Sustainability Considerations Sustainability Considerations in the Design of Big Dams:in the Design of Big Dams:

Merowe, Nile BasinMerowe, Nile Basin

Mentor: Prof. El Fatih EltahirMentor: Prof. El Fatih Eltahir

Group: Anthony Paris, Teresa Yamana, Group: Anthony Paris, Teresa Yamana, Suzanne YoungSuzanne Young

OutlineOutline

Introduction and motivationIntroduction and motivation Nile hydrologyNile hydrology The modelThe model ClimateClimate SedimentationSedimentation Public healthPublic health Future WorkFuture Work

Goals and MotivationGoals and Motivation

Simulate the role of environmental Simulate the role of environmental engineers in large scale projectsengineers in large scale projects

Analyze the effect the Dam will have on Analyze the effect the Dam will have on the environment and local population, the environment and local population, and make recommendations to mitigate and make recommendations to mitigate effectseffects

Assess whether long-term effects will Assess whether long-term effects will significantly decrease Dam’s lifetime and significantly decrease Dam’s lifetime and plan accordinglyplan accordingly

IntroductionIntroduction

Sudan needs EnergySudan needs Energy 19-year old Civil War19-year old Civil War Frequent power blackoutsFrequent power blackouts

Merowe DamMerowe Dam Utilizing hydropowerUtilizing hydropower Creating hopeCreating hope

Dam Design DetailsDam Design Details Ten turbines – 1,250 MW CapacityTen turbines – 1,250 MW Capacity Long in relation to heightLong in relation to height Active reservoir storage 8.3 bcm Active reservoir storage 8.3 bcm

General LayoutGeneral Layout

Average Longterm Monthly Nile flows, 1872-1986

0

5

10

15

20

25

January February March April May June July August September October November December

Dis

char

ge (

km^3

/mon

th)

““The Model”The Model”The New Model

Storage to Elevation RelationshipStorage to Elevation RelationshipReservoir Characteristics

260

270

280

290

300

310

320

330

340

350

0 1E+09 2E+09 3E+09 4E+09 5E+09 6E+09 7E+09

Surface Area (m^2)

Ele

va

tio

n (

m)

Reservoir Characteristics

260

270

280

290

300

310

320

330

340

350

0 2E+10 4E+10 6E+10 8E+10 1E+11 1.2E+11 1.4E+11

Storage (m^3)

Ele

va

tio

n (

m)

Matlab ModelMatlab Model

dS/dt = inflow – evap – Q_out(turbines) – dS/dt = inflow – evap – Q_out(turbines) – Q_out(overflow)Q_out(overflow)

Determines what volume to make available to Determines what volume to make available to turbinesturbines Pessimistic Model – use as much water as possiblePessimistic Model – use as much water as possible Gradual Release Model – ration storage in dry seasonGradual Release Model – ration storage in dry season Constant Head Model – Q_out=Q_in Constant Head Model – Q_out=Q_in

Determines the number of turbines to turn onDetermines the number of turbines to turn on Calculates volume, area, PowerCalculates volume, area, Power

Pessimistic Gradual Release Constant Head

The Effect of Climate Change on Dam The Effect of Climate Change on Dam PerformancePerformance

Suzanne YoungSuzanne Young

Climate changeClimate change

Changes in chemical composition of Changes in chemical composition of atmosphere atmosphere global warming global warming

Temperatures increase, precipitation?Temperatures increase, precipitation? Literature review: Predictions of Nile flows Literature review: Predictions of Nile flows

confounded by different simulations giving confounded by different simulations giving conflicting resultsconflicting results

Range of discharges for major points along the NileRange of discharges for major points along the Nile (Summary of Yates 1998b results)(Summary of Yates 1998b results)

Two numbers on ends of each line represent extreme discharges of six GCM scenarios, whereas boxed number is historic average; Additional tick marks on each line are remaining GCM scenarios, which indicate range of climate change induced flows of Nile Basin.

Climate scenariosClimate scenarios

Climate scenario Years Average flow Deviation from long term

    [km3/yr] average 88 km3/yr

No change 1943-1969 88 --

Wetter climate 1872-1898 102 +15%

Drier climate 1979-1986 74 -15%

Also varied maximum storage height of reservoir from 294 m to 298 m

Nile discharge, 1872-1986

40

50

60

70

80

90

100

110

120

130

1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980

An

nu

al d

isch

arg

e (k

m^3

/yea

r)

Longterm annual average = 88.1 km̂ 3/year

Potential HydropowerPotential Hydropower

Power = γQhγ = ρg

ρ = density of water = 1000 [kg/m3]g = gravity = 9.8 [m/s2]Q = flow at dam [m3/s] h = drop in head between intake to powerhouse and outlet to

river [m]

ResultsResults

Wetter climate = highest power (~30% Wetter climate = highest power (~30% higher than no change in climate)higher than no change in climate)

Reservoir storage height increase gives Reservoir storage height increase gives linear increase in power (~10%/m)linear increase in power (~10%/m)

Pessimistic model > Gradual release Pessimistic model > Gradual release modelmodel

Drier climate power yields higher than no Drier climate power yields higher than no change in climate (!)change in climate (!)

Pessimistic model

Gradual release model

No change in climate Wetter climate Drier climate

Pessimistic model yields higher power than Gradual

Release model

Pessimistic model: Comparison of climate scenarios

2.05E+11

2.10E+11

2.15E+11

2.20E+11

2.25E+11

2.30E+11

2.35E+11

2.40E+11

294 295 296 297 298

Maximum storage height of reservoir [m]

Ave

rag

e an

nu

al p

ow

er [

Wat

ts]

No change

Wetter climate

Drier climate

Seasonal variationsSeasonal variations

Wetter No change DrierJanuary 4.95 3.82 3.30February 3.44 2.84 2.60March 2.79 2.21 2.17April 2.01 1.91 3.20May 1.71 1.95 2.81June 2.04 2.55 2.74July 6.02 6.92 4.87August 20.84 18.50 14.79September 25.05 20.77 18.24October 17.30 14.12 9.95November 9.53 7.62 5.36December 6.70 4.88 3.97Annual 102.39 88.09 73.54

Climate scenario

RecommendationsRecommendations

Use pessimistic model as basis for Use pessimistic model as basis for operating parametersoperating parameters

Increase height of maximum reservoir Increase height of maximum reservoir storage pending economic analysisstorage pending economic analysis

Sedimentation into the ReservoirSedimentation into the Reservoir

Anthony ParisAnthony Paris

Erosion: Sources of Erosion: Sources of Nile SedimentsNile Sediments

Ethiopian Highlands Ethiopian Highlands (~90%)(~90%)

Travels through the Travels through the Blue Nile and AtbaraBlue Nile and Atbara

The sediment load is The sediment load is most significant most significant during flood season during flood season (July-Oct.)(July-Oct.)

50-228 million tones 50-228 million tones per yearper year

Sedimentation AnalysisSedimentation Analysis

1) How much sediment will settle in the 1) How much sediment will settle in the reservoir?reservoir?

2) Where will the sediment settle?2) Where will the sediment settle? 3) How long is the economic life of the 3) How long is the economic life of the

project?project? 4) What things can be done to improve 4) What things can be done to improve

the situation?the situation?

Hand CalculationsHand Calculations

Calculating Trapping Efficiency – 1st RoundCalculating Trapping Efficiency – 1st Round Brune’s CurveBrune’s Curve C = CapacityC = Capacity I = InflowI = Inflow

TI

C

Hand CalculationsHand Calculations

Calculating VCalculating VSS – 1st Round – 1st Round

ββ = = Bulk density of clay loamBulk density of clay loam QQCC = sediment load [tons/yr] = sediment load [tons/yr]

VVSS = Volume of sediment retained [m = Volume of sediment retained [m33/yr]/yr]

CTS QV

Borland & Miller Reservoir Borland & Miller Reservoir ClassificationClassification

H = any water lvl.H = any water lvl. HHO O = lowest bed lvl.= lowest bed lvl.

VVHH = = res. Vol. at Hres. Vol. at H

αα = coef. = coef. M = coef. (slope)M = coef. (slope)

LakeLake 65% dead storage65% dead storage 35% active storage35% active storage

MOH HHV

log H vs log C

y = 4.4794x + 2.2173

8.6

8.8

9

9.2

9.4

9.6

9.8

10

10.2

1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8

log H-Ho

log

C

Economic Life of ReservoirEconomic Life of Reservoir

Scenarios Flow Rate Suspended Load Estimated Bed Load Economic Life

1 44 billion m3/yr 30 million 5% 350 yrs

2 63.7 billion m3/yr 50 million 15% 205 yrs

3 44 billion m3/yr 77 million 5% 105 yrs

4 63.7 billion m3/yr 158 million 15% 65 yrs

5 44 billion m3/yr 137 million 5% 70 yrs

6 63.7 billion m3/yr 228 million 15% 45 yrs

ImprovementsImprovements

1) Trapping1) Trapping Creating dams upstream to catch sedimentCreating dams upstream to catch sediment

2) Sluicing2) Sluicing Opening low level-lying sluices to flush out Opening low level-lying sluices to flush out

sediments, only effects local areasediments, only effects local area 3) Dredging3) Dredging

$$$ May be cost effective towards end of life$$$ May be cost effective towards end of life 4) Flushing4) Flushing

Allow the high sediment filled flood waters to flush Allow the high sediment filled flood waters to flush through the systemthrough the system

The Effect of the Dam on Public HealthThe Effect of the Dam on Public Health

Teresa YamanaTeresa Yamana

Dams’ Threat to Public HealthDams’ Threat to Public Health

As a development project, obligation to As a development project, obligation to protect public healthprotect public health

Merowe Dam expected to increase Merowe Dam expected to increase incidence of Malaria, Schistosomiasis, incidence of Malaria, Schistosomiasis, River Blindness and Rift Valley FeverRiver Blindness and Rift Valley Fever

Stagnant water in reservoirs and irrigation Stagnant water in reservoirs and irrigation ditches provide habitat for vectorsditches provide habitat for vectors

Constant supply of water - Dry season no Constant supply of water - Dry season no longer limits vectors longer limits vectors

MalariaMalaria

Protozoa Protozoa PlasmodiumPlasmodium transmitted by Anopheles transmitted by Anopheles mosquitoesmosquitoes

A. funestusA. funestus breeds in breeds in illuminated shoreline illuminated shoreline throughout the yearthroughout the year

A. gambiaeA. gambiae breeds in breeds in reservoir drawdown area in reservoir drawdown area in dry season (November – dry season (November – June)June)

Drawdown area:129 km2

Illuminated shoreline:2-48 km2

Malaria Control StrategiesMalaria Control Strategies

Reduce Mosquito habitat through Reduce Mosquito habitat through operating parametersoperating parameters

Chemical or biological control strategiesChemical or biological control strategies Reduce bites by using window screens, Reduce bites by using window screens,

bednetsbednets Provide vaccination and treatment for at Provide vaccination and treatment for at

risk or infected populationrisk or infected population

SchistosomiasisSchistosomiasis

Parasite carried by snails living in Parasite carried by snails living in illuminated shore lineilluminated shore line

Reduce human contact to water – piped Reduce human contact to water – piped water supplywater supply

Provide sanitation services – break link in Provide sanitation services – break link in life cyclelife cycle

Control snail populationControl snail population

River BlindnessRiver Blindness

Transmitted by black fly – fast moving waterTransmitted by black fly – fast moving water Water-washed – provide piped water supplyWater-washed – provide piped water supply Stop flow through dam 2 days per 2 weeks July Stop flow through dam 2 days per 2 weeks July

– September– September

Annual Power Generated

normal with RB controlPercent

reduction

Var 1 2.05E+11 1.96E+11 4.39

Var 2 1.99E+11 1.89E+11 5.03

Var 3 1.87E+11 1.77E+11 5.35

River Blindness – Variation 2River Blindness – Variation 2

Rift Valley FeverRift Valley Fever

Transmitted from livestock to humans via Transmitted from livestock to humans via mosquitoesmosquitoes

Occurs when reservoirs are filledOccurs when reservoirs are filled Vaccinate or remove livestockVaccinate or remove livestock Quarantine contaminated livestock and Quarantine contaminated livestock and

meatmeat Warn livestock and meat workersWarn livestock and meat workers Control mosquito habitatControl mosquito habitat

Model PreferencesModel Preferences

A. gambiaeA. gambiae – Variation 3 – Variation 3 A. funestus A. funestus and Schistosomiasis snails – and Schistosomiasis snails –

Variation 1Variation 1 River Blindness blackfly – add controlRiver Blindness blackfly – add control Which is Most Important?Which is Most Important?

Need more data! Need more data! What diseases will cause the most problems?What diseases will cause the most problems? Formulate strategy based on regional priorityFormulate strategy based on regional priority

GOAL – no increase in disease caused by damGOAL – no increase in disease caused by dam

Future WorkFuture Work Integrate 3 Climate, Sedimentology and Public Integrate 3 Climate, Sedimentology and Public

Health concernsHealth concerns Thorough cost-benefit analysisThorough cost-benefit analysis ClimateClimate

More experimentation with various climate scenariosMore experimentation with various climate scenarios SedimentationSedimentation

2-D and 3-D models to predict delta formations and 2-D and 3-D models to predict delta formations and identify problem spotsidentify problem spots

Public HealthPublic Health Prioritize between diseases to find optimal operating Prioritize between diseases to find optimal operating

parametersparameters

THANK YOU!!THANK YOU!!

Prof. El Fatih EltahirProf. El Fatih Eltahir Prof. Dennis McLaughlin & Sheila FrankelProf. Dennis McLaughlin & Sheila Frankel Profs. Ole Madsen & Dara EntekhabiProfs. Ole Madsen & Dara Entekhabi Dr. Sadeqi of the Kuwait FundDr. Sadeqi of the Kuwait Fund Valeri IvanovValeri Ivanov 1E seniors!1E seniors!