{"id":1376,"date":"2026-05-12T21:47:41","date_gmt":"2026-05-12T21:47:41","guid":{"rendered":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/chapter\/exercise-25\/"},"modified":"2026-05-13T03:36:03","modified_gmt":"2026-05-13T03:36:03","slug":"exercise-25","status":"publish","type":"chapter","link":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/chapter\/exercise-25\/","title":{"raw":"Exercise 25","rendered":"Exercise 25"},"content":{"raw":"
\r\n
\r\n\r\nSuppose a mass of 1000 mg is introduce in the center of a large tank of sand in a hydrogeology laboratory with uniform, one-dimensional, flow moving through the tank. The hydraulic conductivity is 0.1 cm\/sec, effective porosity is 0.2, the dispersivity in the x direction is 5 cm, dispersivity in the y direction is 1\/5 of the dispersivity in the x direction, dispersivity in the z direction is 1\/10 of the dispersivity in the x direction, and the head drop across the 100 cm long tank is 10 cm.\r\n\r\n<\/div>\r\n
\r\n
What will the concentration be at:<\/blockquote>\r\n<\/div>\r\n
\r\n
(a) 25 cm after 1000sec?<\/blockquote>\r\n<\/div>\r\n
\r\n
(b) the center of mass of the plume after 1000sec?<\/blockquote>\r\n<\/div>\r\n
\r\n
(c) a point that is 10 cm to the left and 5 cm below the center of mass of the plume after 1000sec?<\/blockquote>\r\n<\/div>\r\n
    \r\n \t
  1. Why is the concentration at 25 cm from the source so different for Exercise 24 part (a) and this exercise part (a)?<\/li>\r\n \t
  2. Would you expect measurements of concentrations in plumes in a field setting to produce the values you calculated? Why, or why not?<\/li>\r\n<\/ol>\r\n
    \r\n\r\nSolution for Exercise 25<\/strong><\/span><\/a>\u2ba7\r\n\r\n<\/div>\r\n
    \r\n\r\nReturn to where text linked to Exercise 25<\/strong><\/span><\/a>\u2ba5\r\n\r\n<\/div>\r\n<\/div>","rendered":"
    \n
    \n

    Suppose a mass of 1000 mg is introduce in the center of a large tank of sand in a hydrogeology laboratory with uniform, one-dimensional, flow moving through the tank. The hydraulic conductivity is 0.1 cm\/sec, effective porosity is 0.2, the dispersivity in the x direction is 5 cm, dispersivity in the y direction is 1\/5 of the dispersivity in the x direction, dispersivity in the z direction is 1\/10 of the dispersivity in the x direction, and the head drop across the 100 cm long tank is 10 cm.<\/p>\n<\/div>\n

    \n

    What will the concentration be at:<\/p><\/blockquote>\n<\/div>\n

    \n

    (a) 25 cm after 1000sec?<\/p><\/blockquote>\n<\/div>\n

    \n

    (b) the center of mass of the plume after 1000sec?<\/p><\/blockquote>\n<\/div>\n

    \n

    (c) a point that is 10 cm to the left and 5 cm below the center of mass of the plume after 1000sec?<\/p><\/blockquote>\n<\/div>\n

      \n
    1. Why is the concentration at 25 cm from the source so different for Exercise 24 part (a) and this exercise part (a)?<\/li>\n
    2. Would you expect measurements of concentrations in plumes in a field setting to produce the values you calculated? Why, or why not?<\/li>\n<\/ol>\n
      \n

      Solution for Exercise 25<\/strong><\/span><\/a>\u2ba7<\/p>\n<\/div>\n

      \n

      Return to where text linked to Exercise 25<\/strong><\/span><\/a>\u2ba5<\/p>\n<\/div>\n<\/div>\n","protected":false},"author":8,"menu_order":108,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1376","chapter","type-chapter","status-publish","hentry"],"part":1522,"_links":{"self":[{"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/pressbooks\/v2\/chapters\/1376","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/wp\/v2\/users\/8"}],"version-history":[{"count":2,"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/pressbooks\/v2\/chapters\/1376\/revisions"}],"predecessor-version":[{"id":1816,"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/pressbooks\/v2\/chapters\/1376\/revisions\/1816"}],"part":[{"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/pressbooks\/v2\/parts\/1522"}],"metadata":[{"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/pressbooks\/v2\/chapters\/1376\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/wp\/v2\/media?parent=1376"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/pressbooks\/v2\/chapter-type?post=1376"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/wp\/v2\/contributor?post=1376"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/basic-hydrogeology-an-introduction-to-the-fundamentals-of-groundwater-science\/wp-json\/wp\/v2\/license?post=1376"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}