Water Resource Associates
A network of consultants in water resources, water quality, hydrology, hydrogeology and flooding.
Hydrological study of the Korle Lagoon, Accra, Ghana
The inflow to the Korle lagoon in Ghana was studied to estimate the effects of urban runoff from the city of Accra.
Background
The Korle lagoon receives virtually all the runoff from the city of Accra, Ghana. As a result it is heavily polluted. In particular a lot of material carried into the lagoon in floods is deposited there. The lagoon is only a short distance from the sea and could be a valuable environmental resource if its water quality could be improved.
Simulated flow with different parameters
Location of Korle Lagoon and Catchment
Scope of work by Water Resource Associates Ltd
WRA provided a senior hydrologist at the start of the project to advise a team of three hydrologists from Tractebel on a suitable approach to adopt. The work covered three main areas:
- Assessment of flood rainfall for given return periods;
- Determination of parameters to be used for calculation of inflows;
- Development of a model of urban flooding to test parameter sensitivity..
Results
During the short study useful guidelines were developed in all three areas:·
- A methodology to maximise use of recent rainfall data in conjunction with a statistical rainfall model developed earlier was produced.
- Advice was given on critical factors in modelling the drainage basin.
- It was found the time of concentration and shape of the rainfall profile were very important but the impermeable proportion had less effect.