Nadir Ahmed Elagib

Hydrological responses to land use/cover changes in the source region of the Upper Blue Nile Basin, Ethiopia

Understanding how changes in distinctive land use/land cover (LULC) types influence the basin hydrology would greatly improve the predictability of the hydrological consequences of LULC dynamics for sustainable water resource management. As the main flow contributor to the River Nile, quantifying the effect of LULC change on water resources in the source regions is very important for the assessment of water resources availability and management downstream in the riparian states in general and the study watersheds in particular. In this study, an integrated approach comprising hydrological modeling and partial least squares regression (PLSR) was used to quantify the contributions of changes in individual LULC classes to changes in hydrological components. Two watersheds, namely Lake Tana and Beles in the Upper Blue Nile Basin in Ethiopia, were considered for the conduction of hydrological modeling using LULC maps and the Soil and Water Assessment Tool (SWAT). In the Tana sub-basin, it is found that expansion of cultivation land and decline in woody shrub are the major contributors to the rise in surface run-off and to the decline in the groundwater component. Similarly, decline of woodland and expansion of cultivation land are the major contributors to the increase in surface run-off and water yield in the Beles sub-basin. Increased run-off and reduced baseflow and actual evapotranspiration would have negative impacts on water resources, especially in relation to erosion and sedimentation in the upper Blue Nile River Basin. As a result, expansion of cultivation land and decline in woody shrub/woodland appear to be major environmental stressors affecting local water resources. The wider implications of the hydrological changes on the Easter Nile water resources are briefly discussed. The approach to assessing changes in basin hydrology could generally be applied to a variety of other watersheds for which temporal digital LULC maps are available.

Lessons learned from Khartoum flash flood impacts: An integrated assessment

This study aims at enabling the compilation of key lessons for decision makers and urban planners in rapidly urbanizing cities regarding the identification of representative, chief causal natural and human factors for the increased level of flash flood risk. To achieve this, the impacts of flash flood events of 2013 and 2014 in the capital of Sudan, Khartoum, were assessed using seven integrated approaches, i.e. rainfall data analysis, document analysis of affected people and houses, observational fieldwork in the worst flood affected areas, peoples perception of causes and mitigation measures through household interviews, reported drinking water quality, reported water-related diseases and social risk assessment. Several lessons have been developed as follows. Urban planners must recognize the devastating risks of building within natural pathways of ephemeral watercourses. They must also ensure effective drainage infrastructures and physio-geographical investigations prior to developing urban areas. The existing urban drainage systems become ineffective due to blockage by urban waste. Building of unauthorized drainage and embankment structures by locals often cause greater flood problems than normal. The urban runoff is especially problematic for residential areas built within low-lying areas having naturally low infiltration capacity, as surface water can rapidly collect within hollows and depressions, or beside elevated roads that preclude the free flow of floodwater. Weak housing and infrastructure quality are especially vulnerable to flash flooding and even to rainfall directly. Establishment of services infrastructure is imperative for flash flood disaster risk reduction. Water supply should be from lower aquifers to avoid contaminant groundwater. Regular monitoring of water quality and archiving of its indicators help identify water-related diseases and sources of water contamination in the event of environmental disasters such as floods. Though the understanding of risk perception by the locals is an important aspect of the decision making and planning processes, it should be advanced enough for proper awareness.

Hydrological, socio-economic and reservoir alterations of Er Roseires Dam in Sudan

Er Roseires Dam plays a key role in controlling the Blue Nile flow in Sudan. This study explores the influence of the dam on the hydrological regimes, which in turn have implications for the ecosystem. The Range of Variability Approach (RVA) - based on a set of 32 indicators - was applied over the period 1965 to 2014 to establish a safe range of river flow. Moreover, remotely-sensed data of the Normalized Difference Vegetation Index (NDVI) was used to analyse the spatio-temporal variation of the dams reservoir area over the period 2000-2014. Significant influence on the dry-season hydrological indicators is expressed by high negative hydrological alteration of the range from -47% to -100%, but the dam contributes positively through flow regulation during the flood season. Impounding water procedure and fluctuation of water flow caused by the dam are found to induce significant alterations. Releasing less water during the dry season and more gradual impounding process, which are not expected to affect the power generation or irrigation practices, are recommended for better ecological restoration. The total surface area of the reservoir has changed post the implementation of the dam heightening project. Since 2012, the lake surface area has expanded by 250%. Relationships between the lake size and the head have been developed to help in the monitoring of the hydrological conditions and, accordingly, in managing the dam operation. A field survey showed that the dam plays a positive social role as the reservoir supports local activities, such as fishery, farming, and collection of wood and fruits. But increased humidity and health problems have also been noted. The Grand Ethiopian Renaissance Dam (GERD) would have a direct effect on Er Roseires Dam and the river flow downstream. High level of coordination among the riparian countries is recommended for better river water management.

Sensitivity of Water-Energy Nexus to dam operation: A Water-Energy Productivity concept

Understanding and modelling the complex nature of interlinkages between water and energy are essential for efficient use of the two resources. Hydropower storage dams represent an interesting example of the water-energy interdependencies since they are often multipurpose. The concept of Water-Energy Productivity (WEP), defined as the amount of energy produced per unit of water lost in the process, is introduced in this study to illustrate the relationship between energy generation and water losses by examining the sensitivity of the Water-Energy Nexus (WEN) to changing dam operation policy. This concept is demonstrated by developing a water allocation model of the White Nile in Sudan, including Jebel Aulia Dam (JAD), using a general river and reservoir simulation software called RiverWare. A number of 77 operation scenarios of JAD are examined for 30 hydrologic years (1980-2009), considering reducing the Full Supply Level (FSL) gradually from its current value to the minimum possible value, increasing the Minimum Operating Level (MOL) gradually to the maximum possible level, and operating the dam at a Constant Operating Level (COL). The results show that raising the operating level does not necessarily increase the WEP. In comparison to the current policy, the analysis shows that a maximum WEP of 32.6GWh/BCM (GWh/Billion Cubic Meters) would be reached by raising the MOL to 375masl (meters above sea level), resulting in an increase in average annual energy generation to 164.6GWh (+18.1%) at the expense of an annual water loss of 5.05BCM (+12.7%). Even though this operation policy results in a more efficient water use compared to the original operation policy, a basin-wide assessment that includes all hydropower storage dams in the Nile basin should be conducted to decide on where and how much energy should be generated. The present analysis and future examination of the multi-dimensions of the WEN in the context of dam operation are imperative to improve the decision making in the quest for efficient resource use and management.

Catchment response to climate and land use changes in the Upper Blue Nile sub-basins, Ethiopia

The impacts of climate and land development on streamflow and water balance components were analyzed in the Tana and Beles watersheds by using the Soil and Water Assessment Tool (SWAT). Streamflow response to simultaneous future land-use and land-cover (fLULC) and climate change (fCC) scenarios on the seasonal scale varied among the key water abstraction locations. The General Circulation Models (GCMs) average simulation of short-term climate indicated wetter and warmer climatic condition compared to that in the baseline period (1971/1980-2013). The near-future climate scenario would intensify extreme flow by increasing rainy season flow and reducing dry period flow. However, conversion of cultivation land on steep slope into forest might mitigate these extreme flows. At the outlet of Tana watershed, streamflow response would be amplified under concurrent scenarios of fLULC and fCC; but the streamflow would have an augmenting response at the outlet of the Beles watershed. Compared to response due to fCC alone, the streamflow and surface runoff components under combined fLULC and fCC scenarios would be alleviated in sub-catchments subject to conversion of cultivation in steep slope into forest land. The present results have significances for water resource management and land use planning in the Tana and Beles watersheds, and for other regions encountering identical pressures from climate change and LULC dynamics. In view of ongoing land use and climate dynamics, environmental policies must be carried out to cope with the potential changes of hydrologic regime. Moreover, catchment management should be adapted to changing hydrological regimes at different water abstraction points.

Spatio-temporal variations in climate, primary productivity and efficiency of water and carbon use of the land cover types in Sudan and Ethiopia

The impact of climate variability on the Net Primary Productivity (NPP) of different land cover types and the reaction of NPP to drought conditions are still unclear, especially in Sub-Saharan Africa. This research utilizes public-domain data for the period 2000 through 2013 to analyze these aspects for several land cover types in Sudan and Ethiopia, as examples of data-scarce countries. Spatio-temporal variation in NPP, water use efficiency (WUE) and carbon use efficiency (CUE) for several land covers were correlated with variations in precipitation, temperature and drought at different time scales, i.e. 1, 3, 6 and 12months using Standardized Precipitation Evapotranspiration Index (SPEI) datasets. WUE and CUE were estimated as the ratios of NPP to actual evapotranspiration and NPP to Gross Primary Productivity (GPP), respectively. Results of this study revealed that NPP, WUE and CUE of the different land cover types in Ethiopia have higher magnitudes than their counterparts in Sudan. Moreover, they exhibit higher sensitivity to drought and variation in precipitation. Whereas savannah represents the most sensitive land cover to drought, croplands and permanent wetlands are the least sensitive ones. The inter-annual variation in NPP, WUE and CUE in Ethiopia is likely to be driven by a drought of time scale of three months. No statistically significant correlation was found for Sudan between the inter-annual variations in these indicators with drought at any of the time scales considered in the study. Our findings are useful from the view point of both food security for a growing population and mitigation to climate change as discussed in the present study.

Socio-hydrological Framework of Farmer-Drought Feedback: Darfur as a Case Study

This paper attempts to conceptualize key socio-hydrological feedback loops between farmers and drought phenomena. To this end, two-fold aspects are considered for the Darfur region in the west of Sudan. The first one is the understanding of farmers’ perception of the major drought conditions, i.e. changes in patterns of rainfall and increase in temperature, in the region in comparison to the observed trends and variability (meteorological records). The second aspect is the identification of the types of concordant adjustments in the farming practices those farmers have made in response to drought conditions. Scheduled interviews composed of 98 farmers formed the basis of establishing the socio-hydrological framework. The interview results are discussed under the reality of human conflict in the context of a prototype cause-effect approach to defining the framework of drivers, pressures, state, impacts and responses (DPSIR) in the farmer-drought system. Climate in the region shows different features of drought, including increasing rainfall variability, changes in wet-season structure to which crop growth is sensitive, and increasing temperatures. Farmers have stronger perception of changes in rainfall patterns than in temperature. They rank the former as the main factor behind the declining crop; however, the results also suggest poor soil fertility as additional important agent. To reduce the drought risk to farming in the region and enhance crop productivity, farmers use a variety of strategies, such as early planting, frequent weeding, diversification of crops, cultivation of early maturing varieties and soil conservation. However, these steps are challenged mainly, in order of priority, by lack of finance, lack of machinery, invasion of insects and pests and shortage of labour. Urgent support from policy-makers is thus needed to enable an environment for sustainable agricultural practices in the region.