Hydrologic effects of a wet prairie restoration

Background/Question/Methods

The Oak Openings Region in Northwest Ohio originally consisted of oak savannas, wet prairies, oak woodlands, oak barrens and floodplain forests. Currently, the Oak Openings supports globally rare oak savanna and wet prairie habitats. It is home to more rare species of plants and animals than any other area of Ohio. Once occupying over one-quarter of the region wet prairies now represent < 0.1% of the Oak Openings’ land area, mostly due to drainage ditches and field tiles. Nowadays, restoration of wet prairie in the region is being hindered by an invasive species, the glossy buckthorn. The large amount of buckthorn in the region likely increases the local evapotranspiration and depresses the water table making it impossible for wet prairie species to exist.

What is the effect of the removal of buckthorn on the water table? What is the interaction between the ditch and the water table?

This study is a first approach to understand the hydrologic system of the region by monitoring the water table at six wet prairie restoration sites and correlating it to rainfall records from a nearby weather station. Six monitoring locations were installed along Wiregrass Ditch, a ditch that runs southwest to northeast through the region. Each location consists of a clustered set of five piezometers positioned on a transect perpendicular to the ditch at different depths. Within each ditch reach, a surface water monitoring location was also installed.

Results/Conclusions

Results show the effect of the transpiration on the water table. The growing season is represented by the general trend of the water table to rise and fall. It rises as the growing season ends and falls as the growing season begins, with smaller peaks showing the response to precipitation. All the deepest piezometers across the six sites show the same behavior of following the growing season. The same pattern is also found on the water level of the ditches. The lag and overall drawdown created by the buckthorn still needs to be teased out. The times and locations of buckthorn removal show which locations have been directly affected.