Ongoing research within the Western Lake Erie Basin watershed indicates that harmful algal blooms are tightly correlated with precipitation events that cause surface and subsurface runoff, delivering nutrients throughout the watershed. Farmers can implement conservation practices to limit the flow of nutrients, and researchers have worked to study which practices are most effective in the watershed.

One new practice, informed by this research effort, is starting to show promise: cascading waterways. These cascading systems — series of retention basins within grassed waterways — are designed to simultaneously prevent erosion and temporarily store water. However, little is known about how they function and their ability to retain nutrients and sediments associated with precipitation and runoff events.

To address this knowledge gap, a team of researchers led by Dr. Steve Lyon of The Ohio State University monitored water flows across several cascading waterways in Ohio. Through the project, funded by the Harmful Algal Bloom Research Initiative (HABR), they measured the water and nutrients coming into and going out of these cascading systems over a few growing seasons.

“Cascading waterways are modifications to traditional grassed waterways that introduce small retention ponds along the waterway,” said Lyon. “The ponds hold water to allow for increased storage, ultimately allowing for infiltration and water treatment.”

From these measurements, researchers were able to estimate the amount of nutrients retained in each cascading waterway being monitored. From here, the team could estimate the cost effectiveness of the practice relative to other more established conservation practices, such as wetlands and edge-of-field phosphorus filters.

“These conservations practices are fairly new to Ohio and have seen rapid adoption in recent years,” Lyon explained. “We need to study them to not only ensure they are working as intended for water quality improvements but also to study their potential, which will help with improving design and maintenance standards.”

Based on observations, the water retention basins in the cascading waterways store water for most storm events and allow for increased water infiltration into the ground. This reduction in runoff results in reduced nutrient and sediment loading at the cascading waterway outlet. The team found this method to have similar cost effectiveness to other conservation practices currently being used in the Lake Erie watershed.

On average, across the cascading waterways being monitored, approximately 83% and 94% of dissolved reactive phosphorus load and nitrate load was reduced, respectively. Researchers are working with state agencies to continue to develop standards around design and maintenance of cascading waterways.

The team will work with partners to establish cascading waterways as an interim conservation practice eligible for cost-share support. This project also allowed the researchers to establish a monitoring platform that can be maintained to extend data on performance under different weather conditions and as the system ages.

For more information about this HABRI-funded project, contact Lyon at lyon.248@osu.edu or watch his recent Freshwater Science webinar.

Ohio Sea Grant is supported by The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) School of Environment and Natural Resources, Ohio State University Extension, and NOAA Sea Grant, a network of 34 Sea Grant programs nation-wide dedicated to the protection and sustainable use of marine and Great Lakes resources. Stone Laboratory is Ohio State’s island campus on Lake Erie and is the research, education, and outreach facility of Ohio Sea Grant and part of CFAES School of Environment and Natural Resources.