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4 Estimating Economic Impacts of Salinity... ~ m QQ; ~ unpleasant taste. Water hardness is most likely to be an incentive to water softening, which in turn can affect the corrosivity of the water. The exchange of sodium for calcium ions during soft- ening creates an even more unpleasant taste, stimulating the expensive purchase of bottled water. Both water salinity and water hardness can cause damages, and since they are so closely interrelated in Colorado River water, it is not necessary to distinguish the effects of these specific constituents. Since some water damage to household ap- pliances or utensils has been shown to occur at salinity levels as low as 50 mgIL TDS, no parti- cular threshold limit can be assigned. Instead, comparative statistics on useful life, from all available secondary data, are combincd with selected baseline TDS values to attribute a reasonable amount of such damage to salinity of Colorado River water. This same procedure is applied to physical damages that might be in- curred by water supply and wastewater treat- ment agencies. The fact that some damage begins to occur at very low TDS levels creates a further problem of attribution to Colorado River water, but this is basically overcome by attribut- ing only incremental damage to the higher salinity of the Colorado River. One new area of damage that can be confi- dently attributed was uncovered during research. According to data from the automobile industry, damage to cooling systems (radiators) hegins at 100 mgIL TDS, and is a significant source of salinity-related economic cost. Another area of economic cost is less clearly attributable, but still closely tied to the effects of saline or hard water - the purchase of bottled water. Some data are available that delineate a relationship between TDS/hardness and bottled water pur- chases, but the relationship is not clcar-cut because of other influences - such as advertis- ing - on consumer behavior. The authors approached the dilemma on causes of household damages by arraying the data on damage and useful life (where available) from previous studies of water quality-related consumer damages. These data were subjected to computer-based regression analysis which derived formulas and generated curves over the study TDS range. The annual dollar damages to households in the metropolitan areas (including business and commercial uses not related to in- dustrial processes) using all or part Colorado River water are presented in ranges. Based on runs of the computer program, using alternated baseline salinity levels and the 1976-1985 average salinity level of the Colorado River, damage in 1986 dollars ranges from a high of $637.6 million to a low damage estimate of $156.1 million. These annual damages range from $64.76 to $108.81 per household. Damages to Water/Wastewater Utilities Damages to water and wastewater utilities were calculated from reductions in the useful life of system facilities and equipment, caused by in- creased corrosion and scale that occur in saline conditions. These damages were determined on the basis of the useful life information, popula- tion projections, and replacement cost of various treatment and distribution facilities affected by salinity deterioration. Annual damage is calcu- lated by dividing capital investment cost per capita by useful life at a predicted TDS level. The annual cost to various Lower Colorado River Basin utilities, depending on the baseline used for measurement, is $3.2 million to $22.8 million, or from $1.34 to $3.88 per household. Damages to Utilities from Policy/Regulation This particular area of damage is not repre- sented in the computer model because no histori- calor basinwide data yet have been found other than those presented by the Santa Ana water- shed in Southern California. The Santa Ana watershed has been using Colorado River water as a substantial part of its supply for a number of years; and, since the adoption of two California Regional Water Quality Control Board regula- tions, the Santa Ana River Watershed Project Authority has been addressing salinity as part of its overall water planning function. One regulation requires that water dis- charged from Riverside County, either in an open channel or through groundwater recharge, not exceed approximately 600 mgIL TDS. If it does, more water must be provided for dilution, the discharge must be treated, or the discharge