botswana/namibia - Cour international de Justice

the River Rovuma in Article I(2) and to the River Aka in Article IV (i) of the 1890
Agreement.
272. The northern channel in the vicinity of Kasikili/Sedudu Island satisfies the treaty makers'
requirement of a 'main channel' through which the Chobe River 'descends' to its confluence
with the Zambezi. Flow through the northern channel is continuous in a downstream direction
with a constant level of 925.6 metres, South African Mean Sea Level, measured at the Kasane
Gauging Station through all seasons of the year. (Mean monthly water levels at the Kasane
Gauging Station are shown on Table 3 in Professor Sefe's Second Opinion, pp.28-35 (in
Appendix 2 of this Counter-Memorial).
273. This flow is demonstrated in the hydrological surveys and gaugings carried out by the
Department of Water Affairs (Botswana) at seven stations along the Kwando-Linyanti-Chobe
system south of the Caprivi Strip from the Upper Kwando down to Shaile, as shown on the
Map D opposite page 13 of this Counter-Memorial.
G9 - Satellite Image, Classified Image (Landsat MSS Bands 4,5,6,7, June 1975)
274. The Chobe River shows higher levels of flow in its lower reaches as it approaches the
confluence with the Zambezi. The summary at the end of Table 3 was used to draw Figures 6
and 7 in Professor Sefe's Second Opinion reproduced at page 104. This Figure 6 shows the
spatial variation of flow in a downstream direction along the Kwando-Linyanti-Chobe River
system. It demonstrates the augmentation of flow as the catchment area increases, which is a
characteristic of perennial rivers, and this is plainly visible at the up-stream stations of Upper
Kwando (GS No. 6115) and Bates Camp (GS No. 6125). At Sajawa Gauging Station No.
6414, where the river begins to emerge from the Linyanti Swamps, the attenuating effect of
the swamp on water levels becomes obvious. From this point onwards water levels rise again
as the catchment area increases. Highest water levels are recorded on the Chobe River at
Kasane (GS No. 6624).
275. Like all perennial rivers that depend upon seasonal rainfall, the Chobe River has high
and low flow seasons. The data in Table 3 show that the Kwando-Linyanti-Chobe River
system experiences seasonal as well as year to year fluctuations.Minimum flow velocities
during the low season are of the order of 0.5 metres per second. Thus the river is never
stagnant except for a two or three-day transition between the backflow and normal
downstream flow.
II. EVIDENCE OF CURRENT IN THE NORTHERN CHANNEL
276. A reference to cross-sections 5 and 6 in the attachment to the Botswana Memorial
(which were plotted by the Joint Survey Team of 1985) reveals that at the outside of the curve
between the Spur channel at Kabuta and the northern channel, the channel falls vertically
down against the north bank to 9 and 7 metres respectively. This drop in depth can only be
explained by current sweeping round the outside of the curve. This effect could not happen in
"stagnant" water. The same effect can be observed at cross-sections 9 and 10 where the
southern channel sweeps left out into the main channel immediately south of Kasane where
the depths of 13.5 metres and 7.5 metres are recorded against the outside of this curve.
277. This effect, however, is not apparent in the southern channel at cross-sections 18, 18A,
18B, and 19, which are the cross-sections around the outside of the curve around the north