Theoretical Baseflow Curves

Baseflow curves are obtained by solving a nonlinear partial differential equation of groundwater flow for different boundary conditions. A theoretical basis is provided for differentiating between these curves for shallow and deep aquifers. Various linearized solutions and their limitations and errors are elucidated. Mathematical expressions are derived for the effects of evapotranspiration and leakage loss in substantially reducing the baseflow and rendering the stream influent or dry. Upward leakage from an underlying artesian aquifer casuses the baseflow to be more sustained and reduces its recession rate. Aquifer recharge of duration T, simulated by a sine function, leads to a baseflow hydrograph which peaks at 0.75 T and becomes parallel to the no-recharge curve after about 1.5 T.