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This document is a comment on a previous article discussing the regulatory design of the Water Sustainability Act (WSA) in British Columbia, Canada. The comment argues that the WSA's regulatory design took a science-forward approach and considered specific regional factors. It addresses criticisms of the WSA and emphasizes the importance of licensing groundwater use for assessing environmental impacts. The WSA allows for nuanced water management through regulation-making authorities, but challenges remain in implementing the regulations, including Indigenous water rights and government resources. Recommendations for improving the WSA's design include defining sustainability goals, regionalizing regulatory action, and long-term planning. Ongoing resourcing and consideration of Indigenous rights are necessary for the effective implementation of the WSA. [Extracted from the article]

This document is a reply to a comment on a previous article about applying a science-forward approach to groundwater regulatory design in British Columbia, Canada. The reply addresses three aspects of the comment: the need for legislation for data collection, the flexibility within the new regulatory regime, and the acknowledgement of Indigenous water rights. The authors of the reply appreciate the insider perspective provided by the comment authors, who were involved in the development of the regulatory regime. The reply also discusses the importance of a science-forward approach to groundwater regulation and the challenges faced in implementing it. It concludes by suggesting ways to course correct and improve the regulatory design in the future. [Extracted from the article]

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Groundwater evapotranspiration (ETg) is a significant component of water and energy balance analyses in arid and semiarid environments; however, it is also one of the most challenging items to estimate. Estimation of ETg using diurnal groundwater-level fluctuation is considered cost-effective and straightforward, while more accurate estimation technology continues to be developed due to the complex set of factors that influence the variation of groundwater level. This paper proposes a method for calculating ETg that combines the analytical solution of the Boussinesq equation and dynamic harmonic regression analysis, which is a nonstationary approach to groundwater-level signal extraction. The presented approach can calculate ETg values with a high time resolution consistent with the groundwater-level monitoring frequency, and it is robust enough to handle large amounts of measurement data. More importantly, this method eliminates the influence of recharge during the groundwater-level-rise stage. The method is tested in bushland dominated by Sminthopsis psammophila in Mu Us Desert (northern China), which has a shallow water table. The results show that this method is easy to perform and it obtains a reasonable estimate of ETg in the unfrozen seasons, regardless of the disturbance of recharge that results in a sharp rise in groundwater level. However, the method does not work well in the frozen seasons because of the physical mechanisms of change in groundwater movement in the vadose zone and a strong barometric effect. Overall, the method provides a step toward accuracy of ETg estimation using diurnal groundwater-level fluctuation, and this paper provides guidelines for its use. [ABSTRACT FROM AUTHOR]

The high groundwater salinity of crystalline aquifers in semiarid areas is generally attributed to the dissolution and leaching of meteoric salts that have been progressively evapoconcentrated in the different hydrological compartments under dry climate conditions. A numerical model, simulating water and salt balances, was developed from a case study in Northeast Brazil to: (1) test the validity of this hypothesis, through the quantification of all relevant water cycle processes in the studied watershed, and (2) demonstrate how changes in land cover can impact groundwater salinity. Computations showed that the aridity and the high evapo(transpi)ration rates from the unsaturated zone and/or surface water (ponds, reservoirs) cannot lead to the observed aquifer salinization levels, but only to concentrations of a few tens or hundreds of mg L–1 (Cl–). The only process that can induce a high groundwater salinity, with chloride concentrations up to several g L–1, is the transpiration of groundwater by the deep roots of the vegetation, with a rate reaching 100% of the annual recharge. In this case study, the vegetation involved is the native Caatinga forest. Simulations of the long-term dynamics of groundwater salinity indicate that aquifer areas with high salinity are relicts of the Caatinga pre-colonization period during which subterranean endorheic conditions were prevailing. Following the Caatinga deforestation linked to colonial agricultural development, aquifer recharge increased and endorheism ceased. Consequently, these aquifers may have now been experiencing a desalination process for about three centuries. The desalination spatial variability drivers are explained in the paper. [ABSTRACT FROM AUTHOR]

An analysis of expert perspectives on groundwater governance arrangements in South Africa is presented, particularly those arrangements that are pertinent to the complex and socially and ecologically significant implications of exploiting unconventional oil and gas (UOG). The paper presents a detailed assessment of literature on groundwater governance research, the findings of which are applied as a framework for a series of expert interviews, comprising hydrogeologists, lawyers, engineers, and governance specialists. This methodological approach was adopted as a means to enable an analysis of opinions on the current situation of groundwater governance in South Africa and how fit-for-purpose this is for managing the exploitation of UOG. The analysis was also informed by observation of participants at several relevant decision-making and stakeholder events. Whilst the findings indicated a generally positive evaluation of the initial steps taken to assess UOG impacts and engage relevant communities, recurrent criticisms also are featured across the interviews. Key implications arising from the research include: (1) the need for continued stakeholder engagement, and government follow-through on the outcomes of these processes, (2) the necessity for detailed groundwater-specific regulations to be drafted at the earliest opportunity, to ensure that the energy policy vacuum does not have a negative knock-on effect for effective groundwater management, and (3) the prevalence of significant governance gaps, particularly regarding regulatory and institutional capacity, and the need for continued development of a functional network of institutions to effectively manage UOG exploitation alongside groundwater resources. [ABSTRACT FROM AUTHOR]

The distribution of saline water in the upper aquifer and freshwater in the lower aquifer is a characteristic of groundwater resources in the North China Plain (NCP). The phenomenon of groundwater depression cones in confined aquifers, primarily caused by excessive groundwater extraction, has been extensively documented. In line with Darcy's law, it is noteworthy that the migration of shallow groundwater into confined aquifers can occur due to a substantial difference in hydraulic head between the unconfined and confined aquifer systems. However, based on the monitoring data, the quality of deep groundwater generally remains good. This paper attempts to explain this phenomenon from the perspective of non-Darcian flow in aquitards. A finite difference method is used to solve low-velocity non-Darcian flow to a well in the NCP. The mathematical model considers the threshold pressure gradient to describe non-Darcian flow in the aquitard and assumes Darcian and horizontal flows for both shallow and confined aquifers. The comparison with traditional Darcian flow indicates that the leaky area decreases rapidly when considering the threshold pressure gradient. The leaky area is negatively correlated with the aquitard thickness and the transmissivity of the confined aquifer, and positively correlated with the pumping rate. The non-Darcian vertical flow velocity is significantly lower than that obtained from Darcian theory. The vertical velocity difference between Darcian and non-Darcian flows is significant under the situation of a small aquitard thickness, large pumping rate, low transmissivity and large leakage coefficient when the threshold pressure gradient is large. [ABSTRACT FROM AUTHOR]

In karstic environments, it is not unusual for an underground river to split into two or more streams (diffluence) and merge back together downstream (confluence). This kind of behavior can generate multipeaked breakthrough curves (BTCs) in dye tracing at a sampling site located downstream of the confluence(s). It is also possible that such a phenomenon is difficult to highlight with dye tracing if the tracer clouds coming from the different streams reach the sampling locations at the same time. In this study, an attempt at quantifying the importance of different criteria in the occurrence of a multipeaked BTC is done by performing a dye tracing campaign in a two-tributaries diffluence-confluence (DC) system and using a one-dimensional solute transport model. The results from both field data and the solute transport model suggest that a double-peaked BTC occurs downstream of a DC system if the following conditions are met: (1) the injection is done close enough to the diffluence, (2) the sampling point is located not too far from the confluence, and (3) the two (or more) streams have sufficiently contrasted travel times from the diffluence to the confluence. The paper illustrates that, even if a diffluence occurs in a karstic river, multipeaked BTCs are not necessarily observed downstream of the confluence if these three conditions are not met. Therefore, characterizing a DC system using dye tracing is a real challenge. This could explain why publications that report studies involving multipeaked BTCs are quite rare. [ABSTRACT FROM AUTHOR]

Abstract: The long-lived radiotoxicity of the high-level radioactive waste generated by nuclear power plants requires safe isolation from the biosphere for many hundreds of thousands of years. An international consensus has emerged that such isolation can best be provided by disposal in mined geologic repositories, a strategy that today is pursued by most countries dealing with radioactive waste. However, the need to predict the performance of such repositories over very long time periods generates large uncertainties that have to be accounted for in safety assessments. The findings from such safety assessments need to be conveyed to all stakeholders in a clear way, such that public confidence in geologic disposal solutions can be achieved. It is suggested here that close international collaboration on the technical aspects of geologic waste disposal has helped, and will continue to help, building trust and increasing confidence. This paper discusses a particular international collaboration initiative referred to as DECOVALEX, which brings together multiple teams and disciplines to collectively tackle complex experimental and modeling challenges related to geologic disposal. By describing how DECOVALEX works and by providing joint research examples, a case is made that such international collaboration contributes to knowledge transfer and confidence building in radioactive waste disposal science. [ABSTRACT FROM AUTHOR]

Research on the hydrogeology of andesitic volcanic aquifers in subduction areas is reviewed. Andesitic aquifers are of high interest in volcanic arc islands and subduction zones, where they constitute a strategic water resource. This review gathers a compilation of worldwide results and case studies to propose a generic hydrogeological conceptual model (GHCM). It is based on the geological conceptual model splitting the volcanic edifice, from upstream to downstream, into central, proximal, medial and distal zones. In this geological structure, the GHCM identifies where the main aquifer types (fractured lava, pyroclastic flows, and the volcano-sedimentary basins downstream) and the typical aquitards (lahars, fine pyroclastic falls and surges, indurated pyroclastic flow, and weathered rocks) are structured and organized. To integrate the evolution of volcanoes and some specific volcanic activities, a specific GHCM for old andesitic volcanoes or andesitic shield volcanoes is detailed. The paper also describes how the GHCM results are of use to hydrogeologists in terms of scale (from the lithological units to the regional scale), to effectively site water wells, and to sustainably manage groundwater resources in such aquifers. Among these various scales, the volcanic “flank continuum” is presented as the most adapted to support groundwater resources management. Several ways to improve this GHCM are suggested, notably to better consider the geological complexity of these aquifers. [ABSTRACT FROM AUTHOR]