Laserfiche WebLink
<br /> <br />wetland can take on a completely different func- <br />tion, or it may be destroyed. Generally, the most <br />devasfating impacts on wetlands result from <br />changes in land use. Wetlands commonly are <br />drained to make land available for agricultural <br />use or filled to make land available for urban and <br />industrial development. Without understanding <br />how wetlands interact with ground water, many <br />plans to use land formerly occupied by wetlands <br />fail. For example, it is operationally straightfor- <br />ward to fill in or drain a wetland, but the ground- <br />water flow system that maintains many wetlands <br />may continue to discharge at that location. Many <br />structures and roads built on former wetlands <br />and many wetland restoration or construction <br />programs fail for this reason. Saline soils in many <br />parts of the central prairies also result from evapo- <br />ration of ground water that continues to discharge <br />to the land surface after the wetlands were <br />drained. <br />Riparian zones also are particularly sensitive <br />to changes in the availability and quality of <br />ground water and surface water because these <br />ecosystems commonly are dependent on both <br />sources of water. If either water source changes, <br />riparian zones may be altered, changing their <br />ability to provide aquatic habitat, mitigate floods <br />and erosion, stabilize shorelines, and process <br />chemicals, including contaminants. Effective <br />management of water resources requires an <br />understanding of the role of riparian zones and <br />their dependence on the interaction of ground <br />water and surface water. <br /> <br /> <br />Characteristics of Aquatic Environments <br /> <br />The interface between ground water and <br />surface water is an areally restricted, but particu- <br />larly sensitive and critical niche in the total envi- <br />ronment. At this interface, ground water that has <br />been affected by environmental conditions on the <br />terrestrial landscape interacts with surface water <br />that has been affected by environmental condi- <br />tions upstream. Furthermore, the chemical reac- <br />tions that take place where chemically distinct <br />surface water meets chemically distinct ground <br />water in the hyporheic zone may result in a <br />biogeochemical environment that in some cases <br />could be used as an indicator of changes in either <br />terrestrial or aquatic ecosystems. The ability to <br />understand this interface is challenging because it <br />requires the focusing of many different scientific <br />and technical disciplines at the same, areally <br />restricted locality. The benefit of this approach <br />to studying the interface of ground water and <br />surface water could be the identification of useful <br />biological or chemical indicators of adverse or <br />positive changes in larger terrestrial and aquatic <br />ecosystems. <br />Wetlands are a type of aquatic environment <br />present in most landscapes; yet, in many areas, <br />their percei ved value is controversial. The prin- <br />cipal characteristics and functions of wetlands are <br />determined by the water and chemical balances <br />that maintain them. These factors in large part <br />determine the value of a wetland for flood control, <br />nutrient retention, and wildlife habitat. As a <br />result, they are especially sensitive to changing <br />hydrological conditions. When the hydrological <br />and chemical balances of a wetland change, the <br /> <br />78 <br />