Science

NNadir

(33,474 posts) Fri Apr 30, 2021, 07:01 PM Apr 2021

Global groundwater wells at risk of running dry

The paper I'll discuss in this post is this one: Global groundwater wells at risk of running dry (BY Scott Jasechko and Debra Perrone Science 372, 418–421 (2021) 23 April 2021)

A news item referring to the paper in the same issue of Science which is likely to be open sourced is here: The hidden crisis beneath our feet (James S. Famiglietti1,2, Grant Ferguson, Science 23 Apr 2021: Vol. 372, Issue 6540, pp. 344-345)

If memory serves me well, I have referred a number of times to a lecture I attended by Dr. Robert Kopp of Rutgers University, this one: Science on Saturday: Managing Coastal Risk in an Age of Sea-level Rise, wherein, in answer to a question from the audience (mine), Dr. Kopp explained that about 10% of sea level rise can be attributed to water pumped out of the ground and allowed to evaporate. Most of this water is used for agriculture, but it is also used in cities and in homes. I am guilty here. The water in my home is well water, which as I happen to know, contains some interesting and unpleasant substances.

This suggests - I've been musing about this a lot lately - that one path to addressing climate change would be restoring shorelines would include refilling the aquifers we've drained in the last 50 years or so in yet another expression of our accelerating contempt for all future generations, along with dried up lakes like Owens Lake in California, and dying bodies of water like Lake Baikal, the Aral Sea, the Caspian Sea, etc...

My most recent episode of such musings out loud is here: Ion-capture electrodialysis using multifunctional adsorptive membranes, which is preceded by a long dull digression on reactor physics and the mercury content of the oceans.

To anyone who argues that refilling ground water by desalination of ocean water, refilling dead lakes, dead seas etc. is geoengineering, let me say this.

There is a television show on the Science channel called Engineering Catastrophes which I watch from time to time to give me ammunition to make fun of my son the engineer. It's all about failures of bridges, buildings, roadways, etc. from things like hydrogen embrittlement, improper analysis of stresses, poor materials etc. However everything on this show is small potatoes compared to the biggest engineering catastrophe, the existing haphazard, uncontrolled and unplanned geoengineering of the entire planet, most of which has been a catastrophe of the last one hundred years.

This is not really a water problem; it is an energy problem. No, wind turbines in lobster fisheries off the coast of Maine, nor any other wind schemes designed to industrialize wilderness, will not produce even a fraction of the energy required owing to thermodynamic, mass intensity, reliability and lifetime considerations. The sooner we lose our affection for this nonsense, the more hope we will have.

The goal of geoengineering should be to restore, and nothing more.

Anyway future generations are in a world of hurt according to this paper. From the paper's introduction:

Groundwater provides nearly half of the water used for irrigated agriculture and supplies drinking water for billions of people (1, 2). Its perennial and distributed nature makes groundwater suitable for providing reliable access to potable water and supporting efforts to adapt to climate change (3). Nevertheless, access to groundwater to meet water demands may be hindered when groundwater levels decline. Groundwater levels are declining in many aquifers around the globe [e.g., (4–6)], causing groundwater wells (7) to run dry (8–10) and leaving farmers unable to irrigate and households without access to reliable and convenient drinking water.

When groundwater wells run dry, one common adaptation strategy is to construct deeper wells (11). Deeper wells tend to be less vulnerable than shallower wells to climate variability (12) and groundwater level declines (13), but even relatively deep wells are not immune to long-term reductions in groundwater storage. Despite the role of wells as a basic infrastructure used to access groundwater, information about the locations and depths of wells has never before been compiled and analyzed at the global scale. Analyzing groundwater resources at the global scale is becoming increasingly important because of groundwater’s role in virtual water trade, international policy, and sustainable development (14, 15). Nevertheless, we emphasize that groundwater is a local resource influenced by hydrogeologic conditions, water policies, sociocultural preferences, and economic drivers.

Here, we compiled ~39 million records of groundwater well locations, depths, purposes, and construction dates (supplementary materials section S1), which provide local information at the global scale. These observations promote a better understanding of spatiotemporal patterns of well locations and depths (16, 17). Groundwater data are notoriously difficult to collect and collate (18, 19). The ~39 million wells are situated in 40 countries or territories that represent ~40% of global ice-free lands (average data density of 0.7 wells/km2; Fig. 1). Half of all global groundwater pumping takes place within our study countries or territories [fig. S2, reference (2), and supplementary materials section S5.1], which are home to >3 billion people (table S1).

Fig. 1 Groundwater well depths in countries around the globe.

The caption:

The dataset contains ~39 million wells in 40 countries or territories (see inset map). Blue points mark shallower wells and red points mark deeper wells in Canada, the United States (white areas mark states where data are unavailable), and Mexico (A); Argentina (partial coverage), Bolivia (partial coverage), Brazil, Chile, and Uruguay (B); Iceland, Portugal, Spain, France, Germany (partial coverage), Denmark, Sweden, Norway, Italy, Slovakia, Slovenia, Belgium, Poland, Latvia, Estonia, Czech Republic, Hungary, United Kingdom, and Ireland (C); Namibia and South Africa (D); Thailand and Cambodia (E); and Australia (F). National-level analyses are available in figs. S37 to S435.

Fig. 2 Fraction of areas with deeper well drilling versus shallower well drilling for five time periods among study countries.

The caption:

Well-deepening trends are more common than well-shallowing trends for the majority of time periods for the majority of countries (national-level analyses in figs. S37 to S435). (A) The fraction of 100 km by 100 km study areas where wells are being drilled deeper over time (Spearman ? > 0; regression of well completion depth versus well construction date). Each diamond represents well construction depth variations over time for a given country (e.g., blue diamonds are regressions for years 2000–2015; see legend above figure); some points overlap. (B to L) Spearman ? determined by regression of well depth versus construction date for the time interval 2000–2015 in 11 countries [i.e., the fraction of all 100 km by 100 km areas in these maps with Spearman ? > 0 correspond to the blue diamonds in (A)]. Blue shades mark 100 km by 100 km areas where wells are being constructed shallower over time (i.e., Spearman ? < ?0.1); orange and red shades mark 100 km by 100 km areas where wells are being constructed deeper over time (i.e., Spearman ? > 0.1.)

Fig. 3 Well construction depth trends at locations close to ( 0) significantly (Spearman P < 0.05) over time.

The caption:

Results derive disproportionately from Australia, Canada, France, Mexico, New Zealand, Sweden, and the United States (tables S64 to S69). The histograms are distributions of Spearman rank coefficients as determined through regression analyses of well completion depths versus well completion dates at sites close to a monitoring well where water levels have declined significantly over time (Spearman ? > 0 and Spearman P < 0.05 determined through regression analyses of measured depth to water in monitoring well versus water level measurement date). Each plot in (A) to (E) represents one study time interval [e.g., (A) presents results for 1950–1975]. Although all distributions skew right (i.e., well deepening where groundwater levels are declining), a substantial number of sites indicate that newer wells are not being constructed substantially deeper than older wells where groundwater levels are declining. Curly brackets above each plot in (A) to (E) provide the percentage of well construction depth trends falling within the following Spearman ? ranges: ?1.0 to ?0.2, ?0.2 to 0.2, and 0.2 to 1.0.

An excerpt of the conclusion of this short paper:

From India to the United States, wells are already running dry because of groundwater level declines (22, 26, 34, 35). When a well runs dry, there are a number of ways to adapt: (i) construct a new and deeper well or deepen the existing well that ran dry (10, 13); (ii) access alternative water sources (10, 29); (iii) conserve water through behavioral changes or technological adoptions [e.g., switching to crops that are less water intensive; adopting irrigation approaches that reduce water losses (25)]; (iv) sell the property (10); or (v) abandon activities that require high water inputs, such as irrigation (35). In Karnataka, India, some households that have had their well run dry have offset lost agricultural profits by seeking off-farm income (35). The transition away from agriculture can have longer-term impacts on the household, such as debt accrual while seeking alternative employment and lost educational opportunities for children who join the workforce early to supplement household income (35). In California’s Central Valley (United States) and several other agricultural hubs around the globe, typical agricultural wells are deeper than domestic wells (supplementary materials sections S5.5 to S5.6); as a result, rural domestic wells are running dry disproportionately relative to agricultural wells...

...Groundwater wells supply water to billions of people around the globe (2, 13, 14, 36). Groundwater depletion is projected to continue in some areas where it is already occurring, and even expand to new areas not yet experiencing depletion (37)...

...Our work highlights the vulnerability of existing wells to groundwater depletion because (i) many wells are not much deeper than the local water table, making them likely to run dry with even modest groundwater level declines (supplementary materials section S6), and (ii) deeper well construction is common but not ubiquitous where groundwater levels are declining...

History will not forgive us, nor should it.

Have a nice weekend.