Many of Earth’s biggest aquifers overstressed
(Scary but interesting reading – taken directly from “EarthSky.org.”)
People around the world rely on groundwater for drinking and crop irrigation. But a new satellite data study says that many of our biggest aquifers are overstressed.
Approximately 2 billion people rely on groundwater for their primary water source, and groundwater is used to irrigate many of the crops that people depend on for food. Needless to say, groundwater is a very valuable resource. As with any valuable resource, it is a good idea to keep track of it, but that can be difficult to do with groundwater because it resides underneath the ground. Now, using new satellite technology, scientists have mapped trends of groundwater depletion in 37 of the world’s biggest aquifers— about one-third showed signs of highly unsustainable water use.
Aerial view of center-pivot irrigated crops in
Colorado. Image Credit: U.S. Geological Survey.
In the new study, published in Water Resources Research , the scientists used data from the GRACE
(Gravity Recovery and Climate Experiment) satellite mission to assess trends in the aquifers. This mission, which began in 2002, is a joint effort between the U.S. National Aeronautics and Space
Administration (NASA) and Germany’s Deutsche Forschungsanstalt für Luft und Raumfahrt (DLR).
Two GRACE satellites are currently in orbit around the Earth, and like their namesake suggests, these spacecraft are measuring changes in Earth’s gravity field. Because large changes in groundwater storage can be detected with the gravity field data, these data are proving to be very valuable for creating a comprehensive picture of Earth’s underground water resources.
Of the 37 aquifers studied, 16 showed positive accumulating trends and 21 showed declining trends.
The aquifers with declining trends are shown in shades of red and yellow in the map below.
Groundwater trends in 37 of the world’s largest aquifers. Image via NASA .
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With the GRACE data and other data on groundwater recharge rates, the scientists built a renewable groundwater stress (RGS) ratio that compares the rate at which the groundwater is being used to its availability as reflected by the rate at which the aquifer is being replenished. High stress ratios are unsustainable because the usage greatly exceeds the availability.
The results showed that 7 aquifers were extremely stressed, 3 were highly stressed, 5 were moderately stressed, and 7 were lowly stressed. Only 15 aquifers had negative RGS ratios, which are indicative of sustainable use rates. Most of the unstressed aquifers were located in remote forested and rain-fed regions. In contrast, many of the stressed aquifers were located in regions with high amounts of rangeland and cropland.
Alexandra Richey, lead author of the study who completed the research as a doctoral student at the University of California at
Irvine, commented on the findings. She said:
!What happens when a highly stressed aquifer is located in a region with socioec onomic or political tensions that can’t supplement declining water supplies fast enough? We’re trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods.
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Despite the new groundwater data, scientists still aren’t quite sure how much water is left in these aquifers
—they have been able to discern trends but they have not yet been able to determine the total volume that exists. That information will be critical to obtain in the years ahead .
Jay Famigliet ti, a professor at the University of California and senior water scientist at NASA’s Jet
Propulsion Laboratory, pressed for such research. He said:
“Given how quickly we are consuming the world’s groundwater reserves, we need a coordinated global effort to determine how much is left.
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Other co-authors of the study included Brian Thomas, Min-Hui Lo, John Reager, Katalyn Voss, Sean
Swenson, and Matther Rodell. This study was made possible through financial support from NASA and the University of California.
B ottom line: Scientists used new satellite data to study trends in 37 of the world’s biggest aquifers and found that 10 of these are either extremely or highly stressed. The new research was published in the journal Water Resources Research on June 16, 2015.
South Africa is a water-stressed, semi-arid country with an average annual rainfall of around 500 mm, which is less than 60% of the world average .
The financial, human and ecological impacts of global and local changes to climate are already evident in South Africa, particularly where water resources are under the greatest pressure.
Groundwater, despite its relatively small contribution to the total water supply in South Africa (~13%), represents an important strategic water resource. Owing to the lack of perennial streams in the semidesert to desert parts, twothirds of South Africa’s surface area is largely dependent on groundwater.
In these water-scarce areas, groundwater is more valuable than gold. Although irrigation is the largest user of groundwater, groundwater provides the water supply to more than 300 towns and smaller settlements.
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In over about 90% of the surface of South Africa, groundwater occurs in hard rock that is rocks with no pore spaces. Here it is contained in faults, fractures and joints and in dolomite and limestone, in dissolved openings called fissures.
Hard rock aquifers are known as secondary aquifers because the groundwater occurs in openings which were formed after the rock was formed. Over the remainder of the country groundwater occurs in primary aquifers. These comprise porous sediments and soils where groundwater is contained in the spaces between sand grains. Primary aquifers are found in river (alluvial) sediments, in coastal sand deposits, and the Kalahari deposits.
On a global scale, groundwater is an essential freshwater resource for both socio-economic and environmental systems. It provides a wide range of diverse goods and functions, described here as ecosystem services, namely, the 'conditions and processes through which natural systems and the species that make them up sustain and fulfil human life'. In many parts of South Africa groundwater allocation and protection has become an important issue, as groundwater represents an important source of freshwater. It has the potential to play a strategic role in providing water for drinking and sanitation, supporting agricultural irrigation schemes and industrial uses, reducing poverty and disease, and maintaining important aquatic and terrestrial ecosystems. The South African hydrogeological community has claimed that groundwater is currently underutilised and undervalued in many parts of the country. Accordingly, groundwater management is neither strongly emphasised in national water legislation, nor is it implemented where it is needed.
The recent impacts of massive groundwater use in many countries, and the increasing demand for water in the same areas, are often a double-edged sword. On the one hand, groundwater use has given rise to several short and medium-term socio-economic benefits, by providing a basis for new standards in human well-being, enhancing the diversity of agricultural and industrial production, supporting urban and rural development, providing for improvements in health, and reducing poverty.
On the other hand, within a very short period of time, many aquifers worldwide and their related ecosystems have been put at risk due to high extraction rates. This mostly results in long-term environmental impacts. In the following discussion, 3 main factors affecting groundwater resources are presented, namely, quantity problems, quality problems, and climate change impacts.
The increase in the demand for water frequently results in the overexploitation of aquifers, which in turn leads to the drying up of wells. The critical reduction in the volume of available subsurface water reserves due to the permanent increase in water demand will represent a major environmental trend of the next 25 years. This trend will be exacerbated by global population growth, agricultural practices and landscape alterations, increases in urban areas and in the demand for domestic and public drinking supplies, industrial activities including thermoelectric production, intensive agriculture and mining, and the growing tourism sector.
Groundwater quality is also impacted upon by pollution by liquids (e.g., liquid waste products or oil), by soluble substances in the soil through which water infiltrates, or by bacteria small enough to pass through soil pores. Often contamination makes groundwater unfit for human use and changes the structures and functioning of ecosystems.
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Another threat to global groundwater security is temporal and spatial climate variability, including an increase in the occurrence of extreme events such as heavy flooding and frequent periods of drought.
The most vulnerable areas are those with an annual precipitation rate of <500 mm, large coastal cities, tropical delta areas and small islands. Information about the water related impacts of climate change is inadequate especially with respect to water quality, aquatic ecosystems and groundwater including their socio-economic dimension'. It is estimated that climate change will negatively impact groundwater recharge and baseflow in arid and semi-arid areas where recharge depends mainly on rainfall events. Groundwater will be less directly, and more slowly, impacted upon than surface water bodies. The main reason for this is that rivers are replenished over a shorter time scale and droughts and floods are quickly reflected in river water levels. Groundwater is affected much more slowly; for
instance, after prolonged droughts aquifer levels starts to decline.
We South Africans must be made aware of the many benefits they derive from healthy aquifer (groundwater)
Amen systems. By recognising the many advantages groundwater provides to human well-being, people may treat and manage subsurface water resources in a more sensitive manner and experience the many benefits groundwater has to offer. http://gwd.org.za
& http://www.scielo.org.za
At the beginning, one river flows out of Eden, to become the watershed that cradles civilisation (Gen 2:10-14) At the very end, a cosmic echo declares the invitation of the One who is called the Alpha and Omega,
“Let everyone who is thirsty come. Let anyone who wishes take the water of life as a gift.” - (Rev22:17)
From start to finish in Bible history fresh water bubbles, bushes, flows, floods, rainbows in the sky, or suddenly dries up Then it pours out of God’s upper chambers all over again, to nurture, sustain, wash, cleanse, baptize, heal or tempest-toss the heroes and heroines of God’s story, towards his good ending. Clean drinking water is closely linked to the mystery of the Bible’s theme of mission.
Access to clean water is acknowledged as basic to healthy living conditions. Yet many of our water sources in South Africa are polluted by industry and by the fact that, without piped water, people in both rural and urban slums are forced to use their only water supply for drinking, cooking and washing, while lack of sanitation facilities means that rivers and streams become polluted by human waste.
These problems are sadly not confined to rivers and streams, as much of our groundwater is being polluted by seepage of pollutants and pathogens and also indiscriminate use.
It is predicted that at our present rate of consumption, SA will run out of water between 2020 and
2040, and groundwater will have to play a far more prominent role in our daily lives.
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Therefore as People of God, we are called to protect ALL our water sources – that includes groundwater – from indiscriminate, irresponsible and unethical use.
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Boil only as much water as you need.
 Don’t rinse anything under running water – turn tap off when brushing teeth and washing dishes.
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Where possible, install rainwater tanks - collect water from roof run-off.
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Plant water-wise plants & mulch (cover with dry plant material or wood bark) to reduce evaporation. Avoid watering in wind or during the heat of the day, water
 Don’t throw oil, paint, medicines, chemicals or poisons down the drain or in areas where thismay result in seepage into underground aquifers
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Get your church involved in a river clean up scheme and wetland conservation.
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Bore-holes often tap water from ancient aquifers which may take thousands of years to be replenished. Bore-hole water should not be ‘wasted’ on suburban gardens. If it is to be utilized, this water should be kept for circumstances of dire need.
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If you see water being wasted – DO SOMETHING ABOUT IT!!
Loving God,
Whose son Jesus Christ called all who were thirsty to come to him, believe and drink,
Look in mercy on your people living in dry lands, and struggling to survive without access to safe drinking water.
Forgive our selfishness in life and our misuse of our natural resources.
We commit ourselves to value and care for your gifts to us.
May rivers of living water and practical compassion for all who suffer flow out from our hearts.
Refreshed by your Spirit, and following in the way of Jesus Christ,
We will continue to serve you in the people and creation entrusted to our care.
Amen
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