ENVIRONMENTAL FLOWS AND THE LESOTHO HIGHLANDS

WATER PROJECT: A CASE STUDY

Cate Brown

Southern Waters Ecological Research and Consulting

The Lesotho Highlands Water

Project

Five Phases• Phase 1 complete

– Katse Dam– Mohale Dam– Matsoku Weir

• Phase 2 in feasibility

Timelines

1950

1960

1970

1980

1990

2000

2010

LHWP conceived

Treaty signed between Lesotho and SA (1986)

Initial Engineering Feasibility studies

Katse Dam (Phase 1a) completedEF determination studies initiatedEF negotiations and IFR PolicyEF implementation

Phase 1b (Mohale and Matsoku)

completedPhase 2 Feasibility studies

Determination• DRIFT

– Holistic– Multidisciplinary

• 1 to 2 years of data• Expert interpretation

– ‘Twinned’ experts• Linked flow changes to:

– Biophysical change– Socio-economic

implications

Results - series of scenarios: IFR Volume and distribution, River condition, Yield; Socio-economic ‘cost’

Negotiations and IFR Policy• Negotiations and decision making• IFR Policy

– Volume and distribution of flows at a series of river sites

– Operating rules– Monitoring programme

IFR Site

River Dam % nMAR Condition (State)

1 Matsoku

Malibamatso

Senqunyane

Masoku Weir 40% 3

2 Katse Dam 15% 4

7 Mohale Dam 22% 4

Negotiated IFRs

Senqunyane

Senqu

Senqu

Senqu

Malibamatso

Senqunyane

Malibamatso

Matsoku

River

--Mohale8

265%All6

262%Matsoku & Katse5

355%Matsoku & Katse4

429%Matsoku & Katse3

422%Mohale Dam7

415%Katse Dam2

340%Masoku Weir1

Condition (State)

% nMARDamIFR Site

10% release14% release PR

OX

IMA

LD

ISTA

L

Compensation payments to locals for predicted loss in resources

Tens of millions of Maloti(millions of US$)

Implementation

• IFR releases began from Phase 1 structures in 2003:– Katse Dam; Mohale Dam,

Matsoku Weir• Monitoring started in 2003:

– hydrology– water quality and RBA

• Up-scaled in 2005:– two years of post-IFR data

• Preliminary results

Releasing the IFRHydrological classification

-1.5-1

-0.50

0.51

1.52

2.5

2003

.320

03.4

2004

.120

04.2

2004

.320

04.4

2005

.120

05.2

2005

.320

05.4

2006

.120

06.2

2006

.3Hydrologicalclassification

2003- 2005 – ‘average’2005- 2006 – ‘wet’

Predicted climatic conditions - ‘wetness’

IFR Site 2

0

50

100

150

200

250

Target (2003/5) Actual (2003/5) Target (2005/6) Actual (2005/6)

Annual Review

MCM

Lowflows Highflows

IFR Site 2

0

50

100

150

200

250

Target (2003/5) Actual (2003/5) Target (2005/6) Actual (2005/6)

Annual Review

MCM

Lowflows Highflows

IFR Site 7

020406080

100120140

Target (2003/5) Actual (2003/5) Target (2005/6) Actual (2005/6)

Annual review

MCM

Lowflows Highflows

Releasing the IFR

Katse Dam

Mohale Dam

Katse outlets not large enough to release mid-size and bigger floods – incorporated into IFR

Extent to which IFR releases have been met

• Bulk allocation met in wet years• Tendency to over release lowflows

and to under release floods• Resultant elevated lowflows that

tend to be constant• Many changes in downstream

rivers can be linked to lack of regular flooding

Why the problems with flood releases?

• ‘Blue sky’ releases – miscommunication– dangerous

• Practicalities of linking releases with rainfall– remote– downstream warnings

• Consequently few floods and dampened variability

Biophysical predictions

Discipline Predictions made

Monitored

Geomorphology 14 10Water Quality 6 5 - plusVegetation 82 9Macroinvertebrates 24 10Fish 6 3Amphibia 7 0Mammals and Birds 28 0

Total c. 167 c. 37

Using the IFR data set as Baseline data

Predictions versus actual(d/s Katse Site 2)

Discipline Total Trend correct

No chang

e

Trend opposit

eGeomorphology 10 9 (90%) 1 0Water Quality 5 -

plus9

10Fish 3 1 (33%) 1 1

Total 37 19 (51%)

2 0

Vegetation

1 (20%)

6 (66%) 2 1Macroinvertebrates 7 22 (20%)

Predictions versus actual(d/s Mohale Site 7)

Discipline Total Trend correct

No chang

e

Trend opposit

e

105 -

plus9

12Fish 3 2 (75%) 1 0

Total 39 25 (64%)

10 4

9 (90%)

1 (20%)

6 (60%)

7 (58%)

Geomorphology 1 0Water Quality 2 0

Vegetation 3 2Macroinvertebrates 3 2

2Woody vegetation

Woody Vegetation• Lesotho Highlands have very few trees and shrubs• Trees and shrubs grow in gullies and along river• No electricity in most villages• Required for cooking, warmth, building, fodder, etc.• Highly valued• Affected by river flows – predicted to decline• Made up the bulk of the compensation costs

Woody vegetation• Increased• Mainly exotic trees• Mainly on newly-formed in-channel

islands– Pattern predicted

• Complicating factors:– Lack of flood releases – Climate factor → large floods will flush

woodies• Query re: need to make

compensation payments

- Nature of EF data and decision making

- Involvement of EF scientists

How do we handle the fact that we are offering imperfect knowledge?

• Hypotheses based on understanding of river systems:– IFR releases are the experiment designed to test the

hypotheses; – monitoring check whether they pass or fail

• We have accepted that:– these hypotheses need to be made in order to guide

development– river scientists have a better understanding of river

systems than people in other professions

But – what level of decisions should be made based on these

hypotheses?

• Overall system health?• Change in individual resources?• What about compensation payments – should

these be decided on the basis of the hypotheses?

EF scientists involvement should extend into

implementation

EFs should be considered at FIRST stage of development

plans

Matsoku Weir

Katse Dam

Matsoku River

Malibamatso River

Matsoku Natural Runoff = c. Matsoku and Katse EF Releases

In closing …

• EFs in early planning stage

• Aim for passive compliance

• Identify key goods and services

• Developing countries - quantitative information

• Be aware of the pressure on scientists