Background
Surface Water Dynamics describe the quantity and movement of
water in a surface body such as a stream or lake. They include
flow or discharge for flowing waterbodies and stage or level
for non-flowing waterbodies To satisfy a variety of ecological
uses (fish and other aquatic organisms, terrestrial wildlife,
riparian and channel vegetation, recharge groundwater) a stream
or other body of water should have sufficient quantity and quality
of water for every day of the year. Height of stream flow varies
seasonally under natural conditions; however any extreme variation
can be stressful to organisms and damaging to the physical environment.
Urban areas have a large number of impervious surfaces such
as parking lots, streets, sidewalks, and buildings. Impervious
surfaces reduce groundwater recharge and baseflow into streams
because less water percolates into the soil, and increase the
velocity and amount of runoff into lakes, rivers, and streams
through overland flow, storm drains, and sewer outfalls.
The intensity of the exposure to potential stressors for stream
organisms depends on how fast water is traveling past the organisms,
and on the dilution factor, which depends on how much water
is in the stream. Surface water dynamics data provides key support
data for other vital signs indicators including freshwater quality,
groundwater dynamics, stream threatened and endangered (T&E)
species and fish assemblages, T&E amphibians and reptiles,
erosion and deposition, wetlands, and riparian habitat.
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