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Projecting Future Demand for Water
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COMPARISON OF TOTAL PROJECTED STATEWIDE DEMANDS OF THE 1984, 1990,
1997, 2002 AND DRAFT 2007 WATER PLANS
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Source: Texas Water Development Board, Draft 2006 Regional Water
Plan Demand Projections (March 2003); Texas Water Development Board, Water for Texas -- 2002 (January 2002), 29; Texas Water Development Board, "Water Use
Projections for State and Counties in Texas" (1998); TWDB, Water for Texas 1997, (June 1997) and TWDB, Water for Texas (December 1990), 3-3.
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The current Texas state water plan was published in 2002. A comparison of state water plans over the years
illustrates how substantially projections can vary. Back in 1984, the Texas Water Development Board predicted that water demand in 2000 would reach some 25
million acre-feet assuming a low precipitation year. Just six years later, assuming the adoption of major conservation measures, they predicted water usage of
about 14 million acre-feet. In fact, in 2000, Texans used some 16.4 million acre-feet, slightly above the 1990 prediction but some nine million acre-feet below the
1984 most-likely scenario. (KEEP OTHER FOOTNOTES< ADD to FOOTNOTE: Texas Water Development Board, "Historical County Water Use, 2000" (2003)).* In fact, total water use in 2000 was close to TWDB's 1997 prediction, assuming low rain, some conservation and
continued use of farm subsidies.
Two fundamental differences between demand projections in the previous water plans and the 1997
plan are: (1) the water conservation effects vary from city to city; and (2) the conservation effects are more aggressive (greater) than in previous plans. Assuming
below-average rainfall, continued federal farm subsidies, some conservation, and the most likely population growth scenario, these projections in the
1997 plan show total demands increasing only from 15.8 to 18.35 million acre-feet over the 60-year period.*
For the 2002 plan, the TWDB used the 1997 water plan consensus-based population numbers, but then worked directly
with the 16 regional planning groups to revise these population and water use projections based upon additional information.* The 2002 plan assumes that population will reach 39.6 million by 2050 and that municipal water
use-assuming below normal rainfall-will increase more than twofold, from 3.2 million to 7.06 million by 2050.* Overall,
the most likely scenario shows total water demand increasing from some 17 million acre-feet to 20 million acre-feet by
2050. Still, there are considerable uncertainties in these demand projections.
For example, just a year after the 2002 water plan was published, current draft water demand projections developed
for the 2007 Water Plan show the population increasing to 40.8 million people -- rather than 39.6 million -- and assume
that total water demand in 2050 will reach 20.6 million acre-feet rather than 20.0 million acre-feet.* These numbers
will be revised as Planning Groups provide additional information to the TWDB. Both the draft projections for the 2007
Plan as well as the projection demand numbers for the 2002 Water Plan have been criticized for overestimating the
amount of water "demanded" in 2050. For example, the new demand projections for municipal use do not take into
account new federal and state laws and rules which should help conserve water in the future. Thus, in 2001, the state
legislature required all new multi-family and multiple use commercial operations to submeter their water use and gives
sales tax exemptions for the purchase of water saving equipment, while additional conservation measures were passed
during the 2003 Legislative Session. At the federal level, new mandates will make clothes washers met new energy efficiency standards, which should reduce water use.* Similarly, analysis of irrigation water demand projections point
out that many of the regional projections estimate greater demand for irrigation water at a time when agricultural
lands are shrinking -- not growing -- and where new technology and monies are helping irrigators become more
efficient. Thus, many believe the projected demands significantly overstate the actual needs in 2050, even in a drought-of-record year*.
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PROJECTED STATEWIDE WATER SUPPLY IN 2050 IN MILLIONS OF ACRE-FEET
PER YEAR ASSUMING A DROUGHT-OF-RECORD
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Source: Texas Water Development Board, "Water for Texas 1997" (June
1997), 3-26 and 3-93
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Estimating the Future Supply of Water
Can Texas meet all of the demands for water? Water supply projections for 2050 take into account the
continued use of existing surface and groundwaters, the use of return flows and reuse of treated wastewater, more efficient reallocation of reservoir storage, freeing
up water through the buying and selling of water rights ("water marketing")-- particularly from irrigation to municipal users -- new surface water supplies
generated by new conveyance systems to move water from one area to another, and new reservoirs,among other sources.
The 2002 Water Plan projects that water supplies from existing sources will decline nearly 20 percent, from
some 17.8 million acre-feet per year to 14.5 million acre-feet per year during a drought of record. This is due to a decline of 19 percent of groundwater supplies
-- mainly due to depletion of the Ogallala Aquifer -- and reductions in supply from the Gulf Coast, Hueco-Mesilla Bolson and Carrizo-Wilcox Aquifers.* Similarly, surface water supplies from existing reservoirs and other sources is expected to decline from some 8.6 million
acre-feet to 7.0 million acre-feet assuming no new conveyance systems and no renewal of existing contracts. Most of this decline is due to reservoir
sedimentation and declines in baseflow from depleted aquifers.*
Because demand is expected to top 20 million acre-feet, the 2002 Water Plan projects that in 2050 Texas existing
supplies would only be able to meet 62.5 percent of total needs.* To meet these needs, the Regional Planning Groups
recommended that some 13.5 percent of the new supplies needed be met by implementing new conservation
measures. When these "new" conservation efforts are combined with the on-going implementation of existing
conservation programs, over two million acre-feet of water per year could be "saved" by 2050. In addition,additional
supplies could be garnered by improving the operations of dams, by reallocating surface water rights -- including
through the use of water markets -- by transferring surface water through conveyance systems and groundwater
through pipes from one area to another. In addition, the regional planning groups have recommended the construction
of eight new reservoirs, which would increase water supplies by roughtly 1.1 million acre-feet in 2050. In addition, the
expanded reuse of wastewaters could provide another 420,000 acre-feet per year for municipal use, while four
planning regions recommended the desalination of brackish groundwater to increase groundwater supply by some
185,000 acre-feet per year. Thus, if all the recommendations of the Regional Planning Groups were implemented, an
estimated 24.6 million acre-feet of water would be available for Texans. Nonetheless, many of the proposed
recommendations -- including reservoirs, interbasin transfers and reallocation of reservoir waters -- are controversial
and will face both legal and political hurdles. In addition, the plan does not consider to a major extent another major
user of Texas's water -- the bays and estuaries and wildlife -- not to mention fishermen -- which depend upon flows.
Finally, while considering each water supply recommendation individually might add up to over 24 million acre-feet, in
actuality, the development of one strategy -- such as reuse of wastewater - might prevent the development of another.
Developing new supplies for Texas will involve a tricky mix of reducing demand, building new infrastructure and further
studies to determine the "environmental" needs of the coastal communities.
An assumption made in the TWDB's 2002 water plan is that the sustainable yield from existing ground- and surface
water (during a drought year) in 2050 is about 14.5 million acre-feet per year, a reduction of more than three million
acre-feet as groundwater is further depleted in quality and quantity. In fact, there is considerable debate about how much water would actually be available.*
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