Management of Rainwater and Small Reservoir for Multiple Uses

Hydrological Modeling-CPWFV303th-05th july , 2012

Presented byFrank ANNOR, KNUST-TUDelftFOWE TAZEN, 2iE Foundation

SCIENCE WORKSHOP : Volta Basin Development Challenge of the CPWF

Annual reflection meeting

Andes • Ganges • Limpopo • Mekong • Nile • Volta

Presentation Outline1. Background2. Methodology

i. Instrumentationii. Modeling

3. Initial Results4. Way forward


Morphometric characteristics of Boura catchment

Surface area (km²) : 155.3Perimeter (m) : 59.6Compactness index : 1.34Mean elevation (m) : 300Specific elevation(m) : 37.24Mean slope (m/km) : 3.4%Global slope index(m/km) : 4

Morphometric characteristics of Binaba catchment

Surface area (km²): 11.8Perimeter (m) : 14.6Compactness index : 1.2Mean elevation (m) : 225Specific elevation (m) : 23.80Mean slope (m/km) : 0.35%Global slope index (m/km) : 6.9

Background


Background× No hydrological monitoring

– Boura and Binaba watersheds are ungauged

• No records of streamflow, evaporation, water level etc

• Difficult to calibrate a hydrological model in the basin at a small watershed without these records

× Management (allocation) of water has not been streamlined especially for the dry season

Objectives Physical and hydrological

characterization of watersheds of both sites

Building of the monthly streamflow time series

Establish the water budget of each reservoir

Determine the heat balance of the reservoir

Model GW-SW interactions


2IE Developing a Hydrological model

(Yates, GIRARD & GR2M) Developing a water allocation

model using WEAP at a smaller watershed level (Boura and Binaba) using the water balance Water Use Other components of the water

balance i.e Runoff, P,ET, etc

TU-Delft Evaporation and seepage losses

in lakes in the Volta basin using water and heat balance

Detailed study in Binaba & (Boura?)

Regionalising for the basin using remote sensing (Images through the TIGER project)

Groundwater surface water interactions (natural Isotopes)


Methodology


?

??

Water budget of the reservoir

Boura only


Getting the water balance right ..1

Rain gauge Evaporation pan

gauge plates

Monitoring wellDTS

EC


Getting the water balance right …2

Thalimedes

Rainfall Sampling

Water Sampling Points for Isotope analyses


Modelling Diagnostic Analyses of

Users/Typologies(Uses)

Model Output from ZonAgri

Evaporation & Seepage Losses model output

Output from other

hydrological models


Some initial results

Seasonal flows in Boura

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

Ecou

lem

ent

moy

en m

ensu

el(m

m/m

ois)

Lame_GR2M Lame_Yates Lame_Girard



Annual flows



Maximum monthly flows per year

0.00

10.00

20.00

30.00

40.00

50.00

60.00

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

Ecou

lem

ents

max

ima

men

suel

s pa

r an

(mm

)GR2M Yates Girard



Maximum monthly flows per year

Modèle GR2M Yates Girard

Lame écoulée annuelle moyenne (mm)

36.02 31.6 34.79

Lame écoulée annuelle médiane(mm) 34.21 28.4 35.3

Ecart-type (mm) 16.84 17.6 20.85

Coefficient Variation (%) 46.77 57.74 59.92

Coefficient d'écoulement annuel moyen (%)

3.94 4.66 5.56



Isotope Analysis



Binaba reservoir

0

5

10

15

20

25

30

35

0

100

200

300

400

500

600

700Water Temperature at bottom of lake

Date/Time

Tem

pera

ture

(oC)

Wat

er le

vel (

m)


Way Forward

More data collectionCalibration and verification of models Scenario building (climate change, water uses, cropping pattern)


Thank you for your attention

Management of Rainwater and Small Reservoir for Multiple Uses

Technology

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