Groundwater: Management Of A Much Neglected Lifeline

Water drop on rose leaf.

It seems obvious that if you dig or drill into the soil, at some point you will hit groundwater. Drill deep enough and you will reach an aquifer containing enormous amounts of fresh water. After this you can just pump water out of these wells and you will have fresh water aplenty. Or so was the thinking among many for the longest time. As enormous the fresh water reserves in the form of groundwater are – with most liquid fresh water being groundwater – we can literally empty them faster than that they’ll refill.

As the Dust Bowl disaster painfully showed in the 1930s and drought along with surface subsidence issues as in e.g. California’s Central Valley shows today is that we cannot simply use the soil and groundwater and expect no consequences. While the 19th century saw many fresh settlers to the West’s arid and semi-arid regions like California believe in the ‘Rain follows the plow‘ mysticism, the 20th century and these first few decades of the 21st century taught us that tilling the soil and drawing groundwater for irrigation does not change an arid climate into a lush one.

Perhaps ironically, even with increasing droughts, most human settlements use stormwater drainage and combined sewage systems to carry rainwater away, rather than letting the groundwater recharge naturally. Fortunately, more and more regions these days are seeing the necessity of managing groundwater.

Waste Not, Want Not

Drought monitor statistics for Germany on September 10th, 2022, showing the drought effects on multiple levels. (Credit: UFZ Drought Monitor)
Drought monitor statistics for Germany on September 10th, 2022, showing the drought effects on multiple levels in the ground. (Credit: UFZ Drought Monitor)

How much one values rainwater and snow melt-off depends largely on how much one has of it. For someone like myself who grew up on a farm in the western regions of the Netherlands – amidst soggy clay and ditches that led straight to pumping stations – capturing rainwater wasn’t a concern, while finding ways to prevent flooding was more essential.

This equation changes completely when the rainwater your area receives is perhaps only barely enough to sustain that year’s crop, with irrigation from a nearby river, or from deep wells, being required to keep crops in the fields from dying. For many cultures over the centuries, the use of dryland farming has been essential to deal with an arid climate. What this means is to minimize evaporation by limited tilling of the soil, increasing spacing between crop rows to minimize competition for limited soil moisture, and growing crops or cultivars that are adapted to an arid climate.

Which is not to say that it’s not possible to grow just about any crop or the like in even a desert environment. For thousands of years now, humans have used irrigation to grow crops in places that otherwise would be completely off-limits. The same is also true for humans themselves, as we too require fresh water on a daily basis, requiring us to draw from the same rivers or groundwater as our crops.

Here the lesson is that the less fresh water is available, the more important it is to capture every last drop of rainwater, and to use it as sparingly as possible. Another essential consideration here is that even if drainage systems don’t immediately whisk the water away, soil structure is essential for allowing rainwater to soak into it. After a prolonged drought, the pores that normally exist between soil particles and that allow for moisture to reside between them will have mostly vanished.

The effect is that this super-dry, ultra-compacted soil will not easily absorb rainwater, which is perhaps ironically what enables flash floods. What one can do here is to give the soil more time to absorb the moisture, through the use of ponds, swales and similar structures in the landscape that prevent run-off and maximize the soak time of the soil. Not only will this increase the amount of moisture in the top level of the soil column, but more crucially assist in groundwater recharging.

That Sinking Feeling

Schematic of an aquifer showing confined zones, groundwater travel times, a spring and a well.
Schematic of an aquifer showing confined zones, groundwater travel times, a spring and a well.

In addition to capturing rainwater and run-off from snowmelt for irrigation, drinking water and recharging groundwater levels, it’s increasingly common to inject treated water back into aquifers, rather than releasing it into rivers and other surface waters. A major benefit of this is that it helps to counteract the subsidence of the soil, which is a common issue when water is extracted faster from an aquifer than it replenishes itself.

Mexico City is an example of a sinking city that is suffering the consequences of overdrafting from the aquifer which it was built upon. As a result the city is sinking at a rate of more than than 15 centimeters per year, while water shortages keep increasing the pressure to draw ever more water from the aquifer. Possibly worse is overdrafting from an aquifer for a coastal region, as this can result in saltwater intrusion, where the salt water flows in and contaminates the fresh. The worse this becomes, the more likely that the aquifer may have to be abandoned completely, or require intensive treatments like desalination.

All of which should make it clear that aquifers, as well as groundwater in general, is a precious resource that should be treated carefully, so that it can be a sustainable resource. This leads us to another major risk factor, namely that of pollution.

Keeping It Clean

Groundwater contamination from a pit latrine. (Credit: CAWST)
Groundwater contamination from a pit latrine. (Credit: CAWST)

Even though the soil matrix will act as a kind of filter, this tends to be only good enough to filter out larger particles. Pathogens, heavy metals and various chemicals may be contained in run-off water. In many regions the use of septic drain fields, cesspits and latrines is quite common, all of which risk introducing pathogens into the groundwater that may end up in the water retrieved from poorly sited wells.

Such types of groundwater pollution have led to the spread of disease and similar in the past, and continue to be a heated subject of debate. The practice of fracking for natural gas involves the injection of chemicals into the rock that often ends up in groundwater and has led to lawsuits and medical studies. Ultimately there is the dawning realization that groundwater is something we all end up sharing, not unlike the water in a public swimming pool.

To prevent pollution from rainwater run-off ending up in groundwater, the concept of bioswales has been introduced fairly recently. This iterates on the basic concept of swales by adding a filtering function, which would allow it to retain heavy metals, silt and debris. By picking specific plants to grow in these bioswales, this growth can act as a natural filter, while also allowing for debris to settle. Heavy metals would be mostly retained in the sediment that settles in these bioswales, allowing for periodical removal and replacement of this sediment for disposal.

In a study of an existing bioswale that has been in place in southern California for a few years, Evans et al. (2018) analyzed the rate at which zinc, lead, cobalt and manganese were retained in the bioswale’s soil. They found that a significant amount of these metals were sequestered.

A Shared Resource

Ultimately fresh water is a precious resource that, if managed carefully, can bring prosperity and health to not just crops and people, but also the environment in general. By using ponds, swales and other retention structures people in semi-arid and arid regions can optimize the small amounts of rainfall, while not burdening aquifers and nearby bodies of water too much, especially if combined with dryland farming.

By injecting stormwater run-off into aquifers, and letting it soak into the soil rather than carrying it away into drainage systems, the impact of droughts can be made significantly less severe, while preventing permanent damage from letting aquifers dry out. Finally, by preventing groundwater pollution, we can ensure that the water that we pump out of wells is not laced with heavy metals, pathogens and similar unpleasantness.

As long as we learn to accept that rain and plentiful groundwater aren’t things we can necessarily count on, and may require effort from our side to maintain or make optimal use of, things should work out fine.

14 thoughts on “Groundwater: Management Of A Much Neglected Lifeline

  1. Ever try to re-use a potted plant’s pot and soil when it has not been watered in a long time?
    The water just runs off the top and doesn’t soak in. I’ve even seen it bead up! Either you have to add little bits at a time until the soil regains the ability to absorb water or you have to mix it in like making dough.

    1. Try setting the pot in water and give it time to soak in.

      I am feeling that this the outcome for the whole ball of dirt we are messing around with, a collapse of all the magic that happens under our feet. Water will just flow off from a poisoned soil biome.

  2. In Queensland Australia we have vast aquifers, some of which contain recoverable levels of dissolved natural gas, several centuries worth at current consumption rates, far longer if it was not exported and was kept for local use. However not all of the water is low in dissolved salts and has to be dealt with in one way or another, fortunately we also have a lot of sunlight, even if it can be intermittent so that opens up the possibility of using that opportunistic energy source for driving desalination processes for fresh water and mineral recovery. Even so human activity can be made to look pitiful when a cyclone decides to head inland and dumps so much rain water over the top of those aquifers that it results in a measurable change in the world’s oceans. I wonder how many times that happens during the up to 100,000 year transit period for rain water passing through those aquifers? Whatever it is there is a very clear indication there of the sorts of time scales you need to be thinking about if you wanted to manage an aquifer so that it was in a reasonably steady state and you were tapping it when there was higher than average flows available.

      1. I’ve come across the concept of water-meadows which in earlier days were advantageous for livestock feed production. Among their positive reported effects is the removal of silt and excess nutrients, thereby combating eutrophication. When a large plane is periodically flooded, there is definitely a flow towards the ground water table as well, unless the piece of land already drains towards a slope with shallow sub-surface flow (is there even a distinction between that and ground water?).
        I don’t think it’s necessary to wait millennia when filtration and (like with bio-swales) removal of pollutants can already take place over the course of years. That however raises the question how porous a layer is allowed to be, and what the requirements are e.g. to prevent contamination with bacteria as mentioned above regarding sewage ingress.

        “Because the cells (hosts) needed for replication of human pathogenic viruses are present in low concentrations in ground water systems, it is often assumed that long-term survival and transport of virus is unlikely. Keswick et al. (1982) showed that poliovirus, coxsackie virus and rotavirus survive much longer in the subsurface environment (on the order of weeks and months) than had generally been assumed”. Probably if it takes a few years, we should be ok?

    1. Sure, for several hundred years here[tm] have been many water mills, each with such a dam (mostly not for groundwater substitution, but maintaining groundwater levels as byproduct). But nowadays these are demonized for being obstacles for fishes going upstream (like salmon) and removed. So in the renaturalized rivers the water rushes down to the ocean, the trees next to the river dry off and fall into the river bed due to the now wildly varying levels of water. Invasive species and predatory fishes (like the Northern pike) are easily moving upstream, eating the small species which were formerly protected by the small dams. The rivers now dry up completely if it doesn’t rain for a few weeks, and when it rains a little more the dead trees get washed downstram and cram before the bridges, forcing the water through the villages next to the bridge. “Ahrtal” anyone?

        1. Go ask the operators of old mills which kind of fishes they see below and above their weirs, and ask any angling club how many waters they know with both pikes and amphibians in them. Go watch the rivers, their shores and the small animal population, and especially the changes after the removal of the weirs.
          When no water is flowing, where do the fish live, if not in the water that remains behind the weir? What happens to trees, which are specialized for their habitat, when it starts to change significantly? Where do they go, if no one is allowed to get them out of the river when they fall into it?

  3. One of my favorite rain water management projects is the Water Cup, organized by the Paani Foundation in India ( ).

    When >70% of the rain falls within a 3-4 month monsoon period, argicultural use of the land is limited to one harvest cycle, and people were forced to relocate to find low-pay jobs to sustain themselves. Through the initiative, over 1000 towns competed over the amount of water capturing and utilization capacity, ultimately reshaping the landscape and turning wasteland (aka wasted land) into useful agricultural assets. (with 2-3 harvests per year).

    There’s an amazing documentary on it. Playlist:

    Through the setup of swales and leaky reservoirs, a valley-sized hydrological system is created which allows water-hungry rice to be grown with sub-surface irrigation and other crops to be watered throughout the year, all while replenishing aquifers to sustain residential water needs. Many of the applied concepts are essentially what makes up permaculture, even if it isn’t called that way.

    If I’m not mistaken, the site shown in the video is 17°26’0.00″N 74°14’10.00″E – worth exploring via google earth, too :)

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