24 research outputs found
Validation of an intrinsic groundwater pollution vulnerability methodology using a national nitrate database.
The importance of groundwater for potable supply, and the many sources of
anthropogenic contamination, has led to the development of intrinsic groundwater
vulnerability mapping. An Analysis of Co-Variance and Analysis of Variance are
used to validate the extensively applied UK methodology, based upon nitrate
concentrations from 1,108 boreholes throughout England and Wales. These largely
confirm the current aquifer and soil leaching potential classifications and
demonstrate the benefits of combining soil and low permeability drift
information. European legislation such as the Water Framework Directive will
require more dynamic assessments of pollutant risk to groundwater. These results
demonstrate that a number of improvements are required to future intrinsic
groundwater vulnerability methodologies. The vertical succession of geological
units must be included, so that non-aquifers can be zoned in the same way as
aquifers for water supply purposes, while at the same time recognising their
role in influencing the quality of groundwater in deeper aquifers.
Classifications within intrinsic vulnerability methodologies should be based
upon defined diagnostic properties rather than expert judgement. Finally the
incorporation into groundwater vulnerability methodologies of preferential flow
in relation to geological deposits, soil type and land management practices
represents a significant, but important, future challenge
A decision tree tool supporting the assessment of groundwater vulnerability.
The Water Framework Directive and Groundwater Directive aim at preserving and improving the groundwater status. Groundwater bodies are classified as being or not being at risk of failing to meet these objectives. Those at risk are subject to more precise risk assessment where the concept of vulnerability is considered in the pathway part of the source–pathway–receptor scheme. However, no further details on implementation strategies are provided. In order to support groundwater managers and decision-makers in implementation of programs protecting groundwater, a systematic operational approach based on a decision tree is proposed, which leads the user through the stages of vulnerability assessment. First, a problem has to be formulated related to a threatening of the quantitative and/or qualitative status of a groundwater body. Next, the stated problem needs to be related to the intrinsic or specific vulnerability. Methods used for the intrinsic vulnerability assessment belong to two categories: subjective rating and objective methods. Method selection depends primarily on: data availability, knowledge and available resources. A key issue is the lag time associated with transport between a source/event of contamination and the water body. This lag time is primarily controlled by the temporal scale of water flow. It provides information about flow processes and at the same time also about timescales required for the implementation of strategies. Effects of any measures taken cannot be observed immediately but at the earliest after these estimated lag times emphasizing the need to also proactively safeguard groundwater resources and preserve their good status