Thanks to population growth, industrialization and climate change, our freshwater resources have experienced unsustainable strain. UN Water, the international body that coordinates the United Nation's work on water and sanitation estimates that by the year 2030, if drastic conservation efforts aren't made, the earth could experience a 40 percent global water deficit. Groundwater—contained in underground stockpiles of water called aquifers—provides drinking water for at least 50 percent of the world's population, with 2.5 billion people relying solely on aquifers for water.
Many of these aquifers are being drained faster than they can be replenished, leading an estimated 20 percent of the world's aquifers to being over-exploited. This is a global issue that affects many nations, both in and out of the developing world, as cities expand rapidly without adequate water regulation and conservation efforts.
But there is hope. A recent study—conducted by researchers from the University at Buffalo, in conjunction with NASA, UC Berkeley, and Purdue University—shows that a new technique of satellite monitoring is an effective method of tracking water levels in aquifers, improving our understanding of these water supplies and helping us to manage them sustainably. For the study, researchers utilized this satellite technology to monitor a drought-plagued Silicon Valley aquifer, and found that aggressive conservation efforts successfully returned groundwater to pre-drought levels this year.
Thanks in part to the findings of this study, NASA has decided to employ similar technology in their upcoming NASA-ISRO (Indian Space Research Organisation) Synthetic Aperture Radar (NISAR) satellite mission, launching in 2021. This system will collect radar information from nearly every aquifer in the world, helping countries with conservation efforts by providing essential data.
VICE Impact spoke with Estelle Chaussard, PhD, lead researcher of the study and Professor of Geology and Geophysics in the Department of Geology of the University at Buffalo, about the significance of these findings and what they mean for water conservation across the globe.
VICE: What are some of the biggest threats to the earth's aquifers, when it comes to drought and over usage?
Estelle Chaussard : When we have a drought, we have low surface water, low streams, and people tend to rely a lot more on our groundwater resources. Now, if we are drying out our groundwater resources and pumping too much from an aquifer, that stress will cause permanent compaction of the structures that usually hold the water and they will not be able to hold water anymore. So, if water levels drop below their historic level, we're gonna have a permanent decrease in the health of the aquifer and we would lose the capability of retaining water in the aquifer in the long term. That's what we are trying to avoid.
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What was the satellite technology used to monitor the aquifer in the study, and how did it help track the health of the aquifer?
We used a technique called InSAR — it stands for Interferometric Synthetic Aperture Radar — which uses satellites that measure very small changes in ground elevation over time. We do this entirely remotely, and it doesn't require any ground-based measurements. We get lots of pixels from these satellite images for how the ground for this area is moving over time. So we can track how much the water levels are decreasing in the aquifer by tracking ground deformation, and we can estimate how much has been pumped physically from the aquifer.
In cases of drought, we can get aquifer information for the time period just before the drought, and compare it with what is happening during the drought. Then we can get a sense of whether or not we have degraded the health of the aquifer, and if it's reached a lower water level than before. For our study, we found that the properties of the aquifer in the Santa Clara Valley did not change during the drought.
The Santa Clara Valley water district did a very large outreach effort to encourage people to reduce the district's water usage. All of these efforts led to a rebound in the water levels in the aquifer system during the drought in late 2014. So basically the water levels decreased but not to a level that was lower than what was previously experienced, so we did not degrade the health of the aquifer. By doing this kind of InSAR monitoring, we can make sure that we are keeping our aquifers healthy, like what we saw in the Santa Clara Valley.
How does this InSAR satellite technique differ from the traditional ground monitoring of aquifers, that require people or instruments to physically collect data from wells?
A lot of places, even in the United States, have a limited number of monitoring wells. If we're ground monitoring only a few wells for a larger spatial area, we have a much lower spatial coverage than we do with InSAR. But with InSAR, we can cover the entire aquifer system; instead of covering a few hundred wells, we have data for hundreds of thousands of points. InSAR is important because we have a very large spatial coverage. There's nothing that's comparable. It's also lot cheaper than ground monitoring.
How can this technique help in water management and conservation efforts across the globe?
Areas that have minimal on-the-ground monitoring, can be monitored with this satellite technique, and we can better understand how much water is being extracted from our aquifers—and that can inform policies for reducing pumping.
For example, in certain areas in Mexico and Indonesia, there is a lot of subsidence [a term referring to the sinking of land that permanently damages aquifers] and that is due to groundwater pumping. We can map it precisely with InSAR, and that can inform policies where we restrict water usage, and where we have to be careful in the future.
NASA plans to utilize this technique in their NISAR satellite mission, which would launch in 2021 and collect radar imagery from almost every aquifer in the world. What are the goals of this mission?
So the NISAR mission, which would be a joint InSAR mission between NASA and ISRO (Indian Space Research Organization), would be the first InSAR satellite mission that NASA is involved in. It's a big deal because the satellite that will be launched, NISAR, would have global coverage. They will be mapping the whole world on a 12-day repeat, meaning we could see how the ground is moving everywhere on earth and track nearly all aquifers, every 12 days. If we really want to do a good job of understanding our water resources globally, we need to have this kind of coverage that NISAR is going to provide.
This interview has been edited for brevity and clarity Learn more about how you can take steps to conserve water in your household and advocate for policy around water issues.