ACORD
>	Introduction
>	Project team
>	Project aims
>	Methods
>	Data
>	Documents
>	Training
>	Publications
>	Links
Department Homepage

ACCORD: An international project to monitor aquatic biodiversity in the Okavango Delta, Botswana and the relationship with climate and hydrology

INTRODUCTION

Globally, wetland systems are rich in biodiversity but are being degraded rapidly. The Okavango Delta in Botswana is one of the world's largest inland wetland regions. The 'delta' is a large alluvial fan created and maintained by the annual flooding of the Okavango River. The Okavango river rises in the highlands of central Angola (as two main tributaries; the Cubango and Cuito rivers) and flows southeast for around 600km towards the centre of the southern African subcontinents where it terminates in the vast floodplane of the Okavango delta, in northwest Botswana (see map).

 

Figure 1.(a) The Okavango river basin and (b) satellite image from the MODIS sensor taken on 1/9/04 during peak flood

During the annual flood event, the flooded area increases from about 5000 km2 to 6000-12000 km2 (Figure 1b and 2). Here the river creates a unique, dynamic mosaic of habitats, including river channels, permanent swamps, seasonally flooded swamps and islands, with exceptionally high beta diversity (Figure 3). It is one of the WWFs top 200 eco-regions of global significance and the world ’s largest Ramsar site. One of the reasons the system is so unique is that the annual flood of the delta is out of phase with the wet season. Rainfall occurs in the local summer (Nov-March) over Angola and Botswana but the low gradient of the river as it exits the Angolan highlands creats a long time lag such that peak flood in the Delta occurs during August in the local dry season. This ensures that the delta is a vital source of water for wildlife in the region during the long dry season.

Figure 2. The Okavango river delta

 

Figure 3. aerial view of delta (source www.okavango.info) and close up of river channel vegetation

Due to the relatively low level of development in the river basin the Okavango may be considered to be perhaps the last near pristine river system in Africa. However, the system is under pressure from (i) potential development in both the river catchment (in Angola, Namibia and Botswana) and the delta region, including land use change (notably resettlement populatons in post civil war Angola), dams, abstractions and tourism (ii) the impacts of climate variability and change. The diverse wildlife for which i the Okavango delta is justly famous (including many endangered species) is dependent on the delta's aquatic system. Yet this field has been neglected and is poorly understood. It is however likely to be highly sensitive to changes in water levels.

 

---