Canadian Forestry Journal, January, 1919 



ture by seepage. This process takes a long 

 time and generally keeps a steady supply of 

 water flowing into the streams all summer long. 

 In effect it acts like a huge reservoir, giving up 

 its contents during the growing season when it 

 is most wanted. The "humus" acts in a similar 

 manner with rain that may fall during the 

 summer. 



Again, when the humus has soaked up its fill 

 and the water starts to run off over the surface 

 of the ground, the roots and trunks of the trees 

 so retard its speed that it cannot assume flood 

 proportions. The roots hold the soil together 

 so that the little streams cannot wash it away 



This causes floods which wash down the soil and 

 rocks into the valley bottoms, silt up farm lands 

 and in some cases has been known to cover an 

 orchard five feet deep in rocks and gravel. 

 When the snow stops melting the run-off is over, 

 but the damage has been done. No further 

 water can be hoped for from that watershed 

 unless there comes a rain and in that case the 

 run-off will be just as quick and the benefits 

 just as problematical. 



The Forest Saves Money. 

 In all cases where a watershed is tapped for 

 water for irrigation, reservoirs have to be se- 

 cured. These need only be small in the case of 



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The foe to fertile vallevs. This ncent photograph shows an almost total obliteration of the 

 valuable forest cover in the Okanagan Valley of British Columbia. View taken 

 from Kathleen Mountain, looking west. 



and so we have absence of floods and pure clear 

 water coming down into the creeks and rivers 

 in the spring. 



When Trees are Absent. 

 Now consider what happens on a watershed 

 that has been denuded of trees by fire or other 

 cause. These effects have all been actually 

 observed to be the result of forest denudation in 

 different parts of the country. The snow melts 

 quickly in the spring, as it is not sheltered in any 

 way from the sun. The bar? mineral soil has 

 very poor absorptive qualities and can soak up 

 little of the water and so the bulk of it must 

 run off over the surface in a very short lime. 



well wooded watersheds on account of the 

 steady flow of water into them as mentioned 

 above. In the case of denuded watersheds, re- 

 servoirs have to be of a huge size to hold suffi- 

 cient of the spring floods to last all summer. 

 This necessitates great outlay of money and 

 there is constant expense on account of the 

 washing down of earth and rocks and th." con- 

 sequent filling up of the reservoir. Luckily, no 

 such problems are presented in the Okanagan. 



Fires are the main cause of the forest denu- 

 dation and in several cases the flow of creeks in 

 the Okanagan has been observed to become less 

 regular with more flood water in the spring and 



