Term Project Outline
CE 394K Surface Water Hydrology
University of Texas at Austin
Austin's Bat Population and Its Effect on
Water Quality in Town Lake
by J. Andrew Tachovsky
From approximately March to November, Austin is home to a sizable bat population.
These bats have made their roost under the Congress Street bridge crossing Town
Lake near the Austin-American Statesman Building. During the late summer months
when dry weather prevails, observers can be seen by the bridge watching the bats as they
begin their daily nocturnal rounds to feed on insects. As the bats have chosen to roost
under a major structure crossing a segment of the Colorado River, it is hypothesized that
the activities of the bats has an effect on the water quality in the Colorado.
The purpose of this project is to investigate the impact of the bats on the water quality
of the Town Lake segment of the Colorado River. Water samples will be collected in
small spatial increments and analyzed for nitrate, sulfate, phosphate, pH and dissolved
oxygen (DO). Several sampling events will occur to monitor the effects as the bat
population slowly departs for Mexico during the late fall and early winter.
Scope and Rationale:
The rationale for this project is based on the potential effects of nitrates in water. At
low concentrations (less than 40 ppm) nitrates in surface water can cause plant growth
and depression in pH. If these conditions are not corrected, eutrophication of
surface water can occur leading to septic conditions and fish kills.
At high concentrations (above 44 ppm) nitrates in drinking water can cause health
effects in humans. High nitrate concentrations in drinking water has been documented
to cause difficulties with prenatal infants, and young children. Accordingly, nitrate
concentrations above 44 ppm is considered unsafe.
Sulfate and phosphate concentrations will be measured as an indication of available
nutrients for microbial activity. Depletion of these nutrients downstream indicates
utilization by plant and microbial sources.
Three sampling events will be conducted. A canoe will be obtained and
taken out to Town Lake. A picnic will be enjoyed, and a frisbee will be
thrown. Sunbathing may take place. Three sampling events will be taken
upstream from the bridge to determine background levels of nitrate,
phosphate and sulfate. Samples will then be taken approximately every
15 feet starting under the bridge and continuing downstream approximately
200 yards. Zero headspace sampling technique will be used to assure
sustained quality of samples.
Samples will be analyzed for pH and DO using appropriate membrane analysis
techniques. Samples will be analyzed for nitrate, sulfate, and phosphate using
Ion Cromatographic Analysis EPA SW 846 Method 9056.
Data and Expected Results:
It is expected that the Congress Street bridge will mark a region of increased
nitrate and phosphate in surface water as a result of bat activity. It is also
expected that DO will depleted as a result of increased plant and microbial
activity in the water. However, It is expected that these abnormal conditions
will dissipate with distance downstream from the bridge.
Sources of Information:
The data that is used in this project will be generated through the sampling
events that have been described. A background literature review will be
conducted to accurately describe the eutrophication and human health
effects associated with increased nitrate in surface water.
If you like the sound of this project and would like to discuss it further,
J. Andrew Tachovsky
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