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12 Arizona Water Resource May - June 2003 <br />Desalination... continued from page 2 <br />evaluation of the problem. He says, "We studied the salt balance in <br />the valley and asked how much salt is coming into the area vs. how <br />much is leaving. We found that about a million tons per year of salt <br />are coming into the valley and staying." <br />Central Arizona Project water and water from the Salt and <br />Verde rivers are responsible for much of the salt. Also contributing <br />to the salt loading is reclaimed water. Water reclaimed for use from <br />a treatment plant increases salinity. Estimates are that one cycle of <br />municipal use increases the salt content of water by 200 to 400 mil- <br />ligrams per liter. Sanitary discharges and water softeners contribute <br />to the salinity of reclaimed water. <br />Rossi asks, "How does the elevated levels of salinity in our <br />source waters affect our ability to use the water down the road? <br />The study is looking at that but also looking at the economics; for <br />example, what does this high salt content mean for consumers and <br />utilities ?" <br />He says the shorter life span of fixtures and appliances and <br />the cost to industry was estimated to be about $30 million per year. <br />"That is a rough number, mostly direct costs, but it is a starting <br />point." <br />Groundwater in the southwest portion of the valley has es- <br />pecially high salinity, with water in the Buckeye area at 2,500 mil- <br />ligrams per liter and even more at times. (Brackish water is generally <br />considered to be over 1,000 mg /l.) Rossi says some of this water <br />could be treated to serve future water demands in the area. He says, <br />"We are in some very preliminary discussions — very preliminary <br />— about a possible regional brackish water desalination plant some- <br />where in the west valley. It could take this brackish water, irrigation <br />tail water and water from the end of the Salt River Project system <br />and convert it to potable supplies." <br />Unlike areas in Southern California the Phoenix area is not <br />overly strapped for water supplies to require immediate adoption of <br />desalination. Rossi says, "From a water resource planning perspec- <br />JkWater Resources Research Center <br />College of Agriculture and Life Sciences <br />The University of Arizona, <br />350 N. Campbell Ave <br />Tucson, AZ 85721 <br />Arizona Water <br />Resource Address Service Requested <br />THE UNIVERS" OF <br />ARIZONA <br />TUCSON ARIZONA <br />tive we are not in a critical situation in the city, but we also realize <br />that our growth path is phenomenal. Desalination of brackish <br />groundwater is not something we need to do soon, but it is part of <br />our long -range plan." <br />Tucson also is participating in the Central Arizona Salinity <br />Study. The city faces future water quality decisions that may involve <br />desalination. In introducing CAP water to its customers, Tucson <br />Water has been delivering a blend of groundwater and CAP water. <br />Eventually, as increased amounts of CAP water are included in the <br />blend, the salinity of water delivered to customers will increase, al- <br />though it is unlikely to be more than 600 to 650 mg /l. <br />Water quality has been at ticklish issue in Tucson, with the <br />troubled introduction of CAP water contributing to citizens' wari- <br />ness in matters of water quality. As a result, the utility is concerned <br />about the public's reaction to increased salinity. It intends to hold <br />public hearings to solicit citizen input about what options to pursue. <br />One option would be to build a desalination plant to ensure a high <br />quality drinking water. This would be an expensive proposition that <br />would increase the cost of water. This is not an immediate issue, <br />but more of a down —the -road concern, to be considered as part of <br />long -range planning. <br />In a sense, Tucson's consideration of desalination is to im- <br />prove the aesthetics of water. Drinking water at 600 to 650 mg /l is <br />not unpalatable, although water users whose supply was once total <br />groundwater and then a blend might object. In Phoenix, where <br />water supplies tend to be of higher salinity than those in Tucson, <br />citizens drink water of about 600 mg /l. <br />With desalination on the national water resource agenda, many <br />areas now look to the treatment process to help maintain sustain- <br />able water supplies. Arizona at this point is not among them. Im- <br />provements in desalination technology, however, will benefit the <br />state. Central Arizona will be better able to confront its salt loading <br />problem, and communities like Tucson can improve the quality of <br />current drinking water supplies. J, <br />�+ i <br />NON- PROFIT ORG. <br />RECEIVED US POSTAGE <br />PAID <br />TUCSON,ARIZONA <br />JUL 17 2003 PERMIT NO. 190 <br />(""do Water Consma#on Board <br />3 -DIGIT 802 S 7 JB 3 <br />OFFICE OF WATER CONSERVATION <br />DEPT OF NATURAL RESOURCES <br />1313 SHERMAN ST STE 721 <br />DENVER CO 80203 -2278 <br />