Abstract The Cretaceous Chalk in England forms dual-porosity aquifers, with low-permeability matrix and high-permeability networks of fissures, which are predominantly stress-relief fractures that have been enlarged by dissolution. This enlargement is a function of the volume of water that has passed along a fracture (the flowrate effect) and its degree of chemical undersaturation. Feedback effects result in the development of a distinctive permeability structure, with four particular characteristics: (i) troughs in the water table with high transmissivity and convergent groundwater flow; (ii) substantial increases in transmissivities in a downgradient direction; (iii) downgradient decreases in hydraulic gradient; and (iv) discharge from the high-transmissivity zones to the surface commonly at substantial springs. This distinctive self-organized permeability structure occurs throughout unconfined chalk aquifers. Early enlargement of fissures at a depth of 50–100 m below the water table is slow, but is much more rapid close to the water table and in the uppermost bedrock due to non-linear dissolution kinetics. A modelled dissolution profile shows that more than 95% of dissolution takes place in the top 1 m of bedrock, and that enlargement of fissures in the saturated zone results from progressive dissolution occurring over a period of a million years or more.

Abstract In Groundwater-Dependent Terrestrial Ecosystems (GWDTEs), atmospheric nitrogen (N) inputs have often been studied in isolation from terrestrial groundwater and surface water inputs. We describe for the first time the development and application of a combined atmospheric and terrestrial N source apportionment methodology, able to identify contributing catchment and N loadings to GWDTEs. We combined all N inputs using a site-specific conceptual model supported by 12 months’ monitoring for a Chalk-fed GWDTE at Newbald Becksies, East Yorkshire. We discuss implications for effective catchment management, wetland protection and development of a source apportionment methodology. Potential sources of nitrate include: atmospheric deposition, mineralization, leaching from agricultural soils, manure heaps, septic tanks, sewer and mains water leakage. Atmospheric deposition was calculated from measurements of ammonia and nitrogen dioxide concentrations together with rainfall inputs of ammonium and nitrate. Quantification of agricultural sources used the FarmScoper modelling tool to estimate nitrate leaching in the groundwater catchment. Comparison between modelled nitrate concentrations in leachate (15–17 mg N l −1 ) and observed groundwater nitrate concentrations (12.3–19.8 mg N l −1 ) are good. The majority of nitrate is leached from arable land. FarmScoper allows mitigation scenarios to be tested, supporting measures to reduce nitrate within a groundwater catchment.

ABSTRACT For science to reliably support new discoveries, its results must be reproducible. Assessing reproducibility is a challenge in many fields—including the geosciences—that rely on computational methods to support these discoveries. Reproducibility in these studies is particularly difficult; the researchers conducting studies must agree to openly share research artifacts, provide documentation of underlying hardware and software dependencies, ensure that computational procedures executed by the original researcher are portable and execute in different environments, and, finally, verify if the results produced are consistent. Often these tasks prove to be tedious and challenging for researchers. Sciunit ( https://sciunit.run ) is a system for easily containerizing, sharing, and tracking deterministic computational applications across environments. Geoscience applications in the fields of hydrology, solid Earth, and space science have actively used Sciunit to encapsulate, port, and repeat workflows across computational environments. In this chapter, we provide a comprehensive survey of geoscience applications that have used Sciunit to improve sharing and reproducibility. We classify the applications based on their reproducibility requirements and show how Sciunit accommodates relevant interfaces and architectural components to support reproducibility requirements within each application. We aim to provide these applications as a Sciunit compendium of use cases for replicability, benchmarking, and improving the conduct of reproducible science in other fields.

ABSTRACT Numerical models have been an integral component in management of the Edwards Aquifer for over four decades. The scale and complexity of the models have varied considerably during this time, with the changes attributed to improvements in both numerical software and the conceptual models on which the models are predicated. Resolution of early models was coarse, which rendered them useful only in large-scale, groundwater-resource assessments. Increased resolution and improved refinement in the conceptualization of the complex hydrostratigraphic framework of the Edwards Aquifer have led to expanded applicability of the ensuing models in terms of accommodating local-scale hydraulic features such as pumping scenarios and changes in recharge/discharge mechanisms (i.e., urbanization and climate change). As part of these improvements and advancements, regional-scale groundwater availability models augmented by local-scale models based upon improved conceptualization provide the ability to: (1) replicate more extreme conditions, such as the drought-of-record; (2) improve boundary conditions by extending models to include natural hydraulic boundaries; and (3) couple groundwater flow models with surface-water flow models so that the entire terrestrial water cycle can be accommodated during water-resource management scenario assessment.

Abstract Pumping tests carried out in three highly tectonized Mediterranean areas, which share similar climate conditions, were used to characterize hard-rock aquifers and examine the issue of the sustainable yield of wells. On the basis of the identified drawdown trends and hydraulic parameters, pumping scenarios were simulated through different methods. The results show that the long-term trend in the drawdown and the initial thickness of the aquifer constrain the sustainable yield of a well. In the worst cases examined, namely those related to an aquifer with a barrier boundary and a delayed response of the aquifer, the sustainable well yield is 1–2 L s −1 . These well discharge values are significant when compared with those found in other regions of the world, and may be related to the dense network of the discontinuities which characterizes the sites.