Flood Forecast and Early Warning

Groundwater holds the promise of closing the gap between water supply and demand, and in buffering the effects of climate variability. The other driver of interest around groundwater is the role that groundwater plays in addressing the SDG 6 target for drinking water. To reach this SDG 6 target, groundwater delivered thorough multiple delivery mechanisms (e.g. boreholes, springs, reticulated systems, dug wells) has a vital role to play. Groundwater use for socio-economic improvements is generally in a growing stage in Africa and in the Nile basin in particular. Experience elsewhere in the world (South East Asian countries) and in some cities in Sub-Saharan Africa show that this precious resource can rapidly degrade and depleted. A UNEP report (Morris et al., 2011) demonstrates that groundwater storage that provides the ultimate resources buffer is threatened with a double jeopardy - depletion and degradation. The pressure is already felt in the numerous small aquifers in the upper Nile riparian countries.

Groundwater monitoring of both levels and quality will depend on where the resource is currently being abstracted or where potential exists to develop its use for various purposes. A typical groundwater monitoring program will involve monthly analysis of both level and quality at key locations. The common practice is that; groundwater monitoring should have certain predefined objectives. The general objective of the monitoring program is to supply data for characterization of the regional groundwater systems, identification of trends in time and prediction of the regional impacts. The design of a cost effective and purposeful monitoring network largely depends on the stages of groundwater (aquifer) assessment and development, the importance of the aquifer, the threats on the aquifers, as well as the natural resilience and fragility of the aquifers. Figure 1 shows some general recommendation as to what type of monitoring is required depending on the degree of groundwater development. Design of groundwater monitoring network also depends on financial and institutional capacity to sustainably run monitoring network.

The Eastern Nile Basin has a special significance in the water resources management of the entire Nile Basin. The Eastern Nile basin contributes the largest volume of surface water flows, the largest amount of renewable groundwater resources and also the largest groundwater storage potential when it is compared with the other sub basins of the Nile. The aquifers in the Eastern Nile Groundwater basins and the other basins connected to the Eastern Nile groundwater basins collectively have a proven groundwater storage amounting to more than 210,000 Billion m3. While the upstream countries are characterized by smaller aquifers with connection to present day renewable groundwater recharge, the aquifers in the lower Nile segment are characterized by large storage with limited groundwater recharge, except along the Nile valley. The Eastern Nile basin is underlain by four major categories of aquifers. The basement rock aquifers occupy 30 % of the basin area, most of which is exposed in arid areas of Sudan and Egypt. The consolidated multilayered sedimentary rock aquifer covers 24% of the surface area of Eastern Nile basin but contain one of the most prolific aquifers with very big storage. The multilayered unconsolidated sediments, occupying 34% of the basin areas is the most exploited aquifer for irrigation water use in Sudan and Egypt. Volcanic rock aquifers cover 12% of the basin area, whereby 80% of the volcanic aquifers are confined within Ethiopia. More than 30 individual aquifers have been identified in the Nile Basin.

The Eastern Nile (EN) Flood Preparedness and Early Warning Project (FPEW) under the Integrated Development of the Eastern Nile (IDEN) is an ongoing project that is being implemented in two phases. The FPEW has created a regional Flood Forecast and Early Warning System (FFEWS) and has strengthened national offices both in terms of capacity and equipment.