Maps of the major river basins of the world

There are maps of the major river basins of the world available on the World Resources Institute web-site at >>>
There one can find the source of the river and its principal tributaries. In addition, the maps present different indicators from the basin such as population density, total area, growth rate, number of important cities (>100,000 habitants), percentage of protected areas, forests, arid zones, and deforestation levels. Following is an example of the rivers and tributaries in South America that one can find on this site: Amazon, Ica-Putumayo, Japurá, Juruá, Madeira, Negro, Purus, Marañón, Tapajos, Ucayali, Xingu, Chutub, Magdalena, Orinoco, Paraná, Paraguay, Parnaiba, Río Colorado, San Francisco, Lagos Titicaca y Salar de Uyuni, Tocantis, Uruguay.

Limnology job and studentship notices

Notices on the availability of limnologically-oriented jobs and graduate student opportunities are now accepted for publication in SILnews and display on the SIL web site >>>
There is no charge for the service at this time, which is available to SIL members and non-members.

Submitters should be aware of the 4 month lead-time for the print edition of SILnews; those advertisements with short deadlines should be directed to the web site.

Submissions should include: 1) a short title describing the position (job or studentship), 2) location and duration of the position, 3) closing date for applications, 4) a short paragraph describing the position, including any citizenship, educational or employment prerequisites; and, 5) information on where potential applicants may obtain further information, including names of contact persons, telephone numbers, fax numbers, e-mail addresses, and web site addresses, where appropriate.

Submissions may be edited for length and clarity. Those deemed inappropriate to the SIL mandate will be rejected at the discretion of the SILnews Editor. Submissions for the print edition of SILnews should be sent to the editor at the address on the cover of this issue.

Submissions for the SIL web site can be sent by e-mail to or by fax to +1 (204) 474-7650, attention: Gordon Goldsborough.

The new role of IAD in Danube research and conservation

When IAD (the International Association for Danube Research, affiliated to SIL) was founded in 1956 by Reinhard Liepolt, the aim was to scientifically unite western and eastern countries bordering the Danube. The political changes since 1989 have provoked new activities within the 11 member countries. IAD has to define its niche relative to the International Commission for the Protection of the Danube (ICPD, founded in October 1998), NGOs such as WWF (Green Danube Programme), and within applied and conceptual research (Bloesch 1999). This has been emphasized by the organisation of a special session “Large River Ecosystems in Europe” at the 27th SIL Congress in Dublin (Dokulil, Bloesch & Morris, 1999).

Although pollution problems of the Danube and its tributaries with regard to nutrient and contaminants input to the Black Sea remain important, morphological destruction will be the target for future Danube research to ensure the river’s ecological functionality and integrity. At present, special efforts are undertaken with benthic monitoring (see below), mapping macrophytes and floodplain vegetation, and restoration of eutrophic delta lakes.

Changes in aquatic communities in the Danube. The manifold and intensive uses of rivers in the past 150 years (pollution, salination, thermal discharges, river training and impoundments, navigation, flood protection, hydropower, fisheries, and recreation) caused radical changes in aquatic ecosystems and consequently deteriorated the habitats and living conditions of aquatic organisms. The benthic communities of free-flowing Danube reaches differ markedly from those in impounded stretches. Upstream of impoundments, the decreasing flow velocity results in a replacement of lotic by lentic organisms. Moreover, increasing sedimentation favours a typical mud fauna instead of dwellers of gravel and stone substrates. Many stenotypic organisms were thus deprived of their life basis, and disappeared. The resulting biocoenosis was poor in species and consisted only of less-demanding eurytypic organisms.

As the Danube was never so heavily polluted like the rivers Rhine or Elbe, severe decreases in populations occurred mainly locally and did not affect the whole river. Sensitive species, that had disappeared from the faunal inventory, could re-establish populations in the river when water quality improved. However, some species of stoneflies and mayflies are still absent. A pristine community, free of anthropogenic influences, however, will never re-establish in the Danube because of the changes to the river from the 18th to the 20th centuries for landscaping purposes, energy generation or economic interests.

Struggle for survival or peaceful coexistence – is our fear of newcomer species justified? Navigation, but also active migration, enables some species to spread from their original areas in the lower Danube further upstream (e.g., Hypania invalida, Jaera istri). Some taxa of crustaceans (e.g., Dikerogammarus villosus, D. haemobaphes) thus entered via the main-Danube Canal of the Rhine River system, while the basket shell, Corbicula fluminalis, and the freshwater shrimp, Atyaephyra desmaresti, were introduced by ships from the Rhine into the Danube (Tittizer, 1996).

Many exotic species, which often originate from remote regions, the so-called “neozoa”, compensated for the faunal deficit (Tittizer, 1997a). About 13 % of all macroinvertebrates that occur in the larger rivers and canals in Germany today belong to the group of neozoa. The explosive reproduction and dispersion of neozoa in our waters is considered by many as a plague and causes fear, because the consequences of such mass developments are not known (Tittizer, 1997b). Often the erroneous conclusion is drawn that neozoa would replace the indigenous animals from our aquatic ecosystems for good. Long term studies at the German Federal Institute of Hydrology (BfG) revealed that to date not a single such case had occurred. It was only observed that species were driven out locally, associated with a decrease in population density of native species and, consequently, changes in the biocoenotic structure. However, an indigenous species never became extinct in a river system. The invasion of new animal species leading to restructuring of communities may thus be overestimated in some cases, as shown for the Danubian ecosystem, but remains an international issue because of increased mobility of man.

IAD on the internet:

Since January 1999 you can find us at:


Bloesch, J. 1999. International Association for Danube Research (IAD): Its future role in Danube research. Arch. Hydrobiol. Suppl. Large Rivers 11, in press. – Extended abstract in: Proceedings XXVII SIL Congress Dublin, August 1998, in press.

Dokulil, M., Bloesch, J. & Morris, M., Eds. 1999. River ecosystem concept. An initiative of the International Association for Danube Research (IAD). Arch. Hydrobiol. Suppl., Large Rivers 11, in press.

Tittizer, T. 1996. Main-Donau-Canal now a short cut for fauna. Danube Watch, Vol.2, No.3, pp.7-8, Vienna.

Tittizer, T. 1997a. Ausbreitung aquatischer Neozoen (Makrozoobenthos) in den europäischen Wasserstrassen, erläutert am Beispiel des Main-Donau-Kanals. Schriftenreihe des Bundesamtes für Wasserwirtschaft, Band 4: 113-134.

Tittizer, T. 1997b. Existenzkampf oder friedliche Koexistenz – wie berechtigt ist unsere Angst vor den Neozoen? Bundesamt für Wasserwirtschaft, Jahresbericht 1997, pp.72-75, Koblenz.

Jürg Bloesch
President of IAD

The Jean-Jacques and Berthe Symoens Prize for Tropical Limnology

On the occasion of Professor J.-J. Symoens’ academic retirement, the Belgian Royal Academy of Overseas Sciences has set up a Fund in order to award every three years the Jean-Jacques and Berthe Symoens Prize for Tropical Limnology to the author of a memoir of great scientific value.

The Prize was granted for the first time in 1996 to Dr. Y. Kizito of Uganda for his contribution on the zooplankton of two Ugandan lakes. The 1999 Prize has been awarded to Dr. Dirk Verschuren for his thesis on “Recent and Late-Holocene Paleolimnology of Lakes Naivasha and Sonachi, Kenya”. He attended graduate school at the University of Minnesota.

The Naivasha-Sonachi system constitutes a natural laboratory to investigate how basin hydrology, morphology, mixing regime, and sedimentation patterns affect the formation and preservation of climatic signatures in the lake sediment record. The results of the study of fossil assemblages of aquatic invertebrates indicate that mixing regime and availability of preferred substrate are, next to salinity, important causative factors driving the immigration, local expansion, and extinction of individual invertebrate species.

For more information, contact:

Professor Dr. Y. Verhasselt
Permanent Secretary
Academie Royale des sciences D’Outre-Mer
1000 Bruxelles (Belgique)
Phone: (02) 538 02 11 – (02) 538 47 72
Fax: (02) 539 23 53