Abstract
AbstractDue to the duality in terms of (1) the groundwater flow field and (2) the discharge conditions, flow patterns of karst aquifer systems are complex. Estimated aquifer parameters may differ by several orders of magnitude from local (borehole) to regional (catchment) scale because of the large contrast in hydraulic parameters between matrix and conduit, their heterogeneity and anisotropy. One approach to deal with the scale effect problem in the estimation of hydraulic parameters of karst aquifers is the application of large‐scale experiments such as long‐term high‐abstraction conduit pumping tests, stimulating measurable groundwater drawdown in both, the karst conduit system as well as the fractured matrix. The numerical discrete conduit‐continuum modeling approach MODFLOW‐2005 Conduit Flow Process Mode 1 (CFPM1) is employed to simulate laminar and nonlaminar conduit flow, induced by large‐scale experiments, in combination with Darcian matrix flow. Effects of large‐scale experiments were simulated for idealized settings. Subsequently, diagnostic plots and analyses of different fluxes are applied to interpret differences in the simulated conduit drawdown and general flow patterns. The main focus is set on the question to which extent different conduit flow regimes will affect the drawdown in conduit and matrix depending on the hydraulic properties of the conduit system, i.e., conduit diameter and relative roughness. In this context, CFPM1 is applied to investigate the importance of considering turbulent conditions for the simulation of karst conduit flow. This work quantifies the relative error that results from assuming laminar conduit flow for the interpretation of a synthetic large‐scale pumping test in karst.
Highlights
Pumping tests and the interpretation of pressure or drawdown curves are frequently applied and essential tools for solving petroleum engineering or hydrogeological problems
Due to the defined hydraulic signal introduced by the water abstraction from the conduit and the preexisting nature of the conduit system, the head loss along the conduit is the only variable of the laminar and turbulent flow equation (see equations (3) and (4))
The friction factor includes information about the pipe roughness and the actual flow conditions indicated by the Reynolds number
Summary
Pumping tests and the interpretation of pressure or drawdown curves are frequently applied and essential tools for solving petroleum engineering or hydrogeological problems. CFPM1 simulates laminar and turbulent pipe flow coupled through linear head-dependent water transfer with a laminar flow matrix continuum This allows the hydraulic simulation of complex karst aquifer systems. Kovacs et al (2005) distinguish between matrix restricted flow for mature and conduit influenced flow models for karst systems with initially enlarged flow features, depending on the general baseflow pattern of the aquifer system Both conceptual models can be separated by a threshold depending on parameters describing the degree of heterogeneity (i.e., hydraulic and geometric properties). Drawdown differences as well as flow pattern changes resulting from the application of laminar and turbulent flow of numerically idealized karst conduits are presented and discussed with respect to the maturity of karst aquifer systems. The study presents the differences in head losses as a function of the hydraulic conduit properties for a defined flow velocity (i.e., drawdown signal)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
