Hydrological processes in the Chalk unsaturated zone – Insights from an intensive field monitoring programme

Ireson, A. M.; Wheater, H. S.; Butler, Adrian P.; Mathias, Simon A.; Finch, J.W.; Cooper, J. David

doi:10.1016/j.jhydrol.2006.04.021

Cited by 63 publications

(59 citation statements)

References 19 publications

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“…The objectives of this study are to determine whether pesticides (and their degradation products) can form stable complexes with colloidal material present in the soil zone, and if these complexes also exist in groundwater beneath a relatively deep unsaturated zone. By considering our findings in relation to recently published field studies (Haria et al, 2003;Ireson et al, 2006) and modelling investigations (Mathias et al, 2005;Mathias et al, 2006), we present two conceptual models for pesticide movement from the point of agricultural application to the groundwater beneath.…”

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confidence: 73%

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The significance of colloids in the transport of pesticides through Chalk

Gooddy

Mathias

Harrison

et al. 2007

Science of The Total Environment

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Agrochemical contamination in groundwater poses a significant long term threat to water quality and is of concern for legislators, water utilities and consumers alike. In the dual porosity, dual permeability aquifers such as the Chalk aquifer, movement of pesticides and their metabolites through the unsaturated zone to groundwater is generally considered to be through one of two pathways; a rapid by-pass flow and a slower 'piston-flow' route via the rock matrix. However, the dissolved form or 'colloidal species' in which pesticides move within the water body is poorly understood. Following heavy rainfall, very high peaks in pesticide concentration have been observed in shallow Chalk aquifers. These concentrations might be well explained by colloidal transport of pesticides. We have sampled a Chalk groundwater beneath a deep (30 m) unsaturated zone known to be contaminated with the pesticide diuron. Using a tangential flow filtration technique we have produced colloidal fractions from 0.45µm to 1kDa. In addition, we have applied agricultural grade diuron to a typical chalk soil and created a soil water suspension which was also subsequently fractionated using the same filtration system. The deep groundwater sample showed no evidence of association between colloidal material and pesticide concentration. In comparison, despite some evidence of particle trapping or sorption to the filters, the soil water clearly showed an association between the <0.45µm and <0.1µm colloidal fractions which displayed significantly higher pesticide concentrations than the unfiltered sample.Degradation products were also observed and found to behave in a similar manner to the parent compound. Although relatively large colloids can be generated in the Chalk soil zone, 2 it appears transport to depth in a colloidal-bound form does not occur. Comparison with other field and monitoring studies suggests that rapid by-pass flow is unlikely to occur beneath 4-5 m. Therefore, shallow groundwaters are most at risk from rapid transport of high concentrations of pesticide-colloidal complexes. The presence of a deep unsaturated zone will mean that most of the colloidal-complexes will be filtered by the narrow chalk pores and the majority of pesticide transport will occur in a 'dissolved' form through the more gradual 'piston-flow' route.

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confidence: 73%

“…In the very shallow unsaturated zone, just below the soil layer, Ireson et al (2006) found that at 0.4 and 1.0 m depth there tends to be a rapid increase in matric potential straight after the main rainfall events, which was followed by a more gradual recession, as the profile drained.…”

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confidence: 97%

The significance of colloids in the transport of pesticides through Chalk

Gooddy

Mathias

Harrison

et al. 2007

Science of The Total Environment

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“…Such a process is normally driven by a motive to meet certain research objectives (e.g. Wigmosta and Burges, 1997;Gilvear and Bradley, 2000;Hodgson et al, 2002;Ireson et al, 2006), but with consideration of the cost implications with regard to construction and acquisition of the various instruments and their maintenance. However, research catchments are typically established in uninhabited areas.…”

Section: Introductionmentioning

confidence: 99%

Establishment of a catchment monitoring network through a participatory approach in a rural community in South Africa

Kongo

Kosgei

Jewitt

et al. 2010

Hydrol. Earth Syst. Sci.

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The establishment of a catchment monitoring network is a process, from the inception of the idea to its implementation, the latter being the construction of relevant gauging structures and installation of the various instruments. It is useful that the local communities and other stakeholders are involved and participate in such a process, as was highlighted during the establishment of the hydrological monitoring network in the Potshini catchment in Bergville District in the KwaZulu-Natal Province, South Africa. The paper highlights the participatory establishment of a hydrological monitoring network in a small rural inhabited catchment, in line with the overall objective of the Smallholder System Innovations (SSI) research programme, to monitor hydrological processes at both field and catchment scale for water resources management research purposes. The engagement and participation of the Potshini community precipitated a learning opportunity for both the researchers and the local community on (i) the understanding of hydrological processes inherent in the catchment (ii) appreciating the inherent dynamics in establishing a catchment monitoring network in the midst of a community (iii) paradigm shift on how to engage different stakeholders at different levels of participation. The participatory engagement in the monitoring process led to appreciation and uptake of some of the research results by the Potshini community and ensured continued support from all stakeholders. This paper is of the view that the participation of the local community and other stakeholders in catchment monitoring and instilling a sense of ownership and management of natural resources to the local communities needs to be encouraged at all times. Success stories in water resources management by local communities can be realized if such a process is integrated with other development plans in the catchment at all forums, with due recognition of the social dynamics of the communities living in the catchment

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“…Groundwater movement in the unsaturated zone ofthe Chalk is primarily controlled by the nature of the porosity and is generally characterized by slow piston flow through the matrix and more rapid, although intermittent, bypass flow through fractures (Smith et al 1970;Foster 1975;Downing et al 1978Downing et al , 1993Gardner et al 1990;Mathias et al 2005;Ireson et al 2006Ireson et al , 2009. In any season, unsaturated zone conditions also depend on antecedent moisture and current weather conditions.…”

Section: Introductionmentioning

confidence: 99%

An early warning system for groundwater flooding in the Chalk

Adams

Bloomfield

Gallagher

et al. 2010

QJEGH

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An early warning system has been developed for groundwater flooding and trialled in the Patcham area of Brighton. It provides a fit-for-purpose approach for forecasting groundwater flood events in the Chalk and is capable of operating across longer time scales than had previously been possible. The method involves a set of nested steps or tasks. Initially, the catchment's response to recharge is determined and, using a representative hydrograph, a simple regression model that relates annual groundwater level minima and autumn and winter rainfall to subsequent annual maxima is developed. The regression model is then applied at the end of each summer recession using the observed annual minimum and estimates of winter rainfall to predict the following groundwater level maximum. Based on the results of this prediction a variety of steps may then be appropriate. Where the model predicts potentially high groundwater levels the frequency of groundwater level monitoring observations can be increased. A novel element of the method developed is the monitoring of changes in the matric potential of the unsaturated zone. Specific trigger levels to initiate either the next step of the method or promulgation of warnings of varying severity will be developed through experience of use of the system.

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Hydrological processes in the Chalk unsaturated zone – Insights from an intensive field monitoring programme

Cited by 63 publications

References 19 publications

The significance of colloids in the transport of pesticides through Chalk

The significance of colloids in the transport of pesticides through Chalk

Establishment of a catchment monitoring network through a participatory approach in a rural community in South Africa

An early warning system for groundwater flooding in the Chalk

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