R.J.Oosterbaan 1), J.Boonstra 1), and K.V.G.K.Rao 2)
1) International Institute for Land Reclamation and
Improvement (ILRI)
P.O. Box 45, 6700 Wageningen, The
Netherlands
2) Central Soil Salinity Research Institute (CSSRI)
Karnal-132001, Haryana, India
Published in: Subsurface-Water Hydrology, p. 153-160
Kluwer Academic publishers, The Netherlands, 1996
On website www.waterlog.info
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ABSTRACT An energy balance of ground water (groundwater) flow is introduced. It is based on equating the change of hydraulic energy flux over a horizontal distance to the conversion rate of hydraulic energy into to friction of flow over that distance. The energy flux is calculated on the basis of a multiplication of the hydraulic potential with the flow velocity, and is integrated over the total flow depth. The conversion rate is determined in analogy to the Joule heat loss equation of an electric current. The hydraulic energy balance is applied to the steady-state flow of water in a phreatic aquifer recharged by downward percolation stemming from rainfall or irrigation, and a quantitative example is given using a numerical solution. It is shown that the gradient of the water table is smaller than that calculated with the current methods, which do not take into account the energy associated with the incoming percolation water. |
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Shape of the water table with and without energy
balance
It is calculated that the depth of the water table diminishes with the distance from the drains. The water table is flat midway between the drains (at half the distance of the drain spacing), elsewhere it is curved. With the energy balance equation the water table is deeper than that calculated with the traditional Darcy equation. |