Inverse Analysis on Regional Groundwater by Tank Model

Abstract

Knowledge of regional groundwater flow behavior is important in water management. However, modeling and estimation of aquifer parameters for very complex aquifer system, like the one considered here for Osaka area, by mathematical models is notoriously difficult. This paper concerns with such complex aquifer system by relatively simple model that is the tank model, so as to understand the major mechanism of such aquifer system. The major difficulty in developing such model is the trade-off between the fit of the observed data to the model response and reliability of the parameter estimation. Random start optimization procedure together with Akaike's Information Criterion, AIC, has been employed to overcome this problem. A stable model is established which is believed to be reliable to simulate the groundwater flow pattern of the Osaka plain aquifer. The results also suggest disconnection of some regional aquifers as well as inflow of seawater to the deeper layers in the studied period. A tank model associated with the optimization technique and statistical procedure proposed in the study offers a promising approach in reliably understanding the mechanism of a complex regional groundwater flow system such as studied in this paper, Osaka plain aquifer system.