CHAPTER VIII 
CONDITIONS AFFECTING THE PLANTING OF WATER 
CATCHMENT AREAS 
In considering the advisability of afforesting a water catch- 
ment area, the principal points to be ascertained are the 
acreage and situation of the land that will prove suitable 
for planting and the species that ought to be employed. 
Before drawing up any scheme a preliminary survey of the 
ground is necessary, careful attention being paid to the 
different factors that influence the growth of trees. In 
other words, the altitude, shelter from wind or exposure, 
the nature and depth of the soil, and the existing vegetation 
must be ascertained for each of the different sections into 
which the area can be conveniently divided. It is very 
seldom that the whole of a watershed can be covered with 
trees. Plantations will not succeed at a high elevation 
or in exposed situations, or where the ground is covered 
with solid rock or with deep wet peat. It is generally 
admitted that the larger the block to be planted, the more 
economical will be the initial cost of fencing and planting, 
and the expense of care and management in after years. 
This argument need not be pushed to extremes in the case 
of municipally owned land, where commercial profit is not 
the sole consideration. On catchment areas where exten- 
sive schemes of afforestation seem impracticable, it will be 
advantageous to plant belts of trees or narrow plantations 
around the reservoirs and above the streams leading into 
them, and by this means diminish the risk of contamination 
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