botswana/namibia - Cour international de Justice

"Representatives of the two national survey organisations accompanied by co-workers from
the Department of Water Affairs have now been to the area to survey the 'Thalweg' in the
vicinity of the island. Specific mention is made to the Thalweg in the 1890 Agreement
between England and Germany". (Botswana Memorial, Annex 48).
(E) The Criteria to determine the main channel in the case of bifurcation
346. The concept of thalweg includes within it the criteria of navigability and the capacity to
carry the greater flow, which also are employed to determine the main channel. Both depend
on the depth of the channel.
(i) Depth is the criterion of navigability
347. The deepest channel determines the navigable channel of the river (see paragraphs 383
and 384). It is to be noted that the one sizeable ship at present navigating this section of the
Chobe River can only use the northern channel. The Zambezi Queen, 42 metres in length and
three storeys high, is operated as a tourist ship and solely uses the northern channel. (See
Photograph opposite page).
(ii) The northern channel is the deeper channel
348. The 1985 Joint Survey carried out by senior qualified hydrologists appointed jointly by
South Africa4 and Botswana, in taking 27 cross-sections, established that the northern
channel is the deeper channel, "its mean depth of 5.7m. exceeds the depth of the south
channel by 2.13 m." (Botswana Memorial, Chapter VII, Professor Sefe's First Opinion, p.4).
These cross-sections were shown on a plan with a linear scale accompanying the Joint Survey
Report.
4. It is interesting to note that two experts, Mr. J.B. Botha and Mr. G.R. van der Merwe, were
supplied by the South African Department of Water Affairs, the very Department in which
Professor Alexander himself served as Chief of the Division of Hydrology and Manager of
Scientific Services until he retired in November 1984.
Pic of Queen Boat on river
349. This finding is not challenged in the Report of Namibia's Expert, Professor Alexander,
who admits "that the depth measurement at the selected cross-sections in the vicinity of the
bifurcation show that the minimum recorded depth of the south channel was marginally less
than that of the north channel". His assertion that "these measurements do not give any
indication of the long-term average depths which vary from season to season and from year to
year", is unsupported by measurement, and in any event gives no basis for maintaining that
the relative depth of the channels compared to each other alters.(Namibian Memorial, Vol.VI,
Part 1, Expert Report, p.32, para.11.6). The aerial photographs, which range from 1925 to the
present day, support the findings of the Joint Survey Report by showing the same unaltered
configuration of the two channels. Analysis of the satellite imageries of 1975, 1995 and 1996
also establishes the greater depth of the northern channel.
Pic of Queen Boat on river
(iii) The criterion of capacity to carry larger flow