The amount of trash and debris dumped into southwest Idaho irrigation canals is on the rise, district managers and water users say.

Lawn clippings and other landscaping debris, household trash and even old tires and couches are showing up in the Treasure Valley’s approximately 1,500 miles of canals, laterals and ditches.

“This issue continues to be a serious problem for our irrigation delivery folks every summer, and it has only gotten worse with the strong residential and commercial growth we have seen in the valley,” Roger Batt, executive director of the Treasure Valley Water Users Association, said in a news release.

State law prohibits dumping any material that can interfere with irrigation water delivery.

The Community Planning Association of Southwest Idaho estimates Ada County’s population at 822,890 this year, up from 801,530 in 2023. Canyon County’s current estimate is 265,300, up from 256,940.

“Our ditch riders are checking the system every day just to keep the racks free of trash, and it is consuming more and more of their time,” Clinton Pine, Nampa and Meridian Irrigation District board chairman, said. Dumping debris onto a district easement or right of way above or near a canal or ditch — usually over a fence — also is a problem as “the debris eventually ends up in the water.”

The potential for flooding and property damage increases as dumped material heads downstream and lodges against trash and debris racks, according to the water users organization. And water available for use by downstream customers can decrease.

Canal operators have seen tree limbs and stumps dumped into canals at night, plugging main spillways. 

Debris in canals and ditches also is causing more problems for residents using pressurized irrigation systems that rely on pumping stations to supply water for lawns, gardens and community park areas, officials said. Trash in the water can clog pumps and cut off a residential subdivision’s water supply.

Residue from landscape treatment chemicals can get into irrigation water after debris is dumped, impacting water quality, according to the water user organization.

Settler’s Irrigation District manager Mack Myers sees a growing problem with residential customers dumping material into canals.

“For some, the canal behind their home is an ‘out-of sight, out-of-mind’ place to get rid of garden litter, including limbs they have trimmed from their trees and even the remnants of building materials left by the homebuilder,” said Myers, whose district is based in central Boise.

“It really comes down to respect for your neighbor and respect for the law,” Batt said. “It’s against the law to dump debris into a canal or ditch, and you live upstream from someone else.”