HGM vs. IBI hydrology
landscape success criteria
floristic quality Abby Rokosch
Jessen Book Siobhan Fennessy
"Hydrology is probably the single most important determinant of the establishment and maintenance of specific types of wetlands and wetland processes." -Mitsch and Gosselink (1993)
Wetland hydrology is perhaps the most key element in all wetland restoration project. Many wetland scientists have referred to wetland hydrology as the most important component of wetland ecosystems (Mitsch and Gosselink, 1993; Erwin, 1990 in Kusler and Kentula, 1990). It is ironic however that restorationists often times know very little about the hydrology of the wetland that they are trying to restore. It is difficult to tackle the restoration of wetland hydrology because there are still so many variables unknown to scientists.
Because wetland hydrology is such a broad topic in wetland restoration, this next paragraph will provide you with a very basic description of the importance of hydrology and its functions in wetland ecosystems. For a more descriptive overview of wetland hydrology, water quality, and associated functions, click here. To see a case study of wetland hydrology manipulation, click here.
Small changes is wetland hydrology can significantly affect the chemical and physical properties of a wetland
such as nutrient availability, degree of substrate anoxia, soil salinity, sediment properties, and pH (Mitsch and
Gosselink, 1993). When hydrologic conditions in wetlands change, plant species composition can shift and ecosystem
productivity can decline (Mitsch and Gosselink, 1993). Because hydrology plays a vital role in the structure of
a wetland's ecosystem, particularly by acting as the main pathway in which nutrients are transported in and out
of the system, the vegetation and species composition are significantly effected when natural or man made hydrologic
alterations occur. Mitsch and Gosselink (1993) list several principles underscoring the importance of hydrology
in wetlands, (click here). Wetland restoration is often centralized
around establishing hydrological equivalence (Bedford) because of the important role it plays in wetland function.
In part, the hydrological regime of a wetland is what defines certain areas of land as wetland ecosystems. Without
certain hydrological criteria and hydric soils, an area of land cannot be defined as a "wetland". (See wetland definitions)
Wetland Hydrology Today
Humans have altered wetland hydrology through a variety of activities: drainage, filling, damn construction, water diversions, groundwater pumping, and dredging (Zedler, 2000). All of these activities alter the timing, amplitude, frequency, and duration of high water (Zedler, 2000). Today, wetland scientists are aware of the importance of hydrology. Despite all the "hype" that wetland hydrology has received, we still know very little about how to manipulate or simulate certain hydrological conditions. However, the future is getting brighter. Many restorationists are manipulating hydrological variables in their restoration restoration projects (see Case studies). It is important that long term monitoring of hydrologic variables including, groundwater flow, surface water recharge, water level fluctuation, and precipitation input, and others, are recorded. After long-term hydrological data is available, restoring wetland hydrology will become "easier" and a more attainable goal.
Restoration methods consisted of the removal of undesirable vegetation and the addition of water.