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Use of artificial groundwater
recharge techniques:
a task in case of aquifer exploitation or depletion
Dr.Ing. Cinzia Miracapillo
Lecturer at the University of Applied Sciences NW Switzerland
Research associate at the Water Research Institute IRSA
Sustainable development: a challenge for European research
Brussels, 26-28 May 2009
Use of artificial groundwater recharge techniques
Introduction
Benefitswith respect to the recent trends on natural
resources conservation and stresses mitigation
Reflections based on two examples in Basel
Artificial recharge in a green area (“Lange Erlen”)
Artificial recharge at the construction site of a tunnel
(Highway A3)
Conclusions
Effortsin the definition of best practices and policy
relevant aspects
Benefits of artificial recharge
Benefits are related to:
Elevation of the water table,
water storage, horizontal discharge,
water budget, flow patterns
Economical value of the benefits depends on:
Context, risk degree, project goals
Cultural values, practice, recent trends
Trend 1: conservation efforts
Open spaces, semi-natural areas in the cities
Strong tendencies to shift some of the major
conservation efforts from the protection of species +
habitats + ecosystems in restricted nature reserves to
the protection of most valuable open spaces (lakes,
streams, urban forests).
Nature in urban areas
Urban areas depend on the ecosystems (street trees,
gardens, parks, streams) for their survival through the
ecosystem services (better air quality,rainwater
drainage, noise reduction, recreational values).
Trend 2: stress mitigation efforts
With respect to climate changes
The scope is to minimize the effects on communities of
shifts in hydro-meteorological trends, increased climate
variability, and extreme events.
At present European strategies for climate change
adaptation are being embedded within national policy
and institutional frameworks.
Trend 2: stress mitigation efforts
With respect to human activities
Main activities in the cities are related to maintenance
and construction work.
The intensive and heterogeneous use of urban land and
the increasing traffic lead developers to resort to
underground alternatives for an increasing number of
road networks and infrastructures (subways, tunnels,
underground parking houses).
There are strong tendencies to minimize the effects of
underground construction during and after the
construction phase.
Artificial recharge systems
in Basel (Switzerland)
Example 1
Efforts in the conservation of natural resources in the
recharge area “Lange Erlen” as a valuable open space
Efforts in the mitigation of stresses due to climate
change and seasonal variability in the area “Lange
Erlen” using a combined recharge-pumping system for
drinking water supply purposes
Example 2
Efforts in the mitigation of stresses due to pumping at the
construction sites of the tunnel on the Highway A3 using
recharge wells
Example1: “Lange Erlen”
The area
Germany
Franc
e
Switzerland the city’s largest
continuous green space
meadows
woodland
cultivated areas
the area is used for water
supply, agriculture and
recreation
Example1: “Lange Erlen”
Problems
1. Clogging in the recharge areas
2. Warming of the water in the recharge areas
3. Insect plague and insufficient regeneration of the soil
4. High temperature and low discharge of the river
Wiese river in dry periods
Example1: “Lange Erlen”
Solutions
1. The raw water is purified in a rapid sand filter plant.
2. The watered meadows are forested recharge areas.
The woodland shields the water from the heat and it
also creates favourable conditions for the biological
purification of the water in the soil.
3. The recharge area is divided into three zones. Each
zone is watered for 10 days and dried out for 20 days.
During the 20-day drying out, the larvae die and the
insect plague is avoided. Simultaneously, the
woodland soil is optimally regenerated.
4. Raw water from the RiverRhein is used to supply water
into the recharge basins.
Example1: “Lange Erlen”
Today’s water supply system: site map
Germany
Franc Today raw water from the
e
Switzerland
Rhine River is used, after
filtration in the sand
filters, to supply water
into the recharge basins.
Example1: “Lange Erlen”
Today’s water supply system: schematic section
There, the filtered water percolates through the humus
layer of the woodland soil and the layer below, thereby
undergoing biological purification.
The time schedule of 10 days watering over 30 days with
a drying out phase of 20 days allows the soil to be aired
and to regain its natural purification capacity.
Example1: “Lange Erlen”
The combined recharge-pumping system
The percolating water
reaches the water table
underneath the recharge
area and flows to the
pumping well in 10-50
days.
Example1: “Lange Erlen”
Recharge technique
The infrastructure
Combined recharge-pumping system:
(10 basins over 22 hectares and 13 well groups)
Basins and wells are „in-line“ with the main flow direction
The management
The amount of water pumped out of the aquifer is
approximately equal to the infiltration water.
The ratio between infiltration and dry out phase is 1/2
Example1: “Lange Erlen”
Results
The captures zones of the pumping wells extend to the
closest recharge basin located upstream
The capture zones are constant in time
The system composed of a pumping well and a recharge
basin is a „closed system“, stable with respect to
seasonal variability.
The water supply system as a whole is less exposed to
climate changes and extreme events.
Example 2: construction site
The situation
Location of the
construction site Outflow
The project deals with the
Bank wall
construction of a highway
Rhine
River
which crosses the city of
Basel.
The project includes the
Outflow
construction of a tunnel at
the intersection of two
Inflow
Inflow
road axes.
Example 2: construction site
The groundwater draw down
There the required water
table drawdown and the
big extension of the
drained area made the
study of the drainage
system a key part of the
realisation of the project.
Example 2: construction site
The conflict situation
As a result of the
groundwater depletion at
pw rw
the construction site,
pw
other groundwater users
pw
pw pw
in the surroundings might
not have had enough
pw
pw
water.
rw
wells
Example 2: construction site
The drainage system
Two aspects were
related to the design of
the drainage system:
1. safety condition at the
construction site
2. water needs of the
groundwater users.
Example 2: construction site
Recharge technique
Three recharge wells
located at the construction
site (2 downstream and
1 upstream)
Half of the water pumped
out of the aquifer is used
to supply the recharge
wells
Example 2: construction site
Results
Effects at the local scale
Reduction of the draw down locally
Reduction of the water stress for the groundwater users
Effects at the regional scale
Shift and rotation of the divide
Rotation of the capture zones of some pumping wells
Risk
Spreading of contaminants initially at rest
No-source contamination
Conclusions
Results
Artificial recharge provides favorable conditions for the
development of ecosystems, healthy conditions for the
groundwater body as a whole.
Artificial recharge is a necessary task to close the man
made cycle of aquifer exploitation.
Combined recharge-pumping systems can reduce the
vulnerability of the community to water stresses.
Conclusions
Needs regarding water supply systems
Artificial recharge systems needs to be tested in
different European areas in order to evaluate, its
efficiency to overcome dry periods.
Application in the Mediterranean countries would
provide interesting results.
Conclusions
Needs regarding construction sites
Guidelines for construction sites with respect to:
Drainage/recharge system at the construction site
designed to ensure safety condition for the workers and
groundwater protection.
Evaluation criteria for groundwater protection
measures in terms of capture zone and their variability,
divide and their shift.
Water management concept at the construction site
based on groundwater protection measures and on the
water needs in the area.
Acknowledgements
Industrielle Werke Basel IWB
Dr. Chem. Richard Wülser
Geotechnisches Institut GI
Dr. Geol. Beat Vögtli
Thank you for your attention
