Presented by IWMI researcher Marlos Mul on potential flow scenarios for of reoptimization and reoperation of the Akosombo and Kpong dams (Ghana). Presented during a stakeholder workshop held in Accra, August 2015, to explore the potential positive and negative impacts of changing flows.

1. Re-optimization and
reoperation study of the
Akosombo and Kpong dams
- Scenario selection
Dr Marloes Mul
Thor Windham-Wright

2. Scenario 1 current flow regime
• Optimising baseload
hydropower generation
• Minimum flow fluctuations
• Average flow of 1,000 m3/s

3. Scenario 2&3 Environmental Management
Classes A & B
• Statistical approach using GEFC
• EMC A: Natural rivers with minor
modification of in-stream and
riparian habitat
• EMC B: Slightly modified and/or
ecologically important rivers with
largely intact biodiversity and
habitats despite water resources
development and/or basin
modifications
Realistic scenarios?
What are the impacts of different
sectors?

4. Scenario 4 Weeds control and fishery
production
• Weeds control through
• Reintroducing saltwater gradient
• Increasing flow velocity
• Fishery production increment
• Clams – increase saltwater intrusion
• Freshwater fish – increase flooded area
during wet season
• Maximize saltwater intrusion during
dry season
• Maximize flood peaks during Sep-Oct
• Gradual transition between seasons
• Total flow is less than natural flow
because of Evap losses of the lake

5. Scenario 4 Weeds control and fishery
production
flow targets/levels correct
dry season
wet season
Additional things to consider in cost-
benefit analysis:
- Breaking sandbar
- Continual manual removing of weeds
(necessary?)
- Moving of intakes
- Protect valuable infrastructure along the
river
- Impact on irrigation

6. Scenario 5 Irrigation optimisation
• Provide sufficient water for
irrigation activities during dry
season
• Provide sufficient water during
dry season so that saltwater
intrusion is not affecting other
water users (intakes)
• Compensated by increment of
wet season flow to benefit
fisheries and other sectors

7. Scenario 5 Irrigation optimisation
flow targets/levels correct
dry season
wet season
Things to consider in C/B analysis
• Protect valuable properties
• Manual removal of weeds

8. Scenario 6 Spilling levels 2010
• Wet season levels at 2010
spillway levels (confirm
discharge from VRA)
• Drawing from knowledge of the
spill and current low flows
(confirm discharge from VRA)

9. Discussion
• For each scenario
• Confirm/estimate flow targets
• Dry season
• Wet season
• Identify impact on (sub-)sectors
• Compared to current or past
situation
• Identify issues/potential conflicts
• Additional measures required

10. Final discussion
• Summarize impact of all scenarios on different (sub-) sectors
Qualitative
• Quantitative Weed Fish Agric Health GW Sed Other
w1 w2
Sc1
Sc2
Sc3
Sc4
Sc5
Sc6
++ very good
+ good
+/- neutral
- bad
-- very bad
Voting on feasibility of scenarios and
selection of scenarios for modelling