Field drains affect flooding

WEST FARGO -- Tile drainage of farm fields has been cast as a villain that aggravates flooding in the Red River Valley, but also held out as a great hope for better managing runoff to minimize flooding.

The debate has raged -- especially since the record 2009 flood -- without a comprehensive scientific assessment of the pros and cons of subsurface field drainage and flooding.

Until now.

The Red River Retention Authority was briefed Tuesday on the findings of a year-long study on tile drainage in the valley that was reviewed by 21 scientists and engineers.

"The impact is, it depends," said Chuck Fritz, a hydrologist and director of the International Water Institute in Fargo, which did the study for the authority.

"If we have a managed system, you could have a positive impact during a flood," and reduce flood peaks, Fritz told the Red River Retention Authority board.

But if poorly managed -- or not managed at all -- tile drains can worsen flooding, by contributing to river crests, he said.

All in the timing

The timing of water releases from field drain tiles, which collect water beneath the surface in pipes, is critical, the study concluded.

Water temporarily stored in drain tile systems can help reduce flooding if the water is released before or after a flood. But stored field water drained during a flood would worsen the impact.

"It all depends on how it's managed," Fritz said.

Jim Lyons, a farmer from Lisbon, N.D., and co-chairman of the retention authority board, said most farmers who use drain tiles in their fields have some way to regulate flows, usually a pump.

"The majority of it is pumped," Lyons said. "The pump is the best control there is."

But there is no coordinated management of field drain flows -- and the cumulative impacts of subsurface drainage on peak flows is unclear, the study panel concluded earlier.

Popular option

Because fields in the Red River Valley have repeatedly been saturated from above-normal moisture in recent years, tile drainage has gained in popularity in recent years.

Also, the North Dakota Legislature passed new laws last year aimed at streamlining permitting for subsurface drain systems by bypassing the state engineer's application process.

The 2011 legislation allows any subsurface drainage project of less than 80 acres to go ahead without a permit. The new law also eased the regulatory burden on larger projects.

Projects larger than 80 acres must apply to the local water resource district for a permit. But the district can't deny the permit unless officials determine it is of statewide significance, or the proposed drainage will flood or adversely affect downstream landowners within a mile of the project.

Legislation passed last year also provides low-interest loans to farmers to install tile drain systems in their fields.

But, the study warned that "rapidly increasing trend of subsurface drainage installation" poses risk in the Red River basin.

"The window of time for consideration and promotion of the managed drainage options may be limited due to the expense and difficulty of retrofitting existing subsurface drainage installation with effective control systems," the study said.

Water credits

To help ease the cost of installing controls, the study lists as an option the creation of tradable water storage credits that would pay farmers for temporarily storing water during a flood.

Mark Brodshaug, chairman of the Cass Joint Watershed District board, said the legislation to ease the regulatory process for drain tile systems is popular among farmers in North Dakota.

"That kind of makes it hard to require controls," he said. Most farmers would agree to temporarily store water to ease flooding "as long as they aren't bearing the entire burden," Brodshaug said.

Doyle Johannes, a farmer near Underwood, N.D., and president of the North Dakota Farm Bureau, agreed that tile drains can help during floods.

"If properly managed they absolutely will help alleviate flood problems," he said.

But farmers want to be sure that any management of field drainage occurs at the local level, and should not be decided by federal officials, he said.

"We don't want to lose control of these water boards and see their power usurped by the Corps of Engineers," he said.

The Red River Retention Authority plans to discuss the study with local water boards and farm groups, co-chairman John Finney said.

"This is going to be an ongoing process," he said. The authority also plans to study the effects of surface field drainage in the Red River Valley.

Springer reports for Forum Communications Co., which owns the Grand Forks Herald and Agweek.