By Brian Luenow
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 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.
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 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.
Republished with permission from HydrateLife.