2. Fundamental Equations of Groundwater Flow 2.1 Darcy's Law Darcy's experiment In 1856, A French engineer Darcy did a laboratory experiment as sketched in Figure 2.1. A one-dimensional steady flow in the sand column is created by keeping water levels in the left and right reservoirs constant P,/Dg Area a P2/Dg Flow n Reference level Figure 2.1 Darcys experiment Darcy measured the total discharge through a sand column when changing the difference between water levels in two reservoirs. He found that the total discharge was proportional to the difference of water levels O=-KA ere Q: total discharge,LTI A: cross-sectional area, LL] K: coefficient of permeability, [LT ];2. Fundamental Equations of Groundwater Flow 2.1 Darcy's Law Darcy's experiment In 1856, A French engineer Darcy did a laboratory experiment as sketched in Figure 2.1. A one-dimensional steady flow in the sand column is created by keeping water levels in the left and right reservoirs constant. Reference level Flow Area A L n2 n1 P1/Dg P2/Dg z2 z1 Q Figure 2.1 Darcy's experiment Darcy measured the total discharge through a sand column when changing the difference between water levels in two reservoirs. He found that the total discharge was proportional to the difference of water levels: L - Q = - K A ϕ2 ϕ1 (2.1) where: Q : total discharge, [L3 T-1]; A : cross-sectional area, [L2 ]; K : coefficient of permeability, [LT-1]; 9