IRRIGATION AND WATER STORAGE. 137 



agency of drainage, natural or artificial, or irrigation is 

 worse than wasted labor. The most effective irrigation is 

 where the soil is saturated from the surface to the subsoil, 

 and is on the move all through. Any layers of dry earth 

 under the wetted surfaces would be ruinous to the crop, 

 whether it were grass, corn, potatoes, fruit, or flowers. 

 We must soak the soil right through. 



Quantity of Water for Grass, Crops, Fruits, &c. 

 The nature of the soil and the crops will regulate the quantity 

 of water necessary. Grass may be effectively irrigated by 

 the application of 5 inches of water during a dry season 

 in which no rain falls. Sugar cane, to make a full crop of 

 40 to 60 tons per acre, requires 30 inches ; maize, 14 

 inches; potatoes, 12 inches.; orchards, 10 inches. The 

 Chinese use about 10 inches, and they water all the 

 year round. Heavy yields of wheat are got from 7 inches 

 of irrigation water. When rain falls during the irrigation 

 time, half an inch of rain has wonderfully brightening 

 effects upon the irrigated crops, and does more good than 

 double the quantity of water by irrigation. 



" But, an Inch of Water ?" For ordinary purposes, 

 25,000 gallons is reckoned as an inch, and is estimated 

 to cover an acre, 1 inch deep. Whether we get the 

 water by pumping, or by other means, we have to 

 allow for 10 Ibs. per gallon as being the weight, and the 

 calculation is useful in working out systems of pumping, 

 or carrying water over tressels, &c. An inch of water 

 saturates soil from 3 to 6 inches, according to its condition. 



Sources of Supply. There are districts in Australia 

 where snow water supplies may be made available during 

 dry spells. But the rainfall has to be depended on in most 

 cases. Hence, water storage by damming rivers, creeks, 

 and water courses has to V>e seen to. Artesian supplies are 

 available where the geological formation is suitable, and 

 very valuable experiences are being gained through 

 the wells sunk in the western districts. Wrlls may 

 supply vast quantities where springs exist. Tanks are 

 used in other places. Rivers, creeks, and lagoons, as 

 storage places, supply the best irrigation water. Wells 

 may contain doubtful mineral substances 



