Maquoketa River Floodplain-River Connectivity 2014-2016 Data

The Maquoketa River carries some of the highest sediment and nutrient loads in the Upper Mississippi River, contributing to eutrophication and hypoxic conditions in the Mississippi River and Gulf of Mexico. Floodplains provide the ability to remove and sequester, sediments, nitrogen, phosphorus, and carbon; however effectiveness of floodplains is limited by the extent and connection of the floodplain to the river. The confluence of the Maquoketa and Mississippi Rivers presents a unique study location because the delta at the confluence is heavily managed by a State-Federal-NGO partnership that has already taken action focusing on evaluating the impact of increased connectivity on numerous ecosystem services, including water quality improvement, flood control, and fish and wildlife productivity. Our objective was to quantify the effects of increased river-floodplain connectivity on ecosystem services, namely potential water quality improvement, in a 93-ha parcel of the floodplain that was reconnected to the Maquoketa River due to levee breaches at Green Island, Iowa. We quantified ecosystem services that include retention of flood transported sediment, C, N, and P on the Maquoketa floodplain; floodplain sediment denitrification and its relation to nitrate (NO3- -N) removal on the floodplain post flood and during dry, inter-flood periods; and factors affecting sediment P retention or release and P soil saturation during inter-flood periods as an indication of whether the floodplain soils act as a source or sink of P.