Lumped model for regional groundwater flow analysis

A lumped model known as Tank model for regional groundwater flows is proposed to estimate the groundwater flow system of the Osaka plain aquifer of Japan. The aquifer is divided into Tanks within which the average values of the groundwater levels is assumed to be representative in the Tanks. For each Tank the mass-balance equations expressing the conservation of water are written. The Quasi–Newton optimization technique together with Akaike’s Information Criterion, AIC, are employed in order to overcome the problem of the trade-off between the fit of the observed data to the model response and reliability of the parameter estimation. A stable model is established which is believed to be reliable to simulate the groundwater flow pattern of the Osaka plain aquifer. The results suggest disconnection of some regional aquifers as well as inflow of seawater to the deeper layers in the studied period.