Along English River, flood model pinpoints priorities

KALONA - A model developed by the Iowa Flood Center will help planners identify high-priority projects for reducing the impacts of flooding and improving soil and water quality along the English River.

'The model will help us pinpoint best management practices to better control both flooding and nutrient pollution,” said Jody Bailey, coordinator of the English River Watershed Management Authority, which unveiled its plan at an open house last week.

Bailey described the plan as 'a non-regulatory road map” to guide stakeholders 'in protecting water quality and soil health in the watershed and reducing flood impacts on communities and farmland.”

'The same water that causes flooding causes water quality problems,” said Adam Kiel, water resources manager for the Iowa Soybean Association, which helped develop the plan.

The Iowa Flood Center, established after the devastating 2008 floods, initially focused on developing mathematics and computer models that predicted the height, extent and timing of floodwaters, said Larry Weber, director of IIHR Hydroscience & Engineering at the University of Iowa.

Its staff has since developed expertise in modeling water quality outcomes based on a wide array of variables, Weber said.

The models can identify, for example, the most cost-effective locations for ponds, wetlands and other conservation practices - a skill in demand with the increased emphasis on reducing nutrient pollution as urged in the state's reduction strategy.

The plan - which incorporates hydrologic assessments, geological characteristics, water quality data, surveys and interviews - outlines goals and identifies specific areas where conservation practices can do the most good.

As in almost all of Iowa, row crop agriculture, primarily corn and soybeans, is the predominant land use in the 639-square-mile watershed, of which nearly half is considered highly erodible.

The English River and its tributaries drain portions of six counties and flow through or near 14 communities, the largest being Kalona, before it empties into the Iowa River near Riverside.

The watershed lies within the southern Iowa drift plain, the state's largest landform, characterized by comparatively old glacial deposits that have been highly eroded over time.

The soil's vulnerability to erosion and the region's landform help explain why phosphorous pollution is a more serious problem than nitrate pollution in the watershed, according to Kiel, whose 2014 sampling showed that nitrate pollution in the watershed is well below the statewide average while phosphorus pollution is well above that standard.

Because phosphorus tends to bond with soil particles, conservation practices that control erosion - such as cover crops and no-till cultivation - would likely prove well-suited to the watershed, Kiel said.

The southern Iowa drift plain stands in contrast with north-central Iowa's Des Moines lobe, which last experienced glaciation just 10,000 to 12,000 years ago.

Accordingly, the soil in that region has a much higher percentage of organic material and less natural drainage - factors that make it prone to leach nitrate into surface water.

Chronically high nitrate levels in the Raccoon River, a Des Moines Water Works source, have prompted the utility to sue the boards of supervisors of Sac, Buena Vista and Calhoun counties, in their capacities as trustees of 10 drainage districts, for the discharge of nitrate pollutants into the Raccoon.

Kalona City Administrator Ryan Schlabaugh said the City Council, concerned primarily about frequent flood damage, directed staff to establish the watershed management authority, which can't levy taxes and must depend primarily on competitive grants for funding.

'This is not a two-year or a five-year project. It will take more like 30 years to make substantial progress,” he said.

Bailey said progress will depend in large part on the watershed authority's ability to secure grants.

'It would help if more money were made available for locally driven water quality initiatives,” she said.