Bangkok under water in 20years time !!!!
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From: Markku Grönroos on 2 May 2007 14:38 "none" <oplegg(a)yahoo.co.uk> kirjoitti viestiss�:1178130883.266920.261890(a)o5g2000hsb.googlegroups.com... > Bangkok gets that sinking feeling > > BangkokPost.com from Reuters reports > > Thailand's best known disaster prognosticator said on Wednesday global > warming will put Bangkok a metre under water in less than 20 years, > adding: "You will need a motorboat instead of a car." > Knowing that the sewerage system in town is not one of the best in the world, this feeling has been there for ages.
From: Nisciuno on 3 May 2007 04:12 barrister_rayong(a)yahoo.com ha scritto: > Most curious. Perhaps Khun Smith is correct. But I saw a story about > 2 weeks ago quoting some scientist from AIT who said that global > warming wouldn't affect the water tables in Thailand because the > glaciers are too far away from Thailand. Ah, Thai logic. I wonder > where that guy got his education. As far as I understand this matter, the scientist from AIT is right. The watertable, if I recall correctly, is not the same thing as sealevel. Watertables are water levels underneath the land. They receive their water from sources of fresh water (lakes, rivers and, ultimately, melting glaciers), not from the sea. So, the glaciers melting are not a concern in the near future to Thailand's water tables: their water does need to travel far too long a distance from the Himalayas; before it could reach its watertables, it's likely to be siphoned out of the soil by the intense agricultural use other countries make of this water. The problem will be in the long term, when the last glaciers in the Himalayas will have melt: then all of South Asia's watertables will be dropping, with perhaps those closest to the sea beeing contaminated by infliltration with salty seawater, like it's already happening in the Middle East in the Gaza strip.
From: maxwell on 3 May 2007 08:41 "Nisciuno" <nisciuno(a)nisciuno.it> wrote in message news:f1c5ia$7l3$1(a)aioe.org... > barrister_rayong(a)yahoo.com ha scritto: > > > Most curious. Perhaps Khun Smith is correct. But I saw a story about > > 2 weeks ago quoting some scientist from AIT who said that global > > warming wouldn't affect the water tables in Thailand because the > > glaciers are too far away from Thailand. Ah, Thai logic. I wonder > > where that guy got his education. > As far as I understand this matter, the scientist from AIT is right. > The watertable, if I recall correctly, is not the same thing as sealevel. Not as one gets inland/upland, or when sufficient outflow from land to sea (high volume or higher elevation of land than sea). > Watertables are water levels underneath the land. They receive their water > from sources of fresh water (lakes, rivers and, ultimately, melting > glaciers), not from the sea. Not always. Sorry, but water is just a dumb liquid that 'seeks its own level,' and if a body of standing water is higher than an adjacent area, that's only temporary *unless* there's a barrier to motion. The natural shape of a terrestial body of standing water, whether in the open or under the ground, is equidistant from the terrestial center of gravity (we see this as flat on top at short distances, and curving over the horizon, at sea). Got that okay? > So, the glaciers melting are not a concern in the near future to Thailand's water tables: their water does need to travel far too long a distance from the Himalayas; before it could reach its watertables, it's likely to be siphoned out of the soil by the intense agricultural use other countries make of this water. Remember what I wrote just now about 'flat top water'? Same goes for the oceans (waves are oscillations above and below the mean level on a short time scale, tides on a much longer time scale). Raise the ocean level, from *whatever* sources of glacial melt, and honestly, what do you expect to happen? > The problem will be in the long term, when the last glaciers in the Himalayas will have melt: > then all of South Asia's watertables will be dropping, with perhaps those closest to the sea beeing contaminated by infliltration with salty seawater, like it's already happening in the Middle East in the Gaza strip. As already happens and has been happening for aeons at the coastlines of land all over the world. That's a funny idea you have--and ignores that as ocean levels rise, brackish (salty) water flows inland, and yes, into the water table wherever the hydraulic outflow pressure of inland subsurface water is less than that of the ocean's inflow. How else do you figure there are swamps with subsurface brackish water kilometers inland from the coastline, in the lowlands?
From: Nisciuno on 3 May 2007 11:20 maxwell ha scritto: > "Nisciuno" <nisciuno(a)nisciuno.it> wrote in message > news:f1c5ia$7l3$1(a)aioe.org... >> barrister_rayong(a)yahoo.com ha scritto: >> >>> Most curious. Perhaps Khun Smith is correct. But I saw a story about >>> 2 weeks ago quoting some scientist from AIT who said that global >>> warming wouldn't affect the water tables in Thailand because the >>> glaciers are too far away from Thailand. Ah, Thai logic. I wonder >>> where that guy got his education. >> As far as I understand this matter, the scientist from AIT is right. >> The watertable, if I recall correctly, is not the same thing as sealevel. > > Not as one gets inland/upland, or when sufficient outflow from land to sea > (high volume or higher elevation of land than sea). Actually, the watertable and the sealevel are *never* the same. Watertable is strongly affected by several factors, the most prominent beeing: soil composition, nature and lay. Because of the different chemical potential, there exists an osmotic equilibrium between the salty sea water and the fresh water usually to be found in watertables. Even if the soil was porous and lacking any bed of impermeable rock capable of holding back the seawater, it could be that is is impermeable enough to the minerals of the sea water to let an osmotic phenomenon to set in. In such a case this happens: * the waters in the sea and in the watertable seek a chemical potential equilibrium that results either in both having the same salinity, or in the two having a different salinity and a different gravitational potential to balance the chemical inequilibrium. * In order to reach it's chemical equilibrium, either fresh water must absorb some of the chemicals of the salty water, or it must seep into the salty water reservoir to dilute it's salinity and/or create a gavitational potential strong enough to create the equilibrium condition. * Sea water chemicals ususally can penetrate the land for a tiny depth: from a few meters to a kilometer or so (on sandy, highly porous land). * Artesian wells caused by geolocical strata and fed by highlands' freshwater also influence. What it happens is that a gradient both chemical and gravitational exist between the seawater and the watertable, more or less strong depending on the nature of the land that is separating the two water levels: ~~~~~~~~~~~____________________________________________ land /\ ^ Seawater / \ | / \ | gravitational / \ | potential / <- \ | / <- \ | / <- osmotic \ | / <- pressure `____ | / <- \ v / <- ______________________ watertable / >> Watertables are water levels underneath the land. They receive their water >> from sources of fresh water (lakes, rivers and, ultimately, melting >> glaciers), not from the sea. > > Not always. Sorry, but water is just a dumb liquid that 'seeks its own > level,' and if a body of standing water is higher than an adjacent area, > that's only temporary *unless* there's a barrier to motion. No. That is not even half the story. There are other factors to consider: chemical potentials (see the above about osmosis), earth dymamics (the earth spinning causes the sealevel not to be "flat", instead it tends to be higher near the equator and lower towards the poles), astronomical gravitational effects involving primarily the moon and the sun (causing tidal effects), possible presence of rock beds or of a impermeable soil bed tilted by geolocycal forces in such a way to form a barrier to water flows within watertables or between watertables and other liquid reservoirs. > The natural shape of a terrestial body of standing water, whether in the > open or under the ground, is equidistant from the terrestial center of > gravity (we see this as flat on top at short distances, and curving over the > horizon, at sea). > Got that okay? No, that never happens in nature. In practice you can almost never find anywhere in the world a large liquid reservoir having a surface that �is equidistant from the terrestial center of gravity�. >> So, the glaciers melting are not a concern in the near future to > Thailand's water tables: their water does need to travel far too long a > distance from the Himalayas; before it could reach its watertables, it's > likely to be siphoned out of the soil by the intense agricultural use other > countries make of this water. > > Remember what I wrote just now about 'flat top water'? Yes, I do. And it is wrong. Again: http://en.wikipedia.org/wiki/Osmosis, http://en.wikipedia.org/wiki/Water_potential [...] > That's a funny idea you have Evidently you never took a chemistry class. >--and ignores that as ocean levels rise, > brackish (salty) water flows inland, Most of the times, almost always it does not. > and yes, into the water table wherever > the hydraulic outflow pressure of inland subsurface water is less than that > of the ocean's inflow. How else do you figure there are swamps with > subsurface brackish water kilometers inland from the coastline, in the > lowlands? Salty water inland is caused by the geological rise of the land.
From: Nisciuno on 3 May 2007 11:35
Nisciuno ha scritto: > maxwell ha scritto: >> Not as one gets inland/upland, or when sufficient outflow from land to sea >> (high volume or higher elevation of land than sea). > Actually, the watertable and the sealevel are *never* the same. Well, they are *almost* never the same. I did however some more reading starting with what happened in the Gaza strip, where the increasing salinity of the watertable is causing less and less drinking water to be available to the local population. I knew it was caused by the drop in the watertable caused by the too strong pumping of fresh water out of it for irrigation and human drinking, and that it is a new phenomenon. And so I happend across this: http://en.wikipedia.org/wiki/Saltwater_intrusion Apparently osmosis is not a relevant force shaping the water levels inland, and the opposite of what i wrote actually happens: �Saltwater intrusion is a natural process that occurs in virtually all coastal aquifers. It consists in salt water (from the sea) flowing inland in freshwater aquifers. This behaviour is caused by the fact that sea water has a higher density (which is because it carries more solutes) than freshwater. This higher density has the effect that the pressure beneath a column of saltwater is larger than that beneath a column of the same height of freshwater. If these columns were connected at the bottom, then the pressure difference would trigger a flow from the saltwater column to the freshwater column. �The flow of saltwater inland is limited to coastal areas. Inland the freshwater column gets higher and the pressure at the bottom also gets higher. This compensates for the higher density of the saltwater column. Where this happens, saltwater intrusion stops.� Other readings of intertest on the Wikipedia include: http://en.wikipedia.org/wiki/Water_table http://en.wikipedia.org/wiki/Aquiclude http://en.wikipedia.org/wiki/Sealevel http://en.wikipedia.org/wiki/Salinity http://en.wikipedia.org/wiki/Hydrogeology |