A Pond Where the Riffles Were
1Since 2019, the ecology club at Cedar Valley Middle School has studied two 200 m stretches of Cutbank Creek: a lower stretch behind the school and an upstream stretch 1 km away. Each July, students measure the water's depth, speed and temperature, scoop insect nymphs from the creek bed with nets, and sort them under dissecting microscopes in the classroom. They also count tadpoles with net sweeps, take one-liter water samples to count tiny drifting animals called zooplankton under a microscope, and help a state fish biologist, Ms. Hana Kowalczyk, count brook trout. Seventh grader Lucas Ferreira keeps the club's records.
2In September 2021, a pair of beavers moved into the lower stretch. Beavers eat bark, twigs and water plants, and they build dams of branches and mud that back up the water into a pond deep enough to protect their lodge. By the next July, a dam about 1 m high had turned the fast, shallow riffles of the lower stretch into a still pond. The upstream stretch had no beavers and no dam. In April 2025, a spring flood broke the dam, and the beavers moved away.
3Ms. Kowalczyk explained what some of the creek's animals usually need. Most of the mayfly nymphs in Cutbank Creek cling to rocks in fast, cool riffles, where moving water brings them plenty of oxygen. Brook trout do best in cold water, and they are often stressed when the water stays above about 20 °C. Dragonfly nymphs and green frog tadpoles are most common in still, shallow water with plants to hide in. Zooplankton drift with the water, so fast currents tend to carry them downstream.
4Table 1 shows the lower stretch each July. Table 2 adds more counts from the lower stretch and compares them with the upstream stretch, where the club used the same nets, sample sizes and survey dates every year.