STUDY OF SALINISATION IN SHALLOW AQUIFERS IN THE ADA EAST-WEST DISTRICTS OF GHANA

摘要

The paper examines the extent and levels of groundwater salinisation in shallow aquifers in the Ada East-West districts of Ghana and possible causes. The samples comprise 11 surface water samples and 37 shallow wells which served as sources of water for the local communities. TDS values in well samples varies from 87.5 to 5160 mg/l with mean value of 1912 mg/l, in lagoon samples from 6350-27100 mg/l, with mean 13506.7 mg/l, in the Volta River from 42.4-165mg/l with a mean of 93mg/l, and in stream samples from 38.4-669mg/l with a mean of 217.5mg/l. Salinity values across the area is in the range from 33.8-43574psu/ppm with mean value of 2451psu/ppm. Among the major ions C1 values range between 2 and 46636.9 mg/l with mean value of 1858 mg/l whilst Ca range from 5.3 -1089.3 mg/l with mean of 107.2 mg/l. River Angor in Dendo and sampled stream in Kodzi has exceptionally high conductivity values compared to the other sampled rivers and streams. Groundwater salinity overall, increases from north to south and away from the Volta River in the direction east towards the Songhor lagoon in the study area. Less saline groundwater and streams are recharged from the Volta River. Between the high saline and low saline groundwater is suspected mixing zone of groundwater with average salinity value of 2451psu/ppm. Groundwaters are generally fresh to brackish in study area using TDS as classification. The salinity in the shallow aquifers is a result of evaporation, diffusion and mixing of coastal water.