by David MacDonald, British Geological Survey
A key component of water resource management is the sound scientific understanding of water flows and storage. Where water supplies are sourced through wells and boreholes in the underlying rocks, we need to understand the volumes of water stored there and how natural climate variability and land cover control how these stores are replenished. For longer term planning purposes, we also need to assess how climate and land use change will impact on the resource.
The BRAVE project aims to provide tools to support water resource management in Ghana and Burkina Faso. This is expected to improve our understanding of the water flows and storage through the instrumentation of a series of small catchments to monitor all aspects of the water balance. The strategy for the BRAVE project was to build on existing monitored catchments, recognizing the cost of monitoring equipment; the time and effort required to build relationships with local communities in the catchments being monitored; and the value of existing contextual and longer-term data sets.
In Burkina Faso, one of the detailed monitoring catchment which BRAVE is working in is around the village of Sanon, 40 km to the north of the capital city, Ouagadougou. Sanon represents much of semi-arid West Africa as the land cover has been significantly changed through farming. The site was first established by BRGM, the French Geological Survey, but has been built up in recent years by the Institut International d’Ingénierie de l’Eau et de l’Environnement (2iE), with input from the Institut de Recherche pour le Développement (IRD). Prior to BRAVE’s involvement, there was a network of monitoring boreholes and a weather station in place, and geophysical surveys had been undertaken to characterise the hydrogeological setting. This, with the time series data collected, had allowed a conceptual model of groundwater flows and storage to be developed. Crucially, 2iE has developed a good relationship with the local community and involved members of the community in this monitoring.
Through the BRAVE project, the further development of the monitoring network at Sanon has been a collaborative activity involving 2iE, the University of Ouagadougou (UO1), IRC Burkina Faso and the British Geological Survey. This has included the drilling and testing of additional boreholes, enhancement of the weather station, installation of a series of transects of access tubes to measure soil moisture and the setting up of a river flow measurement site. It has also involved the construction of three plots (4 x 20 m) containing land use representative of the catchment within which runoff, soil moisture, groundwater level, soil infiltration, soil evaporation and plant growth and transpiration are directly measured. The monitoring is undertaken by members of the local community and by students from 2iE and UO1, as well as by BRAVE project staff.
The other two existing catchments where the BRAVE project has enhanced monitoring, are part of the network of research catchments run by the West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL), a large-scale programme for strengthening research infrastructure and capacity involving ten West African countries and funded by the German government. One of these catchments, Aniabisi, is in Northern Ghana in an area similar to Sanon, where the landscape has been substantially changed through farming; the other, Nazinga, is just across the border in southern Burkina Faso in a nature reserve where the natural land cover is still intact. The infrastructure already in place in these WASCAL catchments has been built upon through collaboration by WASCAL, the Ghanaian Water Research Institute and BGS. Aniabisi now has infrastructure and monitoring equipment similar to that in Sanon, including the three land use plots; Nazinga is a scaled down version of this. As with Sanon, the local relationships with communities has been important in the installation of new infrastructure and local residents are also undertaking some of the monitoring work. Crucial impacts have been the support of WASCAL technical staff in the development and subsequent running of the sites.
The collaboration between BRAVE and West African organisations has been a great success that has seen the value added to established sites. The embedding of BRAVE research will greatly improve the chances that the monitoring sites developed through UPGro will be sustained beyond the period of the Programme. The importance of the resulting datasets cannot be underestimated, as we strive to understand the impacts of environmental change on the water resources that underpin future adaptation and resource management.
Top Photo: Sorghum cropping is a land use type that is included in monitoring plots at both Sanon and Aniabisi