Basinal Groundwater Flow Patterns and Their Transformation and Dominant Factors

Tóth proposed hierarchical groundwater flow-systems in the complex basin based on given head upper-boundaries in the 1960's. However, when the flow patterns with the given head upper-boundary are dealt with (so called Tóth method), changes of hydraulic conductivities or basin geometry result in changes of water budget in a basin synchronously. At the same time, the number of potential sources and sinks and their positions are fixed by the given head upper-boundaries which are not consistent with the actual condition and may result in wrong groundwater flow patterns and their transformation. Based on summarizing the hierarchical characteristics of groundwater flow systems on sand-box experiments, we propose a numerical simulation of groundwater flow patterns using flux as upper-boundaries (so called CUG-GWFS method). The simulated results show that five sequential flow patterns may develop in the basin with several possible potential sources and sinks: (a) simple regional only, (b) nested local-regional, (c) nested local-intermediate-regional, (d) nested local-intermediate, and (e) just local flow systems. The basinal groundwater flow patterns are dominated by the infiltration intensity, hydraulic conductivities, the ratio of length to depth and the number of potential sources and sinks and their positions. The basinal flow patterns will transform orderly as the five patterns above with the increasing of the ratio of infiltration intensity to hydraulic conductivity R_ic or the ratio of length to depth of a basin R_ld while the rest conditions remain the same.