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42 Estimating Economic Impacts of Salinity... N -.J ..... c.o households, multiplied by an extrapolation factor to expand bousehold items to include similar items in commercial buildings,29 The replace- ment cost of the item is determined (in 1986 $), then is divided by the number of years of useful life at the given year's forecasted TDS level, to obtain the annual salinity damages per item. Since even at a very low salinity level, such as 200 mgiL, there will be a limit to useful life, the damages due to salinity at a higher salinity con- centration will be the difference in cost between two salinity levels, the forecasted level and the selected baseline level(s). Household Damage Categories Unrelated to Useful Life of Appliances Not all household salinity damages are functions of useful life. Others are functions of annual cost per household for certain expendi- tures that increase with higher salinity concentra- tions. These are: . Bottled water purchases . Home water treatment systems (e.g., home water softeners or "under~sinku ion ex- change systems or home RO systems) . Soaps and detergents . Clothes replacement (i.e., from textile wear caused by water hardness) All four of these categories are subject to caveats. Bottled water purchases are stimulated in part by advertising, in part by unjustified fear of pollution in public water supplies, and in part by taste. Income level and purchasing power also correlate with bottled water purchases. The same factors influence expenditures on home water treatment systems, with the added factor that home water softening causes some deteriora- tion of water taste (and increases corrosivity) which in turn causes an increase in bottled water purchases. Water hardness causes increases in the amount of soap and detergent used in a household, and may reduce the useful life of tex- liles. Income level and personal preference are probably primary factors in the premature replacement of clothing because of fashion con- siderations rather than wear. Nevertheless, hard- ness and salinity, particularly in the Colorado River, are closely related so that an increase in one usually accompanies an increase in the other. The authors have determined from secon- dary sources what the annual expenditures per household are for these four categories, and what percentage of households make such expen- ditures, at various TDS levels. All costs have been indexed to 1986 dollars. The damages, as before, are the difference in annual expenditures per household at two levels of salinity (the forecasted level and the selected baseline level(s), multiplied by the number of households making those expenditures, multiplied by an ex- trapolation factor to account for similar expendi- tures made outside households, e.g., water treatment systems in commercial buildings, bot- tled water purchases by hotels and restaurants, extra use of soaps and detergents by commercial laundries, and extra damages to hospital and hotel linens. (Damages from commercially laundered textiles, in particular, also can result from the very hot water and strong detergents used). Salinity Damages to Automotive Cooling Systems A final category of household salinity damage is that of damage to automotive cooling systems, particularly radiators, from saline water 29The extrapolation factor calculated for use in the computer program is 53.1 percent, and is based on the relationship be- tween the volumes of water distributed to commercial customers and to residential customers of the City of San Diego Water Utilities, as reported in its F'i~AI19AA AnnUAl FinAn...iAI R~port p.28. These volumes were 2,784 million cubic feet (commer~ cial) and 5,243 million cubic fect (residential). Water distributed to industrial customers was ignored, because the proportion of industrial water used in bathrooms, etc., is assumed to be negligible. The San Diego data did not indicate if, or where, water sales to public authorities are reported. A similar calculation of commercial and residential water use in Denver from p. 64 of the Denver Water Department's 1qRlIj Annual Rr!port indicated an extrapolation factor of 51.0 percent. The Denver cal- culations did not include water used by public authorities (e.g., schools, government offices, street washing, etc.) which repre- sents 15.9 percent of residential use, and therefore they understate non-residential damages.