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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

				
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