In Douala, economic capital of Cameroon, annual rainfall and temperature from its meteorological station (latitude: 4o00'N;longitude: 9o43'E;elevation: 5.0 m) were obtained and analysed to investigate the impa...In Douala, economic capital of Cameroon, annual rainfall and temperature from its meteorological station (latitude: 4o00'N;longitude: 9o43'E;elevation: 5.0 m) were obtained and analysed to investigate the impact of climate variability on groundwater recharge. The climate shows a strong evidence of changes towards persistent weather conditions. The region is mainly characterized by a mean inter-annual temperature of 27.4oC and influenced by the mount Cameroon (4095 m in elevation). A recent decrease in mean annual rainfall occurred since 1982. The average annual rainfall which was 4200 mm with about 220 days of rainfall from 1917 to 1937 has moved to 4049 mm for the period 1937-1957, to 3826 mm for the period 1968-1988 and to 3619 mm for the period 1971-2001. Between, 1997 and 2007, the total number of days of rainfall has not exceeded 220 (193 days of rainfall in 1998 and 216 days of rainfall in 1999). By using Gauss law on 31 years (1971-2001) of annual rainfall, one note that the value 2850 mm has 20% of luck to be not observed and the value 4219 mm has 20% of luck to be exceeded. Douala already suffers from water shortage not because of decrease of rainfall but due to quality of underground water and salty taste of the main river catched for water supply. Moreover, precipitation is considered as the main replenishment source of all water resources in the study area (watershed of Besseke). The calculated interannual groundwater recharge rate (potential recharge, not necessarily real) is about 9% compared to the interannual total precipitation received by this area located closer the Atlantic Ocean (Gulf of Guinea). Groundwater discharge from the aquifer occurs between November and March.展开更多
A baseline study involving analyses of subsurface water samples from the Mingoa river basin (longitude: 11°30′E;latitude: 3°52′N) in migmatitic complex in Yaounde Cameroon (central Africa) was carried out ...A baseline study involving analyses of subsurface water samples from the Mingoa river basin (longitude: 11°30′E;latitude: 3°52′N) in migmatitic complex in Yaounde Cameroon (central Africa) was carried out to assess their suitability for drinking, domestic and agricultural purposes. Study results show that pH is ranged between 5.1≤ pH ≤ 5.8 and then, induces acidic waters. Groundwater samples are generally characterized by low conductivity values, of which 100% are within the range (55 ≤ EC ≤ 1500 μS/cm). The mean values of the major cations (Ca2+, Mg2+, Na+, K+) and anions (SO42– , Cl–, HCO3– ) are all within the World Health Organization (WHO) standards. Two of the springs sampled have nitrate (NO3– ) contamination. Even though contamination and acidic waters exist in some of the springs, the majority of the springs are excellent for agricultural and domestic purposes. Assessment of the groundwater for agricultural irrigation revealed two main categories. These are low salinity-low sodicity (C1-S1) and medium salinity-low sodicity (C2-S1), using the US Salinity Laboratory (USSL) classification scheme. As much as all of the samples plotted in the “excellent to good” and “good to permissible” categories on the Wilcox diagram. The groundwater in the study area may therefore be regarded as good for irrigation activities. The major identifiable geochemical processes responsible for the evolution of the various ions are mineral weathering, chemical reactions and anthropogenic activities.展开更多
文摘In Douala, economic capital of Cameroon, annual rainfall and temperature from its meteorological station (latitude: 4o00'N;longitude: 9o43'E;elevation: 5.0 m) were obtained and analysed to investigate the impact of climate variability on groundwater recharge. The climate shows a strong evidence of changes towards persistent weather conditions. The region is mainly characterized by a mean inter-annual temperature of 27.4oC and influenced by the mount Cameroon (4095 m in elevation). A recent decrease in mean annual rainfall occurred since 1982. The average annual rainfall which was 4200 mm with about 220 days of rainfall from 1917 to 1937 has moved to 4049 mm for the period 1937-1957, to 3826 mm for the period 1968-1988 and to 3619 mm for the period 1971-2001. Between, 1997 and 2007, the total number of days of rainfall has not exceeded 220 (193 days of rainfall in 1998 and 216 days of rainfall in 1999). By using Gauss law on 31 years (1971-2001) of annual rainfall, one note that the value 2850 mm has 20% of luck to be not observed and the value 4219 mm has 20% of luck to be exceeded. Douala already suffers from water shortage not because of decrease of rainfall but due to quality of underground water and salty taste of the main river catched for water supply. Moreover, precipitation is considered as the main replenishment source of all water resources in the study area (watershed of Besseke). The calculated interannual groundwater recharge rate (potential recharge, not necessarily real) is about 9% compared to the interannual total precipitation received by this area located closer the Atlantic Ocean (Gulf of Guinea). Groundwater discharge from the aquifer occurs between November and March.
基金supported by International Development of Research Center(IDRC).
文摘A baseline study involving analyses of subsurface water samples from the Mingoa river basin (longitude: 11°30′E;latitude: 3°52′N) in migmatitic complex in Yaounde Cameroon (central Africa) was carried out to assess their suitability for drinking, domestic and agricultural purposes. Study results show that pH is ranged between 5.1≤ pH ≤ 5.8 and then, induces acidic waters. Groundwater samples are generally characterized by low conductivity values, of which 100% are within the range (55 ≤ EC ≤ 1500 μS/cm). The mean values of the major cations (Ca2+, Mg2+, Na+, K+) and anions (SO42– , Cl–, HCO3– ) are all within the World Health Organization (WHO) standards. Two of the springs sampled have nitrate (NO3– ) contamination. Even though contamination and acidic waters exist in some of the springs, the majority of the springs are excellent for agricultural and domestic purposes. Assessment of the groundwater for agricultural irrigation revealed two main categories. These are low salinity-low sodicity (C1-S1) and medium salinity-low sodicity (C2-S1), using the US Salinity Laboratory (USSL) classification scheme. As much as all of the samples plotted in the “excellent to good” and “good to permissible” categories on the Wilcox diagram. The groundwater in the study area may therefore be regarded as good for irrigation activities. The major identifiable geochemical processes responsible for the evolution of the various ions are mineral weathering, chemical reactions and anthropogenic activities.
