Jürg Bloesch

A review of methods used to measure sediment resuspension

Resuspension of bottom sediments is an important lake-internal process with regard to particle cycling and sedimentation. Current methods to measure sediment resuspension are reviewed, such as optical and acoustical instruments, instantaneous multiple point water samplers, sediment traps, sediment cores and grabs, radiotracers such as Pb210, Cs137 and Be7, mass balance calculations, various modelling approaches, statistical methods (correlation analysis), and laboratory experiments.For the quantification of resuspension, the combined use of sediment traps, sediment cores, near bottom current meters, and turbidity meters to measure suspended and settling particulate matter in the hypolimnion of lakes is recommended; in addition, wind stress, seiches, slumping and sliding, and riverine input may be monitored to elucidate the mechanisms behind the process.

The Danube River Basin

The Danube is the European river par excellence; a river that most effectively defines and integrates Europe. It links more countries than any other river in the world. The Danube River Basin (DRB) collects waters from the territories of 19 nations and it forms the international boundaries for eight of these. The rivers largely eastward course has served as a corridor for both migration and trade and a boundary strongly guarded for thousands of years. This chapter provides an overview of the DRB, including the three main sections: upper, middle, and lower Danube, the delta and 11 major tributaries. Culturally and biologically, the river has always been a separator as well as a connector. It served as a migration corridor for organisms and cultures and has been an area of dispute as well as a major melting pot of cultures. It is also listed as one of the worlds top 10 rivers at risk. The development of the Trans-European Network for Transport, the ongoing construction of small- and medium-sized hydropower plants along its tributaries, bed incision, truncation of sediment transport, and rapid land-use change within the basin pose major threats.

Lead-210 dating of sediments compared with accumulation rates estimated by natural markers and measured with sediment traps

Methods to provide accurate accumulation rates for lake models are discussed. Cores were taken in 1979 in two basins of Lake Lucerne, Switzerland, and accumulation rates were calculated by using Pb-210 dating and by a natural landslide marker of 1795 in one basin (Weggis). In the other basin (Horw Bay) the sediment accumulation rates based on the lead method were compared with yearly sedimentation rates measured by sediment traps in 1969/70. At the Weggis station, the core dating yielded sediment accumulation rates of about 400 g dry wt. m−2 y−1 with the lead method, averaged over a sediment depth of 4–20 cm; accumulation was about 700 g dry wt. m−2 y−1 with the marker method, averaged over 0–33 cm. In Horw Bay, the trap method yielded about 1300 g dry wt. M−2 y−1 compared with 400–1000 g dry wt. m−2 y−1 obtained with the lead method and related to various depth intervals. The characteristic sources of error of the three methods as well as several hypotheses for these discrepancies are discussed.

Managing the world’s most international river: the Danube River Basin

Transboundary river-basin management is a challenging task emerging from lack of on-site expert knowledge, high administrative and socioeconomic complexity, various stakeholder interests, and difficulties enforcing international and national law. Therefore, an efficient ‘science–policy interface’ is a crucial ingredient for the successful development and implementation of adequate management strategies. The Danube River Basin (DRB) drains areas of 19 countries with different cultural, political, and environmental legacies. The European Water Framework Directive (WFD) has provided the guiding legal instrument for DRB management since 2000, supported by several multilateral agreements. The International Commission for the Protection of the Danube River (ICPDR) is responsible for the implementation of the WFD in the DRB. It stimulates management-oriented research and coordinates the various activities of the contracting parties and observers, including those of many NGOs and stakeholders. The development of the first DRB Management Plan in 2009 constituted a milestone of cooperation among scientific, political, and public organisations. Key stressors and pressures have been identified, a new basin-wide monitoring network has been established, and numerous conservation and restoration sites have been designated. A major challenge in DRB management will be to establish synergies among the competing interests of navigation, hydropower production, flood protection and nature conservation. This paper examines the strengths and weaknesses of DRB science–policy interactions and outlines future strategies for sustainable development of the DRB as a template for transboundary river basin management.

The pattern of particle flux variability in Swedish and Swiss lakes

Particle settling flux in the upper and lower water column, measured with cylindrical sediment traps in 11 Swedish and nine Swiss lakes showed high temporal and spatial variability within and among lakes, ranging from 0.1 to 385 g m(-2) day(-1). Such high variability reflects the large differences in lake morphology and trophic state. However, despite these differences, the particle flux variability followed a consistent pattern resulting in a significant relationship between minimum, mean and maximum particle flux. The mean particle flux is significantly related to the dynamic ratio (square root of area divided by mean depth) of the lake, provided that the lake is shallow (mean lake depth < or = 9 m), its dynamic ratio is > or = 0.15 and allochthonous particulate matter input is < or = 10%. In such lakes, typically found in Sweden, the described relationships may be used to predict the variability of particle settling flux without developing complicated models.

Editorial: Sediment resuspension in lakes

Sediment-water interaction has for a long time been a well-developed field in limnological research, as demonstrated by the many proceedings of IASWS (Golterman, 1977; Sly, 1982, 1986; Sly & Hart, 1989; Hart & Sly, 1992) and phosphorus workshops (Psenner & Gunatilaka, 1988; Enell et al., 1989; Boers et al., 1993). Usually the studies related to this topic are focused on release of soluble compounds and gases through chemical processes and bacterial activities, especially on phosphorus as the key element of (internal) eutrophication (Bostrdm et al., 1982; Golterman, 1992; Sinke, 1992; Furrer & Wehrli, 1993; Gachter & Meyer, 1993; Downes &Adams, 1993; Adams, 1993). During the XXVth SIL Congress held in Barcelona, Spain, on August 21-27, 1992, I organized a special session on ‘Lake Sediment Resuspension’, to focus more on the particulate matter exchange along the sediment-water interface. This is a subject which has long been recognized, is continuously studied and nevertheless lacking integrating interpretation. The aim of this special session was to present a state of the art of the phenomenon ‘resuspension’ (Evans, 1994), and of the methods available (Bloesch, 1994) as well as to focus on the application of the different methods and various approaches in individual lake studies. Hence, there are contributions dedicated to the modelling (statistical) approach (Hakanson, 1994), the direct measurement with beam transmissometers (Pierson & Weyhenmeyer, 1994; Gloor et al., 1994), using isotopes (Cornett et al., 1994), sediment traps (Hicks et al., 1994; Kozerski, 1994), and experiments in oscillating chambers (Brassard et al., 1994). Similarly, this special issue reviews a large variety of different limnological systems such as small lakes, large lakes and large slowly flowing rivers. Sediment resuspension is defined as the redistribution into the water column of sediment particles which had been settled on the lake bottom before. This process may repeatedly take place after redeposition, and is referred to as the secondary flux of particles when compared to the primary settling flux out of the upper water layers into the bottom layers. Depending on the lake depth and morphometry and the wave base, the whole water body or deeper layers only are affected by resuspension (Fig. 1, from Evans 1994). Resuspension is closely related to lateral sediment transportation and sediment focusing, since the driving forces, such as currents and waves, do have a horizontal component in addition to the vertical one.

The International Association for Danube Research (IAD)—portrait of a transboundary scientific NGO

IntroductionThe International Association for Danube Research (IAD), a legal association (Verein) according to Austrian law, presently consists of 13 member countries and 12 expert groups covering all water-relevant scientific disciplines. IAD, founded in 1956, represents a traditional and significant stakeholder in the Danube River Basin, fulfilling an important task towards an integrative water and river basin management requested by the EU Water Framework Directive.DiscussionIAD, stretching between basic and applied research, adapted its strategy after the major political changes in 1989. IAD fosters transdisciplinary and transboundary projects to support integrative Danube River protection in line with the governmental International Commission for the Protection of the Danube River (ICPDR) in which IAD has had observer status since 1998. Recent scientific outputs of IAD encompass, amongst others, a water quality map of the Danube and major tributaries, the Sturgeon Action Plan, hydromorphological mapping of the Drava, a macrophyte inventory, and a Mures River study. Further information about IAD can be found on our website http://www.iad.gs.

ESTROM 2008 International Conference

The target audience for the conference was environmental scientists and engineers, water managers, and environment and health authorities. In addition, organizations dealing with the protection of water bodies, e.g., the International Commission for the Protection of the Danube River (ICPDR), stakeholders, nongovernmental organizations, decision makers, and drinking water suppliers, were addressed. The Organizing Committee consisted of Walter Giger, Jurg Bloesch, and Jurg Zobrist (Eawag, Dubendorf, Switzerland), Nicolae Panin and Alina Pavel (Institute GeoEcoMar, Bucharest, Romania), Viorel Ungureanu (University of Bucharest, Romania), Elisabeth Schenker (Swiss National Science Foundation, Bern, Switzerland), and Paolo Demaria (Demaria Event Management, Zurich, Switzerland). Summarized oral reports of the nine ESTROM projects concerning contaminants in wastewaters, surface waters and sediments, and drinking waters of Romania, monitoring and mitigation of pollution, and implementation of respective measures were also presented. The conference was opened by Prof. Anton Anton, State Secretary of the Romanian Ministry of Education, Research and Youth and President of the National Authority of Scientific Research. He welcomed 120 participants from 17 countries (Fig. 1) and reflected in his lively speech on the special current situation of research activities in Romania. Dr. Simon Geissbuhler, Charge d’affaires of the Swiss Embassy in Romania, emphasized the importance of Swiss–Romanian cooperation by stressing that each side can learn from the other, also in the sector of scientific research and environmental protection. The conference was organized in five half-day sessions, of which each included one keynote lecture, two topic talks, and one or two reports of the ESTROM projects. During the whole conference, 46 posters were on display (ESTROM 2008; Fig. 2). The following sections overview the oral presentations of sessions 1 to 5 and the podium discussion. Detailed reports on the ESTROM projects are presented in separate articles contained in this Special Issue of Environmental Science and Pollution Research (see references). The presentations are also downloadable as digital files (ESTROM 2008). Environ Sci Pollut Res (2009) 16 (Suppl 1):S9–S13 DOI 10.1007/s11356-009-0206-5

The unique ecological potential of the Danube and its tributaries: A report on the 33rd IAD-Conference in Osijek, Croatia, 3-9 september 2000

The 33 rd Conference of the International Association for Danube Research (IAD) in Osijek, Croatia, was focused on the general topic Danube and its tributaries: Anthropogenic impacts and revitalization. About 150 scientists from 11 Danubian countries presented contributions that are published in the conference proceedings (HORVATIC 2000). This article provides a review of the proceedings and a summary of, and comment on, the major conference contributions. Moreover, a brief conference report and an outlook on IAD policy are given.