IWRA Executive Office

OS1j IWRM: Sustainable management of complex water systems

abstract 187

Improvement of IWRM integrating enhanced reservoir operation for securing water quality, water quantity and environmental sustainability

Author(s): Mélanie Bauer, Oliver Olsson, Matthias Obermann, Jochen Froebrich
Division of Water Resources Management, Institute for Water Quality and Waste Management (ISAH), Leibniz Universitaet Hannover, Am Kleinen Felde 30, D - 30167 Hannover, Germany, phone: +49 (0)511 762 19477, fax: +49 (0)511 762 19413, email: mb@fggm

Keyword(s): reservoir operation, environmental sustainability, ecology, water quality, IWRM

Article:

Poster:

Session: OS1j IWRM: Sustainable management of complex water systems

AbstractIntroduction
A multitude of factors impacts on the

environment and thereby on the freshwater resource.
Despite the influence of human societies that modify their

environment to their needs, global warming is strongly impacting on precipitation, flow regimes, and the frequency

and intensity of extreme events.
Regulating rivers by dams modifies directly and significantly natural river flow

regimes and, since their operating rules and policies determine the amount and timing of releases, they are an

important starting point for securing water quality, quantity and environmental sustainability.
Enhanced reservoir

operation (enrop) is a concept for operating reservoirs by adapting the inflow and release patterns considering water

quantity and quality dynamics, and including environmental aspects.

Objective
This paper discusses the

application of enhanced reservoir operation (enrop) as a management concept supporting the improvement of

IWRM in water deficient regions. The development of operation schemes by adapting reservoir inflow and releases

addressed the provision of downstream water supply and ecological requirements. The extended understanding of

the interactions between specific reservoir operations and the provided water quality and quantity will support

satisfying the potential conflicting needs of humans and ecosystems.

Method
For integrating enhanced

reservoir operation into IWRM mainly information on the reservoir inflow quality and quantity dynamic as well as

release pattern need to be known. Using reservoir water quality models, like the 1D reservoir model Lac or the 3D

model Mohid, the changing status of the water body is investigated and following the needed information on release

quality is gained. Based on this, site adapted reservoir operations will be developed.
From the vast of existing

methods for assessing environmental flow, e. g. hydraulic rating methods, habitat simulation methods, and holistic

methodologies (Arthington et al., 2006, Dyson et al. 2003, Tharme 2003), predominantly building on a natural flow

paradigm (Poff et al., 1997), will be reviewed and pre-selected against their potential to be linked to the enrop

concept. Environmental requirements will be then incorporated into developed enhanced operation schemes, as they

give thresholds for the water released by the dams and these in turn set boundary conditions for the management of

the reservoir inflow.

Results
The intrinsic natural variability of the environment plays a central role in the

investigation of improved IWRM measures for integrating environmental aspects into enhanced reservoir

operation.
The alteration of the natural flow regime variability by dams is cannot be reconditioned completely.

Studies carried out in regulated streams mostly come to the conclusion that the optimal flow regime to be provided

should be fairly the same as the natural one given before the dam was built, what is completely/eventually not

possible due to the far-reaching changes caused by the dam
It is therefore needed that the assessment of

ecological flow regimes needs to be based on the current state. Investigating different discharge dynamics by

adapted dam operation, it can be stated that the more a flow regime approaches the natural flow, the higher its

potential for assuring environment relevant requirements.

Conclusion
There is the pressuring need of

improving water resources management in order to secure water quality, quantity and environmental

sustainability.
Enhanced reservoir operation allows environmental aspects to be incorporated into water

management by optimising reservoir storage in terms of quantities and quality.
Combining such operational

choices with important issues concerning water resource management the proposed method helps to develop a more

holistic approach to environmental sustainability, avoiding past limits imposed by considering only quantitative

aspects (e.g. minimum flow approach), but implying the understanding of downstream ecosystem needs.
This

method further supports decision makers in the overall water management for determining adaptive reservoir

operation schemes aiming for an improved water quality and quantity for civil use and aquatic ecosystem

protection.

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Improvement of IWRM integrating enhanced reservoir operation for securing water quality, water quantity and environmental sustainability