Page 302 - Hydrogeology Principles and Practice

HYDC08 12/5/05 5:31 PM Page 285

Groundwater resources and environmental management 285

Fig. 8.5 Schematic diagram showing
the operation of an aquifer storage and
recovery (ASR) scheme. ASR involves
storage of available, principally surface or
drinking water-quality water during the
wet season through boreholes completed
in a brackish-water aquifer, with
subsequent retrieval from these same
boreholes during dry periods. The
freshwater forms a ‘bubble’ within
the aquifer around the ASR well and
can be retrieved when needed. The
hydrogeological characteristics of a
successful ASR storage zone include:
moderate aquifer hydraulic conductivity;
confinement above and below by low
permeability strata; and water quality
as fresh as possible to limit mixing
with the native brackish water. After
the United States Geological Survey
(http://sofia.usgs.gov/sfrsf/hydrology/A
SR/storagebig.jpg).

The criteria for deciding how much water can be scheme is the application of ASR technology as part
recovered from an ASR scheme are normally based of the Everglades Restoration Project in South Florida
on water quality parameters. The recovery efficiency (United States Geological Survey 2002). Between 300
is calculated as the volume of water recovered when and 330 ASR boreholes are planned with a combined
−1
6
3
the water quality parameter is reached compared to capacity exceeding 6 × 10 m day , storing fresh-
the volume of water injected. It is not uncommon for water in the deep brackish Upper Floridan Aquifer
recovery efficiencies to approach 100%. Full details of (the ASR zone) using surface water that is currently
ASR programme development, system design and discharged to the tide during the wet season. The
technical and non-technical issues are presented by stored water will be recovered during drought per-
Pyne (1995). iods to sustain delivery of adequate high quality water
By the mid-1990s more than 20 ASR schemes were to the Everglades (Box 8.6). ASR has not previously
operational in the United States with many more been implemented on this scale and key uncertainties
planned. ASR is popular in that improvements in include: the compatibility of the injected water with
water quality in the native aquifer result from the the aquifer water; effects of large volumes of injected
injection of high-quality water, which then allows water on the confining unit; efficiency in terms of
these aquifers to be used for supply purposes at a how much water will be recovered; and the effects of
lower cost than other resource options. One ambitious the recovered water on the environment. To answer