Low Flow Characterization of a Coastal River in Ghana

2012

English

Various probability distribution functions including Normal, Lognormal, Weibul, Gumbel and Gamma distributions were fitted to the mean daily low streamflows for the coastal river Ayensu in Ghana to characterize the low flow regime of the river. The Normal and Gumbel distributions produced the best fit with NSE equaled to 99.17% and 99.19%, respectively. A Flow Duration Curve was developed and used to determine the minimum flow threshold for the Ayensu River using mean daily streamflow series at Okyereko gauging station. Results showed that streamflow in the basin at Okyereko had little tendency to produce unusual extreme low flow with the minimum flow threshold value of 0.20 m³/s which is equaled or exceeded 95% of the time. The probability of occurrence of low extreme flows in the basin is low and that water abstraction in terms of use for water supply for domestic, industrial and agricultural requirement is considered reliable and sustainable.

Bekoe, E. O.; Logah, F. Y.; Kankam-Yeboah, K.; Amisigo, B.