Unusually large loads in 2007 from the Maumee and Sandusky Rivers, tributaries to Lake Erie

Abstract

During water year 2007 (October 1, 2006, through September 30, 2007), the Maumee River and Sandusky River in northern Ohio transported the largest, or nearly the largest, loads of several, water quality constituents that have been observed in 33 years of monitoring. Discharge, total phosphorus, dissolved reactive phosphorus, total Kjeldahl nitrogen, and chloride all recorded 33-year maximum loads, while the loads for nitrate ranked 5th (Sandusky) and 8th (Maumee) out of 33. Loads of particulate phosphorus ranked 2nd (Sandusky) and 4th (Maumee), and those for suspended solids ranked 10th (Sandusky) and 9th (Maumee). This is partly a consequence of total rainfall, which was the largest observed at the Tiffin weather station (Sandusky watershed) and nearly the largest at the Toledo station (Maumee watershed) during this period. It also results from other aspects of the weather in interaction with agricultural practices, notably a warm, wet fall and early winter. Longer-term trends were also significant factors for some parameters. The weather was the major factor responsible for these large loads. Regardless of cause, these loads represent a substantial loss of resources from agricultural fields in the watersheds.This loss could have been reduced by better management. Losses of sediment and phosphorus from these watersheds are higher than average for Midwestern agricultural watersheds, and losses of nitrogen are slightly above average. Based on winter 2008 fertilizer prices from local fertilizer dealers, replacing the nutrients lost from these watersheds in water year 2007 would cost more than $80,000,000 or $166 ha-1 ($67 ac-1) for every field in the watershed receiving fertilizer in a given year.