地理情報学と地球統計学: 概要

Dug-Well Biological Water Quality in Kumba-Cameroon: GIS Evaluation and Seasonal Variation of a Pollution Indicator

Akoachere Richard Ayuk and Ngwese Yolande Mesode

Kumba (latitudes: 4°36‟- 4°40‟, longitudes: 9°23‟- 9°29‟), the economic capital of the Southwest Region - Cameroon, is located along the Cameroon Line at the northwestern edge of the Douala Basin. Dug well water is the major source of water in Kumba. Consumption of water contaminated by human and animal excreta is the greatest risk to public health from microbes that cause waterborne diseases and having the capacity to cause simultaneous infections on a large number of people. Safe drinking water is required for the development of any country. Field tests for physical parameters in ten dug wells was carried out for; total dissolved solids, electrical conductivity, pH, depth to water levels measured and forty (ten per hydrogeological season) water samples collected. Coliform in forty well water samples was enumerated by presumptive laboratory tests to assess biological water quality. Seasonal field and laboratory test results were mounted on GIS platforms and the spatial variations determined. The ‟Most Probable” Number of coliform per 100 ml in all the dug well water samples is far above the WHO standards for drinking water. 10-20% of the wells are suitable only for primary contact and 80-90% are grossly polluted by potentially harmful microorganisms with relatively greater pollution indicated in the wet seasons than the dry seasons. This is probably due to: a) The wet seasons: Shallow water levels, poor well construction, dumpsite leachates, septic tanks, animal feedlots, contaminated streamlets and surface run-off flow into wells. b) Dry seasons: Water stress and scarcity leading to increased frequency and number of users of non-dry dug wells‟ abstraction and increase of poor sanitary conditions (unclean abstraction utensils) in/ around wells.