PNNL

Abstract

Wetlands provide a wide variety of ecological functions and services critical to the overall functioning of many ecosystems. Since, by definition, wetlands are wet for a significant portion of a year, the ability of wetlands to provide these functions is highly dependent on hydrology. Over half of the wetlands globally have been destroyed over the past 150 years or so. Degradation of remaining wetlands is significant in places here studies have been carried out. Much of this degradation has been due to alteration of hydrology through reduction in inputs through construction of hard surfaces, channelization, damming of outflows, introduction of contaminants, introduction of exotic species, and a variety of other impacts. Studies in the Puget Sound trough and in the Portland, Oregon, region, have intensively investigated hydrological alterations and wetlands. In general, increases of impervious surfaces and rerouting of natural hydrology have affected plant and animal species composition and production and have altered the processes of primary production, nutrient cycling, groundwater recharge rates, and sediment dynamics. The close coupling of wetland functions, plant and animal populations, and hydrology is clearly illustrated in these case studies. The studies have resulted in significant contributions to the management of wetland systems in these areas through consideration of the hydrologic processes.