USING SHORT-LIVED RADIONUCLIDES TO EXPLORE THE EFFECTS OF AGRICULTURAL DRAINAGE TILES ON EROSION DEPTH IN THE VERMILLION WATERSHED, OHIO

We used short-lived radionuclides, ¹³⁷Cs and ²¹⁰Pb, to study the relationship between agricultural land use, drainage tiles, and depth of erosion in the Vermillion watershed. We analyzed 26 samples collected from sub-watersheds ranging in size from 0.005 to 408 km² throughout the Vermilion River watershed. Land use in the Vermillion watershed is primarily agricultural and many farmers use drainage tiles to combat clayey and compacted soil. Drainage tiles are installed 3-6 feet below the surface and direct water to ditches, streams, and other water sources. The effect of drainage tiles on erosion is not well constrained. The three counties sampled in, Erie, Huron, and Lorain, contain drainage tiles on 40-60%, 10-20%, and 60-100% of the land, respectively. Assuming that drainage tiles are somewhat uniformly distributed on the landscape, variations in erosion depth among the counties help constrain the effects of drainage tiles on erosion. A germanium detector measured the concentrations of ¹³⁷Cs and ²¹⁰Pb in our samples. The concentrations of ¹³⁷Cs range from 0 to 4.74e-5μCi, and ²¹⁰Pb values range from 2.8e-5 to 8.35e-4μCi. We then used GIS to explore spatial relationships between radionuclide concentrations, upstream area, land use/land cover, slope, and soil type. Future work will include more detailed analysis of drainage tile distribution in the area.