Running through the heart of
downtown Austin, the lake serves as a public water supply, is
a highly valued recreational resource, and provides important
aquatic and riparian habitat for organisms not often found in
an urban area. It is operated as a ‘run of the river’
or ‘pass through’ reservoir, meaning it has no capacity
for storing water and the water level fluctuations are minimal.
Flow through Lady Bird Lake is controlled by LCRA,
and falls into two basic seasons:
- Release season, mid-March through mid-October, when water
is released for downstream irrigation uses. During this period,
the system behaves more like a river than a reservoir.
- Non-release season, mid-October through mid-March, when
irrigation needs diminish and releases are geared primarily
toward requirements of instream flow for the Colorado River,
and freshwater inflow to Matagorda Bay.
Water quality is assessed at three sites: Basin
(near Longhorn Dam), First Street, and Redbud (just downstream
of Redbud Isle). Samples are collected under both baseflow and
storm flow conditions, in each of the two release regimes described
above.
Current objectives of the water quality study are:
- Monitor long-term temporal trends in Lady Bird Lake water
quality
- Continue to assess spatial differences between Lady Bird
Lake sites
- Compare differences between surface and at-depth water quality
in Lady Bird Lake
- Assess Lady Bird Lake water quality using Texas Commission on Environmental Quality screening
levels/water quality standards
Sediment is collected once in each release regime,
at the Basin. Bathymetric surveys are also conducted periodically
under contract with the Texas Water Development Board.
Trash and debris are assessed with a Visual Index
of Pollution, which scores longitudinal sections of the lakeshore
based on coverage by floating trash. The index scores are used
by the City's Watershed Engineering and Field Operations Division
to target their clean up efforts.
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