ENVIRONMENTAL FLOW REQUIREMENTS OF INDIAN RIVER BASINS

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ENVIRONMENTAL FLOW REQUIREMENTS OF INDIAN RIVER
BASINS

• VLADIMIR SMAKHTIN and MARKANDU ANPUTHAS
• International Water Management Institute (IWMI),
  Colombo, Sri Lanka
• Workshop on Indias Water Futures to 2025/2050.
• March 9, 2006, Anand, Gujarat, India

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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

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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.

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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

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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

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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.

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THE APPROACH USED

• Large task limited EFR work limited flow data
  gt 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.

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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).
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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

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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

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LATERAL SHIFT OF THE FLOW DURATION CURVES FOR THE
ESTIMATION OF ENVIRONMENTAL CURVES FOR
DIFFERENT MANAGEMENT CATEGORIES
A
B
C
D
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EFR DURATION CURVES FOR KRISHNA OUTLET
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EFR DURATION CURVES FOR MAHI OUTLET
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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) EWR estimates ( natural MAR) EWR estimates ( natural MAR) EWR estimates ( natural MAR) EWR estimates ( natural MAR) EWR estimates ( natural MAR)
River Natural MAR, BCM 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
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HOW TO GENERATE AN EFR TIME SERIES FROM ITS FDC
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EXTRACTS FROM ACTUAL AND SIMULATED TIME SERIES AT
VIJAYAVADA (KRISHNA OUTLET)
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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

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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.

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THANK YOU !