{"id":609,"date":"2020-11-10T16:53:34","date_gmt":"2020-11-10T16:53:34","guid":{"rendered":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/?post_type=chapter&#038;p=609"},"modified":"2020-12-29T18:04:02","modified_gmt":"2020-12-29T18:04:02","slug":"adding-recharge-to-the-unconfined-aquifer-system","status":"publish","type":"chapter","link":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/chapter\/adding-recharge-to-the-unconfined-aquifer-system\/","title":{"raw":"Box 6  Adding Recharge to the Unconfined Aquifer System","rendered":"Box 6  Adding Recharge to the Unconfined Aquifer System"},"content":{"raw":"Consider the addition of a flux boundary condition on the top of the model. This could represent uniform recharge to the upper surface between the constant-head boundaries (Figure Box 6-1). Now the flow rate will vary from one <em>x<\/em>-location to another. Depending on the relative values of <em>h<\/em><sub>1<\/sub>, <em>h<\/em><sub>2<\/sub>, recharge, <em>W<\/em>, hydraulic conductivity, <em>K<\/em>, and boundary heads, the flow may be entirely to the right, to the left, or a groundwater divide may form within the land mass at which the flow, <em>q'<\/em>, is zero with increasing flow volume in opposite directions from the divide to the boundaries.\r\n\r\n[caption id=\"attachment_612\" align=\"alignnone\" width=\"1024\"]<img class=\"wp-image-612 size-large\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-1024x434.jpg\" alt=\"Figure showing the inclusion of uniform recharge on a steady-state, unconfined groundwater flow system\" width=\"1024\" height=\"434\" \/> <strong>Figure Box 6-1 -<\/strong> Including uniform recharge on a steady-state, unconfined groundwater flow system between fully penetrating surface water bodies of constant head.[\/caption]\r\n\r\nA few schematics of possible configurations are shown in Figure Box 6-2 to illustrate the substantial variations that can occur in this simple one-dimensional system. Flow directions and velocities, as well as the shape of the water table can be drastically different.\r\n\r\n[caption id=\"attachment_615\" align=\"alignnone\" width=\"1008\"]<img class=\"wp-image-615 size-full\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2.jpg\" alt=\"Figure showing the effect of recharge on the water table\" width=\"1008\" height=\"848\" \/> <strong>Figure Box 6-2 -<\/strong> Depending on the relative values of boundary heads, <em>h<\/em><sub>1<\/sub>, <em>h<\/em><sub>2<\/sub>, <em>W<\/em>, and <em>K<\/em>, the flow, <em>q'<\/em> (solid blue arrows) may be entirely to the right, to the left, or a groundwater divide may form within the groundwater system. The response of the water table: a) for recharge, <em>W<\/em>, of zero; b) for a small recharge rate relative to the through flow in the aquifer; c) for a large recharge rate relative to the through flow in the aquifer; d) for a large negative recharge rate (loss of water from the water table, e.g., evapotranspiration) relative to the through flow in the aquifer.[\/caption]\r\n\r\nTo incorporate surficial recharge into the analytical solution, first consider a small prism of the aquifer, as shown in Figure Box 6-3.\r\n\r\n[caption id=\"attachment_616\" align=\"alignnone\" width=\"256\"]<img class=\"wp-image-616 size-full\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-3.jpg\" alt=\"Figure showing a small prism of aquifer\" width=\"256\" height=\"323\" \/> <strong>Figure Box 6-3 -<\/strong> A small prism of the aquifer.[\/caption]\r\n\r\nFlow through the left face of Figure Box 6-3 is shown in Equation Box 6-1.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 10%;\"><\/td>\r\n<td style=\"width: 75%; text-align: center;\">[latex]\\displaystyle q'_{x}dy = -K\\left ( h\\frac{dh}{dx} \\right )_{x}dy[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-1)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nwhere:\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>q'<\/em><sub><em>x<\/em><\/sub><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">flow per unit width (L<sup>2<\/sup>\/T)<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>dy<\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">width of the face into the page (L)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nFlow through the right face of Figure Box 6-3 is shown in Equation Box 6-2.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 10%;\"><\/td>\r\n<td style=\"width: 75%; text-align: center;\">[latex]\\displaystyle q'_{x+dx}dy = -K\\left ( h\\frac{dh}{dx} \\right )_{x+dx}dy[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-2)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nThe value of [latex]h\\left(\\frac{dh}{dx}\\right)[\/latex] is different on each side of the element, so the value of <em>Q<\/em>(<em>q' dy<\/em>) is different on each side. The difference between flow on each side of the element must equal the amount of flow entering as recharge from the top of the system. The difference in flow can be expressed in terms of the one-dimensional, unconfined, steady-state groundwater flow equation, and equated to the amount of flow that enters the element from the top between the two sides (<em>W dx dy<\/em>) as in Equation Box 6-3.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 85%; text-align: center;\">[latex]\\displaystyle (q'_{x+dx}-q'_{x})dy = -K\\frac{d}{dx}\\left ( h\\frac{dh}{dx} \\right )dxdy=W dxdy[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-3)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nwhere:\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>W<\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">recharge rate from the surface (L\/T)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nGathering the derivative terms and dividing both sides by -<em>K<\/em> provides Equation Box 6-4.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 10%;\"><\/td>\r\n<td style=\"width: 75%; text-align: center;\">[latex]\\displaystyle \\frac{1}{2}\\frac{d^{2}h^{2}}{dx^{2}}=-\\frac{W}{K}[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-4)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nIntegrating Equation Box 6-4 yields Equation Box 6-5.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 10%;\"><\/td>\r\n<td style=\"width: 75%; text-align: center;\">[latex]\\displaystyle h^{2}=\\frac{Wx^{2}}{K}+C_{1}x+C_{2}[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-5)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nwhere:\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>C<\/em><sub>1<\/sub>, <em><em>C<\/em><sub>2<\/sub><\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">constants of integration (L, L<sup>2<\/sup>, respectively)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nBy applying boundary conditions as done for the case without recharge (<em>h<\/em> = <em>h<\/em><sub>1<\/sub> at x = 0 and <em>h<\/em> = <em>h<\/em><sub>2<\/sub> at x = <em>L<\/em>), the constants can be determined. Solving for the constants provides Equation Box 6-6. Solving Equation Box 6-6 for <em>h<\/em> at <em>x<\/em> results in Equation Box 6-7. See Figures Box 6-1 and Box 6-3 for terms.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 85%; text-align: center;\">[latex]\\displaystyle {h_{x}}^{2}=h{_{1}}^{2}-\\frac{(h{_{1}}^{2}-h{_{2}}^{2})x}{L}+\\frac{W}{K}(L-x)x[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-6)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 85%; text-align: center;\">[latex]\\displaystyle h_{x}=\\sqrt{h{_{1}}^{2}-\\frac{(h{_{1}}^{2}-h{_{2}}^{2})x}{L}+\\frac{W}{K}(L-x)x}[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-7)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nwhere:\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub><em>x<\/em><\/sub><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">head at <em>x<\/em> some distance from the origin, <em>x<\/em>=0 (L)<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>x<\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">distance from the origin (L)<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub>1<\/sub><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">head at the origin (L)<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub>2<\/sub><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">head at L (L)<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>L<\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">distance from the origin to <em>h<\/em><sub>2<\/sub><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>K<\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">hydraulic conductivity (L\/T)<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>W<\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">recharge rate (L\/T)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nTo determine <em>q'<\/em> as a function of <em>x<\/em>, Equation Box 6-6 can be differentiated with respect to <em>x<\/em> resulting in Equation Box 6-8.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 85%; text-align: center;\">[latex]\\displaystyle h\\frac{dh}{dx}=-\\frac{(h{_{1}}^{2}-h{_{2}}^{2})}{2L}+\\frac{W}{K}\\left ( \\frac{L}{2}-x \\right )[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-8)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nMultiplying Equation Box 6-8 by -<em>K<\/em> provides Equation Box 6-9.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 85%; text-align: center;\">[latex]\\displaystyle -Kh\\frac{dh}{dx}=\\frac{K(h{_{1}}^{2}-h{_{2}}^{2})}{2L}-W\\left ( \\frac{L}{2}-x \\right )[\/latex]<\/td>\r\n<td style=\"width: 15%; text-align: right;\">(Box 6-9)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nSubstituting <em>q'<\/em><sub><em>x<\/em><\/sub> for the left-hand side of Equation Box 6-9 provides Equation Box 6-10.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 80%; text-align: center;\">[latex]\\displaystyle q'_{x}=\\frac{K(h{_{1}}^{2}-h{_{2}}^{2})}{2L}-W\\left ( \\frac{L}{2}-x \\right )[\/latex]<\/td>\r\n<td style=\"width: 20%; text-align: right;\">(Box 6-10)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nThe next task is to determine the location of the groundwater divide. An expression for the location of the divide, <em>d<\/em>, can be determined by setting <em>q'<\/em><sub><em>x<\/em><\/sub> equal to zero in Equation Box 6-10 and solving for the <em>x<\/em> position of the divide (<em>d<\/em>) as shown in Equation Box 6-11.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 80%; text-align: center;\">[latex]\\displaystyle d=\\frac{L}{2}-\\frac{K}{W}\\frac{(h{_{1}}^{2}-h{_{2}}^{2})}{2L}[\/latex]<\/td>\r\n<td style=\"width: 20%; text-align: right;\">(Box 6-11)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nwhere:\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>d<\/em><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\"><em>x<\/em> location of the groundwater divide (L)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nThe maximum head (or minimum in the case of a negative value of <em>W<\/em>) can be determined by substituting <em>d<\/em> for <em>x<\/em> in Equation Box 6-7 resulting in Equation Box 6-12.\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 80%; text-align: center;\">[latex]\\displaystyle h_{max\/min}=\\sqrt{h{_{1}}^{2}-\\frac{(h{_{1}}^{2}-h{_{2}}^{2})d}{L}+\\frac{W}{K}(L-d)d}[\/latex]<\/td>\r\n<td style=\"width: 20%; text-align: right;\">(Box 6-12)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nwhere:\r\n<table style=\"border: none; border-collapse: collapse; width: 100%;\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub><em>max\/min<\/em><\/sub><\/td>\r\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\r\n<td style=\"width: 83%; vertical-align: top;\">maximum head for positive <em>W<\/em> and minimum for negative <em>W<\/em> (L)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<a href=\"https:\/\/gw-project.org\/books\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/\">The spreadsheet provided at this link<\/a> allows you to explore the nature of this flow system for various input parameter values.\r\n\r\n<a href=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/chapter\/applying-governing-equations\/#TextLinkToBox6\">Return to where text links to Box 6<\/a>","rendered":"<p>Consider the addition of a flux boundary condition on the top of the model. This could represent uniform recharge to the upper surface between the constant-head boundaries (Figure Box 6-1). Now the flow rate will vary from one <em>x<\/em>-location to another. Depending on the relative values of <em>h<\/em><sub>1<\/sub>, <em>h<\/em><sub>2<\/sub>, recharge, <em>W<\/em>, hydraulic conductivity, <em>K<\/em>, and boundary heads, the flow may be entirely to the right, to the left, or a groundwater divide may form within the land mass at which the flow, <em>q&#8217;<\/em>, is zero with increasing flow volume in opposite directions from the divide to the boundaries.<\/p>\n<figure id=\"attachment_612\" aria-describedby=\"caption-attachment-612\" style=\"width: 1024px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-612 size-large\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-1024x434.jpg\" alt=\"Figure showing the inclusion of uniform recharge on a steady-state, unconfined groundwater flow system\" width=\"1024\" height=\"434\" srcset=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-1024x434.jpg 1024w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-300x127.jpg 300w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-768x325.jpg 768w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-65x28.jpg 65w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-225x95.jpg 225w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1-350x148.jpg 350w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-1.jpg 1435w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-612\" class=\"wp-caption-text\"><strong>Figure Box 6-1 &#8211;<\/strong> Including uniform recharge on a steady-state, unconfined groundwater flow system between fully penetrating surface water bodies of constant head.<\/figcaption><\/figure>\n<p>A few schematics of possible configurations are shown in Figure Box 6-2 to illustrate the substantial variations that can occur in this simple one-dimensional system. Flow directions and velocities, as well as the shape of the water table can be drastically different.<\/p>\n<figure id=\"attachment_615\" aria-describedby=\"caption-attachment-615\" style=\"width: 1008px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-615 size-full\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2.jpg\" alt=\"Figure showing the effect of recharge on the water table\" width=\"1008\" height=\"848\" srcset=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2.jpg 1008w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2-300x252.jpg 300w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2-768x646.jpg 768w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2-65x55.jpg 65w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2-225x189.jpg 225w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-2-350x294.jpg 350w\" sizes=\"auto, (max-width: 1008px) 100vw, 1008px\" \/><figcaption id=\"caption-attachment-615\" class=\"wp-caption-text\"><strong>Figure Box 6-2 &#8211;<\/strong> Depending on the relative values of boundary heads, <em>h<\/em><sub>1<\/sub>, <em>h<\/em><sub>2<\/sub>, <em>W<\/em>, and <em>K<\/em>, the flow, <em>q&#8217;<\/em> (solid blue arrows) may be entirely to the right, to the left, or a groundwater divide may form within the groundwater system. The response of the water table: a) for recharge, <em>W<\/em>, of zero; b) for a small recharge rate relative to the through flow in the aquifer; c) for a large recharge rate relative to the through flow in the aquifer; d) for a large negative recharge rate (loss of water from the water table, e.g., evapotranspiration) relative to the through flow in the aquifer.<\/figcaption><\/figure>\n<p>To incorporate surficial recharge into the analytical solution, first consider a small prism of the aquifer, as shown in Figure Box 6-3.<\/p>\n<figure id=\"attachment_616\" aria-describedby=\"caption-attachment-616\" style=\"width: 256px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-616 size-full\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-3.jpg\" alt=\"Figure showing a small prism of aquifer\" width=\"256\" height=\"323\" srcset=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-3.jpg 256w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-3-238x300.jpg 238w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-3-65x82.jpg 65w, https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/11\/figBox6-3-225x284.jpg 225w\" sizes=\"auto, (max-width: 256px) 100vw, 256px\" \/><figcaption id=\"caption-attachment-616\" class=\"wp-caption-text\"><strong>Figure Box 6-3 &#8211;<\/strong> A small prism of the aquifer.<\/figcaption><\/figure>\n<p>Flow through the left face of Figure Box 6-3 is shown in Equation Box 6-1.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 10%;\"><\/td>\n<td style=\"width: 75%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-81f949d4006466e556c490c3b440621b_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#113;&#39;&#95;&#123;&#120;&#125;&#100;&#121;&#32;&#61;&#32;&#45;&#75;&#92;&#108;&#101;&#102;&#116;&#32;&#40;&#32;&#104;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#104;&#125;&#123;&#100;&#120;&#125;&#32;&#92;&#114;&#105;&#103;&#104;&#116;&#32;&#41;&#95;&#123;&#120;&#125;&#100;&#121;\" title=\"Rendered by QuickLaTeX.com\" height=\"44\" width=\"181\" style=\"vertical-align: -18px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-1)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>where:<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>q&#8217;<\/em><sub><em>x<\/em><\/sub><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">flow per unit width (L<sup>2<\/sup>\/T)<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>dy<\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">width of the face into the page (L)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Flow through the right face of Figure Box 6-3 is shown in Equation Box 6-2.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 10%;\"><\/td>\n<td style=\"width: 75%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-94de2806d707ca1747d7216297e3d400_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#113;&#39;&#95;&#123;&#120;&#43;&#100;&#120;&#125;&#100;&#121;&#32;&#61;&#32;&#45;&#75;&#92;&#108;&#101;&#102;&#116;&#32;&#40;&#32;&#104;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#104;&#125;&#123;&#100;&#120;&#125;&#32;&#92;&#114;&#105;&#103;&#104;&#116;&#32;&#41;&#95;&#123;&#120;&#43;&#100;&#120;&#125;&#100;&#121;\" title=\"Rendered by QuickLaTeX.com\" height=\"46\" width=\"232\" style=\"vertical-align: -20px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-2)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>The value of <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-4699ad08421d87df833a899813c69d16_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#104;&#92;&#108;&#101;&#102;&#116;&#40;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#104;&#125;&#123;&#100;&#120;&#125;&#92;&#114;&#105;&#103;&#104;&#116;&#41;\" title=\"Rendered by QuickLaTeX.com\" height=\"23\" width=\"46\" style=\"vertical-align: -7px;\" \/> is different on each side of the element, so the value of <em>Q<\/em>(<em>q&#8217; dy<\/em>) is different on each side. The difference between flow on each side of the element must equal the amount of flow entering as recharge from the top of the system. The difference in flow can be expressed in terms of the one-dimensional, unconfined, steady-state groundwater flow equation, and equated to the amount of flow that enters the element from the top between the two sides (<em>W dx dy<\/em>) as in Equation Box 6-3.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 85%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-d1ac46e8b6f34ed10972d792b372d66c_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#40;&#113;&#39;&#95;&#123;&#120;&#43;&#100;&#120;&#125;&#45;&#113;&#39;&#95;&#123;&#120;&#125;&#41;&#100;&#121;&#32;&#61;&#32;&#45;&#75;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#125;&#123;&#100;&#120;&#125;&#92;&#108;&#101;&#102;&#116;&#32;&#40;&#32;&#104;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#104;&#125;&#123;&#100;&#120;&#125;&#32;&#92;&#114;&#105;&#103;&#104;&#116;&#32;&#41;&#100;&#120;&#100;&#121;&#61;&#87;&#32;&#100;&#120;&#100;&#121;\" title=\"Rendered by QuickLaTeX.com\" height=\"43\" width=\"372\" style=\"vertical-align: -17px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-3)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>where:<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>W<\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">recharge rate from the surface (L\/T)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Gathering the derivative terms and dividing both sides by &#8211;<em>K<\/em> provides Equation Box 6-4.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 10%;\"><\/td>\n<td style=\"width: 75%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-8aa7b616a3b191973e90c8e6cd09a59f_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#92;&#102;&#114;&#97;&#99;&#123;&#49;&#125;&#123;&#50;&#125;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#94;&#123;&#50;&#125;&#104;&#94;&#123;&#50;&#125;&#125;&#123;&#100;&#120;&#94;&#123;&#50;&#125;&#125;&#61;&#45;&#92;&#102;&#114;&#97;&#99;&#123;&#87;&#125;&#123;&#75;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"39\" width=\"109\" style=\"vertical-align: -12px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-4)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Integrating Equation Box 6-4 yields Equation Box 6-5.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 10%;\"><\/td>\n<td style=\"width: 75%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-c3acea2360a344a8a0747cd8ef335105_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#104;&#94;&#123;&#50;&#125;&#61;&#92;&#102;&#114;&#97;&#99;&#123;&#87;&#120;&#94;&#123;&#50;&#125;&#125;&#123;&#75;&#125;&#43;&#67;&#95;&#123;&#49;&#125;&#120;&#43;&#67;&#95;&#123;&#50;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"39\" width=\"176\" style=\"vertical-align: -12px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-5)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>where:<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>C<\/em><sub>1<\/sub>, <em><em>C<\/em><sub>2<\/sub><\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">constants of integration (L, L<sup>2<\/sup>, respectively)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>By applying boundary conditions as done for the case without recharge (<em>h<\/em> = <em>h<\/em><sub>1<\/sub> at x = 0 and <em>h<\/em> = <em>h<\/em><sub>2<\/sub> at x = <em>L<\/em>), the constants can be determined. Solving for the constants provides Equation Box 6-6. Solving Equation Box 6-6 for <em>h<\/em> at <em>x<\/em> results in Equation Box 6-7. See Figures Box 6-1 and Box 6-3 for terms.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 85%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-bdb0a2683ed3bf9650d67770737767a1_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#123;&#104;&#95;&#123;&#120;&#125;&#125;&#94;&#123;&#50;&#125;&#61;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#92;&#102;&#114;&#97;&#99;&#123;&#40;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#104;&#123;&#95;&#123;&#50;&#125;&#125;&#94;&#123;&#50;&#125;&#41;&#120;&#125;&#123;&#76;&#125;&#43;&#92;&#102;&#114;&#97;&#99;&#123;&#87;&#125;&#123;&#75;&#125;&#40;&#76;&#45;&#120;&#41;&#120;\" title=\"Rendered by QuickLaTeX.com\" height=\"39\" width=\"310\" style=\"vertical-align: -12px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-6)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 85%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-d94fb9b719f67edf320c0e497cec3801_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#104;&#95;&#123;&#120;&#125;&#61;&#92;&#115;&#113;&#114;&#116;&#123;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#92;&#102;&#114;&#97;&#99;&#123;&#40;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#104;&#123;&#95;&#123;&#50;&#125;&#125;&#94;&#123;&#50;&#125;&#41;&#120;&#125;&#123;&#76;&#125;&#43;&#92;&#102;&#114;&#97;&#99;&#123;&#87;&#125;&#123;&#75;&#125;&#40;&#76;&#45;&#120;&#41;&#120;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"43\" width=\"321\" style=\"vertical-align: -13px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-7)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>where:<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub><em>x<\/em><\/sub><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">head at <em>x<\/em> some distance from the origin, <em>x<\/em>=0 (L)<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>x<\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">distance from the origin (L)<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub>1<\/sub><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">head at the origin (L)<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub>2<\/sub><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">head at L (L)<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>L<\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">distance from the origin to <em>h<\/em><sub>2<\/sub><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>K<\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">hydraulic conductivity (L\/T)<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>W<\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">recharge rate (L\/T)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>To determine <em>q&#8217;<\/em> as a function of <em>x<\/em>, Equation Box 6-6 can be differentiated with respect to <em>x<\/em> resulting in Equation Box 6-8.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 85%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-f6b92cea1e92739d7ec6db6ea2ce0285_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#104;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#104;&#125;&#123;&#100;&#120;&#125;&#61;&#45;&#92;&#102;&#114;&#97;&#99;&#123;&#40;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#104;&#123;&#95;&#123;&#50;&#125;&#125;&#94;&#123;&#50;&#125;&#41;&#125;&#123;&#50;&#76;&#125;&#43;&#92;&#102;&#114;&#97;&#99;&#123;&#87;&#125;&#123;&#75;&#125;&#92;&#108;&#101;&#102;&#116;&#32;&#40;&#32;&#92;&#102;&#114;&#97;&#99;&#123;&#76;&#125;&#123;&#50;&#125;&#45;&#120;&#32;&#92;&#114;&#105;&#103;&#104;&#116;&#32;&#41;\" title=\"Rendered by QuickLaTeX.com\" height=\"44\" width=\"280\" style=\"vertical-align: -17px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-8)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Multiplying Equation Box 6-8 by &#8211;<em>K<\/em> provides Equation Box 6-9.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 85%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-ce214df03f5d4bab7f2c859f4e91df8c_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#45;&#75;&#104;&#92;&#102;&#114;&#97;&#99;&#123;&#100;&#104;&#125;&#123;&#100;&#120;&#125;&#61;&#92;&#102;&#114;&#97;&#99;&#123;&#75;&#40;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#104;&#123;&#95;&#123;&#50;&#125;&#125;&#94;&#123;&#50;&#125;&#41;&#125;&#123;&#50;&#76;&#125;&#45;&#87;&#92;&#108;&#101;&#102;&#116;&#32;&#40;&#32;&#92;&#102;&#114;&#97;&#99;&#123;&#76;&#125;&#123;&#50;&#125;&#45;&#120;&#32;&#92;&#114;&#105;&#103;&#104;&#116;&#32;&#41;\" title=\"Rendered by QuickLaTeX.com\" height=\"44\" width=\"308\" style=\"vertical-align: -17px;\" \/><\/td>\n<td style=\"width: 15%; text-align: right;\">(Box 6-9)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Substituting <em>q&#8217;<\/em><sub><em>x<\/em><\/sub> for the left-hand side of Equation Box 6-9 provides Equation Box 6-10.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 80%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-935a50088c530e804baf2aa5584f2ba4_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#113;&#39;&#95;&#123;&#120;&#125;&#61;&#92;&#102;&#114;&#97;&#99;&#123;&#75;&#40;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#104;&#123;&#95;&#123;&#50;&#125;&#125;&#94;&#123;&#50;&#125;&#41;&#125;&#123;&#50;&#76;&#125;&#45;&#87;&#92;&#108;&#101;&#102;&#116;&#32;&#40;&#32;&#92;&#102;&#114;&#97;&#99;&#123;&#76;&#125;&#123;&#50;&#125;&#45;&#120;&#32;&#92;&#114;&#105;&#103;&#104;&#116;&#32;&#41;\" title=\"Rendered by QuickLaTeX.com\" height=\"44\" width=\"261\" style=\"vertical-align: -17px;\" \/><\/td>\n<td style=\"width: 20%; text-align: right;\">(Box 6-10)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>The next task is to determine the location of the groundwater divide. An expression for the location of the divide, <em>d<\/em>, can be determined by setting <em>q&#8217;<\/em><sub><em>x<\/em><\/sub> equal to zero in Equation Box 6-10 and solving for the <em>x<\/em> position of the divide (<em>d<\/em>) as shown in Equation Box 6-11.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 80%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-529ce309b9647d182fe2bb47775054e9_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#100;&#61;&#92;&#102;&#114;&#97;&#99;&#123;&#76;&#125;&#123;&#50;&#125;&#45;&#92;&#102;&#114;&#97;&#99;&#123;&#75;&#125;&#123;&#87;&#125;&#92;&#102;&#114;&#97;&#99;&#123;&#40;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#104;&#123;&#95;&#123;&#50;&#125;&#125;&#94;&#123;&#50;&#125;&#41;&#125;&#123;&#50;&#76;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"39\" width=\"183\" style=\"vertical-align: -12px;\" \/><\/td>\n<td style=\"width: 20%; text-align: right;\">(Box 6-11)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>where:<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>d<\/em><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\"><em>x<\/em> location of the groundwater divide (L)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>The maximum head (or minimum in the case of a negative value of <em>W<\/em>) can be determined by substituting <em>d<\/em> for <em>x<\/em> in Equation Box 6-7 resulting in Equation Box 6-12.<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 80%; text-align: center;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/ql-cache\/quicklatex.com-5ff722c510a018ebc8492ff21fd7cdc7_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#100;&#105;&#115;&#112;&#108;&#97;&#121;&#115;&#116;&#121;&#108;&#101;&#32;&#104;&#95;&#123;&#109;&#97;&#120;&#47;&#109;&#105;&#110;&#125;&#61;&#92;&#115;&#113;&#114;&#116;&#123;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#92;&#102;&#114;&#97;&#99;&#123;&#40;&#104;&#123;&#95;&#123;&#49;&#125;&#125;&#94;&#123;&#50;&#125;&#45;&#104;&#123;&#95;&#123;&#50;&#125;&#125;&#94;&#123;&#50;&#125;&#41;&#100;&#125;&#123;&#76;&#125;&#43;&#92;&#102;&#114;&#97;&#99;&#123;&#87;&#125;&#123;&#75;&#125;&#40;&#76;&#45;&#100;&#41;&#100;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"43\" width=\"370\" style=\"vertical-align: -13px;\" \/><\/td>\n<td style=\"width: 20%; text-align: right;\">(Box 6-12)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>where:<\/p>\n<table style=\"border: none; border-collapse: collapse; width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 15%; text-align: right; vertical-align: top;\"><em>h<\/em><sub><em>max\/min<\/em><\/sub><\/td>\n<td style=\"width: 2%; text-align: center; vertical-align: top;\">=<\/td>\n<td style=\"width: 83%; vertical-align: top;\">maximum head for positive <em>W<\/em> and minimum for negative <em>W<\/em> (L)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><a href=\"https:\/\/gw-project.org\/books\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/\">The spreadsheet provided at this link<\/a> allows you to explore the nature of this flow system for various input parameter values.<\/p>\n<p><a href=\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/chapter\/applying-governing-equations\/#TextLinkToBox6\">Return to where text links to Box 6<\/a><\/p>\n","protected":false},"author":1,"menu_order":6,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-609","chapter","type-chapter","status-publish","hentry"],"part":117,"_links":{"self":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/chapters\/609","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":20,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/chapters\/609\/revisions"}],"predecessor-version":[{"id":1188,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/chapters\/609\/revisions\/1188"}],"part":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/parts\/117"}],"metadata":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/chapters\/609\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/media?parent=609"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/chapter-type?post=609"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/contributor?post=609"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/license?post=609"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}