Connectivity is defined as the maintenance of lateral, longitudinal, and vertical pathways for biological, hydrological, and physical processes (Annear, 2004). It refers to the flow, exchange, and pathways that move organisms, energy, and matter throughout the watershed. The most obvious example of connectivity may be the free flow of water downstream in a river and the passage of fish upstream. The construction of a high dam across a stream is a vivid and obvious illustration of fragmentation or the loss of connectivity.
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"And so the valley has come to be viewed as the defined stream ecosystem, the basic unit of our river world. This is the holistic view, which considers the system as a whole. In a stream ecosystem, the valley slopes, tributaries, and the channel itself all contribute to the nature of the stream. The borders of this ecosystem are not the stream banks, but the high rims of the valley - the ridge tops where the landscape falls off to a neighboring valley, which is another, contiguous ecosystem." (Waters, pg 74) |
This exchange of energy, nutrients and material does not stop at the water's edge, it can be observed at many scales throughout the surrounding landscape. Complex, interdependent processes are continuously present throughout the watershed landscape and are required to maintain the ecological health of the system as a whole.
For the river system, this continuum of hydrologic, biological, and chemical interactions and connections is described along the same four dimensions used to describe the hydrologic system.
There are four dimensions of connectivity between a river and its contributing watershed. These are longitudinal, lateral, vertical and temporal. |
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