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 info@pmg.org.za]

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 info@pmg.org.za]

The Challenge: GCM RCM QC HRU

[PMG note: maps not incuded, please email info@pmg.org.za]

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 info@pmg.org.za]

DETAIL “EXPLODES” FROM ANNUAL TO MONTHLY TO DAILY VALUES: RAINFALL

[PMG note: maps not incuded, please email info@pmg.org.za]

Potential Evaporation is Projected to Increase by 10 - 20%

Implications: Enhanced dam evaporation lossesIncreased irrigation demands

[PMG note: maps not incuded, please email info@pmg.org.za]

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 info@pmg.org.za]

Fewer, but larger rainfall events may result in more groundwater recharge

[PMG note: maps not incuded, please email info@pmg.org.za]

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 info@pmg.org.za]

Implications to Irrigation are Likely to be Significant

[PMG note: maps not incuded, please email info@pmg.org.za]

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 info@pmg.org.za]

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 info@pmg.org.za]

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 info@pmg.org.za]

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 info@pmg.org.za]

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 info@pmg.org.za]

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 info@pmg.org.za]

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