Assessment of interbasin groundwater flows between catchments using a semi-distributed water balance model

- Groundwater exchanges are included in the hydrological model.
- A semi-distributed model is applied in order to determine interbasin flows.
- The streamflows are simulated in the headwater of the Segura River Basin (SE Spain).
- Interbasin groundwater flows are assessed and they have proved to be significant.
- Interbasin groundwater flows must be included in the modeling of some catchments.

SummaryIn hydrological modeling it is often assumed that the aquifers boundaries are formed by the geographical demarcation of the catchment. However, this assumption is rarely met, given the existence of groundwater flows going beyond the catchment limits. The assessment of interbasin groundwater flows is crucial when managing water resources in areas where baseflows are mainly formed by groundwater, especially when catchments are managed separately. Aiming at estimating the volume and direction of the main groundwater flows, this work presents a new methodological approach for hydrological modeling. This approach employs a semi-distributed water balance model created with lumped models. This model is formulated in such a way that a part of the groundwater discharge of a specific catchment can become baseflows in other catchments, which helps characterize interbasin groundwater flows. This methodology is applied in the headwater of the Segura River Basin (southeast of Spain), where groundwater plays an important role in surface hydrology. The catchments are modeled with a high goodness of fit, and the main interbasin groundwater flows between them is evaluated, proving its importance in the characterization of hydrological modeling.