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 EltahirGroup: 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 Difficulties and lessons learnedDifficulties and lessons learned ConclusionsConclusions

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

Dam Design DetailsDam Design Details Ten turbines – 1,250 MW CapacityTen turbines – 1,250 MW Capacity Length: 10 kmLength: 10 km Height: 65 mHeight: 65 m Reservoir Length: 170 km Reservoir Length: 170 km

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 (k

m^3

/mon

th)

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

Ann

ual d

isch

arge

(km

^3/y

ear)

Longterm annual average = 88.1 km^3/year

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)

Elev

atio

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)

Elev

atio

n (m

)

““The Model”The Model”

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

Suzanne YoungSuzanne Young

ClimateClimate

How do changes in river flow caused by How do changes in river flow caused by climate change affect the Merowe Dam’s climate change affect the Merowe Dam’s power capacity?power capacity?

The Big PictureThe Big Picture Documented changes in chemical composition Documented changes in chemical composition

of atmosphere (e.g. COof atmosphere (e.g. CO22 is rising) is rising) Scientists predict if this activity continues, it will Scientists predict if this activity continues, it will

impact the environmentimpact the environment Lots of studies on climate change and global Lots of studies on climate change and global

warming done by governments in U.S., Europewarming done by governments in U.S., Europe Models agree global temperatures will rise, less Models agree global temperatures will rise, less

certain about regional impacts (precipitation)certain about regional impacts (precipitation) We don’t know what is going to happen to Nile We don’t know what is going to happen to Nile

flows!flows!

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.

TO DOTO DO Show different results of studies, and Show different results of studies, and

convince audience that we don’t know convince audience that we don’t know what will happen = document uncertainty!what will happen = document uncertainty!

Calculate hydropower under different Calculate hydropower under different scenarios of climate change:scenarios of climate change: Last 100 yearsLast 100 years Wetter climateWetter climate Drier climateDrier climate

Make recommendations to dam designMake recommendations to dam design

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]

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.)

~140 million tones per ~140 million tones per yearyear

TransportationTransportation Suspended LoadSuspended Load

particulates that travel particulates that travel while suspended in the while suspended in the water columnwater column

Distribution:Distribution: 30% Clay (<0.002 mm)30% Clay (<0.002 mm) 40% Silt (0.002-0.02 mm)40% Silt (0.002-0.02 mm) 30% Fine Sand (0.02-0.2 30% Fine Sand (0.02-0.2

mm)mm) High level of total High level of total

suspensionsuspension

Reservoir Reservoir Deposition IDeposition I

When river flow enters a reservoir, its velocity When river flow enters a reservoir, its velocity and transport capacity is reduced and its and transport capacity is reduced and its sediment load is deposited.sediment load is deposited.

The depositional pattern usually starts with The depositional pattern usually starts with coarser material depositing first followed by the coarser material depositing first followed by the fine creating a delta.fine creating a delta.

FactorsFactors Detention TimeDetention Time Shape of reservoirShape of reservoir Operating proceduresOperating procedures

Reservoir Reservoir Deposition IIDeposition II

Hand CalculationsHand Calculations

Calculating QCalculating QSS (“Flow” of Sediments) from Q (“Flow” of Sediments) from Q (Flow)(Flow)

Find Hydrograph with corresponding Sediment Find Hydrograph with corresponding Sediment Load ConcentrationsLoad Concentrations

Convert Load from concentration (mg/L)to Convert Load from concentration (mg/L)to volume (mvolume (m33))

Do linear regression to determine correlation Do linear regression to determine correlation between Qbetween QSS and Q; breaking the hydrograph into and Q; breaking the hydrograph into two sections, monsoon, and non-monsoon.two sections, monsoon, and non-monsoon.

Extrapolate over 100 year monthly data set to Extrapolate over 100 year monthly data set to have Qhave QSS

Hand CalculationsHand Calculations

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

TIC

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

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

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

Malaria TransmissionMalaria Transmission Protozoa Protozoa PlasmodiumPlasmodium

transmitted by Anopheles transmitted by Anopheles mosquitoesmosquitoes

Causes 1 million deaths per Causes 1 million deaths per yearyear

Fever-like symptomsFever-like symptoms A. funestusA. funestus breeds in illuminated breeds in illuminated

shoreline throughout the yearshoreline throughout the year A. gambiaeA. gambiae breeds in reservoir breeds in reservoir

drawdown area in dry season drawdown area in dry season (November – June)(November – June)

Drawdown Area: 2.46 x 108 m3

Drawdown Area: 2.46 x 108 m3

RecommendationsRecommendations

Malaria – Whenever possible, relocate Malaria – Whenever possible, relocate communities outside of mosquito flight communities outside of mosquito flight rangerange

River Blindness – Stop flow over spillways River Blindness – Stop flow over spillways for two days every two weeks over wet for two days every two weeks over wet season to inhibit blackfly breedingseason to inhibit blackfly breeding

More to come (hopefully)More to come (hopefully)

Difficulties Difficulties

TOO BROADTOO BROAD Model is stupidModel is stupid Conflicting expectationsConflicting expectations

ConclusionsConclusions

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