Wikipedia:Reference desk/Archives/Science/2018 November 24

= November 24 =

Seawater intrusion into freshwater aquifers
I heard on the news that a new US government report, the National Climate Assessment, volume 2, on climate change said that by the end of the century, seawater could contaminate the freshwater aquifer of Puerto Rico. The NY Times says “No area of the country will be untouched ...to Puerto Rico and the Virgin Islands, where saltwater will taint drinking water.” (My phone does not allow me to copy thenceurl from today’s paper) This made me wonder how, in general, a freshwater aquifer stays that way when ocean water is near. If the aquifer is 100 feet down, and you are 50 feet above sea level, and the aquifer is not solid rock, how does the water stay isolated? I expect well of some sea coast communities near sea level go way deeper. Edison (talk) 12:50, 24 November 2018 (UTC)
 * See Lens (hydrology). {The poster formerly known as 87.81.230.195} 90.200.131.235 (talk) 21:32, 24 November 2018 (UTC)
 * And see saltwater intrusion. Mikenorton (talk) 22:19, 24 November 2018 (UTC)
 * There are actually even known freshwater springs on the ocean ground far away from any coast, but these are feed from ancient and deep sweetwater depods. But these are very rare and unlikely directly beneath an Island. On Islands there is just a natural balance of more sweetwater from Rain pouring into the ground than saltwater sneaking in tru the coast - else most of the vegetation couldnt have survived till now.
 * Of course with 3.3 Million Puertoricans using 50-100 liters fresh water a day, some Farmers, Factories etc. using even much more, that gotten out of balance. Everyone can calculate it himself pretty simple. Is there 3.3 Million times 100 liters rain falling on the 9,104 km² each day? I doubt. --Kharon (talk) 00:19, 26 November 2018 (UTC)
 * Actually there are many orders of magnitude more liters of rainwater falling on Puerto Rico each day. Abductive  (reasoning) 04:43, 26 November 2018 (UTC)
 * Given the surface area, population and climate data in Puerto Rico, the average rainfall is 9587 litres per capita per day. But you have to account for some evaporation and surface runoff. PiusImpavidus (talk) 10:29, 26 November 2018 (UTC)


 * If that is correct, there should not be much danger from Seawater or to a few small, unfortunate areas only. Sorry for my wrong and not scientific at all estimation. The core is still right tho, essentially its a question of balance, --Kharon (talk) 22:01, 26 November 2018 (UTC)
 * "Sorry for my wrong and not scientific at all estimation. The core is still right tho, essentially its a question of balance" You realise, Kharon, that you are claiming your personal estimations trump a major study sponsored by the US Government? As Abductive indicated above, the human use of freshwater in Puerto Rico is vastly outwighed by the natural processes involved and the changes in them resulting from changes in climate. {The poster formerly known as 87.81.230.195}90.200.131.235 (talk) 23:39, 26 November 2018 (UTC)