6th Arab-German Energy Forum, Berlin, Germany, 25.-26.11.2015 1

Sustainable Water Storage���

At the Core of the Water-Energy - Nexus

Dietrich Bartelt DB Sediments GmbH

Bismarckstr. 142, 47057 Duisburg, Germany e-mail: d.bartelt@db-sediments.com

Michael Detering DB Sediments GmbH

Bismarckstr. 142, 47057 Duisburg, Germany e-mail: m.detering@db-sediments.com

Water Storage of surface waters - like in rivers - is at the core of the Water-Energy – and the Water-Energy-Food – Nexus. The storage of water can have many purposes, as i.e. for drinking water, irrigation water, and for hy-dropower generation. Just naming climate change, the expected continuous increase in global population, and the paradigm change of electricity generation - away from nuclear and coal fired power to a more sustainable and renewable power generation - shows the need for an increased built up of water storage capacity.

Globally, thousands of billions of Euros have been spent within the past 30 years, to try to increase the global storage capacity of water. Nevertheless, the World Commission on Dams WCD estimated that each year around 1 % of worldwide storage capacity is lost due to sedimentation (WCD 2001). Almost every reservoir is affected. Even the actual new build of reservoirs does not level out overall storage decrease. Dredging and disposing res-ervoir sediment is extremely expensive.

Therefore, in many reservoirs and hydropower installations sediment is seen as a problem, which should be avoided. High load of sediment in the outflow is seen to cause wear on machinery. Furthermore, some ecologists fear clogging of interstitials, when passing on sediment. On the other hand the caused lack of sediment down-stream of reservoirs leads to erosion damages, substrate deficits and ground water problems.

Operational restrictions for reservoir users caused by sedimentation do not come overnight. They increase gradu-ally over long time periods, usually years. Therefore many operators get used to live with these restrictions and consider them as normal, though they are not. Even worse, they grow over time if no counteraction is taken. Foreseen dead storage capacity to store a bulk of sediment below the actively operated reservoir range often does not fully apply because sediment does not tend to settle plain but accumulates within the foreseen active storage volume (Detering 2014).

Sediment is merely part of nature. Like water and organisms also sediment is an essential ingredient of every river. This solid fraction mostly is of natural origin and finds its way via erosion processes into the water body.

By seeing sediment as a problem in such a way and blocking sediment transport, sediment accumulation in res-ervoirs in the long run leads to even larger problems in both cost and ecology. The only sustainable and envi-ronmentally solution in the end is not to see sediment as a problem, but to enable a cost efficient near-nature sediment transport (Detering, Bartelt 2014).

To foster sustainability in hydro development and operation, a forum of social and environmental NGOs, several countries and the hydropower sector, represented by IHA, developed a tool to assess sustainability on a number of issues. The protocol itself comes as a framework, which provides a consistent, widely applicable methodology on assessing all usually relevant topics, including the topic of sedimentation and erosion (Detering 2014).

The recent judgment of the highest court in Europe, the Court of Justice of the European Union states that the ultimate objective of the Water Framework Directive is to be achieved, by coordinated action, ‘good status’ of all EU surface waters by 2015. „The environmental objectives that the Member States are required to achieve involve two obligations, namely to prevent deterioration of the status of all bodies of surface water (obligation to prevent deterioration) and to protect, enhance and restore all those bodies of water with the aim of achieving good status by the end of 2015 at the latest (obligation to enhance)“ (European Union 2015).

According to Water Framework Directive a barrage should not only be penetrable for water and fish, but also for sediment. Therefore, the general approach is to bring the balance of sedimentation and erosion in a river back to a naturally acceptable or aspired degree to provide a sustainable and permanent solution.

The ConSedTrans Process (Detering, Bartelt 2014) is aiming at keeping and/or restoring the continuity of natural sediment transport in the river. At the same time the application of the ConSedTrans Process keeps the reservoir

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capacity at the original capacity or is restoring to its original or necessary capacity. The process is regarding the transport capacity of the river downstream of the dam as a dynamic framework condition.

In order to evade unnecessary and unwanted deposition of sediments that are transferred to the downstream side of the dam, the flow and its hydrological conditions on the downstream side have to be analyzed and monitored in detail.

The well-known Hjulström-Diagram (Hjulström 1935), see Figure 1, is an indicator for critical velocities and the three stages of deposition, transport or erosion of the bed load.

Figure 1: Erosion, Transport and Deposition of Sediments as a function of Grain Size and Flow Speed (Wikipedia 2015, derived from Hjulström 1935)

As the quasi-natural transport of sediments in the river is depending geomorphological characteristics like: the largest grain size, the grain size distribution, the characteristics and the flow. The transfer of sediments to the downstream should regard these characteristics.

The ConSedTrans Method regards this in a unique manner, evading problems with unwanted erosion or deposi-tion of sediments. Furthermore, the river ecosystem is kept in balance and flooding can be mitigated.

The unnatural deposition of sediments in a reservoir is caused when the river flows into the reservoir. The river flow slows down and deposits coarse sediment first, followed by finer sediments as it flows further downstream into the reservoir. The particle size distribution of deposited sediment is very discrete.

In order to compensate the impact of using the reservoir, the (almost) deposited sediments can be transferred with the ConSedTrans Method from places where they will eventually deposit to areas within or outside the reservoir where flow conditions are favorable for quasi-natural transfer to the downstream side of the reservoir.

With this method, one or more automated vessels are operated within the reservoir for sediment transfer (see Figure 2 and Figure 3). The innovative technical approach makes reservoirs penetrable for sediment avoiding the above-mentioned secondary effects. It is very cost effective, since it focuses on the origin of the impact. Incom-ing as well as already settled sediment is continuously transferred through the reservoir and fed over long time spans in morphologically and ecologically compatible concentrations downstream by applying newly developed equipment (see Figure 2 and Figure 3).

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Figure 2: Sample for Sediment Transfer Equipment “SediMover” (image: DB Sediments)

Several options exist for downstream sediment transfer:

1. Through the turbines 2. Using a new power generating waterway such as hydrodynamic screws or other sediment resistant gen-

eration units 3. Over the weir 4. Over the spillway 5. Directly downstream

All alternatives ensure that the important natural sediment is kept within the river system. In the case of transfer-ring high density currents (high sediment to water ratios) to hydrodynamic screws, the renewable power genera-tion can be increased by up to and about 50 percent (Bartelt, Detering, 2015). Not to overstress the downstream river transfer capacity, the actual sediment ratio is measured online aboard the vessels and adjusted according to the rivers safe transport capacity. This avoids possible disadvantages of flushing or sluicing to downstream aquatic ecology. Oxygen yield can be adjusted by transfer line air injection in case anaerobic sediment condi-tions require doing so.

Figure 3: The Continuous Sediment Transfer Method (ConSedTrans) by DB Sediments The approach is scalable to different dimensions. Ensuring real sustainability of reservoirs, the ConSedTrans Process is so far the only one fulfilling the European Union Water Framework Directive in terms of sediment

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management, also for run of river installations. On cost comparison, it turned out to be far more economic than dredging/landfill, dry excavation or new build of reservoirs. In addition, continuous sediment transfer reduces secondary public cost of downstream river and coastal erosion by restoring sediment transfer in a near nature way.

The application does not affect reservoir management and is performed during daily reservoir operation. The process restores overall sediment transport to a near nature state with overall benefits to ecology and the rivers morphological state, giving the operator back the desired reservoirs operational range. The new technical sedi-ment management approach is transferable on almost any range of plants, small to large and run-of-river to pumped storage.

This approach does not only restores the overall sedimentation process to a near to natural state but also fulfills the requirements of the Water Framework Directive 2000/60 of the European Community. Moreover, as the equipment is fully automated, it is also economically very competitive, even without considering the avoided costs of the secondary effects. We like to mention that this invention has received the PLATTS-Award “Leading Global Sustainable Technology-Innovation of the Year 2011”, the “Outstanding Innovator Award 2014” by the German-American Chambers of Commerce, was nominated for the Zayed Future Energy Prize, just recently for the “Innovationspreis der Deutschen Wirtschaft” – the innovation award of German industry and furthermore has received the Initiative Prize for renewable energies and environment in the state of North-Rhine Westfalia in Germany.

Figure 4: Continuous Sediment Transfer at HPP Rodund/Austria (image: DB Sediments)

The new process is already applied to reservoirs in Germany and Austria (see Figure 4). Most reservoir capacity had been lost due to siltation. By applying the new equipment the reservoir will regain the lost storage capacity without lowering the water level or compromising plant operation. Within the our presentation, we will give details about the technical approach, how the hydropower generation can profit, as well as how the river ecosys-tem can be improved and the impact of using water can be balanced. Furthermore the projects economics and results gained so far will be presented as well as the advantages from point of view of the operator.

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References 1. World Commission on Dams (2001): Dams and development. A new framework for decision-making; the report of

the World Commission on Dams. 1. Aufl. London: Earthscan Publ. 2. Bartelt, D., Bundesmann, R., & Sevis, I. (2011). The River as an ecosystem - Sediments as an important part of the

system: Sustainable Use of Water enabled by using an innovative sediment handling restoring reservoir capacity. In VI International Symposium on Ecology and Environmental Problems.

3. Schüttrumpf, H., Bartelt, D., Cofalla, C., Detering, M., Frings, R., Henkel, S., et al. (2012). Bewertung, Nutzung und Verwertung von Talsperrensedimenten. In TU Dresden (Ed.), STAUBAUWERKE. Planen, Bauen, Betreiben. Dresden, Germany.

4. Bartelt, D., Detering, M., & Rodriguez, E. (2011). Restore reservoir capacity in a sustainable and very cost effective way. In R. R. Garcia (Ed.), Dam maintenance and rehabilitation II (pp. 627–632). Leiden, The Netherlands: CRC Press/Balkema.

5. Bundesmann, R., Bartelt, D. (2009). Neues Verfahren zur Herstellung der geomorphologischen Durchgängigkeit von Staugewässern. Wasserwirtschaft 05 / 2009 (Juni 2009), (05).

6. Bartelt, D., Jokiel, C. (2013). An innovative approach to compensate the impact of using water by applicaton of the Continuous Sediment Transfer method. ICWRER 2013, Water & Environmental Dynamics, Proceedings, Koblenz, Germany.

7. Detering, M., Bartelt, D. (2014). Sediment is not a problem. Innovations and Development Needs for Sustainable Growth of Hydropower. 18th International Seminar on Hydropower Plants, Vienna, Austria.

8. Detering, M. (2014). Are we sustainable? The threats for hydropower. Poster. International Symposium on Dams in a Global Environmental Challenges, CIGB-ICOLD, Bali, Indonesia.

9. Court of Justice of the European Union (2015). The obligations laid down by the Water Framework Directive con-cerning enhancement and prevention of deterioration apply to individual projects such as the deepening of a navigable river. Press Release No 74/15, Luxembourg, Luxembourg.

10. Bartelt, D., Detering, M. (2015). Sustainable Water Storage and Electricity Generation - with technically supported Sediment Transfer. RENEXPO Poland, EXPO XXI Center, 22.09.2015, Warsaw, Poland.

Authors Dietrich Bartelt, PhD, Dipl.-Ing., studied civil engineering and business administration. In 1992 he graduated with a master in civil engineering from the Aachen University of Technology (RWTH Aachen) in Germany, European Union. He special-ized in hydraulic engineering, water resources management, soil mechanics and environmental management. Since 1992 and for 21 years he had been working for a major globally active European Utility and held various technical and management positions. As Senior Manager he had been responsible for the coordination of environmental issues for several hundred com-panies of the Group. In 2012 he published his doctor thesis on “trust of employees’ in their management”. In the fields of renewable power generation, he has been active in setting up multi-national projects, project management structures, site development, authorization procedures, plant operations, and joint implementation projects with a focus on hydropower. Since 2012 he has been globally active to develop and promote the sustainable operation and maintenance of reservoirs and their rehabilitation after partial or complete siltation. He is co-founder and associate of DB Sediments. Since May 2015 he has been Managing Director of Ferrostaal DB Sediments. Michael Detering, PhD, graduated from German RWTH Aachen University of Technology in 1995 with a master in me-chanical engineering and also a commercial background. Later he added a Doctors degree in civil & hydraulic engineering. Since then he has been involved in almost any type of renewable generation but always with a strong focus on hydropower. With on-site experience he conducted a number of projects, rehabs and assessments. Being responsible for a major European Power Producer in Hydro Asset Management for 82 plants in six European countries he took the entire plant fleet back on a sustainably operated course whilst significantly increasing profits. Michael Detering is co-founder and associate of DB Sedi-ments. Besides his business function, he teaches at Aachen University of Technology and contributes to several technical associations, including ICOLD and its TC Environment.