Ensuring the Availability of Groundwater: Managed Aquifer Recharge (MAR)

Photo via bgs.ac.uk

There are many places in the world that depend solely on their groundwater for drinking, irrigating crops, or anything else requiring water. As population increases and industries expand in these areas more groundwater is required which can lead to its unsustainable use.  When this happens wells must be dug deeper at a cost to the owner (if wells can even reach the water anymore), polluted water can fill the void left by low water levels in the aquifer, and for coastal areas the groundwater could be infiltrated with salt water, not to mention people won’t have water.  However, this can be avoided by means of some very simple technologies that have been used around the world for centuries, referred to recently as Managed Aquifer Recharge (MAR).

One of these technologies is infiltration ponds.  An infiltration pond (also called infiltration basins or percolation ponds) is a depression in the landscape, either dug out or occurring naturally, where rainwater/runoff is captured.  Once the water is in the

Photo via bournestreampartnership.org.uk
Graphic via bournestreampartnership.org.uk

pond it slowly flows down into the aquifer and recharges the groundwater.  This method can also reduce salinity in the groundwater by pushing the saltwater out with freshwater. There are some restrictions on where infiltration ponds will work.  The aquifer needs to be shallow; either at or near the ground surface.  Also, the material at the base of the pond needs to be permeable so that the water can get into the aquifer.  Some typical recharge rates are 30 m/year for fine texture soils (e.g. sandy loams), 100 m/year for loamy soils (a combination of clay, sand, and silt), and 300 m/year for coarse clean sands.  If you’re placing your pond where it will be catching runoff then you should include a sedimentation basin to allow the sediment to settle and avoid clogging the permeable soil at the base of your pond.  Another way to do this is to have grasses growing around your pond which will act as a sediment trap.  Either way, at some point you’ll probably have to let the pond’s water level drop so you can dig out the sediment because some will get in over time.   I have read numerous articles about infiltration ponds being very successful throughout the world; however, they require community involvement to maintain the pond which can be hard to come by without first educating the community on how infiltration ponds work and convincing them that it can help in their situation.

Another good way to recharge ground water is a sand dam.  I have previously written about sand dams, and you can read that article here.  Similarly, underground dams can be used to cut off the flow of groundwater that would otherwise migrate out of the area or into the ocean.  The basic idea behind underground dams is building an impermeable wall underground to stop the flow of the groundwater, and therefore the water will stay in place.

Graphic via rainwaterharvesting.org
Graphic via rainwaterharvesting.org

Leaky dams are yet another way to help recharge groundwater.  Leaky dams are made of permeable materials, and are built across seasonal riverbeds.  The idea is that when the rains come the water is held by the dam and sediments settle out.  However, because the dam is permeable the low-sediment water can flow through the dam and continue downstream.  Because there is no sediments in the water, and therefore no sediment downstream, the water is free to infiltrate into the ground downstream of the dam and in doing so will recharge the groundwater.  Infiltration into the soil downstream

Photo via akvo.org
Photo via akvo.org

can be helped by placing plants in the riverbed and then their roots will help break up the soil.  Leaky dams will require maintenance to remove sediment that will build up behind them, and they can become clogged with sediment over time, however this is another option that has been proven successful time and time again.

Further, Aquifer Storage and Recovery (ASR) is another method that can be used to recharge groundwater.  ASR takes advantage of seasonal rains that would otherwise run-off and therefore be of no use.  The idea is that you channel the rainwater run-off/surface water into an existing well, and the water then infiltrates into the soil and recharges the groundwater.  Then when water is needed the same well can be used to pump the water out for use.  This can be a very productive way to recharge your groundwater, however, you need to have a well available.  If you do not have a well available it can be very expensive to dig one, and one of the other options I’ve talked about may work better for you.  ASR is popular for its obvious benefit, but also because it doesn’t require much space, only what you need for the well.  As with any well, you’ll always want to filter your water before using it for drinking or cooking to make sure it’s safe.

Lastly, rainwater harvesting is a great way to recharge groundwater.  One method which relates back to ASR is called Mazhapolima.  I have also previously written about this, and you can read the article here.  Briefly, this method uses the same idea as ASR, however instead of catching runoff to put into the well you catch the water from your roof and then run a pipe into your well.  This method has been proven to transform a well that would dry out during the dry season into a well that is productive throughout the year.  You can also collect rainwater from your roof and pipe it into a pond which would create an infiltration pond.

The ideas presented here can be very helpful in recharging groundwater which can lead to wells that produce water year-round, healthy and productive soil, and an overall happier and healthier life for people in the area.  Also, these ideas (with the exception of digging your own well) are fairly simple, can be completed with local resources, and maintained by the local community, making them sustainable. The effects of Managed Aquifer Recharge (MAR) may take some time to show, but after they do water security will have been achieved.  As with most methods of securing water, education and community involvement is key to success.  Thanks for reading, and let me know if you have any other examples of ways to sustainably recharge groundwater.

Sources:

https://www.akvo.org/wiki/index.php/Infiltration_ponds

https://www.akvo.org/wiki/index.php/Leaky_dams

https://www.asrforum.com/Aquifer-Issues-Solutions.html

https://www.wateraid.org/documents/plugin_documents/wa_nep_report_rwh_26_september_2011.pdf

Ensuring the Availability of Groundwater: Managed Aquifer Recharge (MAR)

6 thoughts on “Ensuring the Availability of Groundwater: Managed Aquifer Recharge (MAR)

  • December 22, 2012 at 1:07 am
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    I have developed following clarity about groundwater quality and quantity(availability):

    1. Nature wants us to keep the groundwater in purest form and that means keeping it low(close to zero) nitrates, sodium, heavy metals, sulfates, and other inorganics.

    2. These are also the requirements of good tasty drinking water.

    3. It’s the rain quality(controlled by air quality) that decides the rate rainwater is able to percolate into the soil. Clean rain is able to infiltrate into the soil at high rate of 100 mm/day(high rainfall) and polluted rain can barely infiltrate upto 10 mm/day.

    4. Polluted rain, thus refuses to recharge the groundwater and runs off to create floods, also soil erosion along with floods.

    5. Without giving thought to these aspects, if we force polluted water into the ground, by removing the topsoil(that has the ability to get choked and prevent seepage of polluted water, into the groundwater basin), we are spoiling the groundwater.

    6. Once the groundwater is spoiled, it becomes very difficult to clean it.

    7. widespread practice of organic farming is one effective way to increase rainwater harvesting.

    8. Another way is to reduce burning of fossil fuels and use biomass fuels that farmers can grow himself. This cleans the air quality, thus rain quality and increase natural rainwater harvesting.

    – Dr Uday Bhawalkar, Pune(India)

    Reply
    • December 24, 2012 at 4:39 am
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      I am interested in your comment: “It’s the rain quality(controlled by air quality) that decides the rate rainwater is able to percolate into the soil. Clean rain is able to infiltrate into the soil at high rate of 100 mm/day(high rainfall) and polluted rain can barely infiltrate up to 10 mm/day.”

      Can you point me to a study or paper on this?

      Reply
      • December 26, 2012 at 9:11 pm
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        I am slow in publishing because of various considerations. I do talk or present my experiential knowledge on invitation at selected conferences.

        Please see my website http://www.wastetohealth.com

        I use following methodology for my research in this field of ecological engineering:

        – Believe fully into the fact that ‘Nature is well designed’ and not attempt to improve Nature.

        – This gives clarity coupled with observations with Nature.

        – We get sensible and sustainable wisdom out of this eco-friendly approach.

        We found that soil(sand or soak-pit) gets choked due to growth of slimy denitrifying bacteria. This is natural mechanism to prevent entry of polluted water into the ground.

        After using our BioSanitizer Ecochips to tackle nitrate and other inorganic pollution, it is seen that we can witness speedy infiltration of water or wastewater, into the soil/sand.

        Reply
  • January 11, 2013 at 7:47 am
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    I agree that in arid and semi-arid regions, where rainfall incidence is erratic and comes most often as brief heavy showers or thunderstorms, rapid run-off or flash flooding discharges large volumes of water very quickly, leaving little for infiltration. Thus infiltration may be substantially enhanced by building small dams at intervals along rivers and streams to retain run-off water and increase infiltration to groundwater.
    Of course enhanced aquifer recharge is a good thing provided run-off water is not too heavily polluted and there is adequate natural filtration capacity in the subsoil overlying aquifers. This is not always so and sometimes dams can be a source of groundwater pollution.
    Two other caveats apply in terms of balancing overall environmental impact and socio-economic benefits. Dams can be counterproductive in some instances.
    In hot climates EVAPORATION rates are very high and soil moisture deficits are the norm open water stored in dams loses a lot of volume through evaporation and this can significantly increase salinity, nitrate, and other pollutant concentrations in the remaining water, causing a deterioration of groundwater quality in the underlying aquifers.
    Also, dams substantially alter the now flow patterns of rivers, including the pattern of erosion and deposition, and can impact negatively on aquatic ecosystems.
    These effects of water impoundment or diversion can have unforeseen negative socio-economic impacts as well, where for example some lowland farming communities depend on occasional floods to bring water and fresh nutrients to their land, and some aquatic ecosystems support thriving fishing industries.

    Reply
    • January 14, 2013 at 6:23 pm
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      I agree with what you say about dams, but these problems can be reduced by keeping the dams small, and/or constructing them in a way that doesn’t completely impede the flow of water. Sand dams also lead to less evaporation since the water is underground. Thanks for the comment

      Reply
  • March 2, 2015 at 6:09 am
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    Thank you very much for sharing these nice techniques for water management. Rain water harvesting is being practiced in Bangladesh for many years. Other techniques you have illustrated like sand dams, infiltration ponds have not been yet tested but Managed Aquifer Recharge or more specifically Aquifer Storage and Recovery has been applied in southwestern coastal belt of Bangladesh and found successful in terms of water quality improvement. Rain water has been used as main source. About 100 Managed Aquifer Recharge sites are going to be built in coastal belt of Bangladesh. Here is a great source that you will find interesting for more information @ https://geobangla.wordpress.com/

    Reply

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