The Energy Balance of Groundwater Flow Applied to Subsurface Drainage in Anisotropic Soils by Pipes or Ditches with Entrance R

The energy balance of groundwater flow developed by Oosterbaan, Boonstra and Rao (1994), and used for the groundwater flow in unconfined aquifers, is applied to subsurface drainage by pipes or ditches with the possibility to introduce entrance resistance and/or (layered) soils with anisotropic hydraulic conductivities. Owing to the energy associated with the recharge by downward percolating water, it is found that use of the energy balance leads to lower water table elevations than when it is ignored. The energy balance cannot be solved analytically and a computerized numerical method is needed. An advantage of the numerical method is that the shape of the water table can be described, which was possible with the traditional methods only in particular situations, like drains without entrance resistance, resting on an impermeable layer in isotropic soils