $2 to $5 per acre per annum. 

 I'Jnder skilful management the most abundant yields 

 ire secured. The most careful management is required 

 n the application of water to prevent serious injury to 

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

 lering the plants tender and liable to disease, and in 

 'naintaining the quality and flavor, both of which are 

 iable to depreciate unless good judgment is displayed 

 n supplying water. 



Sources of Water Supply. The principal sources of 

 vater supply are streams, surface wells, artesian wells, 

 ind the storage of storm waters. For small irrigated 

 racts near cities the city water supply may often be 

 ised to advantage. In other localities the nature of the 

 .onditions will determine the most economical source 

 rom which to obtain the water. Perpetually flowing 

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

 arried to the land by gravity, have the advantage of 

 .heapness of construction and maintenance. On the 

 ,'ther hand, if the stream supplies others in the com- 

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

 ablishing and maintaining water-right claims and in 

 ecuring water when needed for the crop. Questions 

 rising out of the water rights on streams and rivers in 

 he western states, with the various state laws, the 

 aultiplicity of court decisions on the most intricate 

 agal questions both in different states and different 

 ounties along the line of the stream the absence in 

 aost states of adequate police or judicial powers vested 

 n the Irrigation commissioner, have led to the most 

 erplexing and bewildering state of affairs, and havein- 

 olved the states and individuals in enormous costs for 

 iw suits, resulting in many cases in the apportionment 

 f many times the volume of the stream to the settlers 

 long its bank. 



The large planter must seek some perennial and 

 bundant supply of water, as is furnished by streams, 

 ut it is safe to say that all streams of any size in the 

 'estern part of the United States are already appropri- 

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

 riated is not all in present use. Smaller planters are 

 luch more independent with some of the other sources 

 f supply mentioned above. Wells from 10 to 20 feet 

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

 laximum depth of 50 feet operated by many forms of 

 asoline, hot air or portable engines, attached to direct 

 ^ting pumps or centrifugal pumps, form in general a 

 ery satisfactory means of irrigating small areas. 

 I Over limited areas artesian wells have been very suc- 

 3ssfully used. If they are flowing wells delivering a 

 onsiderable stream, they can be used over small areas 

 ithout storage reservoirs, or over much larger areas 

 1 ith reservoirs. They should be capped in all cases, 

 here possible, so that the flow can be stopped when 

 ot actually needed. 



In many places it is possible, at a comparatively small 

 'cpense, to construct a dam to collect the storm waters, 

 he magnitude and expense of such work will depend 

 'itirely on the configuration of the surface, the area 

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

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

 hich the dam is to be constructed. 



Methods of liaising Water. Various methods are 

 <ed for raising water from streams, wells, or storage 



^ervoirs which may lie below the general level of the 

 nd to be irrigated. Hydraulic rams are sometimes 

 : sed for small areas, but these are not economical when 

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

 :>venth of the water can be collected. Open buckets 

 urried on an endless belt, operated by either wind- 



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

 iccess and offer the advantage of cheap construction, 

 he ordinary cylinder or plunger pumps are usually 

 nployed when the water has little or no sediment, and 

 e 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 on the market, and many forms of home-made 

 construction are in use. 



Storing and Conducting Water. 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 difficult kind, 

 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 flow 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 iy 2 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 pond 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 1 

 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 Fhimes.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 wooden 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 flow 

 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 flow 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 



