Abstract:Monitored groundwater level data, well logs, and aquifer data as well as the relevant surface hydrological data were used to conceptualise the hydrogeological system of the Densu Basin in Southern Ghana. The objective was to numerically derive the hydraulic conductivity field for better characterization of the aquifer system and for simulating the effects of increasing groundwater abstraction on the aquifer system in the basin. The hydraulic conductivity field has been generated in this study through model calibration. This study finds that hydraulic conductivity ranges between a low of 2 m/d in the middle sections of the basin and about 40 m/d in the south. Clear differences in the underlying geology have been indicated in the distribution of aquifer hydraulic conductivities. This is in consonance with the general assertion that the hydrogeological properties of the aquifers in the crystalline basement terrains are controlled by the degree of fracturing and/or weathering of the country rock. The results suggest that the system will not be able to sustain this level of abstraction as it would lead to a basin wide drawdown in the hydraulic head by 4 m by the end of the prediction period. It further suggests a safe annual increment in groundwater abstraction by 5% under business as usual recharge conditions. Identification and protection of groundwater recharge areas in the basin are recommended in order to safeguard the integrity of the resource under the scenario of increased abstraction for commercial activities in the basin.

provided a training program in Japan within a SATREPS project to three Ghanaian hydrologists on discharge measurement by using an image analysis software KU-STIV, developed at Kobe University for flow measurement. Then, three delegates from the Kobe University, Japan visited Ghana to actually measure stream flows at three rivers stations on the Densu River basin in Ghana. The flow measurements are carried out by using two techniques, KU-STIV and Vale-port current meter. The measured discharges were very small, less than or equal to 1m 3 /s. The maximum relative measurement error between the two methods is roughly about twenty percent so that it is acceptable considering the measurement condition at the site. The paper briefly summarizes the usefulness of discharge measurement by an image analysis technique to avoid the risks of field measurements in African regions.

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