ABSTRACT

Excess nitrogen pollution is widespread globally, with recent efforts in the USA to use stream and river restoration to solve the problem. But will this work? We used modeling and field work to evaluate stream and river restoration effects on excess nitrogen. Field experiments implemented in-channel structures and overbank floods while measuring effects on hydraulics, transport, and water quality. Numerical studies evaluated effects of groundwater levels, sediment permeability, floodplain area, and watershed-scale cumulative effects. Results show individual projects may have a small effect on overall nitrogen transport, but cumulative effects at the watershed outlet can be substantial. The impact of restoration on nitrogen loading increases with sediment permeability, decreased groundwater gaining, availability of land for floodplain reconnection, and increasing Strahler stream order. Coordination between stream or river restoration and other water quality treatment approaches such as wastewater treatment plants will be necessary to optimize watershed water quality.