Wetland & Fish Ecology - Enviro Dynamics Namibia

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the lakes. As the system that will receive the possibly increased floodwaters diverted
around Oshakati by the proposed dike as well as the storm water draining from the
town via the Okatana River, it is worth looking at the system a little more closely.
The Omadhiya lake complex includes 7 main inter-connected, shallow, ephemeral
lakes or pans that dry out every few (2/3) years (van der Waal, 2000a). All the water
flowing through the Cuvelai system converges on these pans; from the west via the
Etaka oshana water enters Lake Oponono; from the north-west via iishana to the
west of Ombalantu water enters Uupeke and Korolo (24ha); from Ogongo and
Oshikuku in the North water enters Uulidi (100ha), Omanetha (48ha) and Inakulo
Yomadhiya (83ha), from Oshakati into UUludi and Korolo and from Ondangwa in the
north-east floodwaters enter Onamagwena (507ha). From here water can flow east
into Omanetha or south into Inakulo Yomadhiya (grandmother of the lakes) and
eventually into Oshituntu (100ha) from which the main outflow is the Ekuma River
flowing into north-western Etosha. The lake sizes in brackets are low water sizes
calculated from satellite images by Verlinden of the Northern Namibian
Environmental Project after the 1995 efundja, cited by van der Waal (1999, 2000a).
He estimated that the total lake area inundated at low flood was 962ha while at
high flood it would be 7430ha, showing the extreme natural variation of the efundja.
Van der Waal (1999) mentions three sources of input into the lakes: local rainfall (400
mm/a); local floods caused by rain upstream in the oshana region; and floods
(efundja) from Angola. Based on historical records, information from the Department
of Water Affairs and his own observations he calculated that the lakes are likely to be
receive some water every two out of three years and that half of these could be
from a large efundja, i.e. once in three years, but warns that inflows are extremely
variable.
Draft Environmental Impact Assessment: Oshakati Flood Mitigation Project
Specialist Study: Wetland Ecology and Fish Ecology Imputs
July 2012