Click on the link to read the article on The Grand Junction Daily Sentinel website (Dennis Webb). Here is an exerpt :
The Colorado Department of Public Health and Environment’s Water Quality Control Division is proposing limits for 11 Colorado River tributaries in the valley that have impaired water quality due to high levels. dissolved selenium and total recoverable iron, and in the case of two of the tributaries, E. coli. The river itself along this stretch, which meets water quality standards for selenium and E. coli but not for iron, is not itself targeted by the proposal, although it would benefit.
As required by the federal Clean Water Act and Environmental Protection Agency regulations, the state is developing what it calls Total Maximum Daily Loads (TMDLs) that would establish the amount of these pollutants. capable of penetrating each of the tributaries every day while maintaining water quality standards. .
The area targeted by regulators encompasses a total of about 138 square miles, stretching from Lewis Wash in the Clifton area to Salt Creek in western Mesa County. The area is all the way north of the Colorado River and is bounded on the north end by the Government Highline Canal. This location under the channel is notable because selenium occurs naturally in the Mancos Shale geological formation in the area, but at high levels in the water it can be harmful to fish and waterfowl. The Water Quality Control Division, in its draft Grand Valley TMDL public notice, states that “the predominant source of selenium in all watersheds is likely groundwater inflow from the channel infiltration and deep percolation of irrigated land”. In other words, the irrigated agriculture in the valley below the Government Highline canal is the main cause of the selenium problems in the drainages.
But it turns out that state water quality regulators have little to say about this agricultural activity. The Water Quality Control Division has the authority to authorize point source discharges of surface water. Agricultural stormwater discharges and return flows from irrigated agriculture are not considered point sources under the Clean Water Act. The state relies on incentive approaches to encourage partners to work on voluntary measures to address contaminants, which grants are available to support. This can include measures such as lining or piping canals and changing irrigation methods and schedules to reduce selenium leaching… Yet a concern for some people, including Trent Prall, Director of Public Works for the city of Grand Junction, is that due to the state’s lack of authority on the agricultural side of things, it will rely on permitted sources of surface water discharges to solve a problem that is largely related to agriculture.