By the time they reach Mexico the waters of the Colorado River are so laden with salt as to be a danger to crops."About 9 million tons of salt passes Lees Ferry (on the Colorado River in Arizona) every year," said Paul Von Guerard, office chief of the U.S. Geologic Survey in Grand Junction.Since the 1970s, the seven states through which the river flows have agreed to control that burden of salt as much as possible. The USGS monitors the salinity of the river, which has its source in Colorado.Thursday, members of USGS in Grand Junction brought the Energy Advisory Board up to date on efforts to monitor salt in the Colorado reaches of the river.The Colorado, as it flows through the state, picks up a significant amount of salt that is augmented as it is carried downstream, Von Guerard said."Salinity is a major water quality concern in the Colorado River," Von Guerard said.Salt dumps into the river from a variety of sources, among them irrigation of agricultural lands, the Mancos shale geologic formation and the hot springs around Glenwood Springs, Von Guerard said. About 47 percent of the salt in the river comes from natural sources such as hot springs and erosion of soil and the rest is from human actions. Salt causes about $300 million in damage to crops, water pipes and hot water heaters in the lower Colorado River Basin in California and Nevada, as well as in Mexico, Von Guerard said. While the survey has a number of monitoring stations along the river and its tributaries, there is a gap between Glenwood Springs and Grand Junction. "We don't have a good handle on the discharge from Glenwood Springs," he said.About 47 percent of the salt load that goes through Colorado passes the Cameo monitoring station on the west side of DeBeque Canyon just east of Grand Junction, Von Guerard said. But only 18 percent of that load comes from the river above Glenwood Springs, according to data from a station just upstream from the city. The rest of that salt comes from sources between Glenwood and Grand Junction, he said.The USGS needs to monitor that load with at least one new monitoring station between Glenwood and Grand Junction, at a cost of $25,000. Because of flattened funding in the last few years, USGS is seeking to find financial support from local towns and cities in that reach of the river to install a station, Von Guerard said."We are working with the (Colorado River Water Conservation District) on funding," he said. The district also suggested the USGS appeal to the energy companies operating in the county for financial support.Alan Lambert, an Energy Advisory Board member and a Rifle city councilman, agreed salinity is a problem and municipalities need to push for minimum stream flows in the Colorado in order to protect their infrastructure."We have a salinity problem in the water treatment plants," he said.