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Volume 379
Proc. IAHS, 379, 43-47, 2018
https://doi.org/10.5194/piahs-379-43-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Proc. IAHS, 379, 43-47, 2018
https://doi.org/10.5194/piahs-379-43-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Pre-conference publication 05 Jun 2018

Pre-conference publication | 05 Jun 2018

Centralized versus distributed reservoirs: an investigation of their implications on environmental flows and sustainable water resources management

Nishadi Eriyagama1, Vladimir Smakhtin2, and Lakshika Udamulla3 Nishadi Eriyagama et al.
  • 1International Water Management Institute, Battaramulla, 10120, Sri Lanka
  • 2UNU Institute for Water Environment and Health, Hamilton, Ontario, Canada
  • 3Department of Civil Engineering, The Open University of Sri Lanka, Nugegoda, 10250, Sri Lanka

Abstract. Storage of surface water is widely regarded as a form of insurance against rainfall variability. However, creation of surface storage often endanger the functions of natural ecosystems, and, in turn, ecosystem services that benefit humans. The issues of optimal size, placement and the number of reservoirs in a river basin – which maximizes sustainable benefits from storage – remain subjects for debate. This study examines the above issues through the analysis of a range of reservoir configurations in the Malwatu Oya river basin in the dry zone of Sri Lanka. The study produced multiple surface storage development pathways for the basin under different scenarios of environmental flow (EF) releases and reservoir network configurations. The EF scenarios ranged from zero to very healthy releases. It is shown that if the middle ground between the two extreme EF scenarios is considered, the theoretical maximum safe yield from surface storage is about 65–70% of the mean annual runoff (MAR) of the basin. It is also identified that although distribution of reservoirs in the river network reduces the cumulative yield from the basin, this cumulative yield is maximized if the ratio among the storage capacities placed in each sub drainage basin is equivalent to the ratio among their MAR. The study suggests a framework to identify drainage regions having higher surface storage potential, to plan for the right distribution of storage capacity within a river basin, as well as to plan for EF allocations.

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Creation of surface storage often endanger the functions of natural ecosystems and ecosystem services. The issues of optimal size, placement and the number of reservoirs in a river basin, which maximizes sustainable benefits, while minimizing negative impacts on ecosystems remain subjects for debate. This study examines the above issues through the analysis of a range of reservoir configurations and environmental flow release scenarios in the Malwatu Oya river basin in Sri Lanka.
Creation of surface storage often endanger the functions of natural ecosystems and ecosystem...
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