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CLIMATE CHANGE AND WATER RESOURCES:
CHALLENGES AND QUESTIONS FOR THE D.W.A.F.
School of Bioresources Engineering and Environmental HydrologyUniversity of KwaZulu-Natal, Pietermaritzburg
Roland SchulzeProfessor of Hydrology
THE BASIC PREMISE . . .
Climate change is a global phenomenon, but the
problems will be very local and we will have to adapt
and plan
WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD
TO CLIMATE CHANGE?
(a) The water sector is an integrating, cross-
cutting one
Global
Regional
Local
Sectoral
agriculturecoastal health
- INTEGRATED IMPACT ASSESSMENT -
WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD TO
CLIMATE CHANGE?
(b) The hydrological cycle amplifies any changes in
rainfall [PMG note: maps not incuded, please email [email protected]]
WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD
TO CLIMATE CHANGE?
(c) Climate change scenarios have to be
downscaled to the scale at which DWAF operates
[PMG note: maps not incuded, please email [email protected]]
WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD
TO CLIMATE CHANGE?
(d) Climate change impacts have to address key
issues of the National Water Act
Basic Human Needs:Present, Future
Equitable Accessto Water
Sustainable,Efficient, Beneficial
Water Use
Promoting DamSafety
Reducing WaterPollution,
Degradation
ManagingFloods, Droughts
Socio-EconomicDevelopment /
Future Demands
N.W.A.TAKESINTO
ACCOUNT
Redressing PastInequities
MeetingInternationalObligations
Protection ofEcosystems,Biodiversity
Demand Management
Environment Management
Crisis Management
Socio-Political ManagementRES2269
Hillslope and Riparian Zone Processes in ACRU
(after Meier et al., 1997; Schulze, 2000b)
Concepts, Processes and Assumptions in the ACRU Wetlands Module
(after Schulze et al., 1987; with modifications by Schulze, 2001d)
UPSTREAM INFLOWS
DRAINAGE ANDABSTRACTIONS
VARIABLE AREA OF WATER SURFACE
OPEN WATEREVAPORATION
TRIBUTARY INFLOWS
TOTAL EVAPORATION
WATER-SOIL INTERFACE
IMPERVIOUS LAYER
SUBSOIL HORIZONSATURATED
CHANNEL STORAGEAND ROUTING
WETLAND SPILLWAY
VARIABLE
TOPSOIL HORIZON
PERIODICALLYSATURATED
V a ry in gA re a s
V a ry in gC ro p s
MaximumRootDepth
P o te n t ia lE va p o ra tio n
P en m a n -M o n te ith
C ro p W a te r D e m a ndf(Crop, G rowth S tage, E
R a in fa ll
S to rm f lo wE ff ic ie n c y
r)
DeepPercolation
PlannedDeficit
at firr
Fixed Cycle /Fixed Amount
E t , E tm
( E )
VariableRoot Zone
Fixed Cycle /Varying Amounts
Variable Cycle /Variable Amounts(Predetermined
Schedule)
DUL
DULat firr
Es , Esm
fs
F ie ld A p p lic a t io n
IRRIGATION WATER BUDGET AND SCHEDULING OPTIONS
RES947b
R e fe re n c e
A - P a n o rLL
PAW r
Schematic of Irrigation Water Demand and Scheduling Options Available in ACRU
(after Schulze, 1995 and updates)
WHAT HAVE FIRST RESULTS FROM THE W.R.C. PROJECT ON CLIMATE CHANGE AND
WATER RESOURCES IN SOUTH AFRICA SHOWN?
DETAIL “EXPLODES” FROM ANNUAL TOMONTHLY TO DAILY VALUES: TEMPERATURE
[PMG note: maps not incuded, please email [email protected]]
DETAIL “EXPLODES” FROM ANNUAL TO MONTHLY TO DAILY VALUES: RAINFALL
[PMG note: maps not incuded, please email [email protected]]
Potential Evaporation is Projected to Increase by 10 - 20%
Implications: Enhanced dam evaporation lossesIncreased irrigation demands
[PMG note: maps not incuded, please email [email protected]]
Soils are Projected to Become Drier More Often
Implications: Reduced runoff per mm rainfallLand use changesReduced crop yieldsHigher irrigation demands
[PMG note: maps not incuded, please email [email protected]]
Fewer, but larger rainfall events may result in more groundwater recharge
[PMG note: maps not incuded, please email [email protected]]
Shifts in the Distribution of Runoff are Projected to Occur
Implications: Reservoir operating rules changeEcological reserve (IFRs) change
[PMG note: maps not incuded, please email [email protected]]
Implications to Irrigation are Likely to be Significant
[PMG note: maps not incuded, please email [email protected]]
WHAT COULD THIS IMPLY IN AN ACTUAL
CATCHMENT SITUATION?
A case study from Swaziland
14
2
19
9
33
3
12
35
16
34
4
6
5
8
7
15
13
11
40
22
32
37
29
38 3936
21
23
27 28
10
2624
25
18
20
MBULUZI : CONFIGURATION
Mnjoli
1
Irrigation – Local Supply
Irrigation – Inter Basin Transfers
30 31
Irrigation – Mnjoli Dam
17
Irrigation – Multiple Sources
Streamflow Gauge
Inter Basin Transfers
Reservoir
MNJOLI DAM: % OF FULL SUPPLY CAPACITY
POTENTIAL IMPACTS OF CLIMATE CHANGE, MBULUZI CATCHMENT(Scenario: T = T + 2°C; P = P – 10%)
0
10
20
30
40
50
60
J F M A M J J A S O N D
Present: %FSC,1:10 Dry
Future: %FSC,1:10 Dry
DRYYEAR
0
20
40
60
80
100
120
J F M A M J J A S O N D
Present: %FSC,1:2 Med
Future: %FSC,1:2 Med
AVERAGEYEAR
01
234
56
78
J F M A M J J A S O N D
Present 1:10 Dry
Future 1:10 Dry
0
5
10
15
20
25
J F M A M J J A S O N D
Present:Median
Future: Median
MBULUZI OUTFLOWS TO MOZAMBIQUE
POTENTIAL IMPACTS OF CLIMATE CHANGE, MBULUZI CATCHMENT(Scenario: T = T + 2°C; P = P – 10%)
AVERAGEYEAR
DRYYEAR
WHERE TO NOW?
THE NEED TO ADAPT IN WATER RESOURCE
MANAGEMENT
• Acess to information• Experiences of threat• Sensitivity to threat
AWARNESSOF THREAT
• External influences of regulations/ wealth- Government- CMAs/ Water Boards- State of economy
• Internal characterstics- Institutional capacity/ will
• Range of options- Demand- Supply- Culture- Expectations
After Arnell (2005)
INTENTIONTO ADAPT
ACTIVE ADAPTATION
THE ADAPTATION PROCESS
A
B
C
TYPES OF RISK INCREASES OVER TIME
Thresholds may decrease
Variability may increase beyond thresholds
Trends may shift beyond thresholds
DECISION FRAMEWORK ON CLIMATE VARIABILITY ANDCLIMATE CHANGE
TYPE OF DECISION
CLIMATE WEATHER
Long Term (10-50yrs) Medium Term (6-9mths) Short term (0-7days)
Decadal Changes Seasonal Forecasts Real Time → Week
Strategic
Tactical
Operational
•Supply demand •Reservoir safety•Reservoir sizing•Land management
•Operating rules•Water orders•Water allocation•Demand management
•Irrigation scheduling •Flood warning •Field operations
TIME FRAME LEGAL AND POLICY
INSTITUTIONAL AND
MANAGEMENT
MONITORING, RESEARCH AND INFORMATION
LONG TERM
Years to Decades (e.g. climate change)
InternationalNational Water Resource Strategy
National Climate Change Response Strategy
More Specific Policy Requests
Enforcing/Policing Policy
Catchment Management Agencies
Risk ManagementGovernance
InfrastructureWater LicencingEnforcement and Compliance
MONITORINGNetworks and General
DataRESEARCH
General Capacity Building
Climate ModelsHydrological
ModellingSpecific Research
Requirements INFORMATION
Education/TrainingCommunication
S.A. ADAPTATION FRAMEWORK: CLIMATE CHANGE IMPACTS ON
THE WATER SECTOR
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(a) Climate change also means land use change
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(b) Hydrological baselines against which SFRAs are
levied, will shift
[PMG note: graphics not incuded, please email [email protected]]
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(c) “Hotspots” of climate change concern may need priority attention by DWAF
Runoff-Producing Stormflow Events are Projected to Change
Implications: Lower inflows into reservoirs in certain areas
Catchment sediment yields will change
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .(d) Impacts of climate change
on the water sector may be felt sooner than we like
[PMG note: maps not incuded, please email [email protected]]
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(e) Climate change impacts will be superimposed on already existing complex land use
impacts [PMG note: maps not incuded, please email [email protected]]
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(f) The ecological “Reserve” will be impacted
The aquatic environment is a LEGITIMATE water user and NOT a
competing resource
Upstream and downstream ecosystems management will have to adapt with
climate change
[PMG note: graphics not incuded, please email [email protected]]
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(g) Health services will be impacted
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(h) Water quality will be impacted
Chemical Physical Biological
[PMG note: graphics not incuded, please email [email protected]]
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(i) Water availability to the poor will be impacted
[PMG note: graphics not incuded, please email [email protected]]
BUT . . . IS IT AS SIMPLE AS ALL THAT?
NO, BECAUSE . . .
(j) International water agreements with our
neighbouring countries may have to be re-negotiated
THE TAKE-HOME MESSAGE. .
Climate change is a global phenomenon, but the
problems will be very local and we will need to adapt
and plan
