Transformation of the North American Hydrologic Landscape

The cumulative impact of the placement of millions of artificial water bodies on the landscape of North America has not been documented. Nonetheless, it is reasonable to assume that their impacts are both profound and pervasive. There are no major watersheds in the United States without reservoirs, and relatively few minor ones. In Canada the number of relatively undisturbed watersheds is much greater, especially in the north, and Mexico too has several large unregulated watersheds remaining although this is changing. One indication of the effect of these impoundments is that despite very large increases in soil erosion associated with deforestation and agricultural activities, the total flux of sediment from the continent to the seas is apparently little different today from what it was prior to European settlement. Other cumulative impacts are less well known. In arid

Figure 5 Density of small water bodies of the conterminous United States.

Figure 5 Density of small water bodies of the conterminous United States.

and semiarid regions total evaporation from reservoirs can be a significant portion of total stream flow, but the effect is probably minor in humid regions. The greatest impacts are likely in the distribution of biota, both in terms of creation of new habitat for aquatic species where none existed before, and in creation of barriers to fish migration. Another as yet unquantified but potentially large impact of reservoirs is on the carbon cycle. Many reservoirs appear to be net sources of carbon dioxide to the atmosphere as well as significant generators of methane, but at the same time they are major sinks of particulate carbon.

See also: Abundance and Size Distribution of Lakes, Ponds and Impoundments; Geomorphology of Lake Basins; Origins of Types of Lake Basins.

Was this article helpful?

0 0
Project Earth Conservation

Project Earth Conservation

Get All The Support And Guidance You Need To Be A Success At Helping Save The Earth. This Book Is One Of The Most Valuable Resources In The World When It Comes To How To Recycle to Create a Better Future for Our Children.

Get My Free Ebook


Post a comment