Isotopic analyses of oxygen and hydrogen of water (δ¹⁸O and δD) and nitrogen and oxygen of nitrate (δ¹⁵N and δ¹⁸O) are used in conjunction with conventional water chemistry and hydrologic measurements to investigate water flow and nitrogen cycling mechanisms through two riparian zones adjacent to upland agricultural fields. Within the Kankakee watershed of northwestern Indiana, a native riverine wetland was compared to a constructed riverine wetland to assess the wetland restoration in terms of water flow and nitrate attenuation mechanisms and efficiency. Conditions in the constructed wetland are controlled by a system of individual cells separated by dikes and levees and into which water is periodically pumped, while the native wetland occupies an area of remnant river meanders or oxbows. Analyses of samples taken from well transects across both wetlands suggest that water flow across the constructed wetland has been greatly altered. Nitrate cycling characteristics show significant differences between the two wetlands and particularly, nitrate attenuation efficiency is greatly reduced in the constructed wetland.