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Tag Archive: groundwater

  1. NASA satellites reveal major shifts in global freshwater; Groundwater depletion in Central Valley due to drought and agriculture

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    • Researchers see a distinctive pattern of the wet land areas of the world getting wetter — those are the high latitudes and the tropics — and the dry areas in between getting dryer. Embedded within the dry areas we see multiple hotspots resulting from groundwater depletion.
    • Significant groundwater depletion observed in California’s Central Valley from 2007 to 2015, is likely due to both decreased groundwater replenishment from rain and snowfall combined with increased pumping for agriculture.

    May 16, 2018  Read full NASA article here

    See related Guardian UK article here: Water shortages to be key environmental challenge of the century, Nasa warns

    In a first-of-its-kind study, scientists have combined an array of NASA satellite observations of Earth with data on human activities to map locations where freshwater is changing around the globe and why.

    The study, published today in the journal Nature, finds that Earth’s wet land areas are getting wetter and dry areas are getting drier due to a variety of factors, including human water management, climate change and natural cycles.

    ….”What we are witnessing is major hydrologic change,” said co-author Jay Famiglietti of NASA’s Jet Propulsion Laboratory in Pasadena, California, which also managed the GRACE mission for NASA’s Science Mission Directorate in Washington. “We see a distinctive pattern of the wet land areas of the world getting wetter — those are the high latitudes and the tropics — and the dry areas in between getting dryer. Embedded within the dry areas we see multiple hotspots resulting from groundwater depletion.”

    For instance, although pumping groundwater for agricultural uses is a significant contributor to freshwater depletion throughout the world, groundwater levels are also sensitive to cycles of persistent drought or rainy conditions. Famiglietti noted that such a combination was likely the cause of the significant groundwater depletion observed in California’s Central Valley from 2007 to 2015, when decreased groundwater replenishment from rain and snowfall combined with increased pumping for agriculture.

    Southwestern California lost 4 gigatons of freshwater per year during the period. A gigaton of water would fill 400,000 Olympic swimming pools. A majority of California’s freshwater comes in the form of rainfall and snow that collect in the Sierra Nevada snowpack and then is managed as it melts into surface waters through a series of reservoirs. When natural cycles led to less precipitation and caused diminished snowpack and surface waters, people relied on groundwater more heavily….

    M. Rodell et al. Emerging trends in global freshwater availability. Nature (2018) doi:10.1038/s41586-018-0123-1

  2. A Bottom-Up Approach to Groundwater Sustainability

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    • Innovative approaches to addressing groundwater deficits from charges for going over assigned water budgets and water trading to groundwater bank accounts are working in CA’s Kern County.
    • Emphasizing approaches that let growers decide what’s best for them—whether it’s helping them put unused water into a market or compensating them for using their land for recharge– is a key strategy to achieving groundwater sustainability.

    Lori Pottinger February 28, 2018 read full post from the Public Policy Institute of CA (PPIC) here

    California’s Sustainable Groundwater Management Act (SGMA) requires communities with ongoing groundwater deficits to bring their aquifers into balance in the coming years. This will be a difficult and complex process, but it’s also an opportunity to devise workable solutions at the community level. We talked to Eric Averett of the Rosedale–Rio Bravo Water Storage District about groundwater management innovations being tried in his Kern County district and lessons learned that might have wider application.

    …Eric Averett: The most challenging area is managing and mitigating impacts associated with demand reduction. Rather than mandating that individual landowners reduce demand, our district has pursued a path that we think gives individuals greater flexibility. The idea is that every acre will be assigned a water budget based on what the district can provide or considers sustainable. If a landowner uses more than that amount, it triggers a water charge. The district will use those funds to develop water supply programs or purchase land from willing sellers to retire it from production. Either way, this system doesn’t take anything away from landowners’ ability to manage their own water, it just gives them more options.

    Another important area we’re looking at is water trading within our district’s boundaries. We’ve implemented a pilot study that empowers landowners to act as buyers or sellers in managing their water resources. We think water trading will be an essential tool to getting aquifers into balance and maximizing the value of the resource. For example, during a drought, a small grower with row crops may find greater value in fallowing a field and selling the water. At the same time, a grower who may be short of water and facing the loss of a permanent crop may enter the market as a buyer. If we don’t find a way to create these buy/sell opportunities, we strand the asset.

    A third area we’re working on is creating individual groundwater bank accounts for landowners. We have a number of landowners who’ve committed to make their land available for recharge in exchange for a portion of the recharged water being credited to their account. Alternatively, some landowners have acquired a source of water and asked the district to use it for recharge on their behalf. Both types of programs were tested successfully in 2017, and we look forward to expanding the concept.   Ultimately, we’re looking at ways the district can assist landowners in becoming sustainable and mitigating SGMA impacts….

  3. Dangerously Low on Water, Cape Town Now Faces ‘Day Zero’; A Warning for California and the American West?

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    The Theewaterskloof Dam, the city’s largest, is just 13% full. (AP Photo)

    • After a three-year drought, Cape Town is now at serious risk of becoming one of the few major cities in the world to lose piped water to homes and most businesses.
    • As far back as 2007, South Africa’s Department of Water Affairs warned that the city needed to consider increasing its supply with groundwater, desalination and other sources, citing the potential impact of climate change….
    • New water supplies have been part of the city’s plans but “it was not envisaged that it would be required so soon.”
    • Cape Town’s problems embody one of the big dangers of climate change: the growing risk of powerful, recurrent droughts

    CAPE TOWN — It sounds like a Hollywood blockbuster. “Day Zero” is coming to Cape Town this April. Everyone, be warned.

    The government cautions that the Day Zero threat will surpass anything a major city has faced since World War II or the Sept. 11 attacks. Talks are underway with South Africa’s police because “normal policing will be entirely inadequate.” Residents, their nerves increasingly frayed, speak in whispers of impending chaos.

    The reason for the alarm is simple: The city’s water supply is dangerously close to running dry.

    If water levels keep falling, Cape Town will declare Day Zero in less than three months. Taps in homes and businesses will be turned off until the rains come. The city’s four million residents will have to line up for water rations at 200 collection points. The city is bracing for the impact on public health and social order.

    “When Day Zero comes, they’ll have to call in the army,” said Phaldie Ranqueste, who was filling his white S.U.V. with big containers of water at a natural spring where people waited in a long, anxious line.

    It wasn’t supposed to turn out this way for Cape Town. This city is known for its strong environmental policies, including its careful management of water in an increasingly dry corner of the world….

    But after a three-year drought, considered the worst in over a century, South African officials say Cape Town is now at serious risk of becoming one of the few major cities in the world to lose piped water to homes and most businesses.

    Hospitals, schools and other vital institutions will still get water, officials say, but the scale of the shut-off will be severe.

    Cape Town’s problems embody one of the big dangers of climate change: the growing risk of powerful, recurrent droughts. In Africa, a continent particularly vulnerable to the effects of climate change, those problems serve as a particularly potent warning to other governments, which typically don’t have this city’s resources and have done little to adapt.

    the-south-african-weather-service-says-climate-change-is-making-its-historical-models-useless- theeshop dam AP PhotoThe Theewaterskloof Dam, the city’s largest, is just 13% full. (AP Photo)

    For now, political leaders here talk of coming together to “defeat Day Zero.” As water levels in the dams supplying the city continue to drop, the city is scrambling to finish desalination plants and increase groundwater production. Starting in February, residents will face harsher fines if they exceed their new daily limit, which will go down to 50 liters (13.2 gallons) a day per person from 87 liters now…

    …As far back as 2007, South Africa’s Department of Water Affairs warned that the city needed to consider increasing its supply with groundwater, desalination and other sources, citing the potential impact of climate change. Mike Muller, who served as the department’s director between 1997 and 2005, said that the city’s water conservation strategy, without finding new sources, has been “a major contributor to Cape Town’s troubles.”

    “Nature isn’t particularly willing to compromise,” he added. “There will be severe droughts. And if you haven’t prepared for it, you’ll get hammered.” Ian Neilson, the deputy mayor, said that new water supplies have been part of the city’s plans but “it was not envisaged that it would be required so soon.”…

    ….So far, only 55 percent of Cape Town residents have met the target of 87 liters per day. Helen Zille, the premier of Western Cape Province, which includes Cape Town, wrote in The Daily Maverick last week that she considers a shut-off inevitable. The question now, she said, is, “When Day Zero arrives, how do we make water accessible and prevent anarchy?”

    Cutting back is a difficult message to convey in one of the world’s most unequal societies, where access to water reflects Cape Town’s deep divisions. In squatter camps, people share communal taps and carry water in buckets to their shacks. In other parts of the city, millionaires live in mansions with glistening pools….

  4. Discrepancies between satellite and global model estimates of land water storage– Models may underestimate large water storage changes

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    • Overall, the model results calculated a decline in global water storage during the study period, while GRACE data indicate it was on the rise. However, the study notes that while the climate increased water storage globally, humans caused significant declines in certain regions.
    • But ensuring water availability for human consumption and agriculture is in many cases a regional to local issue, and we should put increased emphasis on analyses at this scale by, for example, integrating local data.

    Posted: 22 Jan 2018 01:47 PM PST

    Researchers have found that calculations of water storage in many river basins from commonly used global computer models differ markedly from independent storage estimates from GRACE satellites.

    ….”People are depending more and more on global models to determine projections of the impacts of human water use and climate on water resources,” said lead author Bridget Scanlon, a senior research scientist at the university’s Bureau of Economic Geology. “We are now able to evaluate water storage changes from models with GRACE data, which suggests that the models may underestimate large water storage changes, both large declining and rising storage trends.”

    ….Overall, the model results calculated a decline in global water storage during the study period, while GRACE data indicate it was on the rise. However, the study notes that while the climate increased water storage globally, humans caused significant declines in certain regions. The study area covered about 63 percent of global land area and excluded Greenland and Antarctica because most of the water in those areas is trapped in glaciers or ice sheets….

    …The study also notes that scientists should work on improving regional assessments. “GRACE is great because it highlights the global picture of what’s happening with global water storage, and at a coarse grid-scale it’s really nice to see what’s happening,” Scanlon said. “But ensuring water availability for human consumption and agriculture is in many cases a regional to local issue, and we should put increased emphasis on analyses at this scale by, for example, integrating local data. The specific situation could be much better investigated than with global-scale studies only.”

    Bridget R. Scanlon, Zizhan Zhang, Himanshu Save, Alexander Y. Sun, Hannes Müller Schmied, Ludovicus P. H. van Beek, David N. Wiese, Yoshihide Wada, Di Long, Robert C. Reedy, Laurent Longuevergne, Petra Döll, Marc F. P. Bierkens. Global models underestimate large decadal declining and rising water storage trends relative to GRACE satellite data. Proceedings of the National Academy of Sciences, 2018; 201704665 DOI: 10.1073/pnas.1704665115

  5. Groundwater depletion could be significant source of atmospheric carbon dioxide

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    • If left to its own devices, this carbon-rich water remains below ground for hundreds to thousands of years before surfacing in oceans or freshwater bodies. But humans are now extracting groundwater at an unprecedented pace to sustain a growing population

    November 16, 2017 American Geophysical Union Read full ScienceDaily article here

    Humans may be adding large amounts of carbon dioxide to the atmosphere by using groundwater faster than it is replenished, according to new research. This process, known as groundwater depletion, releases a significant amount of carbon dioxide into the atmosphere that has until now been overlooked by scientists in calculating carbon sources, according to the new study.

    The study’s authors estimate groundwater depletion in the United States could be responsible for releasing 1.7 million metric tons (3.8 billion pounds) of carbon dioxide to the atmosphere every year.

    Based on these figures, groundwater depletion should rank among the top 20 sources of carbon emissions documented by the US Environmental Protection Agency (EPA) and the Intergovernmental Panel on Climate Change (IPCC). This would mean the carbon dioxide emitted through groundwater depletion is comparable to the carbon generated from aluminum, glass, and zinc production in the United States, according to the study’s authors….

    …Rain falling from the sky contains the same amount of carbon dioxide as is present in the atmosphere. But soil carbon dioxide levels are up to 100 times greater than carbon dioxide levels in the atmosphere, because soil microbes degrade organic carbon into carbon dioxide. When rainwater hits the ground and percolates through Earth’s rocks and sediments, the water dissolves extra carbon produced by these microbes.

    If left to its own devices, this carbon-rich water remains below ground for hundreds to thousands of years before surfacing in oceans or freshwater bodies. But humans are now extracting groundwater at an unprecedented pace to sustain a growing population….

    …Groundwater depletion’s impact on carbon emissions is significant yet relatively small compared to the leading contributors, according to the authors. For example, scientists estimate fossil fuel combustion in the United States is responsible for releasing more than 5 billion metric tons (11 trillion pounds) of carbon dioxide into the atmosphere every year, close to 3,000 times the amount released from groundwater depletion. Still, the study authors argue that understanding all sources of carbon dioxide emissions is important for making accurate climate change projections and finding solutions….

    Warren W. Wood, David W. Hyndman. Groundwater Depletion: A Significant Unreported Source of Atmospheric Carbon Dioxide. Earth’s Future, 2017; DOI: 10.1002/2017EF000586

  6. Groundwater recharge in the American west under climate change

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    November 16, 2017 University of Arizona  read full ScienceDaily article here

    Groundwater recharge in the Western US will change as the climate warms — the dry southern regions will have less and the northern regions will have more, according to new research. The new study covers the entire US West, from the High Plains states to the Pacific coast, and provides the first detailed look at how groundwater recharge may change as the climate changes. Groundwater is an important source of freshwater, particularly in the West.

    Groundwater…. is often used to make up for the lack of surface water during droughts, the authors note. In many areas of the West, groundwater pumping currently exceeds the amount of groundwater recharge.

    “The portions of the West that are already stretched in terms of water resources — Arizona, New Mexico, the High Plains of Texas, the southern Central Valley — for those places that are already having problems, climate change is going to tighten the screws,” Meixner said….

    R. Niraula, T. Meixner, F. Dominguez, N. Bhattarai, M. Rodell, H. Ajami, D. Gochis, C. Castro. How Might Recharge Change Under Projected Climate Change in the Western U.S.? Geophysical Research Letters, 2017; 44 (20): 10,407 DOI: 10.1002/2017GL075421

  7. Nitrogen surplus from agriculture impacts groundwater, according to 70 years of monitoring

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    • A 70 years time-series of monitoring data relays a clear message: When farmers apply more nitrogen to their fields than their crops can absorb, the amount of nitrogen in the groundwater increases. When less nitrogen leaches from the soil, due to either improved management or reduced nitrogen application, the amount found in the groundwater decreases.
    • the study also found that socio-economic development stimulates adoption of measures to protect the environment and that economic growth can curb environmental degradation.
    September 26, 2017 Aarhus University  Read full ScienceDaily article here
    A new study based on 70 years of monitoring data highlights the importance of a consistent national groundwater monitoring program and the need for development of future effective nitrogen mitigation measures in intensive agriculture worldwide in order to protect groundwater resources….

    …In the years 1946 to the mid-1980s nitrogen surplus increased continually. Increasing environmental awareness and national environmental plans have since then curbed this trend — while economic growth continues. Like the nitrogen surplus, the nitrate concentrations in oxic (oxygen present) water reached its peak around the turning point in the 1980s….

    Birgitte Hansen, Lærke Thorling, Jörg Schullehner, Mette Termansen, Tommy Dalgaard. Groundwater nitrate response to sustainable nitrogen management. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-07147-2

  8. CA: More than 99 percent of sustainable groundwater agencies have been formed

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    published on August 28, 2017 – 3:48 PM
    Written by The Business Journal Staff- full article here

    In what the state is billing as “a major step toward sustainable groundwater management in California,” more than 99 percent of the state’s groundwater basins have met a key deadline in reporting groundwater pumping.

    According to the state’s Sustainable Groundwater Management Act (SGMA) of 2014, key stakeholders of the state’s 127 high- and medium-priority groundwater basins were required to form a Groundwater Sustainability Agency (GSA) to manage groundwater pumping. The deadline for formation of the GSAs was June 30, and as of this week, more than 99 percent had been formed.

    …The next step for SGMA compliance is to create and implement groundwater sustainability plans that describe the plan for bringing “basins into balanced levels of pumping and recharge.” Basins identified as critically overdrafted are required to have sustainability plans in place by Jan. 21, 2020, while all other high- and medium-priority basins have until Jan. 31, 2022, to adopt plans.\

  9. Study: Heavy Storms May Be Enough to Recharge Central Valley Groundwater

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    • A handful of storms each year could provide enough water to offset annual groundwater overdraft in California’s Central Valley– but work is needed to capture and distribute that water.

    Matt Weiser August 21, 2017  read full Water Deeply article here

    California’s Sustainable Groundwater Management Act, passed in 2014, requires some 250 groundwater basins throughout the state to halt the overdraft in their aquifers. The big question for everyone is: Where will the water come from to do that?

    It could come from “high-magnitude flows” – flooding events, essentially, that occur from just a handful of storms every winter. …A new UC Davis study …attempts to quantify these high flows… one of the first efforts to measure how much water might be available for groundwater recharge from these storm events, and the results are surprising.

    …[the authors] estimate that 2.6 million acre-feet of water is available in an average year from these high-magnitude flows…based on real flows that have occurred. They also estimate this water is surplus to both existing water rights and to environmental flow requirements in the Sacramento-San Joaquin Delta…..this amount of water also nearly equals the average annual groundwater overdraft in the state’s Central Valley. This suggests these high-magnitude flows could be an important tool to recharge stressed aquifers. That is, if the water can be captured by groundwater banking projects, the flooding of farm fields and other means.

    Within a few weeks, the results will be presented online in an interactive format at recharge.ucdavis.edu.

    Water Deeply recently interviewed Kocis to learn more about her findings.see interview with the study’s authors here

    Tiffany N Kocis and Helen E Dahlke. Availability of high-magnitude streamflow for groundwater banking in the Central Valley, California. 31 July 2017 Environmental Research Letters, Volume 12, Number 8

    ABSTRACT: California’s climate is characterized by the largest precipitation and streamflow variability observed within the conterminous US. This, combined with chronic groundwater overdraft … creates the need to identify additional surface water sources available for groundwater recharge using methods such as agricultural groundwater banking, aquifer storage and recovery, and spreading basins. High-magnitude streamflow, i.e. flow above the 90th percentile, that exceeds environmental flow requirements and current surface water allocations under California water rights, could be a viable source of surface water for groundwater banking. Here, we present a comprehensive analysis of the magnitude, frequency, duration and timing of high-magnitude streamflow (HMF) for 93 stream gauges covering the Sacramento, San Joaquin and Tulare basins in California…The results suggest that there is sufficient unmanaged surface water physically available to mitigate long-term groundwater overdraft in the Central Valley.

  10. Trading Sustainably: local groundwater markets in CA under the Sustainable Groundwater Management Act (SGMA)

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    Berkeley Law’s Center for Law, Energy and Environment June 2017

    California’s Sustainable Groundwater Management Act [SGMA] opens the door for local groundwater markets but does not provide guidance about when they’d be appropriate as management tools. This report outlines considerations to help evaluate local groundwater markets as a viable tool that contributes to sustainably managing a particular groundwater basin.

    [In SGMA, sustainable yield is defined as the amount of groundwater that can be withdrawn annually without chronically lowering groundwater levels, causing seawater intrusion, degrading water quality, causing land subsidence or depleting interconnected surface water (for example, creeks, streams and rivers) in a manner that causes significant and adverse impacts.]

    Download the Executive Summary:

    Trading Sustainably – Executive Summary (June 2017)

    Download the Report:

    Trading Sustainably: Critical Considerations for Local Groundwater Markets Under the Sustainable Groundwater Management Act (June 2017)

    Copyright 2017 Nell Green Nylen