Transcript AN ESTIMATE OF ECOSYSTEM WATER NEEDS AT THE …

ENVIRONMENTAL FLOW
REQUIREMENTS OF INDIAN RIVER
BASINS
VLADIMIR SMAKHTIN and MARKANDU ANPUTHAS
International Water Management Institute (IWMI), Colombo, Sri Lanka
Workshop on India’s Water Futures to 2025/2050.
March 9, 2006, Anand, Gujarat, India
OBJECTIVES OF THIS STUDY COMPONENT
• review the current status of environmental flow estimation
methods in the world and examine the applicability of those
in the Indian context
• provide a pilot method for quick estimation of
environmental flow requirements of rivers and apply it for
major Indian river basins
• suggest the way forward in environmental flow assessment
in India, which can be pursued to enhance environmental
water research and policies in India
THE CONTEXT
• Major water transfers are planned between a number of
river basins, but very little if any assessment of
environmental aspects of the plans has been done
• Virtually no previous studies exist in India on
Environmental Flow Requirements (EFR), but interest to
these problems grows
• Access to hydrological time series data (which forms the
basis of EF assessment) is extremely difficult and for many
basins – impossible.
GENEARL PRINCIPLES OF EFR
• Flow is a major determinant of physical habitat in rivers,
which in turn is the major determinant of biotic
composition.
• Flow regime changes lead to habitat alterations, changes in
species distribution and abundance, loss of biodiversity of
native species.
• The invasion and success of exotic and introduced species
in rivers is facilitated by the alteration of flow regimes.
Inter-basin water transfers represent the major mechanism
for the spread of exotic species.
• Maintenance of flow variability is the primary goal of
environmental flow assessment and management
TYPES OF EFR METHODS
• Detailed assessment, using primarily holistic methodologies, or
methods based on habitat modeling. Complex, data intensive
and time consuming.
• Desktop assessment, using primarily ecologically relevant
hydrological characteristics (indices) or analysis of hydrological
time series. Low confidence but quick
• Both types require observed or simulated flow time series
representing unmodified (natural) flow regimes
FLOW DATA
• Most of the observed flow data downloaded from the Internet,
some -primarily for recent 10-15 years - provided by Dr Mohile to
the project. Those are impacted and therefore could be used for
placing the EFR estimates “into the context”, but not usable for
EFR otherwise.
• Monthly time series, with missing data, different periods of
record, etc
• Altogether we are estimating EFR for 13 sites located at the
outlets of 13 major river basins.
THE APPROACH USED
•
Large task +limited EFR work +limited flow data => Desktop EFR method and
major rivers only.
•
The approach still has to cater for all ecosystem components and therefore
has to describe EF variability, not just to set some minimal flow
•
Take the most advanced Desktop EFR method to date and simplify it to avoid
excessive parameter estimation and to make it commensurate with the very
limited flow data available
•
Use management categories (levels of environmental protection) as a concept
useful to set different EFR for different river conditions.
•
Calibrate the newly developed method against the original Desktop for those
limited cases where “reasonably” good flow data are available
•
Develop a draft procedure for the assessment of the most suitable
management category for a basin using local knowledge and expertise –
Indian aquatic ecologists.
CATEGORIES OF ENVIRONMENTAL PROTECTION
(ENVIRONMENTAL FLOW MANAGEMENT CLASSES - EMC)
EMC
ECOLOGICAL DESCRIPTION
MANAGEMENT PERSPECTIVE
A: Natural
Pristine condition or minor modification of
in-stream and riparian habitat
Protected rivers and basins. Reserves and national
parks. No new water projects allowed.
B: Slightly
modified
Largely intact biodiversity and habitats
despite water resources development
and/or basin modifications.
Water supply schemes or irrigation development
present or allowed.
C:
Moderately
modified
The habitats and dynamics of the biota
have been disturbed, but basic ecosystem
functions are intact.
Multiple disturbances associated with the need for
socio-economic development, e.g. dams, diversions,
etc
D: Largely
modified
Large changes in natural habitat, biota and
basic ecosystem functions have occurred. A
clearly lower than expected species
richness.
Significant and clearly visible disturbances associated
with basin and water resources development,
including dams, diversions, transfers, habitat
modification and water quality degradation
E:
Seriously
modified
Habitat diversity and availability have
declined. A strikingly lower than expected
species richness. Alien species have invaded
the ecosystem.
High human population density and extensive water
resources exploitation.
F:
Critically
modified
Modifications have reached a critical level
and ecosystem has been completely
modified with almost total loss of natural
habitat and biota.
This status is not acceptable from the management
perspective. Management interventions are necessary
to restore flow pattern, river habitats etc (if still
possible / feasible).
USE OF ENVIRONMENTAL INDICATORS TO SET
ENVIRONMENTAL MANAGEMENT CATEGORY
•
What is the Ecological Sensitivity and Importance of the river basin?
– The higher the ES and I of a aquatic ecosystems in a river basin,
the higher the environmental category should ideally be.
Consequently, more water should be allocated to aquatic
ecosystems and more flow variability should be preserved.
•
What is the Current Condition of aquatic ecosystems in the river basin?
– The more pristine the current condition of the basin is, the higher
the environmental category should be. Consequently, more water
should be allocated to aquatic ecosystems and more flow variability
should be preserved to maintain it in the existing condition. Also,
the better the current condition, the more incentive should be to
keep it at that.
•
What is the Trend of Change?
– If deterioration of aquatic environment still continues (negative
trend) it will be more difficult to achieve a higher ecological
condition even if it is necessary due to high importance and
sensitivity. The rate of change may also be assessed here and
taken into account. This question may be interpreted as the one
addressing the future vulnerability of the basin
USE OF ENVIRONMENTAL INDICATORS TO SET
ENVIRONMENTAL MANAGEMENT CATEGORY
• Each of the above questions is answered by using a set of
quantitative and qualitative indicators. Each indicator has
its scoring system. The total score leads to placement of a
basin into some environmental category
• Example indicators:
– Rare and endangered aquatic biota (primarily fish)
– Overall richness of aquatic species (fish)
– Presence of protected areas, areas of natural heritage and
pristine areas which are crossed by the main water course in
the basin
– Sensitivity of aquatic ecosystems to flow reduction
– Degree of flow regulation
– % of the basin remaining under natural cover types, etc
• The following basins or parts thereof are currently
assessed by local experts in aquatic ecology:
– Krishna, Narmada, Cauvery, Peryar and parts of Ganga
LATERAL SHIFT OF THE FLOW DURATION CURVES FOR THE
ESTIMATION OF “ENVIRONMENTAL” CURVES FOR DIFFERENT
MANAGEMENT CATEGORIES
10000.0
Reference (original) FDC
Monthly Flow (MCM)
A
Direction of
shift
C B
D
1000.0
100.0
0.01
0.1
1
5
10
20
30
40
50
60
70
80
90
95
% Time flow exceeded
Original
A class
B class
C class
D class
99
99.9 99.99
EFR DURATION CURVES FOR KRISHNA OUTLET
100000.0
Monthly Flow (MCM)
10000.0
1000.0
100.0
10.0
1.0
0.1
0.01
0.1
1
5
10
20
30
40
50
60
70
80
90
95
99
99.9 99.99
% Time flow exceeded
Original
A class
B class
C class
D class
Class E
Class F
EFR DURATION CURVES FOR MAHI OUTLET
100000.0
Monthly Flow (MCM)
10000.0
1000.0
100.0
10.0
1.0
0.01
0.1
1
5
10
20
30
40
50
60
70
80
90
95
99
99.9 99.99
% Time flow exceeded
Original
Class A
Class B
Class C
Class D
Class E
Class F
Estimates of long-term EWR volumes (expressed as % of natural MAR)
at river basin outlets for different environmental management classes
River
Natural
MAR,
BCM*
EWR estimates (% natural MAR)
Class A
Class B
Class C
Class D
Class E
Class F
Brahmaputra
585
78.2
60.2
45.7
34.7
26.5
20.7
Cauvery
21.4
61.5
35.7
19.6
10.6
5.8
3.2
Ganga
525
67.6
44.2
28.9
20.0
14.9
12.1
Godavary
110
58.8
32.2
16.1
7.4
3.6
2.0
Krishna
77.6
62.5
35.7
18.3
8.4
3.5
1.5
Mahanadi
66.9
61.3
34.8
18.5
9.7
5.6
3.6
Mahi
11.0
41.9
17.1
6.5
2.3
0.8
0.3
Narmada
45.6
55.5
28.8
14.0
7.1
3.9
2.5
Pennar
6.3
52.7
27.9
14.3
7.3
3.8
2.0
Tapi
14.9
53.2
29.9
16.6
9.0
4.9
2.6
Periyar
5.1
62.9
37.3
21.2
12.1
6.9
3.9
Sabarmati
3.8
49.6
24.2
12.1
6.6
3.7
2.1
Subarnarekha
12.4
55.0
29.9
15.4
7.4
3.4
1.5
HOW TO GENERATE AN EFR TIME SERIES FROM ITS FDC
EXTRACTS FROM ACTUAL AND SIMULATED TIME SERIES AT
VIJAYAVADA (KRISHNA OUTLET)
35000
35000
Monthly
Monthlyflows
flows(MCM)
(MCM)
30000
30000
25000
25000
20000
20000
15000
15000
10000
10000
5000
5000
0
0
1
11
21
31
41
51
Months since January 1991
Observed at present
Simulated natural
EFR Class B
EFR Class D
61
OUTPUTS OF THIS STUDY
• A new EFR methodology which could be replicated in other
basins and in the same basins – with addition data, at
different reaches
• A summary of EFR for each basin outlet in the form of Flow
Duration Curves for each environmental management
category
• Corresponding EFR estimates as % of the natural MAR
• Corresponding EFR time series
• A draft methodology for the assessment of the most
suitable environmental management category for a basin
• IWMI Research Report (submitted), CPWF report and
journal article – later in the year
CONCLUSIONS
•
A new EFR method is simple and quick to apply and is the first-ever EFR method actually
developed for Indian conditions. At the same time, it is generic and can be used elsewhere
•
The study was conducted in the conditions of extreme lack of flow data. The method needs to
be tested more in different Indian rivers and at much smaller scales than used herein. Lack of
access to data will impede all EFR initiatives in India in the future, if not resolved.
•
A requirement for better ecological justification of the method represents an ideal opportunity
to initiate several comprehensive EFA studies and feed the future ecological information into
the method.
•
A few studies on ecological sensitivity and value of rivers in India have been initiated. But they
are largely illustrative at present – they show what can be done. This needs to be done in other
basins and at finer scales.
•
EFR are estimated to achieve specific ecological objective (e.g. provide ecologically important
flow-related habitat). EFR are not motivated to solve water quality problems by dilution.
Severely polluted Indian rivers are at risk if only the recommended EF remain in the river
without non-point source pollution control and without effluent treatment at source.
•
Actual environmental flow provisions are not the same as environmental water demand
estimates. No matter how advanced and accurate the EFA is, its output remains on paper if no
actual releases are made or if the prescribed limit of water resource exploitation is violated.
•
Ideally, each planned water transfer of NRLP should go through at least quick EFR assessment
– at donor and recipient sites.
THANK YOU !