Characterizing hydrology and the importance of ground-water discharge in natural and constructed wetlands

Although considered the most important component for the establishment and persistence of wetlands, hydrology has been hard to characterize and linkag es between hydrology and other environmental conditions are often poorly un derstood. In this work, methods for characterizing a wetland's hydrology fr om hydrographs were developed, and the importance of ground water to the ph ysical and geochemical conditions in the root zone was investigated. Detail ed sampling of neatly continuous hydrographs showed that sites with greater ground-water discharge had higher water tables and more stable hydrographs . Subsampling of the continuous hydrograph failed to characterize the sites correctly, even though the wetland complex is located in a strong regional ground-water-discharge area. By comparing soil-moisture-potential measurem ents to the water-table hydrograph at one site, we noted that the amount of root-zone saturation was not necessarily driven by the water-table hydrogr aph but can be a result of other soil parameters (i.e., soil texture and as sociated capillary fringe). Ground-water discharge was not a significant de terminant of maximum or average temperatures in the root zone. High ground- water discharge was associated with earliest date of thaw and shortest peri od of time that the root zone was frozen, however. Finally, the direction a nd magnitude of shallow ground-water flow was found to affect the migration and importance of a geochemical species. Areas of higher ground-water disc harge had less downward penetration of CO2 generated in cheroot zone. In co ntrast, biotically derived CO2 was able to penetrate the deeper ground-wate r system in areas of groundwater recharge. Although ground-water flows are difficult to characterize, understanding these components is critical to th e success of wetland restoration and creation efforts.