Journal of Hydrology (2006) 331, 1– 2

ava i lab le a t www.sc iencedi rec t . com

journal homepage: www.elsevier .com/ locate / jhydrol

EDITORIAL

Water resources in regional development:The Okavango river

For much of the world the availability of adequate waterposes a significant challenge to development and environ-mental sustainability. For the people living in the semi-aridclimate of southwest Africa, in particular, water scarcityprovides a major stumbling block to increasing societaland individual wellbeing. One of the major water resourcesin this region is the Okavango river system. Spanning threecountries, Angola, Namibia and Botswana, the river basincovers an area of approximately 192,500 km2. The systemis perhaps best known for the Okavango delta in Botswana,an alluvial fan formed, where the river terminates. The del-ta is maintained by the annual pulse flooding of the Okav-ango River (from the highlands of central Angola) creatingone of the world’s largest inland wetland systems. TheOkavango delta contains unique habitats with exceptionallyhigh beta diversity and as such is one of the WWFs top 200eco-regions of global significance and the world’s largestRamsar site. The Okavango river system presents an idealcase study to understand the workings of a large but rela-tively undeveloped hydrological system. To the ripariancountries however the river is of much more immediateimportance; supporting local livelihoods through tourism,national water supply, irrigation and horticulture andpotentially for energy supply. These often competing de-mands on the hydrological system are set against a back-ground of climate variability and future change. It iswithin this context that in recent years the river Okavangohas widely been seen as a source of potential conflict bothbetween and within nations.

Unfortunately, in part due to a prolonged civil war in An-gola, there have been few hydrological/climatological mea-surements in the Angolan sector of the river catchment overthe last 30 years. It is in this part of the catchment that thevast majority of the rainfall, which drives the system oc-curs. While a number of excellent studies have exploredthe hydrology of the Delta (e.g. McCarthy et al., 1998;Gumbricht et al., 2004; Gieske, 1997) the lack of data onthe upper parts of the river have meant that little, if any,research has previously been carried out on the Okavangohydrological system as a whole. In this special issue of the

0022-1694/$ - see front matter �c 2006 Elsevier B.V. All rights reserveddoi:10.1016/j.jhydrol.2006.04.038

Journal of Hydrology we bring together a series of comple-mentary articles by international scientists analysing thehydrology of the Okavango river system.

The interdisciplinary research outlined in this collectionof papers was largely supported by an EU FP5 INCO-DEV pro-ject ‘Water and Ecosystem Resources for Regional Develop-ment’. The research aims to further the understanding ofone of Africa’s great river systems and to provide modellingtools to inform dialogue on future management of the riversystem at the national and international level. By recogniz-ing that the water flow is the integrated response of naturalfluctuations and human interventions (governed by nationaland international policy, socio-economic structures and lo-cal knowledge and value systems) the papers attempt to linkthe components of the natural resource system to the socio-economic dynamics acting in the basin. This overarching aimis achieved by: (i) developing hydrological models of the riv-er catchment and delta systems; (ii) developing scenarios ofpossible human-induced development interventions in theriver basin related to water abstractions, land-use change,and climate change; (iii) undertaking simulations of thehydrological response to the various scenarios.

The special edition starts with a paper by Kgathi et al.introducing the Okavango River, its people environmentand economic development potential. As such it outlinesthe present and potential future pressures on the hydrolog-ical system due to rapid increases in population, resettle-ment activities arising from the peace process in Angolaand the possible major development initiatives of increasedwater abstraction and hydro-power generation. A discussionof the issues associated with balancing conservation witheconomic development concludes by recommending thedevelopment of sustainable tourism and community-basednatural resource management initiatives for the basin inthe future.

The second paper by Wilk et al. describes the collationand construction of the necessary hydro-climatological datarequired by the modelling process. In particular, the paperoutlines the derivation of rainfall fields from historicalraingauge and satellite data in order to provide base data

.

2 Editorial

with which to calibrate the hydrological models of the riverand its delta.

The third paper by Hughes et al. outlines the calibrationand validation of a hydrological model of the Okavango Riv-er basin upstream of the delta region. The hydrologicalmodel is a modified version of the Pitman model, includingmore explicit ground and surface water interactions. Thepaper finds that despite the limited data access, the modeladequately represents the hydrological response of the ba-sin and concludes that it can be used to assess the impactof future development and climate change scenarios.

The fourth paper by Andersson et al. is the first of twokey papers in the special issue that assess the impact ofthe various development and climate change scenarios onthe Okavango hydrology. The paper outlines three futuresets of development scenarios derived with participationof stakeholders (low impact, ‘‘business-as-usual’’ (medium)and high impact development). Climate change scenariosare based on various general circulation model (GCM) simu-lations of future regional climate under the Intergovern-mental Panel on Climate Change (IPCC) SRES A2 and B2greenhouse gas emission scenarios. The hydrological re-sponse in the river basin to these development scenariosis simulated using multiple runs of the Pitman model. Thepaper finds that with the exception of the high impactdevelopment scenario of hydropower schemes, the simu-lated impacts of climate change are considerably largerthan those of the development scenarios, although the re-sults are sensitive to the choice of GCM and the IPCC SRESgreenhouse gas emission scenarios.

The fifth paper by Wolski et al. presents a hydrologicalmodel of the Okavango Delta wetland system. The model in-cludes a physically detailed representation of surfacewater–groundwater interactions and the use of measure-ment-based rather than model calibrated parameterisationsof topographic controls of floodplain water storage. The pa-per also outlines a GIS model developed for the spatial dis-tribution of the simulated floods. The model successfullyrepresents historical observed outflows and flood extent.The last paper (by Murray-Hudson et al.) is the second ofthe key results papers quantifying the impact of the devel-opment and climate change scenarios in this case on the

flood extent and duration in the delta. Results indicate thatupstream abstractions for human use are likely to havesmall short term effects on the flooding pattern in the Del-ta, while other upstream developments such as damming ordeforestation have more pronounced effects. However, thepaper finds that these effects are relatively small in com-parison to changes resulting from historic climatic variabil-ity and to the potential effects of future climate change.The combined potential impact of human abstraction andclimate change is simulated to involve significant delta dry-ing and changes in the delta floodplain ecosystems.

The issue of water scarcity presents a fundamental prob-lem to the people of southern Africa and this special editionprovides details of an in-depth study of the hydrologicalworkings of a complex river system.

References

Gieske, A., 1997. Modelling outflow from the Jao/Boro River systemin the Okavango Delta. Botswana. J. Hydrol. 193, 214–239.

Gumbricht, T., Wolski, P., McCarthy, T.S., 2004. Forecasting thespatial extent of the annual flood in the Okavango Delta.Botswana. J. Hydrol. 290, 178–191.

McCarthy, T.S., Bloem, A., Larkin, P.A., 1998. Observations on thehydrology and geohydrology of the Okavango Delta. S. Afr. J.Geol. 101 (2), 101–117.

Dominic R. KnivetonDepartment of Geography,

University of Sussex, Falmer,Brighton BN1 9QJ, United Kingdom

Fax: +44 1273 677196E-mail address: d.r.kniveton@sussex.ac.uk

Martin C. ToddDepartment of Geography,

UCL (University College London),26 Bedford Way, London WC1 8HR,

United Kingdom