10 BULLETIN 1430, U. S. DEPARTMENT OF AGRICULTURE 
of leaves and humus forms an uninterrupted cover, and the deep 
roots render the subsoil very permeable to water. 
COST AND VALUE OF REDUCTION IN EROSION THROUGH FOREST 
PLANTING 
In the Southeast there are already many reservoirs which have in 
whole or in part lost their storage capacity through silting because 
the catchment basins were not so protected as to prevent erosion of 
the soil (pi. 8) ; but, as has been pointed out, excessive erosion of soil 
is not a normal condition, and the fact that certain reservoirs have 
been impaired by siltage in no way reflects upon the value of storage 
reservoirs well located, and for which, if they are efficiently pro- 
tected, permanence can be assured. 
In the regions of deleterious erosion it is desirable for the hydro- 
electric engineer who contemplates complete development of water 
resources — that is, the utilization of storm water by storage — to have 
the benefit of a protective cover for impounding basins. It is not 
a difficult matter to compute, on the one hand, the relative value to a 
community of farm land of comparatively low productivity and on 
the other hand, that of the same land in forest supporting a perma- 
nent forest industry and affording the assurance of permanent 
power for nonforest industries. This permanency of additional 
power, obtained through storage of water, may in itself far more 
than offset the loss of the use of the land for agriculture. Water- 
power resources are essential to the continued future development 
of a region. 
There are undoubtedly cases where it would be desirable to go 
to the expense of protecting the surface of land by forest planting 
in order to obtain a reduction in erosion. In considering a policy 
of planting to protect the surface, those lands should be selected 
first which are eroding at the most rapid rate and which are so 
situated, that the detritus from their surface is deposited most 
directly in the reservoir. 
In case lands can be acquired below certain prices, these prices 
varying in proportion to the earning capacity of the lands, it will 
be possible to plant them to forest with the expectation that the 
growth of timber will pay or more than pay the carrying charges 
and interest on the investment in planting. The lands which are 
most urgently in need of planting are largely either idle farm 
lands or farm lands which are being cultivated and consequently 
are comparatively high priced. Frequently the combined cost of 
land and of planting is so high that the returns in timber probably 
would not be equal to the current rate of interest. In case it is 
found that the land can not be acquired at a price which will 
justify the purchase for growing timber alone, it may be possible 
to meet the increased costs by investing an amount which represents 
the capitalized value of the enchanced or lengthened utility of the 
reservoir. 
AN EXAMPLE 
A reservoir has an initial utility value for storage of $2,000,000 or 
32,000,000 kilowatt hours a year, the cost of storage being well within 
the limits of profits on the investment. It is determined that the 
