Groundwater Resources Recharge Faster than Previously Estimated

New research pub­lished in the Geophysical Research Letter Journal sheds light on the con­nec­tion between ground­wa­ter and sur­face water fluxes. The results show that ground­wa­ter resources replen­ish at a sig­nif­i­cantly faster rate than pre­vi­ously thought.

The find­ings also hint at the sig­nif­i­cant role played by ground­wa­ter resources in evap­o­tran­spi­ra­tion and stream­flow. Such knowl­edge should improve cur­rent and future ground­wa­ter assess­ment.

Groundwater resources play a cru­cial role in sus­tain­ing farm­ing activ­i­ties and drink­ing water avail­abil­ity around the globe.

The team of American and European sci­en­tists noted that the rate at which pre­cip­i­ta­tions replen­ish ground­wa­ter stor­age directly impacts sus­tain­able ground­wa­ter use.

“Groundwater is an invalu­able global resource, but its long-term via­bil­ity as a resource for con­sump­tion, agri­cul­ture and ecosys­tems depends on pre­cip­i­ta­tion recharg­ing aquifers. How much pre­cip­i­ta­tion recharges ground­wa­ters varies enor­mously across Earth’s sur­face, yet recharge rates often remain uncer­tain,” the researchers wrote.

To mea­sure ground­wa­ter resource recharge rates, the researchers designed a cal­cu­la­tion model based on avail­able regional ground­wa­ter mea­sure­ment data from six con­ti­nents. That model showed how cli­mate deter­mines ground­wa­ter recharge rates, espe­cially arid­ity and pre­cip­i­ta­tion.

Using the cli­mate arid­ity para­me­ter, the sci­en­tists found that the global recharge rate of ground­wa­ter resources hap­pens twice as fast as pre­vi­ously esti­mated.

The paper’s authors explained that their find­ings show a higher-than-esti­mated per­cent­age of ground­wa­ter return­ing to the sur­face via river flow or when used by veg­e­ta­tion.

The higher recharge rates sug­gest that nat­ural phe­nom­ena, such as evap­o­tran­spi­ra­tion and stream­flow, depend on ground­wa­ter much more than pre­vi­ously thought. This result is espe­cially evi­dent when com­pared to the con­tri­bu­tion of other sur­face fluxes, such as over­land flow, shal­low sub­sur­face flows and soil-mois­ture-fed evap­o­tran­spi­ra­tion.

Consequences of the study could include the abil­ity to assess the impacts of cli­mate change on ground­wa­ter recharge, which is con­sid­ered highly uncer­tain and has not been glob­ally quan­ti­fied by cur­rent mod­els.

“Strengthening the ground­wa­ter con­nec­tion to sur­face fluxes in these mod­els is essen­tial, given that mod­els are the foun­da­tion of our under­stand­ing of our planet and under­pin present-day envi­ron­men­tal sci­ence and pol­i­cy­mak­ing,” the authors wrote.

Finally, the sci­en­tists warned that their find­ings do not dis­re­gard the cur­rent under­stand­ing of ground­wa­ter overuse and the risk it rep­re­sents for global water secu­rity. ​“Groundwater overuse results in stor­age deple­tion and declin­ing water lev­els that have been robustly doc­u­mented in (…) arid areas across the globe,” they wrote.

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