Transcript AN ESTIMATE OF ECOSYSTEM WATER NEEDS AT THE …

ENVIRONMENTAL FLOW
REQUIREMENTS OF INDIAN RIVER
BASINS
VLADIMIR SMAKHTIN
International Water Management Institute (IWMI),
Colombo, Sri Lanka
CP-NRLP Progress Review Meeting, Delhi, January 2006
OBJECTIVES
• collect and review the information on the current status of
knowledge and school of thought in environmental flow field in
India
• 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 test it in Indian river basins, for which
relevant data are available
• suggest the way forward in environmental flow assessment in
India, which can be pursued in the next 5 to 10 years in order to
significantly improve 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, 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.
STARTING POINTS
• 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.
• Desktop, rapid assessment, using primarily
ecologically relevant hydrological characteristics
(indices) or analysis of hydrological time series
FLOW DATA
• Most of the data downloaded from the Internet, some (primarily for
Krishna) provided by CWC to IWMI as part of our previous efforts,
some (primarily) for recent 10-15 years provided by Dr Mohile to the
project (impacted and therefore could be used for placing the EFR
estimates “into the context”
• Monthly time series, with missing data, different periods of record, etc
• Altogether we are estimating EFR for approximately 15 sites located as
close to the outlet of 15 major river basins as possible.
THE APPROACH
•
Large task+limited EFR work+limited flow data = Desktop EFR method and
major rivers only.
•
It 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 ecologists.
CATEGORIES OF ENVIRONMENTAL PROTECTION
(ENVIRONMENTAL FLOW MANAGEMENT CLASSES)
Environmental Management
Category/ objective
Ecological description
Management perspective
EF limit
Natural (unmodified or
slightly modified)
(Class A rivers)
Pristine condition or minor
modification of in-stream and
riparian habitat
Protected rivers and basins.
Reserves and national parks.
No new water projects (dams,
diversions etc.) allowed
Lateral shift of FDC 1 or 2
percentage points to the left
along the time axis from the
original FDC position. Low
acceptable limit – 2 points
shift
Good (slightly or moderately
modified)
(Class B rivers)
Largely intact biodiversity and
habitats despite water
resources development and/or
basin modifications
Water supply schemes or
irrigation development present
and / or allowed.
Lateral shift of FDC 3 or 4
percentage points to the left
along the time axis from the
original FDC position. Low
acceptable limit – 4 points
shift
Fair (moderately or
considerably modified)
(Class C and class D rivers)
The dynamics of the biota
have been disturbed. Some
sensitive species are lost
and/or reduced in extent. Alien
species present.
Multiple disturbances
associated with the need for
socio-economic development,
e.g. dams, diversions and
transfers, habitat modification
and water quality degradation
Lateral shift of FDC 5 or 6
percentage points to the left
along the time axis from the
original FDC position. Low
limit – 6 points shift
USE OF ENVIRONMENTAL INDICATORS TO SET
ENVIRONMENTAL MANAGEMENT CATEGORY
•
•
•
What is the Ecological Sensitivity and Importance of the river basin?
– The higher they 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:
– Krishna, Narmada, Cauvery, Peryar, potential – 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 AT VIJAYAWADA
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
HOW TO GENERATE AN EFR TIME SERIES FROM ITS FDC
EXTRACTS FROM ACTUAL AND SIMULATED TIME SERIES AT
VIJAYAVADA
35000
Monthly flows (MCM)
30000
25000
20000
15000
10000
5000
0
1
11
21
31
41
51
Months since January 1991
Observed at present
Simulated natural
EFR Class B
EFR Class D
61
TYPES OF OUTPUTS
•
Overall EFR methodology which could be replicated in other basins and
in the same basins – with addition data
•
EFR Duration Curves for each selected site and for each management
category (A, B, C and D).
•
Corresponding EFR time series for each category and site
•
Corresponding EFR estimates as % of the natural MAR
•
The draft methodology for the assessment of the most suitable
management category for a basin/site
•
Final Report and most likely IWMI RR and or refereed publication
•
EFR network initiation in India
•
Recommendations / suggestion on the future of EFR work in India