Abstractions and Alterations

[1]
The section, Anatomy of a River,  argues that a river's character is espoused to a catchment's geology and proximate conditions.  Acting as drainage for the catchment, flooding and occasional obstructions (a felled tree, packs of detritus) are normal occurrences in a river ecosystem and are incorporated as organic input.  But anthropogenic impositions that attempt to quell natural flooding and redirect wetland drainage through means of damming, channel straightening (diagrammed right), enclosing, or lining (with concrete), detrimentally impact sediment transport, natural nutrient cycling, and the biota that depend on it.   From a water quality and biological standpoint these types of river modifications cause wide fluctuations in water levels over short periods of time, increase channel scour, and provide poor habitat conditions for aquatic life (DNR).  The majority of these modifications are implemented in areas of urban a agricultural developmental. As a result, (and with few exceptions), the lower quality streams are located in the most densely populated areas within a basin (DNR). These methods of flood control and water storage, while popular 35 years ago are now considered somewhat ineffective (DNR).

Dams 

And how they figure into this whole thing

[2]

The rivers, ponds, and wetlands in the Milwaukee River Basin contain about 70 dams of varying size and function (DNR).  Regardless of size, dams can have profound effects on stream ecosystems(DNR).  Dams can transform once flowing streams into standing bodies of water, displacing species that thrived in the formally dynamic environment. Organisms that are sensitive to the cold, well oxygenated conditions of a lotic habitat cannot withstand the stress of temperature stratification and oxygen depression concomitant with a lentic habitat. The disappearance of these lotic-specific organisms is readily manifest in the food chain. By preventing or slowing the migration of fish and other aquatic life within the stream ecosystem, dam structures prompt a complete restructuring of trophic composition. Dams dampen natural patterns of sediment transport, undercutting a stream community's reliance on periodic high flows to move and cycle sediment and nutrients downstream.   Instead of being suspended in the water column and depositing at river bends, sediments become impounded behind dams, covering course substratum that many species rely on for reproduction and habitat (DNR). 

Not All Dams are Created Equal

[3]
Anthropogenic dams as engineering feats are instituted to usurp and slow flow for domestic supply, irrigation, industry, hydroelectric power, or flood regulation. A dam’s design and expanse is relative to its function and locality. But one thing is certain concerning a dam's lifespan (be it weir or super dam): Dams, whatever their size and rationale, inevitably succumb to sedimentation (Goldsmith).

Weirs and Low-head Dams
The impoundments at Kletzsch and Estabrook are concrete low-head dams, originally installed to promote recreation, help regulate flooding, and increase the regional property values. These man-made structures were designed to give the appearance of a natural waterfall. The images below and to the right show how the design of the dam structure effects both crest and deposition.

[4]

The installment of a weir or low-head dam, modifies flow regime by designating two distinct habitats. Nutrient rich sediment normally transported the length of the river becomes sedimented behind the structure. In these cases of no flow or in lentic habitats, the surface of the large pool (pond, lake, or reservoir in some cases) is more easily heated and prone to evaporate. The area immediately below the structure can become degraded from the force of falling water and the has less sediment introduced to its lotic habitat. The effects of the structures are neatly outlined in the illustration below. (How fortuitous!)

[5]

Project Objective Recap

Damming as a repeated measure along the Milwaukee River alters the aquatic-terrestrial interface, effectively reshaping the stream community above and below an impoundment. Because organisms in streams and rivers are limited to specific ranges of physicochemical environments by their physiological tolerance, the collected data illustrates how the effects of local damming have manifested themselves in benthic macroinvertebrates communities.

[6]

Dams and The River Continuum Concept
The River Continuum Concept, a testable hypothesis proposed by Vannote et al 1980, suggests consistent, observable patterns of community structure and function along the length of a natural, unperturbed river.  Within this model, damming and other regulating measures act as “reset mechanisms,” effectively recreating headwater conditions and correlative headwater biota.

Profiling selected the transects of the Milwaukee River will generate data that can be compared to predictions made by The RCC. We'll see if dams truly act as “reset mechanisms” for stream community structure and if this postulated ‘reset’ is observable in the Milwaukee River.

Infographics!>>>


Refs--
Goldsmith, Edward, and Nicholas Hildyard. The Social and Environmental Effects of Large Dams. Camelford, Cornwall: Wadebridge Ecological Centre, 1984. Print.
Vannote, Robin L., G. Wayne Minshall, Kenneth W. Cummins, James R. Sedell, and Colbert E. Cushing. "The River Continuum Concept." Canadian Journal of Fisheries and Aquatic Sciences 37.1 (1980): 130-37. Print.


Wisconsin. Department of Natural Resources. N.p., n.d. Web. 10 July 2012. <http://dnr.wi.gov/water/basin/milw/milwaukee_801.pdf>.

Images:
[1]http://www.vtwaterquality.org/wqd_mgtplan/images/DamEffects02.jpg
[2] Still from Planet of the Apes
http://s1.hubimg.com/u/6123756_f496.jpg
[3] http://www.fao.org/docrep/X5744E/x5744ees.gif
[4] http://www.australiangeographic.com.au/assets/dam-diagram.jpg
[5] http://www.coolgeography.co.uk/GCSE/AQA/Water%20on%20the%20Land/Managing%20Floods/River%20straightening.jpg
[6] Vector Illustration