tic and land-based ecosystems are damaged by the advent of a dam (Pielou 209). Upstream of the barricade, the once flowing water that housed the riverine habitat becomes still, oxygen depleted, deepens into darkness, temperature stratified, and susceptible to enhanced evaporation which adjusts the entire hydrologic cycle (e.g., Pielou 207, 210; Ocean Planet n. pag.; Leopold 157). Moreover, drowned vegetation in the stagnant water is subject to rotting and may thereby pollute the atmosphere and reservoir with methane and carbon dioxide (Leopold 158; Pielou 208).Another change in the water chemistry that alters many river-based systems is the inclusion of heavy metals (and minerals) such as methyl mercury due to reactions between the reservoir bed and the standing water (Pielou 114, 207). If undetected, these toxins may bioaccumulate by moving through the trophic levels of the food web, eventually reaching humans.Aside from the changes in the chemical constituencies of the water, a dam will also physically augment the river by modifying the shape of the channel. This is primarily due to the retention of sediments behind the dam wall. Water that was once entrained with silts has the increased erosive power to degrade the riverbanks downstream while upstream, the deposition process is shallowing and narrowing the river reaches (e.g., Moffat 1116; Pielou 210). These alterations in channel shape can also shift the elevation of the groundwater table and can amplify the severity of the floods that the dams may have been built to prevent (de Villiers 155-56; PCFFA n. pag.).The silting process, though, can have other effects on riverine environments. With the deprivation of sediments, valuable nutrients are withheld from the floodplains and the delta of the river. Ultimately, agricultural land suffers from fertility loss and coastlines recede (e.g., DRIIA n. pag.; Pielou 212). In addition to the above noted deterioration of wetland envi...
