Presented by IWMI researcher, Marloes Mul, on the Re-optimization and reoperation study of the Akosombo and Kpong dams - Ghana, August 2015. Presented during a stakeholder a workshop held in Accra to explore the potential positive and negative impacts of changing flows.

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

2. RE-OPTIMIZATION AND REOPERATION
Improving livelihood of people living downstream of
Akosombo and Kpong that were affected by
construction of the two dams through:
• Re-operating dams
– Releasing flows to improve ecosystems downstream
– Considering impact on downstream developments in the
floodplains
– While increasing hydropower production (hypothesis)
• Supporting downstream livelihoods
Q2: What will be the impact of
releasing these flow requirements on
- Infrastructural developments in the
floodplains affected by releasing
flood peaks
- Intakes affected by increased
saltwater intrusion
- …
 Feasible operation scenarios

3. RESTORATION HYDROGRAPH WORKSHOP
• Objectives
– Establish flow targets for Akosombo and Kpong dams
• Establish flow targets for different components
– Fisheries
– Aquatic weeds
– Agriculture
– Health
– Groundwater
– Sediments
• Combine targets into flow scenarios

4. CONSTRUCTING HYDROGRAPHUser
groups/is
sues
Step 1 Step 2 Step 3
From interviews and data, form
“ideal” hydrographs for various
ecological and agricultural processes
Combine to form
“signature” hydrograph for
each user group/issue
Combine to form “overall” monthly “ideal restoration”
hydrograph with monthly ranges – overlay historical and
current hydrographs and physical limits (dashed lines) imposed
by dam/hydro structures and electric power base load etc.
Fish
Weeds
Clams
Disease
Agriculture
Structures

5. ESTABLISHING FLOW TARGETS
sues From interviews and data, form
“ideal” hydrographs for various
ecological and agricultural processes
Combine to
“signature”
each user g
Fish
Weeds
Clams
Disease
Agriculture
Structures
• Examples
– Hydrology-based
• Percentage of flow
• Minimum flow requirement
– Field based experiments
• Detailed fieldwork
– Expert opinion
• Comparison of pre- and post dam situations
• Using proxies to estimate responses

6. ESTABLISHING FLOW TARGETS
• Hydrology based approach (using Global Environmental Flow
Calculator)

7. ESTABLISHING FLOW TARGETS
PRE- AND POST DAM ACTIVITIES
Pre-dam
Post-dam

8. ESTABLISHING FLOW TARGETS
• Expert opinion (examples)
– Estimating water demands (Discharge, [m3/s])
• Domestic water use
• Irrigation water requirements
– Flood requirements (Location, Water level/ peak [m], Duration)
• Spawning grounds
• Flood recession agriculture
– Flow velocity ([m/s])
• Flushing aquatic weeds
• Sediment transport (unblocking sand bar, flushing sediments into the sea)

9. ESTABLISHING FLOW TARGETS
• Expert opinion (examples)
– Low flow requirements (Saltwater intrusion length [m])
• Clams
• Brackish water fish
• Intakes for domestic water use
• Aquatic weeds
– Water level (Location [m])
• Intakes for irrigation
• Intakes for domestic water use
– Water level fluctuations (Location, Δ[m])
• Bilharzia snails
• Aquatic weeds

10. ESTABLISHING FLOW TARGETS (DAY 2)
• Combining individual flow targets
into restoration hydrographs
– Prioritization/ scoring of different
components
– Identify targets that are in agreement
with each other
– Identifying conflicting targets (trade-
offs)
– Develop 3-5 different scenarios aiming
for different objectives (eg irrigation vs
fisheries)
by dam/hydro structures and electric power base load etc.
Fish
Weeds
Clams
Disease
Agriculture
Structures

11. ESTABLISHING FLOW TARGETS (DAY 2)
• Combining individual flow targets
into restoration hydrographs
– Identifying key targets for each
scenario
• Peak flow target
• Dry season flow target
by dam/hydro structures and electric power base load etc.
Fish
Weeds
Clams
Disease
Agriculture
Structures

12. ESTABLISHING FLOW TARGETS (DAY 2)
• Estimating ecosystems response
to selected restoration flow
hydrographs
– Quantitatively or qualitatively
• Absolute values per scenario (fish
catch, $ revenue, yield, …)
• Relative values (compared to base
case, x times)
• Qualitative indicators (++, +, +/-, -,--)
– Estimating damages/ sectors affected
• Prioritization of flow scenarios
by dam/hydro structures and electric power base load etc.
Fish
Weeds
Clams
Disease
Agriculture
Structures

13. PROGRAMME DAY 1
time topic institution
DAY 1 Establishing environmental requirements per each sector
8:30-8:40 Welcome and introduction WRC
8:40-9:00 Introduction and scope of the workshop IWMI
9:00-9:30 Outcomes of community consultations
Quantification of restoration objectives
CAW
9:30-10:30 Fish
- River fish
- Clams
- Aquaculture
WRI
10:30-11:00 Coffee break
11:00-12:00 Aquatic weeds WRI
12:00-12:30 Health
- Schistosomasiasis
- Malaria
IESS
12:30-14:00 Lunch
14:00-15:00 Agriculture
- Flood recession farming
- Irrigation
IWMI
15:00-15:30 Groundwater WRI
15:30-16:30 Sediments
16:30-17:00 Conclusion day 1 WRC/IWMI

14. PROGRAMME DAY 2
DAY 2 Constructing restoration hydrographs
8:30-8:40 Welcome back WRC Ben Ampomah & Eric Ofosu
8:40-9:00 Presentation of selected scenarios for
restoration flow
IWMI Marloes Mul
9:00-10:40 Discussion of flow scenarios (20min each)
- Key targets and indicators
- Impact on different sectors
Facilitation
by IWMI
Thor Windham-Wright
10:40-11:00 Coffee break
11:00-12:30 Estimation and quantification of impact per
sector per scenario
Facilitation
by IWMI
Thor Windham-Wright
12:30-14:00 Lunch
14:00-15:00 Way forward
- Information gaps to be addressed
Facilitation
by IWMI
Thor Windham-Wright
15:00-15:30 Conclusion day 2 WRC/IWMI

15. Thank you for your attention
Thor Windham-Wright