Hydrology and forests in the Blue Nile basin

Forest cover change is considered a major cause of water scarcity during the dry season in the Blue Nile River Basin of Ethiopia, which is part of the Nile River system. However, this is an over-simplification of the complex reality of forest and flow relationships, especially in the tropics. The objectives of this study were to explore the spatial relationship of land use and flow regime, detect temporal changes in the hydrological regime, determine changes in the forest cover, and summarize the results to define the relationship between forest cover and hydrological regime. Two broad approaches were used to address these aims: observational data analysis and community perception. Thirty-two watersheds were covered in the spatial study, and 45 years of data for a dozen of these watersheds were analyzed in the temporal study. Statistical methods were used to explore the spatial relationship of land use and flow, and both statistical and modeling methods were used to detect hydrological change over time. Remote sensing analysis was used to document forest cover changes. Natural grassland and woodland had a positive, while grazing land and open bush land had a negative correlation with low flow regimes at the spatial scale. There were no major temporal changes in the flow regime, or clear results to attribute land degradation or land use change to hydrological changes and specific changes within each watershed. The change related to forest cover were watershed specific, although there were general differences between southern and northern watersheds regarding the time of deforestation. The community perception indicated the relationship of forest cover change and flow regime was more complex than just deforestation causing loss of dry season flow. According to the elders, forest and flow relationships were watershed specific, even sub-watershed specific. The lack of a clear relationship between forest cover change and flow regime in the temporal dimension could be attributed to the scale of watersheds, uncertainty about the measurement of flow extremes, and the impact of variability in rainfall within the region. The watershed-specific nature of the relationship between forest and flow within the Basin, confirmed by the community perception, indicates forest hydrology studies should be tailored to watershed scale, or even sub-watershed scale i. e. hill-slope scale, and address the relevance of water availability at farm and river scale

Hydrological characterization of watersheds in the Blue Nile Basin, Ethiopia

Thirty-two watersheds (31–4350 km2), in the Blue Nile Basin, Ethiopia, were hydrologically characterized with data from a study of water and land resources by the US Department of Interior, Bureau of Reclamation (USBR) published in 1964. The USBR document contains data on flow, topography, geology, soil type, and land use for the period 1959 to 1963. The aim of the study was to identify watershed variables best explaining the variation in the hydrological regime, with a special focus on low flows. Moreover, this study aimed to identify variables that may be susceptible to management policies for developing and securing water resources in dry periods. Principal Component Analysis (PCA) and Partial Least Square (PLS) were used to analyze the relationship between five hydrologic response variables (total flow, high flow, low flow, runoff coefficient, low flow index) and 30 potential explanatory watershed variables. The explanatory watershed variables were classified into three groups: land use, climate and topography as well as geology and soil type. Each of the three groups had almost equal influence on the variation in hydrologic variables (R2 values ranging from 0.3 to 0.4). Specific variables from within each of the three groups of explanatory variables were better in explaining the variation. Low flow and low flow index were positively correlated to land use types woodland, dense wet forest and savannah grassland, whereas grazing land and bush land were negatively correlated. We concluded that extra care for preserving low flow should be taken on tuffs/basalts which comprise 52% of the Blue Nile Basin. Land use management plans should recognize that woodland, dense wet forest and savannah grassland can promote higher low flows, while grazing land diminishes low flows

Citizen Science as Democratic Innovation That Renews Environmental Monitoring and Assessment for the Sustainable Development Goals in Rural Areas

This commentary focuses on analyzing the potential of citizen science to address legitimacy issues in the knowledge base used to guide transformative governance in the context of the United Nation's Sustainable Development Goals (henceforth SDGs). The commentary develops two interrelated arguments for better understanding the limits of what we term "traditional" Environmental Monitoring and Assessment (EMA) as well as the potential of citizen science (CS) for strengthening the legitimacy of EMA in the local implementation of SDGs. We start by arguing that there is an urgent need for a profound renewal of traditional EMA to better implement the SDGs. Then, we present CS as a democratic innovation that provides a path to EMA renewal that incorporates, develops, and extends the role of CS in data production and use by EMA. The commentary substantiates such arguments based on current approaches to CS and traditional EMA. From this starting point, we theorize the potential of CS as a democratic innovation that can repurpose EMA as a tool for the implementation of the SDGs. With a focus on the implementation of SDG15 (Life on Land) in local contexts, the commentary presents CS as a democratic innovation for legitimate transformative governance that can affect socio-ecological transitions. We see this approach as especially appropriate to analyze the implementation of SDGs in rural settings where a specific resource nexus can create conflict-laden contexts with much potential for a renewed EMA to support transformative governance towards Agenda 2030

Impact of landscape management scenarios on ecosystem service values in Central Ethiopia

This study aimed at modeling scenarios of future land use and land cover (LULC) change and estimating ecosystem service (ES) values for the year 2051 compared to 2021 in Central Ethiopia. The future LULC changes for the year 2051 were simulated for four scenarios, namely Business-as-Usual (BAU), Rapid Agricultural Expansion (RAE), Ecosystems Protection and Agricultural Development (EPAD) and Landscape Ecosystems Restoration and Conservation (LERC). The four LULC change scenarios were simulated based on anticipated assumptions that were derived from existing spatial policies, a consultation workshop report on scenarios of agricultural development in Ethiopia, suitability analysis, population growth analysis and expert knowledge of the study area characteristics. We used a Multi-Layer Perceptron–Artificial Neuron Network (MLP–ANN) model-based projected LULC for the BAU scenario and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model to generate RAE, EPAD and LERC scenarios in the study landscape. The benefit transfer method was used to estimate the total ES values and for trade-off analysis. The result showed that LULC changes in the study area varied across simulated scenarios compared to the base year 2021. Under the BAU and RAE scenarios, cultivated land increased by 146,548 ha (22%) and 193,965 ha (29%), whereas forest, water body, wetland and shrub-bush land were reduced. However, forest cover increased by 31,725 ha and 100,080 ha but bare land was reduced by 8466 ha (21%) and 10,379 ha (25%) under the EPAD and LERC scenarios. The forest cover annual rate of change was 3.2% and 6% under the EPAD and LERC scenarios. As a result, the total ES value increased by USD 24.5 and 78.5 million under the EPAD and LERC scenarios for the year 2051, whereas the total ES value was reduced under the BAU and RAE scenarios by USD 27.1 and 73.2 million. The trade-offs among ecosystem services were significantly synergized under the LERC scenario compared to RAE. Therefore, EPAD and LERC could be used as a reference for sustainable landscape planning and management. Landscape ecosystems restoration integrated with a sustainable agricultural intensification approach would enable us to ensure the sustainability of both agricultural production and ecosystem service synergies without negatively affecting the natural environment

Ecosystem service valuation along landscape transformation in Central Ethiopia

Land degradation and discontinuation of ecosystem services (ES) are a common phe nomenon that causes socio-economic and environmental problems in Ethiopia. However, a dearth of information is known about how ES are changing from the past to the future with regard to land use land cover (LULC) changes. This study aimed at estimating the values of ES based on the past and future LULC changes in central Ethiopia. Maximum likelihood classifier and cellular automata artificial neuron network (CA-ANN) models that integrate the module for land use change evaluation (MOLUSE) were used to classify and predict LULC. The CA-ANN model learning and validation was employed to predict LULC of 2031 and 2051. Following LULC change detection and prediction, the total ES values were estimated using the benefit transfer method. Results revealed that forests, wetlands, grazing lands, shrub-bush-woodlands, and water bodies were reduced by 9755 ha (37%), 4092 ha (38.4%), 21,263 ha (81%), 63,161 ha (25.7%), and 905 ha (1%), respectively, between 1986 and 2021. Similarly, forests, wetlands, grazing lands, shrub-bush lands, and water bodies will experience a decline of 1.5%, 0.5%, 2.6%, 19.6%, and 0.1%, respectively. Meanwhile, cultivated lands, bare-lands, and built-up areas will experience an increase between 1986 and 2051. The estimated total ES values were reduced by US$58.3 and 85.4 million in the period 1986–2021 and 1986–2051. Food production and biological control value increased while 15 other ES decreased throughout the study periods. Proper land use policy with strategic actions, including enforcement laws for natural ecosystems protection, afforestation, ecosystems restoration, and conservation practices, are recommended to be undertaken to enhance multiple ES provision

Trees, forests and water: Cool insights for a hot world

Forest-driven water and energy cycles are poorly integrated into regional, national, continental and global decision-making on climate change adaptation, mitigation, land use and water management. This constrains humanity’s ability to protect our planet’s climate and life-sustaining functions. The substantial body of research we review reveals that forest, water and energy interactions provide the foundations for carbon storage, for cooling terrestrial surfaces and for distributing water resources. Forests and trees must be recognized as prime regulators within the water, energy and carbon cycles. If these functions are ignored, planners will be unable to assess, adapt to or mitigate the impacts of changing land cover and climate. Our call to action targets a reversal of paradigms, from a carbon-centric model to one that treats the hydrologic and climate-cooling effects of trees and forests as the first order of priority. For reasons of sustainability, carbon storage must remain a secondary, though valuable, by-product. The effects of tree cover on climate at local, regional and continental scales offer benefits that demand wider recognition. The forest- and tree-centered research insights we review and analyze provide a knowledge-base for improving plans, policies and actions. Our understanding of how trees and forests influence water, energy and carbon cycles has important implications, both for the structure of planning, management and governance institutions, as well as for how trees and forests might be used to improve sustainability, adaptation and mitigation efforts

The Nile Basin waters and the West African rainforest : Rethinking the boundaries

This focus article presents the state of the West African rainforest (WARF), its role in atmospheric moisture transport to the Nile Basin, and the potential impact of its deforestation on the Nile Basin's water regime, as well as options for improving transboundary water governance. The Nile is the longest river in the world, but delivers less water per unit area than other major rivers. Pressures from the Basin's rapidly growing population and agricultural demand risk exacerbating transboundary water conflicts. About 85% of the surface water reaching Aswan in Egypt originates from the Ethiopian Highlands which comprise less than 10% of the Nile Basin's total area (3.3 million km(2)). Some of the atmospheric moisture reaching the Highlands crosses over the WARF; other moisture source areas include the Mediterranean Sea, the Indian Ocean, and the Atlantic Ocean. The WARF adds atmospheric moisture and modifies the regional climate system. Deforestation in the WARF has the potential to alter rainfall patterns over the Ethiopian Highlands and thus flows in the Nile River, with reductions a likely outcome. Transregional governance that looks beyond basin boundaries to the sources and routes of moisture transport (the precipitationshed) has yet to be integrated into land-atmosphere and water management negotiations. To better achieve sustainable land management and water resource development in the Nile Basin, scientific and governance frameworks need to be established that include the WARF region states in the ongoing negotiations between the Nile riparian states. This article is categorized under: Engineering Water > Planning Water Human Water > Water Governance Science of Water > Method

Tackling Complexity: Understanding the Food-Energy-Environment Nexus in Ethiopia’s Lake Tana Sub-basin

Ethiopia has embarked upon a rapid growth and development trajectory aiming to become a middle-income country by 2025. To achieve this goal, an agricultural development led industrialization strategy is being implemented which aims to intensify and transform agriculture, thereby boosting yields and, subsequently, economic returns. At the same time, the energy use which currently consists of more than 90% traditional biomass use is shifting towards increasing electricity production predominantly from large-scale hydropower plants, with the aim to improve access to modern energy sources. While the targets are commendable it is not clear that either all direct impacts or potential conflicts between goals have been considered. In this paper we evaluate and compare the impacts of alternative development trajectories pertaining to agriculture, energy and environment for a case-study location, the Lake Tana Subbasin, with a focus on current national plans and accounting for cross-sector interlinkages and competing resource use: the food-energy-environment nexus. Applying a nexus toolkit (WEAP and LEAP) in participatory scenario development we compare and evaluate three different future scenarios. We conclude that the two processes – agricultural transformation and energy transition – are interdependent and could be partly competitive. As agriculture becomes increasingly intensified, it relies on more energy. At the same time, the energy system will, at least in the foreseeable future, continue to be largely supported by biomass, partly originating from croplands. Two outstanding dilemmas pertaining to resources scarcity were identified. Water needed for energy and agricultural production, and to sustain ecosystem services, sometimes exceeds water availability. Moreover, the region seems to be hitting a biomass ceiling where the annual increments in biomass from all terrestrial ecosystems are in the same order of magnitude as biomass needs for food, fodder and fuel. We propose that a stakeholder-driven nexus approach, underpinned by quantitative and spatially explicit scenario and planning tools, can help to resolve these outstanding dilemmas and can support more consistent policy and decision making, towards improved resource productivities, lower environmental pressures and enhanced human securities

Hydrological change detection using modeling: Half a century of runoff from four rivers in the Blue Nile Basin

Land cover changes can have significant impacts on hydrological regime. The objective of this study was to detect possible hydrological changes of four watersheds in the Blue Nile Basin using a model-based method for hydrological change detection. The four watersheds, Birr, Upper-Didesa, Gilgel Abbay, and Koga range in size from 260 to 1800 km2. The changes were assessed based on model parameters, model residuals, and in the overall function of the watersheds in transferring rainfall into runoff. The entire time series (1960–2004) was divided into three periods based on political and land management policy changes. A conceptual rainfall-runoff model, the HBV (Hydrologiska Byråns Vattenbalansavdelning) model, was used for the analysis, and suitable parameter sets for each period were found based on a Monte Carlo approach. The values of six out of nine parameters changed significantly between the periods. Model residuals also showed significant changes between the three periods in three of the four watersheds. On the other hand, the overall functioning of the watersheds in processing rainfall to runoff changed little. So even though the individual parameters and model residuals were changing, the integrated functioning of the watersheds showed minimal changes. This study demonstrated the value of using different approaches for detecting hydrological change and highlighted the sensitivity of the outcome to the applied modeling and statistical methods

The long-term hydrology of East Africa’s water tower: statistical change detection in the watersheds of the Abbay Basin

Forty-five years (1960–2004) of hydrological data from 12 watersheds in the Abbay Basin, Ethiopia, were tested for possible trends over the entire time series and differences in medians (step-wise changes) between three sub-periods. The classification of the sub-periods was based on the major political changes in 1975 and 1991. Variables investigated were rainfall (P), total flow (Qt), high flow (Qh), low flow (Ql), low flow index (LFI) and run-off coefficient (C). Data were checked for outliers, errors and homogeneity. Trend was tested after serial and cross-correlation tests. The data for each variable were serially uncorrelated from 1 to 10 lag years. There were five globally significant trends out of 50 test cases and 36 significant step-wise changes out of 180 tests. The majority of the significant changes were watershed specific. Run-off coefficient was the single variable showing a consistently increasing trend and stood for ca. 25 % of the total significant trends and step-wise changes. Half of these changes occurred after 1991. We concluded that despite the land use policy changes in 1975 and 1991, as well as the long-term soil degradation, the hydrological regime was quite stable over the 45-year period, with the exception of an increase in the run-off coefficient in the latter part of the run-off record in some watersheds