Chapter 4: Water Balance Concepts

A review of water balance concepts and historic efforts to measure groundwater components in the mass balances of Swan Coastal Plain wetlands. The limitations of simple mass balances are reviewed. On the basis of a mass balance alone groundwater can only be differentiated as a net input or loss. There is no way to differentiate or quantify groundwater discharge to the lake or lake recharge to the aquifer. The concept of simultaneous multiple rigorous balances is introduced. These are rigorous in the sense that (within practical limitations) every effort is made to measure every component of each balance. They are simultaneous in the sense that solute and isotope balances are calculated along with simple water mass. Integrating the balances allows the elusive groundwater flux components to be calculated. The detail on just how this is accomplished forms a large portion of Chapter 6.