Groundwater compartmentalisation

Introduction Conclusions References Tables Figures Back Close Papers published in Hydrology and Earth System Sciences Discussions are under open-access review for the journal Hydrology and Earth System Sciences Groundwater compartmentalisation: a geochemical analysis of the structural controls on the subdivision of a major aquifer, Abstract Introduction Conclusions References Tables Figures Back Close Abstract The study was initiated to assess the local groundwater flow, the extent of seawater invasion and the controls on recharge in the aquifer and to try to understand whether the aquifer is broken into discrete compartments. The study area is located in the northwest of England and encompasses the urban area of Liverpool and surround-5 ing countryside and extends east-west from Liverpool to Widnes and as far north as Formby. The Irish Sea marks the western margin of the area while the Mersey estuary defines the southern margin. The Triassic sandstone in this area has been, and remains, an important aquifer although industrialisation and groundwater exploitation have led to significant water quality problems. and schematic cross-sections of the water table height along the faults were prepared to trace any effect of these faults on water table height across. Studying the water table maps and cross sections revealed that: 1) there are substantial differences in water table height across some of the NNW-SSE trending faults implying that groundwater flow is strongly limited 15 by fault, 2) an anticline in the east of the area acts as a groundwater divide and 3) the water table seems to follow the topography in some places, although steep changes in water table occur across faults showings that they locally control the water table elevation. The aquifer was thus provisionally subdivided into several hydrogeological sub-basins based on water table height patterns and the occurrence of major structural 20 features (faults and a fold). Using groundwater geochemistry data, contour maps of chloride and sulphate concentration largely support the structural subdivision of the area into hydrogeological sub-basins. Scrutiny of groundwater geochemical data, averaged for each sub-basin, confirmed the degree of compartmentalisation and the occurrence of sealed faults. The 25 variation of the geochemical composition of the groundwater not only relates to the different , localised geochemical processes and seawater intrusion but also relate to com-partmentalisation due to faulting. Faults have limited the degree of mixing between the 940 HESSD Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Print Version Interactive Discussion …