5.3 Basin Groundwater Modeling

In addition to hydrograph separation models, basin scale exchange processes can be examined using numerical groundwater models, coupled surface water-groundwater models and lumped streamflow routing models (e.g., Anderson et al., 2015). Modeling is used to conceptualize and assess river exchanges at the basin, valley segment, reach and channel scales (including hyporheic zones); lake and wetland exchange.

Modeling emphasizing the groundwater system (e.g., the MODFLOW family of codes; and FEFLOW (Diersch, 2014) account for groundwater exchanging with surface-water features under effluent, influent, flow-through and disconnected or zero-exchange conditions. Models contain specific coding that directs how, when and where groundwater passes to and from rivers, lakes and wetlands. In addition, model and local water budgets are computed from which exchange can be inferred (e.g., Anderson et al., 2015). Groundwater focused models allow the evaluation of anisotropic and heterogeneous three-dimensional groundwater flow, and exchange with surface-water features. The book by Anderson and others (2015) covers a wide range material including the basic development of conceptual groundwater models and methods to address uncertainty in modeling results. They describe how groundwater models can be used to assess exchange with rivers, lakes and wetlands, and how some codes link standard hydrologic (surface water) models to groundwater models. A more detailed discussion of model application is discussed elsewhere in this book.