Gradients and directionality

A one-directional longitudinal gradient with maximum depth at the downstream end is typical of impoundments created by damming a river. In lakes, the deepest region is typically more central, with the major flows being rotational, driven mainly by wind. The continuous declination of the impoundment bottom from the inflow to the

Figure 1 Ford Lake dam and power station, southeastern Michigan, USA, forming one of hundreds of impoundments constructed in the early twentieth century to supply electrical power to industry.

dam is usually accompanied by broadening at the inflow end. The result is a mostly unidirectional movement of water from inflow to outflow.

Longitudinal gradients in many properties are seen along the length of an impoundment. The inflow region receives high concentrations of particles, organic matter, nutrients, and other chemical components from the upstream catchment. Localized flushing rates are faster and biological activity is lower than in more slowly flushed, larger volume elements down the impoundment. In the transition zone as flow is slackened, primary production is increased toward the capacity provided by nutrients, underwater light availability, and predation pressure of zooplankton. Increased phytoplankton chlorophyll a concentrations, coupled with sinking and decomposition of organic matter result in lower oxygen concentrations near the bottom, low redox potentials, and higher concentrations of ammonium, manganese, iron, and hydrogen sulfide.

10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook


Post a comment