Focused groundwater flow in a carbonate aquifer in a semi-arid environment

- A well-developed groundwater/surface water conveyance system in karst was characterized.
- The conveyance system developed coincident with the pre-existing river channel system.
- A strong correlation between well capacity and proximity to river channels was detected.
- Enhanced permeability conduits formed near river channels during uplift.
- River gain/loss studies supported the concept of the conveyance system.

SummaryAn efficient conveyance system for groundwater is shown to have formed in a carbonate aquifer even though it is situated in a semi-arid environment. This conveyance system comprises preferential flow pathways that developed coincident with river channels. A strong correlation between high capacity wells and proximity to higher-order river channels (i.e., within 2.5 km) is used as evidence of preferential flow pathways. Factors that contributed to development of the preferential flow paths: (i) karst development in carbonate rocks, (ii) structural exhumation of a carbonate plateau, and (iii) the requirement that the groundwater regime of the watershed has adequate capacity to convey sufficient quantities of water at the required rates across the full extent of the watershed. Recognition of these preferential pathways in proximity to river channels provides a basis to locate where high capacity wells are likely (and unlikely) and indicates that groundwater flow within the watershed is relatively rapid, consistent with flow rates representative of karstic aquifers. This understanding provides a basis for better informed decisions regarding water-resource management of a carbonate aquifer in a semi-arid environment.