Abstract Regional groundwater resource models are often built to improve confidence in predicted groundwater abstraction impacts on river flows and groundwater levels. By explicitly representing the aquifer system geometry, properties and boundaries, together with transient recharge and abstraction pressures, such models provide a robust platform to support abstraction impact assessment, alongside evidence from field data and investigations. Regulatory drivers include the European Union Habitats and Water Framework Directives and other abstraction licensing decisions. This paper presents examples of the spatial and temporal patterns of groundwater abstraction impacts predicted by several models. A variety of presentation formats are used to illustrate the simulated flow impacts of abstractions both individually, and in combination with other surface water abstractions and discharges. Model predictions from a range of abstraction, aquifer, and river settings are often more complex than would be suggested by simpler tools and approaches. In many cases, absolute low-flow impacts are less than long-term groundwater abstraction rates. The ‘real world’ hydrogeological mechanisms behind these impact patterns are discussed. The paper also recommends a protocol for using regional models to assess individual licensed groundwater abstraction impacts across the full range of historic climate conditions (typically, as monitored since 1970) and in the context of other operational artificial influences.

Abstract Groundwater has been used in the UK as a source of drinking water for centuries. For example, certain springs have been used to supply small urban areas for more than a thousand years. However, extensive use of groundwater began during the industrial revolution that started in the eighteenth century. The technology from the industrial revolution provided the means to access greater quantities of groundwater. Nevertheless, probably the more important factor was the increasing urbanization, with industrial cities such as Birmingham, Liverpool and Nottingham expanding at a phenomenal rate. With the higher population came an increased demand for water, which could be provided from local aquifers. The trigger for extensive exploitation was the 1848 Public Health Act that required local authorities to ensure a source of clean drinking water. From 1850 onwards, large red-brick Victorian pumping stations (Figs 1 & 2 ) started to appear on the outcrops of the principal aquifers in England, and abstraction steadily increased until the 1990s. In 2003, the use of groundwater in England and Wales was c. 6400 Ml/day (6 400 000 m 3 /day), of which c. 5000 Ml/day was for public supply ( Environment Agency 2006 ), comprising about a third of the total drinking water supply in England and Wales. The abstraction is predominantly from the Chalk and Permo-Triassic Sandstone (Fig. 3 ), which account for 60 and 25% of total groundwater abstraction, respectively ( Downing 1998 ). Outcrops of these two aquifers are located mainly in the SE and Midlands

Abstract Over the last 10 years there has been a unique regulator-led programme involving extensive development of regional groundwater models across England and Wales for water resources purposes by the Environment Agency for England and Wales. Eight regionally managed programmes are underpinned by a framework, which has allowed a coordinated national approach. The main uses of the models are for catchment abstraction management and licensing. Models have also assisted in monitoring network design, investigating groundwater quality and implementing groundwater source protection zones. A five-yearly review of the programmes recognized the importance of benefit realization and stakeholder involvement as well as technical good practice. The programme already delivered provides a solid foundation for supporting the management decisions required in areas such as climate change mitigation and integrated catchment management using appropriate tools at a time of rapid organization change and financial uncertainty.

Abstract Six regional recharge and groundwater models have been recently developed of the Chalk and Upper Greensand from Dorset to Kent. Updated Chalk stratigraphy and mapping have improved understanding of geological structure and the development of preferential groundwater flow pathways along hardground horizons. Where shallow dipping folds bring these into the zone of active groundwater flow, extensive ‘underdrainage’ may result in marked differences between surface and groundwater catchments. Hardgrounds and marls are also associated with spring discharges, as are some faults and the clay formations that underlie or confine the aquifer system. Higher specific yield within the Upper Greensand helps support summer baseflow, as do local groundwater discharges from augmentation schemes, watercress and fish farm operations. The aquifer system has been successfully modelled using the ‘variable hydraulic conductivity with depth’ version of MODFLOW. Depths of secondary permeability development have been distributed according to ground and groundwater level data. Interfluve–valley contrasts overlie a base hydraulic conductivity set according to the formation saturated at the water table and enhanced by active hardgrounds. Local parameter overrides may also be needed. The Wessex Basin conceptual and numerical model is described before summarizing similarities and contrasts from the other five regional model areas.

Abstract The Environment Agency of England and Wales uses its calibrated regional models to estimate the reduction in river flows resulting from proposed groundwater abstractions. Where there is no regional model, analytical equations can produce quick initial estimates of river flow depletion. However, users often want more confidence in their estimates by representing more faithfully their understanding of the real river–aquifer system. This paper shows that, when using a numerical model designed to predict river flow depletion, it is important to include adjacent catchments and intermittent streams and less important to include river elevations and variations in transmissivity with groundwater head. Recharge does not usually need to be included unless part of the river becomes disconnected or dry. Therefore, for rivers where stream length is constant and transmissivity variations are small, it is valid to use a ‘no-recharge’ depletion model, which can be built quickly (within a month). A case study on the River Leith in NW England illustrates the use of such a model to assess the ecological impact of two groundwater abstraction licences under the European Union Habitats Directive.

Abstract The predictions from a numerical time-variant distributed groundwater model are used to assess the spatial and temporal impacts of groundwater abstraction for an unconfined and layered, moderate diffusivity aquifer; the West Midlands–Worfe Permo-Triassic Sandstone in the UK. These impacts have been determined by comparing a recent actual baseline predictive simulation with simulations where groundwater abstractions are switched off, including a ‘naturalized’ simulation. By reference to the historic simulation, the predictive model results are compared against observed groundwater levels. The predictive simulations demonstrate that observed groundwater levels could be an indicator of groundwater abstraction impacts on surface water flows where widespread stream disconnection has occurred due to high rates of abstraction. This relationship also depends on the aquifer hydraulic characteristics, the interaction between groundwater levels and the surface drainage network and other artificial flow influences. Abstraction impacts on groundwater levels are large for the West Midlands–Worfe aquifer, but can be obscured by the climatic recharge signal in observed groundwater level records. This is a consequence of the moderate diffusivity and the main groundwater abstraction development preceding systematic monitoring. The groundwater model can be used to identify which observation boreholes have negligible abstraction impacts; this may be valuable for identifying groundwater level records that are useful for climate change analysis.

Abstract A diverse and abundant Late Pleistocene pteropod (pelagic gastropod) fauna is described from marine cores near the island of Montserrat, Lesser Antilles. In several of the cores, there are ‘floods’ of pteropods at particular levels, usually associated with glacial periods within the Late Pleistocene. These levels of abundant pteropods appear to be of regional significance, having been reported from other locations in the Caribbean Sea, the Gulf Coast of Florida and other ocean basins. The concentrations appear to reflect the enhanced preservation of aragonite during cooler periods within the Pleistocene.