While caring for more than 180,000 Sudanese refugees gathered in the desert landscape of eastern Chad, the United Nations High Commissioner for Refugees has begun using satellite data to identify hidden water resources and site new camps. By permission of the Chad government, there are currently nine United Nations High Commissioner for Refugees (UNHCR) camps in place. UNHCR has transferred the vast majority of the refugees from the volatile border to the camps. Thousands more have come on their own from the border, further straining already scarce resources. And concerns remain high that more refugees could still flee from Darfur. A huge volume of people has to be kept supplied with food, water and basic necessities in this remote region, linked by inadequate roads made worse by the onset of the rainy season. The greatest single need is water. UNHCR standards call for 15 litres of water per person per day, but some camps in eastern Chad are still below this minimum requirement.
In March UNHCR requested UNOSAT assist with locating hidden water resources and proposing optimal locations for new camps in the region. The ESA-backed UNOSAT consortium provides United Nations agencies and the international humanitarian community with geographical information products derived from satellite imagery. Based on a preliminary analysis of the water conditions there, UNHCR proposed a water development strategy, and in collaboration with UNOSAT designed the water survey. “They asked us to address this major problem of obtaining water for refugees, and working with consultant firm Radar Technologies France (RTF) we designed a solution,” said Olivier Senegas of UNOSAT. “By the beginning of July we supplied water target maps covering over 22500 square kilometres of territory around the refugee camps of Oure Cassoni, Touloum and Iridimi.
Over the course of July UNHCR and RTF were able to successfully confirm these water sources detected by satellite with ground truth; which at the moment is being further examined through more focused geophysical analysis on-site to assess the actual potential/productivity of such water sources. The technique is based on merging results from different satellites: multispectral optical imagery from Landsat, C-band radar imagery from ESA’s ERS spacecraft and L-band radar imagery from Japan’s JERS-1. In addition a digital elevation model (DEM) derived from the Space Shuttle Radar Topography Mission (SRTM) is applied.
In Chad the refugees are in a desperate state, and water represents a precious commodity. Previously, well diggers had been pretty much digging employing essentially the local knowledge and basic geophysical techniques – they had a success rate of 50%, not bad in the circumstances, but still a waste of time and money. Now the maps direct them where best to go, they just have to follow them.
The second phase of the project has been to use the maps to review proposed sites of new camps. Five new camps had been provisionally planned but the survey showed they had no nearby water supplies. Instead seven more suitable locations were highlighted that combine nearby water resources with nearness to transport links and suitable topography and dry ground. The plan is to extend coverage across eastern Chad as the situation demands. Farmers in Chad can also use the same data in future, and the highly accurate and geo-referenced maps could potentially become part of a GIS meeting national needs.