Abstract
River ecosystems are interlinked with river hydrology. However, construction of dams can modify the natural flow patterns which can lead to unpredictable consequences. Environmental flow (EF) releases can restore ecosystems or reverse the already occurred degradation. Having understood the importance of EF, large number of methods has been developed to estimate the EF. The objective of this study was to make a comparison between these methods to identify the most comprehensive method and to develop a novel approach to estimate EF based on the concept of minimum information requirement. Among the EF calculation methods studied, holistic method was identified as the most reliable category and the building block methodology (BBM) was identified as the best holistic method which requires more resources or data. The new methodology developed to assess EF basically based on BBM but efforts were taken to identify minimum data requirement approaches to calculate individual water uses. It consists of the flow requirement of riverine flora and fauna, social and cultural water requirement, wetland water requirement, longitudinal connectivity, flushing flow requirement, groundwater recharge and coastal water requirement. The EF requirement of downstream of DeduruOya reservoir was estimated using the developed method. The results were compared with the EF calculated using the Sri Lanka Environmental Flow Calculator model developed by IWMI. There was a significant difference between the EF calculated using new method and the results obtained using model developed by IWMI. Hence, it is recommended to further improve and verify the findings of the new method.
Highlights
Environmental flow (EF) is defined as the quantity, quality and timing of water flows required for sustaining freshwater ecosystems and the human livelihoods and wellbeing that depend on these ecosystems (Brisbane Declaration, 2007)
An EF can secure the ecosystems and ecosystem services that are essential for human wellbeing since it tends to mimic with the natural flow pattern (UNEP, 2003)
Flow pattern of DeduruOya Ecosystems are adapted to the general flow pattern of the river identification of the natural flow regime is important
Summary
Environmental flow (EF) is defined as the quantity, quality and timing of water flows required for sustaining freshwater ecosystems and the human livelihoods and wellbeing that depend on these ecosystems (Brisbane Declaration, 2007). An EF can secure the ecosystems and ecosystem services that are essential for human wellbeing since it tends to mimic with the natural flow pattern (UNEP, 2003). The dependent downstream is interlinked with hydrology that is being changing with hydrological alterations such as dam construction and it may leads to unpredictable consequences Considering these importance, EFs and ecological considerations must be taken in to account seriously in development activities. To adopt the best suit EF assessment method for a particular location, present methods are necessary to study with the aim of identifying their capabilities, strengths and weaknesses including the availability of data records and other resources to carry out an assessment successfully. A detailed study and comparison of existing methods is a necessity to identify a best fit method for a particular location
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