» 
INTERNATIONAL 
Figure 42—Net annual growth can be increased 
by harvesting and regenerating mature stands. 
agriculture, but there are implications 
for all users of water, especially fish 
and wildlife. Unlike most other kinds 
of water withdrawals, irrigation 1s a 
large consumer of water. In some 
places, such as the areas on the High 
Plains of Texas and adjoining States 
where ground-water mining occurs, 
water production costs will rise and the 
water for crop and pastureland 
irrigation will become less economic. 
That will induce some shifts to dryland 
farming or range grazing. In most other 
water resource regions where 
expanding water demands pressure 
existing supplies, such as California 
and upper and lower Colorado, more 
and more of the available water is 
likely to go to the higher value uses 
such as domestic and manufacturing. 
The changes in agriculture will also 
contribute to changes in land use 
around the country, with economic 
adjustments to local communities and 
established industries. For example, 
movement of more agriculture into the 
lower Mississippi Valley would add 
further pressure on the wetlands 
resource. 
46 
Irrigation based on surface water from 
streams and impoundments has 
implications for both fish and wildlife 
habitat (fig. 43). Meeting the demands 
projected for water use in irrigation 
implies that additional streamflows will 
be drawn down to the point where they 
can no longer support preferred species 
of fish or some species of water- 
dependent wildlife. 
The expected increases in population 
and economic growth for the United 
States carry with them the expansion of 
possible sources of water pollution. 
However, enforcement of national 
water quality goals should alleviate the 
potential for new sources of pollution. 
Increases in America’s population will 
also add pressures for development of 
floodplains. 
Opportunities—There are 
opportunities in local areas on forest 
and range lands to increase and extend 
water supplies, ameliorate the effects of 
flooding, and improve water quality. 
Depending on the local situation, these 
opportunities can be achieved by: 
—TImproving vegetation management 
to enhance the natural recharge of 
surface and ground water, to reduce 
evaporation and transpiration losses, 
and to change the timing of waterflows. 
—TImproving protection of watersheds 
from wildfire. 
—RMaintaining wetlands. 
In addition, 
Water supplies can be increased by: 
—Expanding and improving reservoirs 
to increase storage, regulate flows, and 
reduce evaporation. 
—Improving snow management. 
Water supplies can be extended by: 
—Improving conservation, including 
more reuse. 
Expected increases in flood damage 
can be limited by: 
—Controlling floatable debris, such as 
logging residues. 
—Increasing use of structures to 
control waterflows, providing that 
Figure 43—The Snake River, on the border between Idaho and Oregon, provides both irrigation 
and recreation. 
