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For developed countries with large budgets and effective environmental legislation (such as France and the United States) decommissioning dams is a solution for aiding fish in special habitats (especially salmon) (WCD). While short-term effects of dam removal include large-scale sediment flushing, over relatively short time scales fish will return and spawn in those areas. However, dam removal is costly and must be studied beforehand; in many cases, toxins and chemicals can build up behind dams and the effects of these toxins washing downstream can be severe (Francisco).
Works Cited
Francisco, Edna. "Tales of the Undammed." Science News 10 Apr. 2004. 28 Oct. 2007 <http://www.sciencenews.org/articles/20040410/bob9.asp
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Human Appropriation of the World's Fresh Water. University of Michigan. 2000. 28 Oct. 2007 <http://www.globalchange.umich.edu.ezproxyberklee.flo.org/globalchange2/current/lectures/freshwater_supply/freshwater.html>.
Richardson, Carl. "Migratory Fish Restoration." PA Fish and Boat Commission. 2000. PA Fish and Boat Commission. 28 Oct. 2007 <http://www.fish.state.pa.us/anglerboater/2000/maju00/migrestr.pdf>.
World Commission On Dams. Dams and Development: a New Framework for Decision Making. World Commission on Dams. London: Earthscan Publications Ltd., 2000. 28 Oct. 2007 <http://www.dams.org>.
Wuest, Alfred, Lorenz Moosmann, and Gabriela Friedl. "Alpine Hydroelectric Power Plants and the "Long-Range Effects" on Downstream Waters." EAWAG 55. 17 Oct. 2007 <http://www.eawag.ch/publications/eawagnews/www_en55/en55e_screen/en55e_wuest_s.pdf>.
Young, Leroy M. Fish Habitat and Flow: What's the Connection. PA Fish and Boat Commission. PA Fish and Boat Commission, 1997. 28 Oct. 2007 http://www.fish.state.pa.us/anglerboater/2001/ma2001/habtflow.htm.
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Riparian Buffers
Importance:
Riparian buffers provide various important stream functions.
(1) Leaves that fall into the water provide energy for headwaters (i.e. a food source).
(2) Branches and roots provide shelter for in-stream organisms.
(3) Overhead leaf cover shades water and keeps it cool, by as much as 10° in summertime (Great Fishing).
(4) Roots hold stream banks in place and prevent erosion.
(5) Vegetation slows water velocity, thus reducing run-off induced erosion and also allows particulates (including many water contaminants) to settle out.
(6) Soils and root systems filter nutrients and pollutants (especially from agriculture and residential areas) before they reach surface areas from groundwater (Haberstock).
These functions are not only important to the biota that lives in these regions year round, but also to anadromous species that come to spawn. For example, salmon require clean gravel for spawning; if silt settles over the gravel, it not only destroys suitable spawning substrate, but it can also smother eggs and the invertebrates that juveniles feed upon (Haberstock). Haberstock also reports that branches and other woody structures provide places for invertebrate prey to live, as well as structural habitat and varied flow patterns that are important for salmon. The improved water quality provided by riparian buffers and the cooling effect they provide are also critical (Haberstock).
Solution:
Riparian buffers should be established along rivers; the width should be determined based on various criteria as detailed below. To implement this, focus should be placed on education of farmers to take up these measures voluntarily. Governments and agencies that can afford to provide funds to help establish these buffers, offer tax incentives, or to rent land to take it out of production should do so.
The width of the buffer depends on many factors, especially the slope of the land (steeper slopes require wider buffers), the permeability of the soil (less permeable soils require wider buffers because water takes longer to infiltrate), and the presence of overland water sources--like intermittent streams or gullies-which can render small buffers ineffective (Haberstock). The type of vegetation-such as wooded or ground level vegetation--as well as factors such as duff height can influence buffer efficacy (Haberstock). Buffer width is measured from the end of alluvial soils (floodplain edge) (Haberstock). Haberstock also notes that wetlands in these areas should be preserved, because they function more effectively in nitrogen-fixation and retention of contaminants and sediments.
However, if it is not economically feasible to establish a buffer of the recommended width, it is still beneficial to establish a riparian buffer of a smaller width. Studies have found that buffers of 20 feet of native grasses can remove up to 90% of nutrients and 80% of sediments (Lutz). Furthermore, a riparian buffer does not mean that no human activity or industry can take place in these zones; for example, selective logging can take place if best-management practices are followed and some agriculture such as growing nut trees can easily serve as a buffer and a source of income.
Haberstock Recommendations:
Zone 1: 35 feet
Zone 2: For width determinations, see the method outlined in Haberstock pages 8-14. (see attached document) Works Cited
A Conservation Catalog. Pennsylvania Conservation Partnership. Pennsylvania Conservation Partnership. 29 Oct. 2007 <http://www.envirothonpa.org/documents/conscatalog.pdf>.
Great Fishing Needs Great Habitat. PA Fish and Boat Commission. 1997. 29 Oct. 2007 <http://www.fish.state.pa.us/anglerboater/2001/jf2001/greathab.htm>.
Haberstock, Alan E., et al. "METHOD TO IDENTIFY EFFECTWE RIPARIAN BUFFER WIDTHS FOR ATLANTIC SALMON HABITAT PROTECTION1." Journal of the American Water Resources Association 36.6 (2000): 1271-86.
Lutz, Karl J. A Fish and Livestock Tale. PA Fish and Boat Commission. PA Fish and Boat Commission. 8 Nov. 2007 <http://www.fish.state.pa.us/anglerboater/2001/01_nov-dec/AFishandLivestockTale.pdf>.
The Basics of Water Pollution. PA Fish and Boat Commission. PA Fish and Boat Commission. 29 Oct. 2007 <http://www.fish.state.pa.us/anglerboater/2001/jf2001/waterpoll.pdf>.