Recharge of aquifers can only occur where excess water is able to penetrate beyond the reach of plant roots and shallow sub-surface flow. The rate and generic behavior of recharge lie at the interface of understanding between hillslope, vadose zone, groundwater, and eco hydrology. Hillslope and karstic recharge may be driven by water infiltrating during major storm events, particularly in semi-arid areas. In colder regions, snow melt may be the dominant factor. Catchment hydrologists may view 'subsurface runoff' as a simple loss term, while groundwater modelers may approximate 'recharge' merely as a fraction of rainfall. Both groups try to quantify the complicated, non-linear process of that part of the rainfall that makes it through the vadose zone to the groundwater table. The study of recharge is inherently a multi-disciplinary field where experts in catchment hydrology, vadose zone hydrology, and groundwater hydrology need to work together. The purpose of this session is to bring these different groups together and to discuss recent advances in the spatial and temporal modeling of groundwater recharge. Relevant issues include:
- different sources of recharge: rainfall, leaking pipes and canals, ephermal streams, etc.;
- signature in head fluctuations; alternatives for Richards equation;
- methods for estimation of recharge rates
- residence times in relation to solute transport and transformations;
- regionalization of local information
- predictive modeling