A Water Allocation System for the Volta Basin:
The impact of agricultural and hydropower development on
the water resources of the basin.
Constanze Leemhuis, Barnabas Amisigo, Gerlinde Jung, Wilson Agyei Agyare,
Raymond Kasei, Tyler Frazier, Benjamin Kofi Nyarko, Nicos Perez, Anik Bhaduri, Jens Liebe
Climate, Land Use, Hydrology
Economics, Institutions, Stakeholders
Field Investigations
Processes of decision making and information flows
Land Conversion
Remote Sensing
Institutional Analysis
Instrumentation
Water Supply
Mesoscale Climate
Hydrology
Institutional Analysis
Integrated Basin Model
OUTLINE
•Agricultural and hydropower development
•The Volta Basin Water Allocation System (VB-WAS)
•Climate and Reservoir Scenarios
•Small and medium reservoir development
•Large reservoir development: The Bui Case
•Real time operational Water Management
AGRICULTURAL AND HYDROPOWER DEVELOPMENT
Ziga Reservoir
NIGER
Volume: 0.2 km³
2000
Lery Reservoir
MALI
Volume: 0.6 km³
1976
B
U
R
K
I
N
A
F
A
S
Bagre Reservoir
Volume: 1.7 km³
1992
O
BURKINA FASO
Small Reservoirs
Volume: 0.6 km³
Kompienga Reservoir
Volume: 2.0 km³
1984
Tono Reservoir
Volume: 0.1 km³
1980
BENIN
Bui Reservoir
Volume: 12.3 km³
IVORY COAST
2009/2010
lake
TOGO
Volta
Lake Volta
Volume: 148 km³
1964
GHANA
Small Reservoirs
Volume: 0.1 km³
G
H
A
N
A
Kpong Reservoir
Volume: 0.2 km³
1982
AGRICULTURAL AND HYDROPOWER DEVELOPMENT
•Climate variabilty has an impact on agricultural and hydropower
development and management in the Volta basin.
•In the 80s of the last century a series of spatial significant drought years
severly hit the socio-economy of the Volta basin.
1982
1983
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Yearly areal precipitation generated from observed meteorological station data.
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Value
(mm)
High : 2404
Low : 363
CLIMATE AND RESERVOIR SCENARIOS
The years of recurrent drought provoked structural food shortages and hunger.
Source: Phillipe Cecchi, SRP Tool Kit.
AGRICULTURAL AND HYDROPOWER DEVELOPMENT
minimum operational water level
•Awareness of the importance of the reservoir water level since
the mid 80`s.
AGRICULTURAL AND HYDROPOWER DEVELOPMENT
VRA Supply / Demand Balance Forecast
VRA Transmission Network
AGRICULTURAL AND HYDROPOWER DEVELOPMENT
Small & Medium Reservoirs:
Irrigation
Large Reservoirs:
Livestock
Fishery
Household
VOLTA BASIN WATER ALLOCATION SYSTEM
Volta Basin Water Allocation System (VB‐WAS)
Global climate model (GCM)
Estimated water demand
climate‐hydrological model
MM5‐WASIM
water supply
Historical demand
water demand
Historical
time series
small
1991‐2000:
and large reservoirs
1991‐2000
Library
of water
use
and demand scenarios
Global climate
Selection of time series:
change
surface
(IS92a) scenario
water
withdrawal
dry
normal 2030‐2039 wet
(Volta
Basin
DATA
BASE)
specific discharge
water use
River Basin Management Model
MIKE BASIN
water availability
multisectoral demand
ecosystem studies
infrastructure planning
Selection
of time series
or water use
scenario
Selection
of climate and policy
scenario
VOLTA BASIN WATER ALLOCATION SYSTEM
•Delineation of hydro-economic catchments for VB-WAS according to national
borders and large reservoir catchments.
NIGER
NIGER
MALI
MALI
R
B
U
R
K
I
N
A
F
A
S
K
O
I
N
B
A
U
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I
F
A
A
F
N
S
A
S
O
O
BENIN
IVORY COAST
TOGO
G
H
A
N
A
MM5/WASIM catchments
BENIN
IVORY COAST
TOGO
G
H
A
N
A
VB-WAS catchments
3000
Hydropower
2000
1000
0
215
²³
²³
220
225
230
235
240
²³
²³
²³
²³
²³
Water user per catchment
²³
²³
#
*
²³
²³
²³
²³
²³
²³
²³
!d
²³
²³
²³
²³
²³
²³
²³
•small reservoir abstraction
Water demand
[m^3/s]
Deficit carry-over fraction [()]
Groundwater use fraction [()]
Groundwater use absolute [m^3/s]
²³
60
²³
²³
²³
!d
²³
²³
²³
#
*
²³
#
*
40
²³
20
0
²³
1991
²³
´
50
1993
1994
1995
1996
1997
1998
²³
100
Kilometers
200
1999
2000
•surface water withdrawal
population density
access to safe water source
!d
#
*
0
1992
²³
²³
#
*
VOLTA BASIN WATER ALLOCATION SYSTEM
Area
[km^2]
Volume [10^6m^3]
Reservoir
!d
•large reservoir abstraction
large scale irrigation
plant discharge
simulated_water_level_lake_Volta
[m]
Simulated water level lake Volta
(m)
VRA_observed__water_level_lake_Volta
(m) [-]
VRA observed water level
(m)
ESA_observed_water_level_lake_volta
Satellite observed water level
(m) (m) [-]
80
75
1992
TSID 81257 - R41|Water level [m]
VOLTA BASIN WATER ALLOCATION SYSTEM
VB-WAS Validation period 1992-2000:
simulated vs. observed water level lake Volta
1993
1994
1995
1996
1997
1998
1999
2000
TSID 1071 - VRA_observed__water_level_lake_Volta (m) vs TSID 81257 - R41|Water level; Y = 0.798809 X + 16.2075 (R2 = 0.854); LOWESS fit (R2 = 0.858)
82.0
80.0
78.0
76.0
74.0
73
74
75
76
77
78
VRA_observed__water_level_lake_Volta (m) [-]
79
80
81
82
CLIMATE AND RESERVOIR SCENARIOS
1992
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A following dry year with an equal magnitude and coverage would have been devastating.
dry
below average
average
above average
wet
1992
2000
MM5-WASIM simulation 1992-2000
1992
2000
Dry year scenario 1992-2000
2030
2039
MM5-WASIM simulation 2030-2039
CLIMATE AND RESERVOIR SCENARIOS
Small and medium Reservoirs
Baseline Simulation:
Distributed small & medium reservoir development 1991-2000.
Historical Scenario:
No small & medium reservoir development .
Large Reservoirs: the Bui case
Bui 2 case:
183 m.a.s.l. full supply
73 m rated head
432 km² flooded area
Plant Capacity: 200 m³/s plant discharge
500 m³/s plant discharge
Bui reservoir after construction (plus Inundation period)
Operational Bui reservoir
(no Inundation period)
SMALL & MEDIUM RESERVOIR DEVELOPMENT
Small and medium reservoir scenario with MM5-WASIM simulation 1992-2000:
Baseline simulation vs. historical scenario (no reservoir development)
Stored volume lake Volta 1992-2000 baseline simulation
[10^6m^3]
Stored volume lake Volta 1992-2000 no small reservoirs in Ghana
[10^6m^3]
Stored volume lake Volta 1992-2000 no small reservoirs in the Volta basin [10^6m^3]
140000
120000
100000
80000
1992
1993
1994
1995
1996
1997
1998
1999
2000
No reservoirs simulation vs. no reservoirs + dry years scenario
Stored volume lake Volta 1992-2000 no small reservoirs
[10^6m^3]
Stored volume lake Volta 1992-2000 no small reservoirs + dry years scenario [10^6m^3]
140000
120000
100000
80000
1992
1993
1994
1995
1996
1997
1998
1999
2000
SMALL & MEDIUM RESERVOIR DEVELOPMENT
•The impact of the small and medium reservoir development amounts to a
loss of storage of lake Volta of about 6 km³ for the time period 1992-2000.
•For the period 1992-2000 the simulated yearly inflow to lake Volta
was highly variable (11 – 59 km³).
•Climate variabilty, like e.g. a sequence of two dry years causes severe
storage losses of lake Volta.
•The impact of small and medium reservoirs on the water resources of the
Volta basin is marginal compared to their benefit of securing food
production during the dry period.
LARGE RESERVOIR DEVELOPMENT: THE BUI CASE
Impact of operational Bui reservoir on lake Volta storage with inundation period
(MM5-WASIM simulation1994-2000).
Stored volume lake Volta 1994-2000
[10^6m^3]
Stored volume lake Volta 1994-2000 with Bui 200 m³/s plant discharge [10^6m^3]
Stored volume lake Volta 1994-2000 with Bui 500 m³/s plant discharge [10^6m^3]
140000
120000
100000
80000
1994
1995
1996
1997
1998
1999
2000
Impact of operational Bui reservoir on lake Volta storage without inundation period
(MM5-WASIM simulation 2034-2039).
Stored volume lake Volta 2034-239
[10^6m^3]
Stored volume lake Volta 2034-239 with Bui reservoir 200 m³/s plant discharge [10^6m^3]
Stored volume lake Volta 2034-2039 with Bui reservoir 500 m³/s plant discharge [10^6m^3]
140000
120000
100000
80000
2034
2035
2036
2037
2038
2039
LARGE RESERVOIR DEVELOPMENT: THE BUI CASE
•The mean annual evaporation of the Bui reservoir amounts to 55 Mm³
(0.05 km³) for the period 1996-2000 with a projected plant discharge of
500 m³/s.
•The Volta basin Water Allocation System (VB-WAS) is a suitable tool to
predict the impact of climate variability on the reservoir performance and
supports decisions on reservoir management.
•A jointly sustainable management of the Akosombo and Bui hydroplants
is required to reduce the short term impact of climate variability on the
reservoirs performance.
REAL TIME OPERATIONAL WATER MANAGEMENT
Real time measurements are needed for operational water management:
•A data driven modelling framework generating streamflow data from climate
data with nonlinear-linear modelling:
HYBRID METRIC-CONCEPTUAL (HMC) CATCHMENT MODEL
•Network of five hydrological gauging stations that are equipped with
satellite transmission systems (Argos) in cooperation with the
Hydrological Service Department Ghana (HSD):
HYDRO ARGOS HYDROLOGICAL MONITORING SYSTEM
CONCLUSIONS
Volta basin Water Allocation System (VB-WAS)
• Introduce real time discharge data for operational watershed management.
• Powerful tool for watershed management considering the impact of
climate variability.
•Coupled to a dynamic hydrological-economic model (M³ Water) for water
policy scenario analysis.
•Accounts for national water management strategies and can be used as a
supportive tool for transboundary water management.
Eva Youkhana
Sven Wagner
Irit Eguavoen
Sonabel Burkina Faso
Jan Friesen
Nick van de Giesen
Ghana Meteorological Agency
Hydrological Service Ghana (HSD)
Volta River Authority (VRA)
Gerald Forkuor
Bruno Barbier
Julia Eyring
Philippe Cecchi
Boubacar Barry
Wolfram Laube
Antonio Rogmann
Almut Brunner
Charles Rodgers
Thank you very much for your attention!!!
Je vous remercie de votre attention!!!