HOSPITAL II LUIS NEGREIROS VEGA,
4.2. DISCUSIÓN Y ANÁLISIS
Efforts to reduce the wasteful use of water in California have been underway for many years. Indeed, water conservation efforts have already made a big difference in improving the reliability of California’s water resources, both by reducing demand and freeing up new supply, reducing pressures to take any more water from the state’s overtapped river, lakes, and aquifers. Beginning in the early 1980s, Californians have participated in a range of programs to replace inefficient toilets, shower- heads, and faucets; to audit heavy water users looking for leaks; and to reduce water use in gardens and other outdoor landscapes. We estimate that over 700,000 acre-feet per year (AF/yr) of indoor savings have already been captured through a combination of smart regulation, improved technology, and educational programs. If used efficiently, this is enough water to meet the entire indoor residential needs of 17 million people each year.1
Among the first devices that agencies will chose for conservation pro- grams are showerheads and toilets, because they have a short payback period and are relatively uncomplicated to manage and install. In con- trast, we estimate that there has been little significant penetration of higher-efficiency dishwashers (a relatively newly available technology) or reductions in leak rates (because of limited leak detection and prevention programs and inadequate data). In between these two extremes is the growing use of high-efficiency washing machines – these did not begin to appear in significant numbers until the late 1990s, but are now increas- ingly available and popular. For example, in 1999, an estimated 10,000 rebates were issued for high-efficiency washers in California (based on reporting data from the California Urban Water Conservation Council (CUWCC)); in 2002 more than 24,000 rebates were awarded, and a total of 64,000 rebates have been awarded in the four years since 1999 (Dickinson, personal communications, 2003).
Figure 2-1 shows the indoor water savings that have already been achieved through current efforts and programs to replace inefficient toilets and showerheads. The top line is our estimate of what indoor residential water use in California would have been with no improvements in efficiency since 1980. The bottom line is our estimate of current indoor residential water use. As noted, we estimate that current use is around 750,000 AF/yr below what it would have been without existing conservation efforts.
Toilets 734,000 32 Showers 496,000 22 Washing Machines 330,000 14 Dishwashers 28,000 1 Leaks 285,000 12 Faucets 423,000 19
Total Indoor Residential Use 2,296,000 100
End Use Current Use Fraction of Total
(AF/yr) Indoor Use (%) Table 2-1
Estimated Current Indoor Residential Water Use in California (Year 2000)
1 One acre-foot currently satisfies the indoor residential needs of approximately 15 people in California. If currently available efficiency technology were used, one acre-foot could meet the indoor residential needs of 25 people. An acre-foot of water would cover one acre to a depth of one foot and equals 326,000 gallons.
Far more can be done to improve water efficiency, even with existing technology. The amount of water we estimate could be saved through comprehensive adoption of efficient technology and practices is presented in Figure 2-2. Table 2-2 summarizes the potential savings over current use for 2000 by specific end use. Although toilets have already had the single largest effect on indoor residential demand reduction, they still hold the greatest potential for savings. Leak reduction is also a worthwhile target for agencies’ efforts. Reducing leaks usually requires adjustment of existing fixtures rather than complete replacement, which reduces overall costs. The savings potential of showers and washing machines is also rel- atively high, while that of dishwashers is modest. We estimate that full implementation of current conservation potential would cut current use by another 890,000 acre-feet – approximately a further 40 percent reduc- tion. This would have the effect of reducing current indoor residential use, on average, from around 60 gallons per person per day (excluding some uses not evaluated here) to around 37 gallons per person per day.
Water Use with Current Policies and Programs
Water Use with Full Adoption of Efficient Technologies 3,000,000 2,500,000 2,000,000 1,500,000 1,000,000 500,000 0 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020
Acre-Feet Per Year
3,500,000 3,000,000 2,500,000 2,000,000 1,500,000 1,000,000 500,000 0 1980 1985 1990 1995 2000
Indoor Water Use Without Conservation
Estimated Actual Water Use
Acre-Feet Per Year
Figure 2-1
Total Indoor Residential Water Use with and Without Current Conservation Efforts (1980-2000)
Figure 2-2
Potential Indoor Residential Water Savings by End Use (1998-2020)
Water usage with savings from efficient ... Washing machines Showers Leak repair Toilets
40 Indoor Residential Water Use and Conservation Potential
For all indoor uses, additional temporary “savings” can be achieved during droughts by behavioral modifications (e.g., cutting back on fre- quency of actions like flushing, showering, washing). We do not consider these to be “conservation” or “efficiency” improvements.
Figure 2-3 summarizes both the water savings that have been achieved between 1980 and the present and a projection of future potential indoor residential savings with both existing programs and all cost-effective sav- ings to 2020, as a measure of the potential that remains. The top line is a projection of use if no conservation activities had been initiated in the state (i.e., using pre-1980 conditions). The middle line is our “current use” projection (i.e., assuming the current mix of efficient and inefficient uses). The bottom line is our estimate of the further reduction in indoor residential water demand that is possible with all cost-effective savings using existing technology (for more detailed calculations, see the Appendices at http://www.pacinst.org/reports/urban_usage/).
The following analysis is based on successful conservation and research programs, research on technologies for reducing water use, and an exami- nation of current water-use patterns in California. The availability of reli-
Water Use Without Current Conservation Program
Water Use Capturing Remaining Available Potential with Current Technology
Water Use with Current Efficiency Policies and Programs
4,500,000 4,000,000 3,500,000 3,000,000 2,500,000 2,000,000 1,500,000 1,000,000 500,000 0 1980 1985 1990 1995 2000 2005 2010 2015 2020
Acre-Feet Per Year
Toilets 420,000 (a) 57
Showers 120,000 (b) 24
Washing Machines 110,000 (c) 33
Dishwashers 13,000 46
Leaks 230,000 (d) 80
Faucets/Fixed Volume Uses (e) (e)
Total Additional Indoor Savings 893,000 40
Indoor Residential Best Estimate of Additional Conservation
Water Use (Year 2000) Cost-Effective Water Potential: Percent
Conservation Potential (2000) Reduction Over
(AF/yr) Current Use
Table 2-2 Indoor Residential
Conservation Potential for 2000
(a) For toilets, this requires full replacement of inefficient toilets with 1.6 gallon per flush models.
(b) For showers, this requires full replacement of showerheads with 2.5 gallon per minute models (with actual flow rates averaging 1.7 gallons per minute).
(c) For washing machines, these savings would result from the complete replacement of current models with the average (not the best) of the efficient machines currently on the market.
(d) The 80 percent savings estimate comes from assuming that leak rates are reduced to the median value now observed. At the same time, CDWR (2003b) estimates that half of all leaks can be saved for less than $100 per acre-foot and 80% for less than $200 per acre-foot. See Section 2 for more detail.
(e) For faucets and other fixed volume uses such as baths, no additional “technical” savings are assumed.
Figure 2-3
Indoor Water Use 1980-2020: The Effect of Conservation Policies
able data on water use varies widely from sector to sector. For example, the information on water use and potential savings from toilets is fairly comprehensive and significantly more reliable and accessible than infor- mation on landscape water use. Some significant gaps in our under- standing of water use remain, however, and we urge state and local water agencies to collect more information on use patterns and the penetration of water-use technologies and to make that information widely available. Without good information we cannot make good decisions.