Temperature of Water for Irrigation 249 



one time, and especially if a flooding system were 

 adopted by which the cold water were kept moving 

 over the ground in the growing season during several 

 days, the temperature of the soil might easily be 

 brought so low as to seriously interfere with normal 

 growth. 



The dangers, however, from using cold irrigation 

 waters are not as great as might at first be supposed; 

 and it is seldom, where good judgment is exercised, that 

 the low temperature of the water of wells and springs 

 need prohibit its use for the purposes of irrigation. 



In the first place, there are few cases where the 

 temperature of well or spring water during the irri- 

 gation season will be found as cold as 45 F., the 

 more usual temperature being nearly 50 or above. 

 In the second place, water warms very rapidly during 

 bright summer days, when spread over the surface 

 of the ground, or when led along furrows, and even 

 while flowing through ditches, for it absorbs the direct 

 heat from the sun readily, as the rays of light pene- 

 trate it, and is further indirectly warmed by the 

 balance of the sunshine which, passing through the 

 water, is arrested by the dark soil beneath. While 

 the water is flowing over the surface of the ground, 

 if its temperature is below that of the soil, it really 

 stores much heat which otherwise would be lost, be- 

 cause relatively much less will be lost by radiation 

 from the hot surface of the soil and stored in the 

 water, leaving less to pass away from the dry ground 

 whose immediate surface becomes very warm, and 

 hence fitted to lose heat rapidly. 



