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PAST AND PROJECTED POPULATION STATISTICS AND WATER DEMAND PER SECTOR
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Source: Texas Water Development Board, "Summary Historical Water
USe 2000" (2003); and Texas Water Development Board, Water For Texas 2002 (January 2003), 29.
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Texas water is divided into surface water -- water held in streams, rivers and reservoirs -- and groundwater,
whether in deep underground aquifers or shallow local aquifers. Using both resources, Texans consumed an estimated 16.43 million acre-feet in domestic and
commercial use, manufacturing, mining, irrigating, watering their livestock, and providing electric power*.
Texas has only one natural lake-Caddo Lake in East Texas. The other 6,700 lakes are reservoirs that have
been constructed by humans.* About 97 percent of the surface water consumed by Texas is drawn from 211
reservoirs that each hold more than 5,000 acre-feet of water.*
While these reservoirs have the capacity to hold some 35 million acre-feet, according to the State of Texas's
2002 Water Plan, Texas currently has 14.9 million acre-feet of "firm-yield" water available in its rivers and reservoirs during a drought year. However, the TWDB
estimates that only 8.6 million acre-feet of surface waters can currently be used because of restrictions in infrastructure capacity, water permits and contracts .
At present, the state uses about 75 percent of this "available" surface water. For example, in 2000, Texas used 6.4 million acre-feet of surface water.*
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FYI
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What in the Heck is an Acre-foot?
An acre-foot of water is an area about the size of a football field
covered in one foot of water. To be more precise, it is equal to 325,851 gallons of water.
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Texas also has an estimated 3 to 4 billion acre-feet of groundwater
stored in 9 major aquifers and 20 minor aquifers, underground natural rock formations that hold groundwater. However, only about 10 percent
of this groundwater is recoverable through the use of traditional technology.* Each year, about 5.3 million acre-feet of annual rainfall
recharges the state's aquifers. In 2000 the estimated 10.03 million acre-feet of water pumped from underground exceeded natural recharge
- the downward replenishing flow of rainfall through the soil to the aquifer.*
Between 1930 and 1980, statewide water use increased more than fivefold, from 3 million to about 18 million acre-feet
per year. Over the same period, the population more than doubled, growing from 5.8 million to 14.2 million.* Between
1980 and 1990, however, statewide water use actually declined to 15.7 million acre-feet, largely because the number
of irrigated acres declined. Between 1990 and 2000, water use increased slightly, totaling about 16.43 million acre-feet. With the exception of irrigation for agriculture, which is expected to continue declining, all of the major use categories- including steam electric power, municipal and industrial use - are likely to increase, according to the 2002 Water for Texas plan. In fact, assuming drought conditions, the plan estimates that total demand for water will increase by some
18 percent -- to 20 million acre-feet -- between 2000 and 2050..*
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2000 WATER USE IN TEXAS
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CATEGORY
OF USE
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TOTAL
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GROUND-
WATER
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SURFACE WATER
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% OF TOTAL
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Irrigation
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9.77
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7.88
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2.75
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59.5%
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Municipal
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4.08
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1.36
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2.72
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24.8%
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Manufacturing
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1.42
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0.36
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1.06
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8.7%
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Power
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0.62
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0.09
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0.52
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3.8%
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Mining
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0.24
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0.14
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0.09
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1.4%
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Livestock
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0.30
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0.12
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0.18
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1.8%
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Total
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16.43
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10.03
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6.40
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100%
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In millions of acre-feet
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Source: Texas Water Development Board, "Summary Historical Water
Use, 2000," 2003.
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Of the 16.43 million acre-feet of water Texas consumed in 2000, groundwater supplied 10.0
million acre-feet, or about 61 percent, with surface water provided the rest .* Almost 95 percent of the groundwater came from 9 major aquifers; the remaining 5 percent was drawn from 20 minor aquifers.* The consumption pattern for water
pumped from the ground is different from the pattern for water taken from rivers and reservoirs. Irrigation used about 79 percent of groundwater,
while municipalities and their residents used less than 14 percent in 2000.* In contrast, that same year municipalities consumed 42 percent of all surface water, manufacturers consumed almost 17
percent, while irrigators utilized 28 percent .* The share of water demands met by groundwater and surface water has changed over time. Groundwater
use has dropped from 70 percent of all water used in 1974 to 61 percent in 2000. Water use also varies geographically.
While most of West Texas relies principally upon groundwater -- with a few exceptions like El Paso County which has
moved increasingly toward use of surface water-- most of South, North and East Texas rely upon surface water for the majority of their uses.
Reliance on groundwater should continue to decline for two reasons. First, the decline of agricultural acreage overall
has reduced the number of irrigated acres in the state, and the acres dropped were almost all irrigated by
groundwater. For example, total irrigated acreage declined from 8.6 million in 1974 to 6.1 million in 1989. Since then,
there has been only a slight increase in the number of acres irrigated and a slight decline in total water used. Second,
many of the large metropolitan areas are converting to surface water or mixing groundwater with surface water.* For
example, Houston has gradually switched from groundwater sources because of subsidence problems-the ground is
actually sinking as water is pumped out. El Paso and Midland have been switching to surface water because of the
increasingly elevated salinity-and declining quality-of groundwater resources, although groundwater continues to be an
important source for these cities. Though this trend is expected to continue, groundwater will still supply most of the water for large, arid areas of the state.*
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