CLASSIFICATION IN BELATION TO WATER EESOUECES. 183 



the records for the purpose of determining what proportion of the 

 water so granted can be beneficially used for irrigation. Such a study 

 involves a determination of the duty of water, a subject which is dis- 

 cussed below. It is clear, however, that the determination ol 

 beneficial use involves an examination of the reservoirs, headworks, 

 canals, and ditches, and the amount of lands embraced in irrigation 

 systems under operation, and this is frequently a most difficult mat- 

 ter. It is the rule rather than the exception that the irrigator uses 

 more water than is necessary for the growth and maturity of his 

 crops ; indeed, his use of water is not uncommonly so extravagant that 

 the agricultural value of his land is greatly damaged. On few of 

 the irrigation systems of the West, especially the older ones, has 

 any record of the amount of water used been collected or preserved 

 or the capacity of the irrigation canals been determined. This capac- 

 ity may be variable, depending largely on the care with which the 

 canals are maintained. Thus the engineer is obliged to investigate 

 thoroughly all the working features of the systems already installed, 

 so that he may make a report as to the actual amount of water neces- 

 sary and thereby determine how much if any is available for the irri- 

 gation of new lands. Water-right matters are usually complicated 

 and a proper study of them requires some working knowledge of the 

 water laws and the decisions relating thereto. Although in many of 

 the Western States the water laws are similar, they differ in some 

 respects and some of the differences are very wide. To cover all the 

 necessary points the engineer must examine into the grants and ad- 

 judications at the county or State offices where such matters are on 

 record. Closely connected with this study of water laws is the obser- 

 vation and possibly the measurement of flow in existing canals to 

 determine seepage losses. Such losses frequently represent 50 per 

 cent or more of the water that is diverted from the streams, and it 

 is necessary to consider the question of preventing such losses so that 

 the water may be applied to lands not under cultivation. Where ex- 

 travagant use or unreasonable loss is discovered the question then 

 arises whether that water may not be filed upon for the benefit of the 

 new lands under consideration. The determination of this point 

 usually requires adjudication either by the courts or by State officials 

 appointed for this specific purpose. 



DUTY OF WATBB. 



The determination of the duty of water, or the amount of water 

 necessary to irrigate a piece of arid land suitably, is another difficult 

 task of the engineer. In some part^ o»f the West the necessary amount 

 of water has been determined by scientific study. Over the greater 

 portion of this region, however, the amount has been determined 



