Assessing the effect of sustainable land management on improving water security in the Blue Nile Highlands: a paired catchment approach.

The Blue Nile Highlands, Ethiopia, has been experiencing serious land degradation, menacing water security, and then human well-being. However, sustainable land management (SLM) may be the way to curb land degradation and improve water security. Therefore, in order to assess benefits after a 5-year catchment restoration effort, we conducted a paired-catchment study to investigate runoff and soil moisture dynamics. First and second catchments were used as control and treated, respectively. After comparing observations gathered from four sites within each of the study catchments, we found that implementing SLM reduced runoff curve numbers by -13.9 to -21.6 units and increased soil moisture storage by 15.6 to 800%, then promoting rapid recovery of the hydrologic functionality of the natural landscapes. We conclude that SLM initiatives can greatly improve water security in the drought-prone Blue Nile Highlands.

Summer rains and dry seasons in the upper Blue Nile Basin: the predictability of half a century of past and future spatiotemporal patterns.

During the last 100 years the Ethiopian upper Blue Nile Basin (BNB) has undergone major changes in land use, and is now potentially facing changes in climate. Rainfall over BNB supplies over two-thirds of the water to the Nile and supports a large local population living mainly on subsistence agriculture. Regional food security is sensitive to both the amount and timing of rain and is already an important political challenge that will be further complicated if scenarios of climate change are realized. In this study a simple spatial model of the timing and duration of summer rains (Kiremt) and dry season (Bega), and annual rain over the upper BNB was established from observed data between 1952 and 2004. The model was used to explore potential impacts of climate change on these rains, using a down-scaled ECHAM5/MP1-OM scenario between 2050 and 2100. Over the observed period the amount, onset and duration of Kiremt rains and rain-free Bega days have exhibited a consistent spatial pattern. The spatially averaged annual rainfall was 1490 mm of which 93% was Kiremt rain. The average Kiremt rain and number of rainy days was higher in the southwest (322 days) and decreased towards the north (136 days). Under the 2050-2100 scenario, the annual mean rainfall is predicted to increase by 6% and maintain the same spatial pattern as in the past. A larger change in annual rainfall is expected in the southwest (ca. +130 mm) with a gradually smaller change towards the north (ca. +70 mm). Results highlight the need to account for the characteristic spatiotemporal zonation when planning water management and climate adaptation within the upper BNB. The presented simple spatial resolved models of the presence of Kiremt and annual total rainfall could be used as a baseline for such long-term planning.