Emails (excerpted), responses to PolitiFact Texas, Steve Scheibal, Policy and Communications director, Office of Sen. Kirk Watson, Oct. 25, Oct. 31, Nov. 1, 2012
Oct. 25, 2012
First off, please keep in mind that the League of Women Voters gave candidates a very firm 450-character limit. Also, generally speaking, Senator Watson tries to be conservative in discussing projections, and was juggling both statewide projections and regional projections for an Austin-area audience.
With that, all of this is from the state water plan produced by the Texas Water Development Board. On population:
The 2012 Texas State Water Plan projected population growth – Figure 3.1 p. 130 and Table 3.1 p. 132 demonstrating that Texas population is expected to increase from 25.4 million in 2010 to 46.3 million in 2060 (an increase of 82 percent).
On water availability:
The 2012 Texas State Water Plan says that “Total surface water availability in Texas in 2010 is estimated at 13.5 million acre feet per year and decreases to 13.3 million acre-feet per year by 2060.” Page 161 and see Figure 5.3 page 159.
The plan also predicts zero percent change for surface water in the Colorado River Basin (that supplies water to Central Texas). See Table 5.1 p. 160.
Overall, existing water supplies are projected to decrease about 10 percent, from 17.0 million acre feet in 2010 to about 15.3 million acre feet in 2060, as groundwater supplies are projected to decrease from about 8 million acre-feet in 2010 to about 5.7 million acre feet in 2060. Surface Water supplies are projected to increase by about 6 percent, from about 8.4 million acre-feet in 2010 to about 9.0 million acre-feet in 2060. [The plan distinguishes between “supply” and “availability,” but uses “availability for planning purposes.] See Figure 5.1 p. 158 and Figure 5.3 p. 159
[Senator Watson used the phrase “about where it is now” to acknowledge the likelihood of some change, but also clarify that the fundamental effort is to stretch current supplies further.]
Finally, the notion of a constant water supply is intuitive for many lay-people given a basic understanding of how water moves around:
The water cycle, also known as the hydrological cycle or H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go, in and out of the atmosphere. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation,infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid (ice), and gas (vapor).