Storage Coefficients/Specific Yield

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Storage Coefficients/Specific Yield
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Storage Coefficient/Storativity

• S storage coefficient or storativity The amount
  of water stored or released per unit area of
  aquifer given unit head change
• Ss specific storage
• The amount of water stored or released per unit
  volume of aquifer given unit head change
• S Ss b, where b is the aquifer thickness
• Storage change is accomplished via compression of
  the aquifer matrix and the fluid. Fluid
  compressibility 10-10 Pa-1 while typical (sand)
  aquifer compressibility is 10-8 Pa-1
• Typical values of S (dimensionless) are 10-5
  10-3
• Measuring storativity derived from observations
  of multi-well tests
• GEOS 4310/5310 Lecture Notes, Fall 2002Dr. T.
  Brikowski, UTD

http//www.utdallas.edu/brikowi/Teaching/Geohydro
logy/LectureNotes/Regional_Flow/Storativity.html
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Storage Coefficient/Storativity
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Specific Yield
Determination of Specific Yield for the Biscayne
Aquifer with a Canal-Drawdown Test by Carl H.
Bolster, David P. Genereux, and James E.
Saiers Abstract Data from a large-scale
canal-drawdown test were used to estimate the
specific yield (sy) of the Biscayne Aquifer, an
unconfined limestone aquifer in southeast
Florida. The drawdown test involved dropping the
water level in a canal by about 30 cm and
monitoring the response of hydraulic head in the
surrounding aquifer. Specific yield was
determined by analyzing data from the unsteady
portion of the drawdown test using an analytical
stream-aquifer interaction model (Zlotnik and
Huang 1999). Specific yield values computed from
drawdown at individual piezometers ranged from
0.050 to 0.57, most likely indicating
heterogeneity of specific yield within the
aquifer (small-scale variation in hydraulic
conductivity may also have contributed to the
differences in Sy among piezometers). A value of
0.15 (our best estimate) was computed based on
all drawdown data from all piezometers. We
incorporated our best estimate of specific yield
into a large-scale two-dimensional numerical
MODFLOW-based ground water flow model and made
predictions of head during a 183-day period at
four wells located 337 to 2546 m from the canal.
We found good agreement between observed and
predicted heads, indicating our estimate of
specific yield is representative of the large
portion of the Biscayne Aquifer studied here.
This work represents a practical and novel
approach to the determination of a key
hydrogeological parameter (the storage parameter
needed for simulation and calculation of
transient unconfined ground water flow), at a
large spatial scale (a common scale for water
resource modeling), for a highly transmissive
limestone aquifer (in which execution of a
traditional pump test would be impractical and
would likely yield ambiguous results).  
Ground Water Abstracts Volume 39 Number 5
September/October 2001/