DIEL CALCIUM AND MAGNESIUM BEHAVIOR IN A SMALL AGRICULTURAL STREAM, BEAVER CREEK, SPRINGFIELD, OHIO

In recent decades, calcium and magnesium ions in small and large watersheds in the United States have increased in association with liming additions, and acid-generating fertilizers that enhance the release of base cations. Urban landscapes can also increase these ions. More work is needed to understand how the delivery of these ions relates to flow. This study examines the diel behavior of calcium and magnesium in the Beaver Creek (101 km²), Ohio a headwater sub-watershed of the Ohio River basin. Beaver Creek is primarily agricultural (80%), but also includes urban land use (3%) as it enters Springfield, Ohio and joins Buck Creek. Diel samples were collected from the base of Beaver Creek during a July 20-21, 2013 storm event. During this event the flow ranged from 1.7-3.6 m³s^-1 while Ca+Mg molar concentrations ranged from 0.36-0.40 mmol. The total Ca+Mg yield during the 24 hour period was 2306 kg. Interestingly, Ca+Mg concentrations did not decrease in the falling limb of the hydrograph. This lack of dilution and source-mixing explorations will help to identify agricultural and or urban sources of these ions. This study will examine diel Ca+Mg behavior alongside, pH, and dissolved inorganic nitrogen (DIN), alkalinity, to determine the source of response. Additional reflection on the role of flow in ion delivery in other agro-urban rivers will be considered.