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Mountains and Groundwater

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  • Mountains and Groundwater

    http://gizmodo.com/a-map-showing-the...ear-1742770066

    Okay, I wanna make sure I understood what i was looking at - and no, I don't have time to read up (unless it is about insurance... ) I'm assuming the white areas are where little or no data exists (why dig wells in Greenland, anyway?) but what really puzzles me is the mountain ranges. According to the legend, the darker the color, the deeper the water would be if it were on the surface. So, virtually all the darkest areas correspond to mountain ranges ( Passed geography, thank you very much). I'm guessing it assumes a sea level pool but still, the mountains seem to hold the most ground water which strikes me as counter intuitive. Wouldn't water tend to head for the valleys/adjacent plains?

    "He is no fool who gives what he cannot keep to gain that which he cannot lose." - Jim Elliot

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  • #2
    Depends on underground structures. Ground water does not come from the ocean.
    Micah 6:8 He has told you, O man, what is good; and what does the LORD require of you but to do justice, and to love kindness, and to walk humbly with your God?

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    • #3
      Originally posted by Teallaura View Post
      http://gizmodo.com/a-map-showing-the...ear-1742770066

      Okay, I wanna make sure I understood what i was looking at - and no, I don't have time to read up (unless it is about insurance... ) I'm assuming the white areas are where little or no data exists (why dig wells in Greenland, anyway?) but what really puzzles me is the mountain ranges. According to the legend, the darker the color, the deeper the water would be if it were on the surface. So, virtually all the darkest areas correspond to mountain ranges ( Passed geography, thank you very much). I'm guessing it assumes a sea level pool but still, the mountains seem to hold the most ground water which strikes me as counter intuitive. Wouldn't water tend to head for the valleys/adjacent plains?

      The map itself is not particularly helpful to help understanding groundwater of the world. The scale of the map is too general, and does not provide meaningful detail or information into the actual yield. There may be a lot of water in the total volume, but availability of the water may be a problem. The ground water amount is related to the nature of the underlying rock and the rainfall, and not necessarily the topography.

      If you will notice the vast desert regions have low resources, except for location where there is deep water pooled were ancient seas and large lakes like the Sahara. Large areas of Asia and North America extensive underlying granitic, metamorphic, and basalt rock which will not have a lot of groundwater resources. Mississippi River Valley and the coastal plain of the Eastern USA and Gulf Coast has good water resources.
      Glendower: I can call spirits from the vasty deep.
      Hotspur: Why, so can I, or so can any man;
      But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

      go with the flow the river knows . . .

      Frank

      I do not know, therefore everything is in pencil.

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      • #4
        Thanks guys.

        I still don't get it. Rainfall or pooled water, it still runs downhill so why would mountains show huge reserves?

        I'll be back when I have time to make my question clearer - thanks again!
        "He is no fool who gives what he cannot keep to gain that which he cannot lose." - Jim Elliot

        "Forgiveness is the way of love." Gary Chapman

        My Personal Blog

        My Novella blog (Current Novella Begins on 7/25/14)

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        • #5
          Originally posted by Teallaura View Post
          Thanks guys.

          I still don't get it. Rainfall or pooled water, it still runs downhill so why would mountains show huge reserves?

          I'll be back when I have time to make my question clearer - thanks again!
          Its what's under the mountains that holds the water. Mountains are often underlain by highly fractured and folded rocks because of the recent tectonic forces that uplifted the mountains. If you had a more detailed map it would show more of the smaller groundwater resources that under lie rivers. It remains in regions where the valley are underlain by granitic and basalt rocks that are not fractured and folded by recent mountain building events.
          Glendower: I can call spirits from the vasty deep.
          Hotspur: Why, so can I, or so can any man;
          But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

          go with the flow the river knows . . .

          Frank

          I do not know, therefore everything is in pencil.

          Comment


          • #6
            Originally posted by Teallaura View Post
            Thanks guys.

            I still don't get it. Rainfall or pooled water, it still runs downhill so why would mountains show huge reserves?

            I'll be back when I have time to make my question clearer - thanks again!
            Water is limited by permeability (primarily determined by how big the holes in it are). Water on the surface, like in rivers, is either moving too fast for it to be completely absorbed OR it's on surfaces that don't readily absorb liquid. Rivers and lakes demonstrate both. We can stop water on the surface by putting impermeable objects in front of it (e.g., dams or levees). Permeability differs by substance. Most rocks don't allow water to flow through it very well. Clay doesn't either, which is partly why it's popular for holding water (availability and pliability are other factors). Tightly formed rocks, like bedrock, don't allow water to flow through it. Mountains are huge upthrusts of rock which are fractured in all sorts of ways. Water can't really flow through the rock, but there are lots of places where the water can flow between rock layers. The problem is that the water still doesn't have anywhere to go. The water fills up all the cracks between the rocks and then gets stuck. This is part of the answer to your question.

            The second part has to do with rainfall and wind patterns. The short version is that cold air drops down and flows along the earth. The earth heats the air, and the air absorbs moisture. As it heats up, the air expands and rises. As the air rises, it begins to cool, causing the water vapor in the air to condense and fall as rain. That's what normally happens. When air meets a mountain, it typically gets pushed up. As it rises, the air cools and water vapor condenses just like it normally would. The rains are falling on a surface that's mostly rock, though, so it's not terribly permeable. Some of it gets absorbed through the soil, but from there the water just fills up more cracks.

            So you have two pieces: mountains have a lot of storage but little room for flow, and they force rain to fall by pushing the air up. Lots of rainfall on a lot of storage means a lot of water reserve.
            I'm not here anymore.

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            • #7
              The Mojave River runs underground here because of the nature of the ground - too porous to push the volume above ground except in very rainy seasons when the dams upstream release their overflow.

              Also, just to show off our contrary nature here, the upside down river is also wrong way...it begins in a mountain and flows east into a lake well beyond Newberry Springs, I believe.

              EDIT: nope, it drains into Soda Lake, near Baker. Also I should clarify that the water comes up in locations west and east of Barstow where the bedrock becomes more impermable.
              Last edited by DesertBerean; 11-21-2015, 03:18 PM.
              Watch your links! http://www.theologyweb.com/campus/fa...corumetiquette

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              • #8
                I previously mentioned that regions with shallow granitic rocks that are not a part of recently formed mountains have the least groundwater resources. These regions form the continent cores, are the oldest rocks and are called the cratons - 'Cratons are pieces of continents that have been stable for a over a billion years.'. If you look at the craton maps of the world, there is a close correlation to regions with the least groundwater resources and the maps showing where in the world there is the greatest groundwater crisis.

                Craton maps here: http://all-geo.org/metageologist/201...ld-and-strong/

                Other maps available just google; 'craton world maps.'
                Glendower: I can call spirits from the vasty deep.
                Hotspur: Why, so can I, or so can any man;
                But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

                go with the flow the river knows . . .

                Frank

                I do not know, therefore everything is in pencil.

                Comment


                • #9
                  Okay, I get it now!Thanks Shuny and Carry! Permeability was what I was missing - big rocks shouldn't collect water so that was tripping me up.

                  I've got reread your post tomorrow, DB - I missed something and I'm too worn out to figure it out.

                  Thanks, everyone!
                  "He is no fool who gives what he cannot keep to gain that which he cannot lose." - Jim Elliot

                  "Forgiveness is the way of love." Gary Chapman

                  My Personal Blog

                  My Novella blog (Current Novella Begins on 7/25/14)

                  Quill Sword

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                  • #10
                    Originally posted by Teallaura View Post
                    Okay, I get it now!Thanks Shuny and Carry! Permeability was what I was missing - big rocks shouldn't collect water so that was tripping me up.



                    Originally posted by Teallaura View Post
                    I've got reread your post tomorrow, DB - I missed something and I'm too worn out to figure it out.
                    It's an extension of the same permeability concept. In this case, the ground is permeable enough that the entire river is actually flowing below ground level*. Bedrock is highly impermeable, so where it's closer to the surface it will force water to be higher.





                    *which I didn't know, that's neat DB
                    I'm not here anymore.

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                    • #11
                      Originally posted by Carrikature View Post


                      It's an extension of the same permeability concept. In this case, the ground is permeable enough that the entire river is actually flowing below ground level*. Bedrock is highly impermeable, so where it's closer to the surface it will force water to be higher.

                      *which I didn't know, that's neat DB
                      Most underground rivers are due to cavernous limestone regions and not permeability of the rock itself. Limestone is often relatively impervious, but dissolves to form cavernous and cracked formations.
                      Glendower: I can call spirits from the vasty deep.
                      Hotspur: Why, so can I, or so can any man;
                      But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

                      go with the flow the river knows . . .

                      Frank

                      I do not know, therefore everything is in pencil.

                      Comment


                      • #12
                        Originally posted by Carrikature View Post





                        It's an extension of the same permeability concept. In this case, the ground is permeable enough that the entire river is actually flowing below ground level*. Bedrock is highly impermeable, so where it's closer to the surface it will force water to be higher.





                        *which I didn't know, that's neat DB
                        Ah, I was thinking it was flowing backwards which means I was way too tired to make sense of it.
                        "He is no fool who gives what he cannot keep to gain that which he cannot lose." - Jim Elliot

                        "Forgiveness is the way of love." Gary Chapman

                        My Personal Blog

                        My Novella blog (Current Novella Begins on 7/25/14)

                        Quill Sword

                        Comment


                        • #13
                          Originally posted by shunyadragon View Post
                          Most underground rivers are due to cavernous limestone regions and not permeability of the rock itself. Limestone is often relatively impervious, but dissolves to form cavernous and cracked formations.
                          Not true in the case of the Mojave River.
                          Micah 6:8 He has told you, O man, what is good; and what does the LORD require of you but to do justice, and to love kindness, and to walk humbly with your God?

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                          • #14
                            Originally posted by shunyadragon View Post
                            Most underground rivers are due to cavernous limestone regions and not permeability of the rock itself. Limestone is often relatively impervious, but dissolves to form cavernous and cracked formations.
                            Shuny, you're thinking of an entirely different scenario. The Mojave springs from the confluence of two rivers up in the mountains, and runs through desert land that consists of differing depths of ground compositions. Where the riverbed becomes more porous, the water sinks down to where the bedrock is. Only when the bedrock is closer to the surface of the desert floor does the water flow rise above ground.
                            Watch your links! http://www.theologyweb.com/campus/fa...corumetiquette

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                            • #15
                              Originally posted by Teallaura View Post
                              Ah, I was thinking it was flowing backwards..
                              It does. I just threw that bit of trivia in to mess you up.
                              Watch your links! http://www.theologyweb.com/campus/fa...corumetiquette

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