GUIDELINES FOR A POLLUTION MONITORING AND EARLY WARNING NETWORK

THE VULNERABILITY OF AFRICA'S SURFICIAL AND GROUNDWATER AQUIFERS TO URBAN POLLUTION

GUIDELINES FOR A POLLUTION MONITORING AND EARLY WARNING NETWORK

The countries involved in the project first submitted hydrogeological and hydrochemical data on pollution progression in their urban centres at a workshop on groundwater mapping held in Ouagadougou in June 1998. It is intended that the progressive stages of this project will effectively serve as technical guidelines for a comprehensive information network for the future monitoring of groundwater vulnerability in all West African cities.

For technical reasons, any organisation involved in evaluating urban pollution pressures on surficial aquifers that are in contact with aquifers tapped for drinking water should identify one or several sites where reliable data is available and should be comparable to hydrologically stable control zones. The following activities and information are necessary in the establishment of a control zone:

An objective evaluation of surface or other pollution through a Vulnerability Map;
Knowledge of the unsaturated zone affected by wastewater, including the status of observation wells and boreholes;
A strong understanding of the hydrogeology (underflows) in the aquifers under study;
Knowledge of recharge phenomena (rainfall), to be processed alongside local meteorological data;
A regularly updated database comparing the evolution of local urban development with the presence and concentration of one or several pollutant sources (based on water analyses);
Interpretation of such data for the production of reliable Early Warning Bulletins;
Dissemination of national, regional and sub-regional Early Warning Bulletins.

The sustainability of the project’s activities should be guaranteed by the production and dissemination of a quarterly Early Warning Bulletin in each participating country. In terms of dissemination, a website (at http://www.unep.org/groundwater/English/GWhmEng/GwPhase2/Archive/Archive.html) has been launched, which was initially supervised in Dakar, Senegal, in connection with UNEP/UNESCO/UN-HABITAT and ECA, but has now been transferred to UNEP Headquarters in Nairobi.

With regard to each country’s technical capabilities and environmental contexts, it has been necessary to file data in several formats according to their different measurements and scales. Special attention has been focussed on the sampling process in order to pave the way for more standardised usage of the Early Warning system. It is important to realise that the observation wells sampled in each location will not meet the expected criteria of many other developed countries, in terms of their number, the quality of their management, or the diversity and extent of their pollution sources.