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Re-optimization and
reoperation study of the
Akosombo and Kpong dams
Dr Marloes Mul
Thor Windham-Wright
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
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
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
ESTABLISHING FLOW TARGETS
User
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
• 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
ESTABLISHING FLOW TARGETS • Hydrology based approach (using Global Environmental Flow
Calculator)
ESTABLISHING FLOW TARGETSPRE- AND POST DAM ACTIVITIES
Pre-damPost-dam
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)
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
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)
User
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
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
User
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
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
User
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
PROGRAMME DAY 1time 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
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
Thank you for your attention
Thor Windham-Wright