Présentations Colloques

Oral Presentation
Session 8.10: Recent developments in groundwater modeling and mathematical tools in Hydrogeology
Daughney Christopher J.
Loosely coupled modeling of a regional groundwater-surface water system, Southland, New Zealand
There is a global trend towards increasingly conjunctive management of groundwater and surface water. Fully coupled groundwater-surface water modeling tools are available and suit certain applications. However, fully coupled models can be slow to run and cumbersome to calibrate. In comparison, loosely coupled models may run more quickly because their groundwater and surface water components are independent and exchange input-output datasets only to the minimum extent necessary for adequate process representation (e.g. data exchange may be between but not within individual model time steps). **This study involves the construction of a finite element groundwater model covering 8,400 km2 of the Southland region of New Zealand, including 2,300 km of streams. Conceptualization was informed by a recently developed 3D geological model for the study area and rich data set of hydrochemistry, radon (for identifying locations of groundwater inflow to rivers) and age tracers (tritium, chlorofluorocarbons, sulphur hexafluoride, halon 1301). The groundwater model was loosely coupled to the TopNet surface water flow model. TopNet was used to route precipitation inputs into infiltration excess, saturation excess, soil water content or recharge to groundwater. The groundwater recharge was applied as input to the groundwater model. The groundwater flow solution was used to determine discharge of groundwater into the stream network, which was then added to TopNet’s infiltration excess and saturation excess to derive stream flow for each stream reach. The loose coupling involved a limited number of iterations of data exchange between the two models, aiming to achieve a good match to measured stream flows and groundwater levels. Overall, this study has shown that a loosely coupled, regional scale groundwater-surface water model can be developed for New Zealand conditions. **
New Zealand