Watershed moment: The Grand Valley grapples with proposed #water quality standards — The #GrandJunction Daily Sentinel

Bicycling the Colorado National Monument, Grand Valley in the distance via Colorado.com

Click the link to read the article on The Grand Junction Daily Sentinel website (Dennis Webb). Here’s an excerpt:

The Colorado Department of Public Health and Environment’s Water Quality Control Division is proposing the limits for 11 Colorado River tributaries in the valley with impaired water quality because of high levels of dissolved selenium and total recoverable iron, and in the case of two of the tributaries, E. coli. The river itself along that stretch, which meets water quality standards for selenium and E. coli, but not iron, is not itself targeted by the proposal, although it would benefit from it.

As required by the federal Clean Water Act and by Environmental Protection Agency regulations, the state is developing what it calls total maximum daily loads (TMDL) that would establish how much of those pollutants can enter each of the tributaries each day while maintaining water quality standards.

The Government Highline Canal flows past Highline State Park in the Grand Valley. CREDIT: BETHANY BLITZ/ASPEN JOURNALISM

The area being targeted by regulators altogether encompasses about 138 square miles, stretching from Lewis Wash in the Clifton area to Salt Creek in western Mesa County. The area is all north of the Colorado River and is bounded on the northern end by the Government Highline Canal. That location beneath the canal is noteworthy because selenium is naturally occurring in the Mancos shale geological formation in the area, but at high levels in water can be harmful to fish and aquatic birds. The Water Quality Control Division, in its draft Grand Valley TMDL public notice, says that “the predominant source of selenium in all of the watersheds is likely groundwater inflow from canal seepage and deep percolation from irrigated lands.” Put another way, the valley’s irrigated agriculture, lying downgrade of the Government Highline Canal, is mostly driving the selenium problems in the drainages.

But as it happens, state water-quality regulators have little say over that agricultural activity. The Water Quality Control Division holds permitting authority over point sources of surface water discharges. Agricultural stormwater discharges, and return flows from irrigated agriculture, aren’t considered point sources under the Clean Water Act. The state relies on incentive-based approaches to encourage partners to work on voluntary measures to address contaminants, something that grant funding is available to support. This can include measures such as lining or piping canals and changing irrigation methods and schedules to reduce the leaching of selenium…Still, a concern for some people, including Trent Prall, public works director for the city of Grand Junction, is that because of the state’s lack of authority over the agricultural side of things, it will lean on permitted sources of surface water discharges to fix a problem that is largely agriculture-driven.

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