Groundwater quality issues

NOTE - change page name to Groundwater Quality

Groundwater quality is usually naturally good. This is not always the case: there are a few natural chemicals that can be present in groundwater at quantities that are harmful to health. Groundwater is also naturally more protected from contamination than surface water, because of the natural filtration through geological materials. But groundwater can be naturally vulnerable to contamination in some hydrogeological environments - such as springs, or highly permeable shallow aquifers - and can be made vulnerable by the construction methods used to access groundwater sources - such as open wells.

The following provides a brief summary of some of the key groundwater quality issues across Africa, and links to more information elsewhere.

A detailed review of groundwater quality issues in Africa can be found in:

Xu Y and Usher B (eds). 2006. Groundwater pollution in Africa. Taylor & Francis/Balkema, Netherlands.

Geogenic Contamination

Geogenic contamination refers to naturally occurring elevated concentrations of certain elements in groundwater which have a negative health effect on humans consuming this water. Geogenic contamination of groundwater might be a result of geochemical characteristics of the aquifer material - e.g. high concentrations of the contaminant in the rock matrix, dissolving during water-rock interaction - or might occur due to environmental conditions such as an arid climate or reducing conditions in the aquifer which facilitate the contaminant to occur in a more mobile state.

The most wide-spread geogenic contaminants are arsenic and fluoride, affecting the health of hundreds of millions of people worldwide. Others include selenium and uranium.

The Swiss aquatic research organisation Eawag has produced a Geogenic Contamination Handbook and a series of global and regional probability maps of arsenic and fluoride contamination in groundwater.

Further information on the methodology for developing these maps can be found in the following publications:

Amini M, Mueller K, Abbaspour KC, Rosenberg T, Afyuni M, Moller KN, Sarr M, Johnson A. 2008. Statistical Modeling of Global Geogenic Fluoride Contamination in Groundwaters. Environmental Science and Technology, 42, 3662-3668.

Amini M, Abbaspour KC, Berg M, Winkel L, Hug SJ, Hoehn E, Yang H, Johnson A. 2008. Statistical Modeling of Global Geogenic Arsenic Contamination in Groundwater. Environmental Science and Technology, 42, 3669-3675.

IGRAC provides resources on arsenic and fluoride in groundwater worldwide, including information on their geological sources; the probability of their occurrence in groundwater; maps of known areas of high concentrations; treatment methods; and references for more information. IGRAC also provide the IAH publication Arsenic in Groundwater: a world problem as a free download.

UNICEF has produced an Arsenic Primer, with guidance for UNICEF country offices on the investigation and mitigation of arsenic contamination.

BGS and WaterAid have produced short fact sheets on arsenic and fluoride in groundwater.

Salinisation

Groundwater salinisation can occur near coasts by seawater intrusion, or anywhere due to the effects of irrigation. It is a significant problem in many coastal areas of Africa, particularly in areas of higher population density and/or agriculture.

IGRAC have produced a series of global maps of groundwater salinity.

Agricultural Pollution

With the increasing intensity of agriculture in many parts of Africa, including the use of artificial fertilisers, more intensive livestock farming, and enhanced irrigation, agricultural pollutants are beginning to impact in groundwater in some areas. So far the impacts are not widespread, but are likely to grown in future.

WaterAid/BGS provide a factsheet on The Impact of Agriculture on groundwater

Nitrate in groundwater

Nitrate is a significant groundwater pollutant in Europe, largely derived from intensive agriculture. Nitrate can be present naturally in groundwater in arid and semi-arid areas, as a result of enhanced evaporation. It can also derive from inadequate sanitation, particularly in larger villages, towns and cities. Agricultural sources of nitrate in groundwater include artificial fertilisers and animal slurry. Nitrate pollution is not widespread in Africa, but occurs locally, both in rural and urban areas.

IGRAC have produced a map Further information on global nitrate occurrence can be found at IGRAC's website.

Urban Pollution

Groundwater pollution is a major issue in many cities and fast growing towns across Africa. The rapid growth of urban areas without suitable municipal water supply and sanitation can lead to widespread contamination of groundwater below urban areas, while at the same time an increasing number of people relying on urban groundwater for water supply. 'Traditional' pollutants such as microbiological contaminants deriving from inadequate sanitation are widespread, but increasingly so are inorganic and organic chemical contaminants, and 'emerging' contaminants such as pharmaceutical drugs.

Useful references for more information on urban groundwater quality issues are:

Lapworth DJ, Stuart ME, Pedley S, Nkhuwa DCW & Tijani MN. 2014. A review of urban and peri-urban groundwater quality studies in sub-Saharan Africa. British Geological Survey (Report Number)

British Geological Survey/WaterAid. 2008. Groundwater Information Sheet: The Impact of Urbanisation on Groundwater Quality. Leaflet.

Grounndwater Quality Monitoring

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