THIS ARTICLE IS A CASE STUDY OF HISTORICAL PROJECTS HYDROSOLUTIONS HAVE WORKED ON.
NATIONAL RIVERS AUTHORITY UK (now ENVIRONMENTAL PROTECTION AGENCY):
National Groundwater Protection Policy- Determination of Groundwater Protection Zones, 750 Public Water Supply sources, throughout England and Wales.
Groundwater protection zones (GPZ’s) were developed for 750 public water supply groundwater sources as
part of the National Groundwater Protection Policy for England & Wales. A consistent methodology was
developed for each source. A data request proforma was used to obtain hydrogeological data from regional water authorities. The quality of data was evaluated and a decision made on the most appropriate method to delineate the GPZs. Like sources/locations were grouped where possible.
Analytical methods were used initially to provide a simple check on the catchment & time of travel zones
using recharge estimates. The analytical result was adopted for sources with poor data quality. GPZ for
sources with intermediate data quality were determined using the USEPA computerised analytical model
WHPA (“Well Head Protection Area”) using backward particle back-tracking methods.
Sources with ‘good’ data were analysed using the numerical finite difference model FLOWPATH (WHI). A hydrogeological conceptual model was developed & agreed, which was represented as a numerical flow domain. The following isochrone & catchment zones were defined:
- The 50-day (inner) protection zone (biological & sanitary protection)
- The 400-day (outer) protection zone (response zone in the event of a contaminant release to the aquifer
- Total catchment zone: Steady state based on recharge estimates.
A standardised report was produced for each group of sources, including:
- All data & evaluations
- Analytical determinations
- Numerical model & source codes/files
- Time of travel & total catchment maps as Geographical Information System (GIS) files
Stuart Jeffries
Hydrosolutions Pty Ltd
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via Hydrosolutions | Groundwater and Environmental Consultants http://hydrosolutions.com.au
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