摘要：The pollution generated by
human activities in the area “Vridi canal-Grand Bassam” puts more at risk the
quaternary groundwater that supplies water to a large part of the population of
the southern part of Abidjan city. This paper deals with the combined approach
of geographic information systems and multicriteria analysis to delineate areas
at risk of pollution of groundwater in the study area. The multicriteria
analysis also incorporated the statistical and geostatistical techniques for
defining the factor ratings and weightings of all the parameters under a GIS
environment. The criterion for these factor
ratings and weightings was the correlation
coefficient of each parameter with the nitrates concentration in groundwater. Two indicators were
combined for creating situations of pollution risks according to their
importance: the intrinsic vulnerability indicators which combined the depth to
groundwater, the net recharge, the slope, the soil media, the unsaturated
hydraulic conductivity and extrinsic vulnerability characterized by the land
use. The results showed that all to the site presents nitrate pollution risks
with 50.7% of moderate risk, and 49.3% of high and very high risks. The areas
which present the highest risks of pollution are the densely urbanized communes
of Treichville, Marcory, Koumasi, Port-Bouet and Grand-Bassam. The sensitivity
analysis indicates that parameters causing high sensitivity on the nitrate
pollution risks map are the depth to groundwater and the recharge. The errors
committed on the maps establishment are ±0.15%, ±0.40% and ±6% respectively for IV map, EV map and pollution risk map.
