I.I. Development
of Water
Resources
5
merits and costs of water-saving devices, additions to the housing stock by
various categories, municipal water system loss and repairs, and other
pertinent factors.
Future national residential water demands, currently the largest fraction
of the total urban water usage (30-60%, depending on location), depend
on price and are expected to range from an additional 4.6 Χ 10
9
gal/yr
(14 Χ 10
6 acre-ft) at $0.20/gal to 2.7 X 10
9 gal/yr (8.3 Χ 10
6 acre-ft) at
$1.20/gal. Of this about 30% will be consumptive use and 70% returned
via the sewage systems. The Water Resources Council [1969] estimates
that the increase by 1990 for municipal and rural domestic usage will be
5.9 X 10
9 gal/yr. To put the forecasts in the proper perspective, an increase
of 4.0 X 10
9 gal/yr represents a 70-80% increase over the 1965 level of
residential usage and a 47% increase in the total municipal production.
Commercial uses (hotels, restaurants, car washes, laundries, hospitals,
golf courses, and so on) represent 10-25% of the urban water demands
and are expected to be roughly the same in 1990.
Industrial demands (7-40% of urban water usage, depending on location) for 1990 are much more difficult to predict because they depend on
future cost of water, effluent standards, costs of improving water quality,
and type of heat discharge. Howe forecast that withdrawals of water for
thermal electric generation would be 7.6 X 10
13
gal/yr in 1990 (versus
5.0 Χ 10
13 in 1970) and that consumptive use in 1990 would be approximately 2.0 X 10
12 gal/yr (versus 1.4 X 10
u
in 1970). The figures for consumptive use differ somewhat from those of the Water Resources Council
(1968) of 4.3 X 10
u
(1970) and 1.3 Χ 10
12
(1990). Indications for some
other industries are that more stringent pollution controls will prevent
water usage from increasing substantially.
As to agricultural demands, public policies in 1990 with regard to support prices for agricultural commodities and low-cost irrigation water may
change with increasing urbanization of the United States population.
Water uses for agriculture are quite sensitive to these policies as well as to
farm and processing technology. Higher prices for irrigation water in the
arid regions of the West would drastically reduce the agricultural usage of
water in 1990. For example, Howe estimated that the water usage of a
typical 860 acre farm would be reduced from 5600 acre-ft/yr to 1100
acre-ft/yr, a reduction of 80%, if the cost of water went from the current
$2-3 to $25/acre-ft. Since public investments for water in Southern California run close to $100/acre-ft, there may be some tendency to increase
irrigation water costs in the future. Reduction in price supports for wheat,
feed grains, and cotton would have relatively little effect on irrigation
water demands. Because irrigation of crops currently accounts for over
of Water
Resources
5
merits and costs of water-saving devices, additions to the housing stock by
various categories, municipal water system loss and repairs, and other
pertinent factors.
Future national residential water demands, currently the largest fraction
of the total urban water usage (30-60%, depending on location), depend
on price and are expected to range from an additional 4.6 Χ 10
9
gal/yr
(14 Χ 10
6 acre-ft) at $0.20/gal to 2.7 X 10
9 gal/yr (8.3 Χ 10
6 acre-ft) at
$1.20/gal. Of this about 30% will be consumptive use and 70% returned
via the sewage systems. The Water Resources Council [1969] estimates
that the increase by 1990 for municipal and rural domestic usage will be
5.9 X 10
9 gal/yr. To put the forecasts in the proper perspective, an increase
of 4.0 X 10
9 gal/yr represents a 70-80% increase over the 1965 level of
residential usage and a 47% increase in the total municipal production.
Commercial uses (hotels, restaurants, car washes, laundries, hospitals,
golf courses, and so on) represent 10-25% of the urban water demands
and are expected to be roughly the same in 1990.
Industrial demands (7-40% of urban water usage, depending on location) for 1990 are much more difficult to predict because they depend on
future cost of water, effluent standards, costs of improving water quality,
and type of heat discharge. Howe forecast that withdrawals of water for
thermal electric generation would be 7.6 X 10
13
gal/yr in 1990 (versus
5.0 Χ 10
13 in 1970) and that consumptive use in 1990 would be approximately 2.0 X 10
12 gal/yr (versus 1.4 X 10
u
in 1970). The figures for consumptive use differ somewhat from those of the Water Resources Council
(1968) of 4.3 X 10
u
(1970) and 1.3 Χ 10
12
(1990). Indications for some
other industries are that more stringent pollution controls will prevent
water usage from increasing substantially.
As to agricultural demands, public policies in 1990 with regard to support prices for agricultural commodities and low-cost irrigation water may
change with increasing urbanization of the United States population.
Water uses for agriculture are quite sensitive to these policies as well as to
farm and processing technology. Higher prices for irrigation water in the
arid regions of the West would drastically reduce the agricultural usage of
water in 1990. For example, Howe estimated that the water usage of a
typical 860 acre farm would be reduced from 5600 acre-ft/yr to 1100
acre-ft/yr, a reduction of 80%, if the cost of water went from the current
$2-3 to $25/acre-ft. Since public investments for water in Southern California run close to $100/acre-ft, there may be some tendency to increase
irrigation water costs in the future. Reduction in price supports for wheat,
feed grains, and cotton would have relatively little effect on irrigation
water demands. Because irrigation of crops currently accounts for over