COST OF IRRIGATION. 



Chapter V of the Commissioners' Report is devoted to a summing up 

 of the matter in the preceding Chapter, and contains the most practical 

 portions of the report. In the first portion the Commissioners discuss 

 the question regarding 



THE PROBABLE COST 



Of irrigating the great valley of California. On this subject they say: 

 Before making any estimate of the cost of canals, it is necessary to 

 inquire how much water is required to irrigate an acre of land. It will 

 be readily understood that the quantity will depend upon a number of 

 considerations. In the first place, it will depend upon the character of 

 the soil, whether sandy or clayey; upon the character of the substratum, 

 whether pervious or impervious, and upon the depth and inclination of 

 an impervious stratum. It will depend upon the character of the culti- 

 vation. Rice and sugar fields, vegetable gardens, orchards, and meadows 

 require more water than cereals. The present staples of this country 

 are cereals. There is some cotton cultivation, which will probably be 

 extended; and with abundance of water we shall doubtless have a good 

 deal of alfalfa or lucerne grass. Every farmer will have a little or- 

 chard, and will raise the vegetables required for home consumption. 

 The evaporation is high in the interior valleys of the State — quite equal* 

 to that in Madrid, where it is about thirteen inches in July. 



THE AMOUNT OF WATER LOST 



By absorption in the bed and banks of the canal" is an unknown and 

 variable quantity, depending on the dimensions of the canals and on the 

 character of the soil. In the absence of the exact data upon these points, 

 we may, for the present, adopt the rule laid down by engineers for other 

 countries of similar climate, and estimate the loss of water from these 

 causes at fifteen per cent. The rivers in California generally run full 

 for about seven months. The rains of the Winter increase their dis- 

 charge, and the melting of the snows keeps it up, so that we may say 

 that the streams from the Sierra Nevada are well supplied with water 

 from December to August. The streams from the Coast Range have no 

 snow reservoirs of much extent, and they are generally dry in Summer. 

 Let us assume that the streams on the east side of the valley are well 

 supplied with water for two hundred days in the year, and to make up 



