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