{"id":438699,"date":"2026-01-28T13:34:23","date_gmt":"2026-01-28T13:34:23","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/438699\/"},"modified":"2026-01-28T13:34:23","modified_gmt":"2026-01-28T13:34:23","slug":"scientists-finally-figured-out-how-much-groundwater-there-is-under-the-us-and-it-is-enough-to-fill-the-great-lakes-13-times-over","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/438699\/","title":{"rendered":"Scientists Finally Figured Out How Much Groundwater There Is Under the US and It Is Enough to Fill the Great Lakes 13 Times Over"},"content":{"rendered":"

\"Water <\/a><\/p>\n

It\u2019s not easy to determine how much water there is across a landscape.\u00a0A measly 1%<\/a>\u00a0of Earth\u2019s freshwater is on the surface, where it can be seen and measured with relative ease. But beneath that, measurements vary massively depending on water table depth and ground porosity we can\u2019t directly see.<\/p>\n

Reed Maxwell<\/a>, a hydrologist at Princeton University, likes to think of rainfall, snow, and surface water as a checking account used for short-term water management needs and groundwater as a savings account, where a larger sum should, ideally, be building up over time.<\/p>\n

\u201cWe\u2019re operating in a situation where we don\u2019t know how much is going into the savings account every month, and we don\u2019t know how much is in our savings account,\u201d he said.<\/p>\n

But\u00a0a new groundwater map<\/a>\u00a0by Maxwell and colleagues offers the highest-resolution estimate so far of the amount of groundwater in the contiguous United States: about 306,500 cubic kilometers. That\u2019s 13 times the volume of all the Great Lakes combined, almost 7 times the amount of water discharged by all rivers on Earth in a year. This estimate, made at 30-meter resolution, includes all groundwater to a depth of 392 meters, the deepest for which reliable porosity data exist. Previous estimates using similar constraints have ranged from 159,000 to 570,000 cubic kilometers.<\/p>\n

\u201cIt\u2019s definitely a move forward from some of the previous [mapping] efforts,\u201d said\u00a0Grant Ferguson<\/a>, a hydrogeologist at the University of Saskatchewan who was not involved in the research. \u201cThey\u2019re looking at much better resolution than we have in the past and using some interesting techniques.\u201d<\/p>\n

Well, Well, Well<\/p>\n

Past estimations of groundwater quantity have been based largely on well observations.<\/p>\n

\u201cThat\u2019s the really crazy thing about groundwater in general,\u201d said\u00a0Laura Condon<\/a>, a hydrologist at the University of Arizona and a coauthor of the paper. \u201cWe have these pinpricks into the subsurface where there\u2019s a well, they take a measurement of how deep down the water table depth is, and that\u2019s what we have to work with.\u201d<\/p>\n

But not all wells are measured regularly. For obvious reasons, there tend to be more wells in places where more groundwater is present, making data on areas with less groundwater scarcer. And a well represents just one point, whereas\u00a0water table depth<\/a>\u00a0can vary greatly over short distances.<\/p>\n

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Researchers have used these data points, as well as knowledge of the physics of how water flows underground, to model water table depth at a resolution of about 1 kilometer. They\u2019ve also used satellite data to capture large-scale trends in water movement. But those data are of lower resolution: Data from\u00a0NASA\u2019s GRACE (Gravity Recovery and Climate Experiment) Tellus mission<\/a>, for instance, have a resolution of about 300 kilometers, about 10,000 times coarser than the new map.<\/p>\n

To demonstrate the value of high-resolution data, the team showed what happened when they decreased the resolution of their entire map from 30 meters to 100 kilometers\u2014the spatial resolution of many global hydrologic models. The resulting more pixelated map estimated just above 252,000 cubic kilometers of water, an underestimation of 18% compared to the new map.<\/p>\n

In addition to identifying groundwater quantities at high resolution, the new map reveals more nuanced information about known groundwater sources.<\/p>\n

For instance, it shows that about 40% of the land in the contiguous United States has a water table depth shallower than 10 meters. \u201cThat 10-meter range is that range where you can have groundwater\u2013plant\u2013land surface interactions,\u201d Condon said. \u201cAnd so that\u2019s just really pointing to how connected those systems are.\u201d<\/p>\n

Bias for Good<\/p>\n

The new work used direct well measurements as well as satellite data\u2014about a million measurements, made between 1895 and 2023\u2014along with maps of precipitation, temperature, hydraulic conductivity, soil texture, elevation, and distance of streams. Then, the scientists used the data to train a machine learning model.<\/p>\n

In addition to its being able to quickly sort through so many data points, Maxwell noted another benefit of the machine learning approach that might sound unexpected: its bias. Early groundwater estimates were relatively simplistic, not accounting for either hydrogeology or the fact that humans themselves pump water out of the ground. The team\u2019s machine learning approach was able to incorporate that information because evidence of groundwater pumping was present in the data used to train it.<\/p>\n

\u201cWhen you hear about bias in machine learning all the time, it\u2019s usually in a negative connotation, right?\u201d Maxwell said. \u201cAs it turns out, when you can\u2019t disentangle the signal of groundwater pumping and groundwater depletion from the almost 1 million observations that we used to train this machine learning approach, it implicitly learned that bias.\u2026 It\u2019s learned the pumping signals, it\u2019s learned the human depletion signal.\u201d<\/p>\n

Maxwell and the other researchers hope the map can be a resource for regional water management decisionmakers, as well as for farmers making decisions about irrigation. Condon added that she hopes it raises awareness of groundwater in general.<\/p>\n

\u201cGroundwater is literally everywhere all the time,\u201d she said. The map is \u201cfilled in everywhere, wherever you are. Some places it\u2019s 300 meters deep, some places it\u2019s 1 meter deep. But wherever you\u2019re standing, dig down, and there\u2019s water down there somewhere.\u201d<\/p>\n

This article originally appeared in EOS Magazine<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"It\u2019s not easy to determine how much water there is across a landscape.\u00a0A measly 1%\u00a0of Earth\u2019s freshwater is…\n","protected":false},"author":2,"featured_media":438700,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[181975,49,48,100869,76935,65537,66,11547],"class_list":{"0":"post-438699","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-acquifer","9":"tag-ca","10":"tag-canada","11":"tag-freshwater","12":"tag-great-lakes","13":"tag-groundwater","14":"tag-science","15":"tag-water"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/438699","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=438699"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/438699\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/438700"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=438699"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=438699"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=438699"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}