ENVIRONMENTAL FLOW REQUIREMENTS OF INDIAN RIVER BASINS

1. 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

2. 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

3. 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.

4. 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

5. 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

6. 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.

7. 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.

8. CATEGORIES OF ENVIRONMENTAL PROTECTION (ENVIRONMENTAL FLOW MANAGEMENT CLASSES)

9. 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

10. 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

11. Reference (original) FDC Direction of shift LATERAL SHIFT OF THE FLOW DURATION CURVES FOR THE ESTIMATION OF “ENVIRONMENTAL” CURVES FOR DIFFERENT MANAGEMENT CATEGORIES A B C D

12. EFR DURATION CURVES FOR KRISHNA AT VIJAYAWADA

13. HOW TO GENERATE AN EFR TIME SERIES FROM ITS FDC

14. EXTRACTS FROM ACTUAL AND SIMULATED TIME SERIES AT VIJAYAVADA

15. 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