Tree height and diameter at breast height (dbh) were measured on four tree species namely Acada erioloba, faidherbia albida, Tamarix usneoides and Em-lea pseudebenus in relation to the main river channel at two study sites along the Kuiseb River. The two sites Gobabeb and Swartbank were pre selected by the Gobabeb Training and Research Centre as part of their long-term ecological research programme. The main aim of the study was to find out whether actual size is affected by the position from the main channel. The results obtained at Gobabeb shows that size for Acacia erioloba is not affected by the position but has to do much with the plant morphological characteristics like having a deep taproot to access underground water. For Faidherbia albida it's more distributed closer to the main river channel therefore position for this tree species plays a role. Keywords: Kuiseb river, ephemeral rivers, Tamarix usneoide, Acalia erioloba.