Karstic behaviour of groundwater in the English Chalk

Maurice, Louise; Atkinson, T. C.; Barker, John A.; Bloomfield, John P.; Farrant, Andrew; Williams, A. T.

doi:10.1016/j.jhydrol.2006.04.012

Cited by 59 publications

(38 citation statements)

References 12 publications

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“…Chalk is a pure but fine-grained biogenic carbonate rock and often not considered to be karstifiable; however, many chalk aquifers are actually karstified, although karst features are less prominent than in classical limestone karst. In many regions, chalk aquifers contribute substantially to freshwater supplies (Maurice et al 2006). Metamorphic carbonate rocks such as marble and calcite schist, also constitute important karst aquifers in some regions of the world.…”

Section: Basic Mapping Approach and Legendmentioning

confidence: 99%

The World Karst Aquifer Mapping project: concept, mapping procedure and map of Europe

et al. 2017

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Karst aquifers contribute substantially to freshwater supplies in many regions of the world, but are vulnerable to contamination and difficult to manage because of their unique hydrogeological characteristics. Many karst systems are hydraulically connected over wide areas and require transboundary exploration, protection and management. In order to obtain a better global overview of karst aquifers, to create a basis for sustainable international water-resources management, and to increase the awareness in the public and among decision makers, the World Karst Aquifer Mapping (WOKAM) project was established. The goal is to create a world map and database of karst aquifers, as a further development of earlier maps. This paper presents the basic concepts and the detailed mapping procedure, using France as an example to illustrate the step-by-step workflow, which includes generalization, differentiation of continuous and discontinuous carbonate and evaporite rock areas, and the identification of non-exposed karst aquifers. The map also shows selected caves and karst springs, which are collected in an associated global database. The draft karst aquifer map of Europe shows that 21.6% of the European land surface is characterized by the presence of (continuous or discontinuous) carbonate rocks; about 13.8% of the land surface is carbonate rock outcrop.

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Section: Basic Mapping Approach and Legendmentioning

confidence: 99%

The World Karst Aquifer Mapping project: concept, mapping procedure and map of Europe

et al. 2017

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“…The sites are part of the UKs long-term observation borehole network (Marsh and Hannaford, 2008) and consist of a broad range of unconfined consolidated aquifer types (Bloomfield et al, 2009). The sites include those located on the Lincolnshire Limestone, a fractured limestone aquifer (Allen et al, 1997); the Chalk aquifer, a dual porosity, dual permeability carbonate aquifer with local karstic development (Bloomfield, 1996;Maurice et al, 2006); and the Permo-Triassic Sandstone and Lower Greensand aquifers (Allen et al, 1997;Bloomfield et al, 2001) where intergranular flow predominates. Figure 1 shows the location of the observation boreholes in relation to the major aquifers in the UK, and summary information about the sites and groundwater hydrographs is given in Table 1.…”

Section: Study Sites and Datamentioning

confidence: 99%

Analysis of groundwater drought building on the standardised precipitation index approach

Bloomfield

Marchant

2013

Hydrol. Earth Syst. Sci.

307

308

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Abstract.A new index for standardising groundwater level time series and characterising groundwater droughts, the Standardised Groundwater level Index (SGI), is described. The SGI builds on the Standardised Precipitation Index (SPI) to account for differences in the form and characteristics of groundwater level and precipitation time series. The SGI is estimated using a non-parametric normal scores transform of groundwater level data for each calendar month. These monthly estimates are then merged to form a continuous index. The SGI has been calculated for 14 relatively long, up to 103 yr, groundwater level hydrographs from a variety of aquifers and compared with SPI for the same sites. The relationship between SGI and SPI is site specific and the SPI accumulation period which leads to the strongest correlation between SGI and SPI, q max , varies between sites. However, there is a consistent positive linear correlation between a measure of the range of significant autocorrelation in the SGI series, m max , and q max across all sites. Given this correlation between SGI m max and SPI q max , and given that periods of low values of SGI can be shown to coincide with previously independently documented droughts, SGI is taken to be a robust and meaningful index of groundwater drought. The maximum length of groundwater droughts defined by SGI is an increasing function of m max , meaning that relatively long groundwater droughts are generally more prevalent at sites where SGI has a relatively long autocorrelation range. Based on correlations between m max , average unsaturated zone thickness and aquifer hydraulic diffusivity, the source of autocorrelation in SGI is inferred to be dependent on dominant aquifer flow and storage characteristics. For fractured aquifers, such as the Cretaceous Chalk, autocorrelation in SGI is inferred to be primarily related to autocorrelation in the recharge time series, while in granular aquifers, such as the Permo-Triassic sandstones, autocorrelation in SGI is inferred to be primarily a function of intrinsic saturated flow and storage properties of aquifer. These results highlight the need to take into account the hydrogeological context of groundwater monitoring sites when designing and interpreting data from groundwater drought monitoring networks.

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“…Storage and transmissivity are controlled by local sub-karstic development of the fracture network (Bloomfield, 1996;Maurice et al, 2006). The Chalk group reaches a thickness of over 250 m. Groundwater flows from the recharge areas in the west, eastward down-dip towards and into the confined Chalk to the east.…”

Section: Geology and Hydrogeologymentioning

confidence: 99%

Regional analysis of groundwater droughts using hydrograph classification

Bloomfield

Marchant

Bricker

et al. 2015

Hydrol. Earth Syst. Sci.

102

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Abstract. Groundwater drought is a spatially and temporally variable phenomenon. Here we describe the development of a method to regionally analyse and quantify groundwater drought. The method uses a cluster analysis technique (nonhierarchical k-means) to classify standardised groundwater level hydrographs (the standardised groundwater level index, SGI) prior to analysis of their groundwater drought characteristics, and has been tested using 74 groundwater level time series from Lincolnshire, UK. Using the test data set, six clusters of hydrographs have been identified. For each cluster a correlation can be established between the mean SGI and a mean standardised precipitation index (SPI), where each cluster is associated with a different SPI accumulation period. Based on a comparison of SPI time series for each cluster and for the study area as a whole, it is inferred that the clusters are independent of the driving meteorology and are primarily a function of catchment and hydrogeological factors. This inference is supported by the observation that the majority of sites in each cluster are associated with one of the principal aquifers in the study region. The groundwater drought characteristics of the three largest clusters, which constitute ∼ 80 % of the sites, have been analysed. There are differences in the distributions of drought duration, magnitude and intensity of groundwater drought events between the three clusters as a function of autocorrelation of the mean SGI time series for each cluster. In addition, there are differences between the clusters in their response to three major multi-annual droughts that occurred during the analysis period. For example, sites in the cluster with the longest SGI autocorrelation experience the greatest-magnitude droughts and are the slowest to recover from major droughts, with groundwater drought conditions typically persisting at least 6 months longer than at sites in the other clusters. Membership of the clusters is shown to be related to unsaturated zone thickness at individual boreholes. This last observation emphasises the importance of catchment and aquifer characteristics as (non-trivial) controls on groundwater drought hydrographs. The method of analysis is flexible and can be adapted to a wide range of hydrogeological settings while enabling a consistent approach to the quantification of regional differences in response of groundwater to meteorological drought.

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Karstic behaviour of groundwater in the English Chalk

Cited by 59 publications

References 12 publications

The World Karst Aquifer Mapping project: concept, mapping procedure and map of Europe

The World Karst Aquifer Mapping project: concept, mapping procedure and map of Europe

Analysis of groundwater drought building on the standardised precipitation index approach

Regional analysis of groundwater droughts using hydrograph classification

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