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Project title: Hydrological study of the Korle lagoon, Accra, Ghana Summary: The inflow to the Korle lagoon in Ghana was studied to estimate the effects of urban runoff..
Client: Government of Ghana. Financed by: OPEC special fund
Period of assignment: 1997 Location: Ghana
Project Value: $3 000 000 WRA services: Short term specialised consultancy.
In co-operation with: Tractebel, Belgium  

 

 

 

 

Simulated flow with different parameters

Simulated flow with different parameters

 

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.

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.
  • 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.