Non-Darcy Flow and its Implications to Seepage Problems

Analytical solutions for the problems of drainage spacing in a ditch drainage system and steady-state seepagee through confined aquifer of variable thickness incorporating Izbash's nonlinear velocity-gradient response v=Min are presented. The effect of nonlinearity in the flow response on the drainage spacing, discharge characteristics, and piezometric pressure distribution in relation to the corresponding Darcian linear case is brought out. The solutions derived show that nonrecognition of even a weakly non-Darcy flow would lead either to an uneconomical or unsafe (depending on the value of non-Darcy parameter n) drainage spacing for ditch drainage problems and would lead to considerable over or under prediction of discharge for confined aquifer problem. Apart from the previously mentioned analytical solutions, a perspective view of non-Darcy flow through porous media is incorporated and its importance in various drainage projects is examined.