Abstract The Cam and Ely Ouse Chalk aquifer has been an important source of public water supply for over 100 years. In response to growing demand for water in the area in the 1970s and 1980 s, the National Rivers Authority developed the Lodes–Granta scheme to provide augmentation water to key rivers, subject to low flows. However, during the droughts in the late 1990s, the River Granta, which derives baseflow from the Chalk aquifer, was dry in some locations for several months. In response, the Environment Agency and Cambridge Water carried out investigations into the impacts of abstraction on the flow and ecology of the Granta and agreed to restrict abstraction from two operational groundwater sources during low flow periods. However, these abstraction restrictions could potentially result in a shortfall within the relevant public water supply zone under some climatic conditions and so Cambridge Water was considering increasing abstraction from an alternative source of groundwater within the catchment to retain the level of resilience of its supply. The Environment Agency was concerned that use of this abstraction could pose a risk of deterioration of the ecological status of the water body under the EU Water Framework Directive. This paper describes the investigations undertaken to assess the risk of deterioration and shows how these are being used to manage this risk going forward.

The Penobscot orogeny in the Appalachians, the Grampian orogeny in the British Isles, and the Finnmarkian orogeny in the Scandinavian Caledonides are Late Cambrian–Early Ordovician events that characterize terranes having similar pre- and post-deformation features. Together they record a major orogen-wide closing of the Cambrian Iapetus Ocean basin. The Penobscottian is the principal pre-Acadian deformation event in the Gander and related terranes of the Appalachians. The upper Proterozoic–Cambrian rocks deformed by it include subduction-related mélanges. In the northern Appalachians its timing is best constrained in northern Penobscot County, Maine, where polydeformed slate and sandstone (Grand Pitch Formation), dated Cambrian(?) by Oldhamia, are overlain by the singly deformed Arenig-age Shin Brook Formation. Basal conglomerate of the Shin Brook contains Grand Pitch clasts, and higher tuff contains Early Ordovician (late Arenig) Celtic province shelly fossils that indicate deposition around a volcanic island in cool waters of moderate to high latitude, remotely distant from contemporaneous warm equatorial waters of the North American (Laurentian) continental margin. The Grampian, in the Scottish–Irish orthotectonic Caledonides, deformed and metamorphosed miogeoclinal, upper Precambrian to lower Middle Cambrian Dalradian rocks that were largely derived from the Laurentian craton. An early tectonothermal phase, probably associated with subduction that produced blueschists, was followed by the main Barrovian metamorphism (510 to 480 Ma). Fossils in the Arenigian post-tectonic rocks of the South Mayo trough have strong North American affinities. Dalradian equivalents in the paratectonic Caledonides (Howth Peninsula, Ireland; Anglesey, Wales) suggest rifting of the Cambrian miogeocline, confirmed by the cool-water Celtic province Arenig shelly fauna of Anglesey. The Finnmarkian event deformed and metamorphosed rocks of the Late Proterozoic–Cambrian(?) Baltic continental-rise prism of Baltic provenance and obducted slabs of ophiolite. The minimum of its isotopic age range, 540 to 480 Ma, is confirmed by the Llanvirnian Otta serpentinite conglomerate that unconformably overlies an ophiolite remnant. Fossils from the conglomerate suggest cool-water Baltic and ocean-island affinities. The sequences deformed by these penecontemporaneous events record a complex history of the Late Proterozoic–Cambrian Iapetus Ocean, including miogeoclinal sedimentation on the margins of Laurentian, Baltic, and Armorican cratons, and the rifting and closing of intervening oceanic tracts. At the time of their deformation, these sedimentary sequences occupied the margins of a very large Early Ordovician Iapetus Ocean.