is likely to be too rich in solids unless the water in the tank 

 is rain-water and not water containing an excess of solids 

 in solution to begin with. Here comes the danger of utilis- 

 ing water pumped up from a well or shallow pool of water 

 and stored in a tank for future use for watering plants in the 

 dry season. As evaporation goes on, the residual water 

 becomes more and more concentrated in soluble salts, and 

 the water used for irrigation afterwards may do more harm 

 than good. If storage tanks are made at all for irrigation, 

 and well or pool water stored in such tanks, they must be 

 made as deep as possible, or evaporation should be pre- 

 vented. But storing of water for agricultural purposes in 

 high level masonry tanks, is not a practicable project, except 

 for such purposes as irrigation of seed-bed &c. But it is in 

 the watering of seedlings specially that the question of 

 the proportion of solids in solution in the water assumes 

 importance. 



206. Quantity. The question of quantity of water 

 needed for irrigation is also of great importance. Wherever 

 canal irrigation has been introduced there raiyats feel that 

 the more water they use the better value they get for the 

 water rates they pay. This is a very serious error which it 

 is the duty of irrigation officers to dispel. By using too much 

 canal or well water one is bound to suffer sooner or later from 

 the effects of over-irrigation. The complaint is already 

 being heard, that canal irrigation has ruined large tracts of 

 land in the N.-W. P. and Oudh. It is not the fault of the 

 canals, but of over-irrigation, and of utilizing the water at 

 the driest season when it is low down, and when it contains 

 in solution too high a proportion of solids, i inch of water 

 once a month, or at most twice a month, should be the 

 maximum allowance in the cold weather, and 2 to 6 inches 

 in the dry weather, according to the period of growth of the 

 plants. From this the quantity obtained by rainfall should 

 be deducted. For rice a larger amount of water is required 



