Groundwater compartmentalisation: a water table height and geochemical analysis of the structural controls on the subdivision of a major aquifer, the Sherwood Sandstone, Merseyside, UK

International audienceCompartmentalisation, the subdivision of an aquifer into discrete and relatively isolated units, may be of critical importance for the protection of groundwater although it has been largely ignored in the groundwater literature. The Lower Triassic Sherwood Sandstone, in north west of England, UK, may be a good example of an aquifer that has been compartmentalised by numerous high angle faults with displacements of up to 300 m. 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. Maps and schematic cross-sections of groundwater heads for the years 1993, and 2002 were prepared to trace any structural controls on the groundwater heads across the area. Studying the contour maps and cross sections revealed that: 1) there are substantial differences in groundwater head across some of the NNW-SSE trending faults implying that groundwater flow is strongly limited by faults, 2) an anticline in the east of the area acts as a groundwater divide and 3) the groundwater head seems to follow the topography in some places, although steep changes in groundwater head occur across faults showing that they locally control the groundwater head. The aquifer was thus provisionally subdivided into several hydrogeological sub-basins based on groundwater head patterns and the occurrence of major structural features (faults and a fold). Using groundwater geochemistry data, contour maps of chloride and sulphate concentration largely support the structural sub-division 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 variation of the geochemical composition of the groundwater not only relates to the different, localised geochemical processes and seawater intrusion but also relates to compartmentalisation due to faulting. Faults have limited the degree of mixing between the groundwater types thus retaining the specific characteristics of each sub-basin. Highly localised seawater intrusion is mainly controlled by low permeability fault close to the Irish Sea and Mersey estuary. There is effectively no invasion of seawater beyond the faults that lie closest to the coastline. Freshwater recharge to the aquifer seems to be highly localised and mainly occurs by vertical percolation of rain and surface water rather than whole aquifer-scale groundwater flow. This study provides a detailed understanding of the groundwater flow processes in Liverpool as an example of methods can be applied to groundwater management elsewhere

Groundwater compartmentalisation: a geochemical analysis of the structural controls on the subdivision of a major aquifer, the Sherwood Sandstone, Merseyside, UK

International audienceThe 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 surrounding 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. Maps of water table for the years 1993, 1997, 2000 and 2002 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 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 features (faults and a fold). Using groundwater geochemistry data, contour maps of chloride and sulphate concentration largely support the structural sub-division 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 variation of the geochemical composition of the groundwater not only relates to the different, localised geochemical processes and seawater intrusion but also relate to compartmentalisation due to faulting. Faults have limited the degree of mixing between the groundwater types thus retaining the specific characteristics of each sub-basin. Highly localised seawater intrusion is mainly controlled by low permeability fault close to the Irish Sea and Mersey estuary. There is no effectively no invasion of seawater beyond the faults that lie closest to the coastline. Freshwater recharge to the aquifer must be highly localised and will mainly occur by vertical percolation of rain and surface water rather than whole aquifer-scale groundwater flow

Ascorbic Acid Metabolisms: A review

Ascorbic acid (vitamin C) is a water-soluble, hexonic sugar, with a molecular weight of 176. It is known to play vital roles in numerous functions of the body, especially in hydroxylation reactions. Its requirement by animals may be increased when challenged in the form of immune and metabolic stress. The main objective of this brief review is to outline the catabolic and anabolic pathways of ascorbic acid as well as its metabolic functions

Can deficit irrigations be an optimum solution for increasing water productivity under arid conditions? A case study on wheat plants

Water scarcity is of growing concern in many countries around the world, especially within the arid and semi-arid zones. Accordingly, rationalizing irrigation water has become an obligation to achieve the sustainable developmental goals of these countries. This may take place via using deficit irrigation which is long thought to be an effective strategy to save and improve water productivity. The current study is a trial to evaluate the pros and cons of using 50 and 75 % of the irrigation requirements (IR) of wheat (deficit irrigations) versus 100 %IR, while precisely charting changes in wheat growth parameters, antioxidant enzymes in plant shoots and the overall nutritional status of plants (NPK contents). Accordingly, a field experiment was conducted for two successive seasons, followed a split-plot design in which deficit irrigations (two irrigations to achieve 50 % of the irrigations requirements (IR), three irrigations to attain 75 % IR, and four irrigations to fulfill 100 % IR) were placed in main plots while four different studied wheat cultivars were in subplots. Results obtained herein indicate that deficit irrigations led to significant reductions in growth parameters and productivity of all wheat cultivars, especially when using 50 % IR. It also decreased NPK contents within plant shoots while elevated their contents of proline, peroxidase, and catalase enzymes. On the other hand, this type of irrigation decreased virtual water content (VWC, the amount of water used in production on ton of wheat grains). Stress tolerance index (STI), and financial revenues per unit area were also assessed. The obtained values of grain productivity, STI, VWC and financial revenues were weighted via PCA analyses, and then introduced in a novel model to estimate the efficiency of deficit irrigations (ODEI) whose results specified that the overall efficiency decreased as follows: 50 %IR < 75 %IR < 100 %IR. In conclusion, deficit irrigation is not deemed appropriate for rationalizing irrigation water while growing wheat on arid soils