DES MOINES, Iowa (AP) — State natural resources officials say Iowa will report 622 river, lake and wetland segments with impairments to the Environmental Protection Agency as part of its 2018 summary of water quality. That’s a 2% increase over the 608 reported in the 2016 report.

The Iowa Department of Natural Resources says Thursday the 622 water body segments on this year’s list had 831 impairments. An impairment means a segment of a water body doesn’t meet established quality standards.

The most common river impairments in Iowa include bacteria presence and fish kills, for which the most common cause is animal waste. Iowa has more pigs and egg-laying chickens than any other state, and it constantly struggles to balance water quality and agricultural interests.

The most severe problem for lakes is algae growth. That’s often the result of nutrients such as phosphorous from farm fertilizer washing from fields into the water. Environmental activists Iowa Citizens for Community Improvement say it’s evidence the state is failing when it comes to improving water quality.