Spatiotemporal variation and the role of wildlife in seasonal water quality declines in the Chobe River, Botswana
In water-stressed regions of southern Africa, freshwater resources are under increasing extractive pressures. Sustainable management of dryland river systems is often complicated by extreme variability of rainfall in time and space, especially across large catchment areas. The Chobe River is the only permanent surface water source in the remote Chobe District of northern Botswana, and its floodplain and associated wetlands ecosystem are among the most biodiverse in the world. Seasonal rainfall and floods in the Chobe River system exert a significant impact on the timing of human activities, as well as the movement and ecology of native wildlife. Further, significant temporal relationships have been identified between hydrological dynamics in this system and diarrheal disease outbreaks in the local community. Because of the extensive provision of ecosystem services and high subsistence value of the Chobe River, and other southern African dryland rivers and wetlands, there is a critical need to better understand the interdependent drivers of water quality changes in the region. Using field-transect data, GIS, remote sensing, geospatial analysis, and a spatiotemporal modeling framework, we examined seasonal variation of the fecal indicator bacteria, Escherichia coli, and total suspended solids (TSS) in the Chobe River in relation to landuse and hydrology.
We observed a strong seasonal influence on the variability of E. coli and TSS concentrations in the Chobe River coinciding with a transition period between wet and dry seasons. Areas of protected land use (national park) and presence of river floodplain were significantly associated with higher E. coli concentrations. E. coli levels within the national park were higher in locations where high-density wildlife populations occur. The results suggest seasonal wildlife movements, floodplain distribution, rainfall, and annual flood pulses influence the timing of water quality declines in this dryland river system.