Many firms, including RTF, are exploiting these recent trends to offer new solutions to traditional problems such as groundwater exploration. The UNHCR, together with UNOPS and UNOSAT, recognized that commercial geospatial technologies could be used to respond to the Darfur refugee crisis, creating an excellent example of the positive role the private sector expertise can play in humanitarian assistance and sustainable development. Although such cooperation is not without controversy, the need to encourage public-private partnerships is now firmly established. (See “Ethics” box below)
Data & Methods WATEX is a proprietary groundwater exploration process used to locate renewable groundwater reserves in arid and semi-arid environments. Developed over a period of several years, the process dramatically improves the ability of humanitarian and development organizations to identify areas suitable for (temporary and permanent) settlement, cultivation, and development. The process is economical, rapid, and highly effective for water potential mapping even over heterogeneous areas several hundred thousand square kilometers in size. This section details the types of data and the general methodology used to assess the water potential of the eastern Chadian region of Ouaddaï, along the border of Darfur, Sudan. Data The following raw data inputs were used to facilitate the assessment of water potential of the project area:
Method As suggested in the Introduction, the goal of this project was to detect large renewable water reserves capable of supporting refugee settlements of 20,000 per camp, for up to 200,000 Sudanese refugees, in accordance with the UNHCR’s target provision rate of 15 liters/day/person. This automatically precluded water exploration of small or non-renewable reserves, and limited analysis to areas of sizeable, renewable water potential. This section describes the methodology employed during the project, using a case study of one of the areas identified as being capable of meeting this goal. This area, called Wadi Dalal, was one of several sites identified as having the potential to support at least 20,000 people (Gachet 2005). In February 2005 the UNHCR announced the establishment of the Gaga refugee camp along Wadi Dalal and began resettlement of thousands of refugees soon thereafter (Chamberlain 2005). Proven water reserves at the site are capable of supporting up to 30,000 refugees, making the case study of Wadi Dalal a dramatic example of the impact geospatial technologies can have on humanitarian relief operations (IRIN 2005). The first phase of analysis involved mapping features which directly (or indirectly) affect the likelihood of finding large, renewable reservoirs. A variety of data sources and imagery were used to determine lithology, weathering processes, vegetation cover, and land use. The SRTM terrain model was used to delineate watersheds, slopes and river profiles, and to estimate energy level of transportation along wadi (i.e. riverbed) courses. The SAR images were processed to map fractures, uplifts and subsidence; these features can determine river direction as well as accretionary or erosionary impacts upon reservoir thickness. WATEX was then employed to map the relative moisture of surface and underlying strata. The penetration and soil moisture sensitivity of SAR imagery has been well established, and known to be optimal in fine, dry sand with minimum volumetric water content (Ulaby, Moore et al. 1986; Williams and Greeley 2000). However, even under ideal conditions, the penetration of microwave signals is restricted to near-surface moisture detection. RTF focused upon the assessment of alluvial water potential along existing wadis and nearby fractures and faults, since deeper reservoirs can still be detectable if capillary moisture flow reaches near-surface strata. After each region of interest had been sufficiently mapped, an assessment of the following key parameters was undertaken in order to establish an overall rank of each “radar anomaly” with water potential: 1. Size of the radar anomaly, which is an indicator of the water storage volume of a buried reservoir within a wadi. As previously indicated, a reservoir with a sustainable production of 90,000 m3/year is able to support a camp of 20,000 refugees. Assuming an average rock porosity of 10%, this implies the need to find a buried reservoir with an overall productivity of nearly 1 million m3/year. This is equivalent to a wadi reservoir of about 2 km long and 60 m wide, assuming a reservoir thickness of 7.5 m at an average depth of 10 to 15 m). Accordingly, only radar anomalies covering a minimum surface of 12 hectares (2 km x 60 m) were considered in order to meet the above project goal. At this stage of the WATEX process, it is impossible to know if anomalies are associated with buried reservoirs (versus surface moisture linked to clay or silts deposits), and more analysis is required. Figure 1 illustrates an image showing the radar anomaly along the Wadi Dalal.  Fig 1 - Radar backscattering anomaly revealed by WATEX processing, indicating the potential existence of buried aquifer within the wadi course. (All images © RTF 2004) 2. Amount of upstream watershed drainage, since each potentially suitable target must also be fed by an upstream watershed capable of supplying at least 1 million m3/year of water to the reservoir. (The watershed surface area and average annual rainfall were used to estimate total yearly catchment, which was then corrected for evaporation, erratic runoff, and other water losses.) 3. Quality of reservoir gravels, since the origin and nature of the gravels which supply the reservoir determine its ability to reliably absorb and store sufficient water volumes. It is necessary to discriminate between “reservoir feeders” and ”reservoir poisoners”. For example, basaltic rock types can create excessive silt and reduce reservoir porosity and permeability, and are called “reservoir poisoners”. Alternatively, “reservoir feeders” such as quartzite and sandstone can produce gravels that are ideal for sustaining large volumes of water storage. Figure 2 illustrates the large granitic feeder directly above the Wadi Dalal campsite.  Fig 2 – Landsat 7 ETM image in Sultan Combination showing the watershed upstream of Wadi Dalal campsite, and reservoir feeder that provides high-quality gravels to the downstream water reservoir within the wadi. |