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Alterations to Hydrology
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As a result of human activities such as water withdrawal, water diversion, and channelization many important aquatic resources have experienced alterations in their natural hydrologic conditions. These alterations include changes in the water table, water level, and flow rate.
Changes in natural water levels threaten biodiversity by reducing the ability of aquatic habitats to flush out nutrients and organic matter resulting in a decrease in primary productivity. In addition, lower water levels can also alter habitat condition causing the removal of certain aquatic species that require specific water heights to survive.
Alterations in water flow have also been known to adversely affect aquatic biodiversity. When water flow is reduced, it may decrease water levels, damaging spawning habitats of important fish species such as the lake sturgeon. Problems may also occur when water flow increases including the degradation of river and stream bottoms due to scouring, and the destruction of habitats relied upon by fish and other benthic organisms.
Water withdrawal for irrigation, mining excavations and land drainage, has caused problems in aquatic ecosystems including significant reductions in the water tables of many areas of the United States. By reducing the level of the water table, drought conditions have occurred in many wetland ecosystems. As a result, wetlands have shrunk in size and species unable to adjust to drought conditions have begun to die off at alarming rates.
The construction of channels and canals has also contributed to changes in the hydrology of aquatic ecosystems. Some of the impacts to aquatic ecosystems associated with channalization include:
- Alterations to natural water flow
- Increased erosion and/or sedimentation due to flow alterations
- Introduction of exotics species by the canal and increased shipping
- Increased pollution due to increased shipping and boating traffic
