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Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Because of the small radius of investigation of hydrogeological standard testing methods, the characterization of karst aquifers is still a challenge. The development of a karst conduit system introduces an element of large contrast in hydraulic conductivity in the hydraulic parameter field of a karst aquifer. It leads to complex flow patterns and transport phenomena that differ significantly from those observed in porous and fissured media. While on a local, i.e., borehole scale, the fissured matrix of karst aquifers can be regarded as a continuum, on a regional, i.e., catchment scale, the drainage of the aquifer system is controlled by the conduit system, which may have a highly anisotropic geometry. Therefore, characterization of karst aquifers requires a differentiated approach by the combination of various hydrogeological field methods or the application of large-scale tests, which cover the scale of dominant aquifer heterogeneities. Existing numerical modeling approaches can be applied for integral data interpretation on catchment scale. [ABSTRACT FROM AUTHOR]

Karst aquifers exhibit highly conductive features caused from rock dissolution processes. Flow within these structures can become turbulent and therefore can be expressed by nonlinear gradient functions. One way to account for these effects is by coupling a continuum model with a conduit network. Alternatively, turbulent flow can be considered by adapting the hydraulic conductivity within the continuum model. Consequently, the significance of turbulent flow on the dynamic behavior of karst springs is investigated by an enhanced single-continuum model that results in conduit-type flow in continuum cells (CTFC). The single-continuum approach CTFC represents laminar and turbulent flow as well as more complex hybrid models that require additional programming and numerical efforts. A parameter study is conducted to investigate the effects of turbulent flow on the response of karst springs to recharge events using the new CTFC approach, existing hybrid models, and MODFLOW-2005. Results reflect the importance of representing (1) turbulent flow in karst conduits and (2) the exchange between conduits and continuum cells. More specifically, laminar models overestimate maximum spring discharge and underestimate hydraulic gradients within the conduit. It follows that aquifer properties inferred from spring hydrographs are potentially impaired by ignoring flow effects due to turbulence. The exchange factor used for hybrid models is necessary to account for the scale dependency between hydraulic properties of the matrix continuum and conduits. This functionality, which is not included in CTFC, can be mimicked by appropriate use of the Horizontal Flow Barrier package for MODFLOW. [ABSTRACT FROM AUTHOR]

Pesticide leaching into groundwater may be affected by changing climate directly and indirectly. Increased temperatures, changes in precipitation intensity, amounts and seasonality are thought to be the main direct climate drivers for changing pesticide fate and transport behaviour. Although it is well understood, in which range possible factors will influence pesticide fate and transport behaviour under changing climate conditions, only few studies have investigated these impacts quantitatively (Steffens et al., Sci Total Environ 2015). Increased temperatures for example enhance degradation, increase volatilisation, weaker sorption (for most compounds) of pesticide and fasten diffusion. More intense precipitation events for example may lead to more by-pass flow, which might increase pesticide leaching. In contrast, a drier soil for example has lower hydraulic conductivities, leading to slower substance transport, but degradation rates are lower too.This study aims to assess pesticide leaching into groundwater under changing climate conditions for a region in south-eastern Austria. For this purpose, a one-dimensional pesticide fate and transport model is used. The simulations focus on different representative pesticides, with varying properties, different common soil types and different climate scenarios, rather than indirect effects, such as changing cropping patterns, crop growth or pesticide applications. This work thus contributes to a better understanding of the impacts of climate change on pesticide leaching. [ABSTRACT FROM AUTHOR]