Multi-site calibration of SWAT for the spatial distribution of sediment yield, Middle Awash Dam watershed, Ethiopia

Multi-site calibration of sediment yield has a significant effect on evaluating the spatial distribution of sediment yield of watershed and reservoirs sedimentation. Multi-site calibration was conducted at three gauging stations of the Proposed Middle Awash Dam watershed. The sequential Uncertainty fitting (SUFI-2) calibration uncertainty program (SWAT-CUP) has been used to calibrate and validate flow and sediment parameters using monthly flow and sediment rate observed data. P-factor and R-factor measured model calibration and uncertainty where the P-factor recorded 0.56-0.86/0.54-0.77 and R-factor 0.52-0.93/0.68-0.84 values respectively during the calibration and validation period for the three gauging stations. Model result showed the performance model was excellent during the calibration period with the coefficient of determination R2=0.78-0.82, Nash-Sutcliffe Efficiency ENS=0.77-0.79, Observation Standard Deviation Ratio RSR=0.44-0.48 and percent bias PBIAS=-13.3 to +14.3. Following the calibration process, the model estimated mean annual spatial distribution of sediment yield 7.23 ton/ha/yr at the outlet. Sediment yields spatial distribution showed that among the 19 sub-watersheds ranked based on their sediment yield contributions, eight sub-watersheds have a slope greater than 5%, which is relatively steeper and contributed average annual sediment yields of 16 ton/ha/yr. The temporal variability hydrograph showed 70.8 % of yearly sediment yield in the study area during the rainy season. The study results informed to development of watershed management strategies to minimize the sediment problems in the entire watershed

Mapping geographical inequalities in childhood diarrhoeal morbidity and mortality in low-income and middle-income countries, 2000–17 : analysis for the Global Burden of Disease Study 2017

Background Across low-income and middle-income countries (LMICs), one in ten deaths in children younger than 5 years is attributable to diarrhoea. The substantial between-country variation in both diarrhoea incidence and mortality is attributable to interventions that protect children, prevent infection, and treat disease. Identifying subnational regions with the highest burden and mapping associated risk factors can aid in reducing preventable childhood diarrhoea. Methods We used Bayesian model-based geostatistics and a geolocated dataset comprising 15 072 746 children younger than 5 years from 466 surveys in 94 LMICs, in combination with findings of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017, to estimate posterior distributions of diarrhoea prevalence, incidence, and mortality from 2000 to 2017. From these data, we estimated the burden of diarrhoea at varying subnational levels (termed units) by spatially aggregating draws, and we investigated the drivers of subnational patterns by creating aggregated risk factor estimates. Findings The greatest declines in diarrhoeal mortality were seen in south and southeast Asia and South America, where 54·0% (95% uncertainty interval [UI] 38·1–65·8), 17·4% (7·7–28·4), and 59·5% (34·2–86·9) of units, respectively, recorded decreases in deaths from diarrhoea greater than 10%. Although children in much of Africa remain at high risk of death due to diarrhoea, regions with the most deaths were outside Africa, with the highest mortality units located in Pakistan. Indonesia showed the greatest within-country geographical inequality; some regions had mortality rates nearly four times the average country rate. Reductions in mortality were correlated to improvements in water, sanitation, and hygiene (WASH) or reductions in child growth failure (CGF). Similarly, most high-risk areas had poor WASH, high CGF, or low oral rehydration therapy coverage. Interpretation By co-analysing geospatial trends in diarrhoeal burden and its key risk factors, we could assess candidate drivers of subnational death reduction. Further, by doing a counterfactual analysis of the remaining disease burden using key risk factors, we identified potential intervention strategies for vulnerable populations. In view of the demands for limited resources in LMICs, accurately quantifying the burden of diarrhoea and its drivers is important for precision public health

Mapping local patterns of childhood overweight and wasting in low- and middle-income countries between 2000 and 2017

A double burden of malnutrition occurs when individuals, household members or communities experience both undernutrition and overweight. Here, we show geospatial estimates of overweight and wasting prevalence among children under 5 years of age in 105 low- and middle-income countries (LMICs) from 2000 to 2017 and aggregate these to policy-relevant administrative units. Wasting decreased overall across LMICs between 2000 and 2017, from 8.4% (62.3 (55.1–70.8) million) to 6.4% (58.3 (47.6–70.7) million), but is predicted to remain above the World Health Organization’s Global Nutrition Target of <5% in over half of LMICs by 2025. Prevalence of overweight increased from 5.2% (30 (22.8–38.5) million) in 2000 to 6.0% (55.5 (44.8–67.9) million) children aged under 5 years in 2017. Areas most affected by double burden of malnutrition were located in Indonesia, Thailand, southeastern China, Botswana, Cameroon and central Nigeria. Our estimates provide a new perspective to researchers, policy makers and public health agencies in their efforts to address this global childhood syndemic

Mapping local patterns of childhood overweight and wasting in low- and middle-income countries between 2000 and 2017

A double burden of malnutrition occurs when individuals, household members or communities experience both undernutrition and overweight. Here, we show geospatial estimates of overweight and wasting prevalence among children under 5 years of age in 105 low- and middle-income countries (LMICs) from 2000 to 2017 and aggregate these to policy-relevant administrative units. Wasting decreased overall across LMICs between 2000 and 2017, from 8.4 (62.3 (55.1�70.8) million) to 6.4 (58.3 (47.6�70.7) million), but is predicted to remain above the World Health Organization�s Global Nutrition Target of <5 in over half of LMICs by 2025. Prevalence of overweight increased from 5.2 (30 (22.8�38.5) million) in 2000 to 6.0 (55.5 (44.8�67.9) million) children aged under 5 years in 2017. Areas most affected by double burden of malnutrition were located in Indonesia, Thailand, southeastern China, Botswana, Cameroon and central Nigeria. Our estimates provide a new perspective to researchers, policy makers and public health agencies in their efforts to address this global childhood syndemic. © 2020, The Author(s)

Global fertility in 204 countries and territories, 1950–2021, with forecasts to 2100: a comprehensive demographic analysis for the Global Burden of Disease Study 2021

Background Accurate assessments of current and future fertility—including overall trends and changing population age structures across countries and regions—are essential to help plan for the profound social, economic, environmental, and geopolitical challenges that these changes will bring. Estimates and projections of fertility are necessary to inform policies involving resource and health-care needs, labour supply, education, gender equality, and family planning and support. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 produced up-to-date and comprehensive demographic assessments of key fertility indicators at global, regional, and national levels from 1950 to 2021 and forecast fertility metrics to 2100 based on a reference scenario and key policy-dependent alternative scenarios. Methods To estimate fertility indicators from 1950 to 2021, mixed-effects regression models and spatiotemporal Gaussian process regression were used to synthesise data from 8709 country-years of vital and sample registrations, 1455 surveys and censuses, and 150 other sources, and to generate age-specific fertility rates (ASFRs) for 5-year age groups from age 10 years to 54 years. ASFRs were summed across age groups to produce estimates of total fertility rate (TFR). Livebirths were calculated by multiplying ASFR and age-specific female population, then summing across ages 10–54 years. To forecast future fertility up to 2100, our Institute for Health Metrics and Evaluation (IHME) forecasting model was based on projections of completed cohort fertility at age 50 years (CCF50; the average number of children born over time to females from a specified birth cohort), which yields more stable and accurate measures of fertility than directly modelling TFR. CCF50 was modelled using an ensemble approach in which three sub-models (with two, three, and four covariates variously consisting of female educational attainment, contraceptive met need, population density in habitable areas, and under-5 mortality) were given equal weights, and analyses were conducted utilising the MR-BRT (meta-regression—Bayesian, regularised, trimmed) tool. To capture time-series trends in CCF50 not explained by these covariates, we used a first-order autoregressive model on the residual term. CCF50 as a proportion of each 5-year ASFR was predicted using a linear mixed-effects model with fixed-effects covariates (female educational attainment and contraceptive met need) and random intercepts for geographical regions. Projected TFRs were then computed for each calendar year as the sum of single-year ASFRs across age groups. The reference forecast is our estimate of the most likely fertility future given the model, past fertility, forecasts of covariates, and historical relationships between covariates and fertility. We additionally produced forecasts for multiple alternative scenarios in each location: the UN Sustainable Development Goal (SDG) for education is achieved by 2030; the contraceptive met need SDG is achieved by 2030; pro-natal policies are enacted to create supportive environments for those who give birth; and the previous three scenarios combined. Uncertainty from past data inputs and model estimation was propagated throughout analyses by taking 1000 draws for past and present fertility estimates and 500 draws for future forecasts from the estimated distribution for each metric, with 95% uncertainty intervals (UIs) given as the 2·5 and 97·5 percentiles of the draws. To evaluate the forecasting performance of our model and others, we computed skill values—a metric assessing gain in forecasting accuracy—by comparing predicted versus observed ASFRs from the past 15 years (2007–21). A positive skill metric indicates that the model being evaluated performs better than the baseline model (here, a simplified model holding 2007 values constant in the future), and a negative metric indicates that the evaluated model performs worse than baseline. Findings During the period from 1950 to 2021, global TFR more than halved, from 4·84 (95% UI 4·63–5·06) to 2·23 (2·09–2·38). Global annual livebirths peaked in 2016 at 142 million (95% UI 137–147), declining to 129 million (121–138) in 2021. Fertility rates declined in all countries and territories since 1950, with TFR remaining above 2·1—canonically considered replacement-level fertility—in 94 (46·1%) countries and territories in 2021. This included 44 of 46 countries in sub-Saharan Africa, which was the super-region with the largest share of livebirths in 2021 (29·2% [28·7–29·6]). 47 countries and territories in which lowest estimated fertility between 1950 and 2021 was below replacement experienced one or more subsequent years with higher fertility; only three of these locations rebounded above replacement levels. Future fertility rates were projected to continue to decline worldwide, reaching a global TFR of 1·83 (1·59–2·08) in 2050 and 1·59 (1·25–1·96) in 2100 under the reference scenario. The number of countries and territories with fertility rates remaining above replacement was forecast to be 49 (24·0%) in 2050 and only six (2·9%) in 2100, with three of these six countries included in the 2021 World Bank-defined low-income group, all located in the GBD super-region of sub-Saharan Africa. The proportion of livebirths occurring in sub-Saharan Africa was forecast to increase to more than half of the world's livebirths in 2100, to 41·3% (39·6–43·1) in 2050 and 54·3% (47·1–59·5) in 2100. The share of livebirths was projected to decline between 2021 and 2100 in most of the six other super-regions—decreasing, for example, in south Asia from 24·8% (23·7–25·8) in 2021 to 16·7% (14·3–19·1) in 2050 and 7·1% (4·4–10·1) in 2100—but was forecast to increase modestly in the north Africa and Middle East and high-income super-regions. Forecast estimates for the alternative combined scenario suggest that meeting SDG targets for education and contraceptive met need, as well as implementing pro-natal policies, would result in global TFRs of 1·65 (1·40–1·92) in 2050 and 1·62 (1·35–1·95) in 2100. The forecasting skill metric values for the IHME model were positive across all age groups, indicating that the model is better than the constant prediction. Interpretation Fertility is declining globally, with rates in more than half of all countries and territories in 2021 below replacement level. Trends since 2000 show considerable heterogeneity in the steepness of declines, and only a small number of countries experienced even a slight fertility rebound after their lowest observed rate, with none reaching replacement level. Additionally, the distribution of livebirths across the globe is shifting, with a greater proportion occurring in the lowest-income countries. Future fertility rates will continue to decline worldwide and will remain low even under successful implementation of pro-natal policies. These changes will have far-reaching economic and societal consequences due to ageing populations and declining workforces in higher-income countries, combined with an increasing share of livebirths among the already poorest regions of the world

Global incidence, prevalence, years lived with disability (YLDs), disability-adjusted life-years (DALYs), and healthy life expectancy (HALE) for 371 diseases and injuries in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Background Detailed, comprehensive, and timely reporting on population health by underlying causes of disability and premature death is crucial to understanding and responding to complex patterns of disease and injury burden over time and across age groups, sexes, and locations. The availability of disease burden estimates can promote evidence-based interventions that enable public health researchers, policy makers, and other professionals to implement strategies that can mitigate diseases. It can also facilitate more rigorous monitoring of progress towards national and international health targets, such as the Sustainable Development Goals. For three decades, the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) has filled that need. A global network of collaborators contributed to the production of GBD 2021 by providing, reviewing, and analysing all available data. GBD estimates are updated routinely with additional data and refined analytical methods. GBD 2021 presents, for the first time, estimates of health loss due to the COVID-19 pandemic. Methods The GBD 2021 disease and injury burden analysis estimated years lived with disability (YLDs), years of life lost (YLLs), disability-adjusted life-years (DALYs), and healthy life expectancy (HALE) for 371 diseases and injuries using 100 983 data sources. Data were extracted from vital registration systems, verbal autopsies, censuses, household surveys, disease-specific registries, health service contact data, and other sources. YLDs were calculated by multiplying cause-age-sex-location-year-specific prevalence of sequelae by their respective disability weights, for each disease and injury. YLLs were calculated by multiplying cause-age-sex-location-year-specific deaths by the standard life expectancy at the age that death occurred. DALYs were calculated by summing YLDs and YLLs. HALE estimates were produced using YLDs per capita and age-specific mortality rates by location, age, sex, year, and cause. 95% uncertainty intervals (UIs) were generated for all final estimates as the 2·5th and 97·5th percentiles values of 500 draws. Uncertainty was propagated at each step of the estimation process. Counts and age-standardised rates were calculated globally, for seven super-regions, 21 regions, 204 countries and territories (including 21 countries with subnational locations), and 811 subnational locations, from 1990 to 2021. Here we report data for 2010 to 2021 to highlight trends in disease burden over the past decade and through the first 2 years of the COVID-19 pandemic. Findings Global DALYs increased from 2·63 billion (95% UI 2·44–2·85) in 2010 to 2·88 billion (2·64–3·15) in 2021 for all causes combined. Much of this increase in the number of DALYs was due to population growth and ageing, as indicated by a decrease in global age-standardised all-cause DALY rates of 14·2% (95% UI 10·7–17·3) between 2010 and 2019. Notably, however, this decrease in rates reversed during the first 2 years of the COVID-19 pandemic, with increases in global age-standardised all-cause DALY rates since 2019 of 4·1% (1·8–6·3) in 2020 and 7·2% (4·7–10·0) in 2021. In 2021, COVID-19 was the leading cause of DALYs globally (212·0 million [198·0–234·5] DALYs), followed by ischaemic heart disease (188·3 million [176·7–198·3]), neonatal disorders (186·3 million [162·3–214·9]), and stroke (160·4 million [148·0–171·7]). However, notable health gains were seen among other leading communicable, maternal, neonatal, and nutritional (CMNN) diseases. Globally between 2010 and 2021, the age-standardised DALY rates for HIV/AIDS decreased by 47·8% (43·3–51·7) and for diarrhoeal diseases decreased by 47·0% (39·9–52·9). Non-communicable diseases contributed 1·73 billion (95% UI 1·54–1·94) DALYs in 2021, with a decrease in age-standardised DALY rates since 2010 of 6·4% (95% UI 3·5–9·5). Between 2010 and 2021, among the 25 leading Level 3 causes, age-standardised DALY rates increased most substantially for anxiety disorders (16·7% [14·0–19·8]), depressive disorders (16·4% [11·9–21·3]), and diabetes (14·0% [10·0–17·4]). Age-standardised DALY rates due to injuries decreased globally by 24·0% (20·7–27·2) between 2010 and 2021, although improvements were not uniform across locations, ages, and sexes. Globally, HALE at birth improved slightly, from 61·3 years (58·6–63·6) in 2010 to 62·2 years (59·4–64·7) in 2021. However, despite this overall increase, HALE decreased by 2·2% (1·6–2·9) between 2019 and 2021. Interpretation Putting the COVID-19 pandemic in the context of a mutually exclusive and collectively exhaustive list of causes of health loss is crucial to understanding its impact and ensuring that health funding and policy address needs at both local and global levels through cost-effective and evidence-based interventions. A global epidemiological transition remains underway. Our findings suggest that prioritising non-communicable disease prevention and treatment policies, as well as strengthening health systems, continues to be crucially important. The progress on reducing the burden of CMNN diseases must not stall; although global trends are improving, the burden of CMNN diseases remains unacceptably high. Evidence-based interventions will help save the lives of young children and mothers and improve the overall health and economic conditions of societies across the world. Governments and multilateral organisations should prioritise pandemic preparedness planning alongside efforts to reduce the burden of diseases and injuries that will strain resources in the coming decades

Author Correction: Mapping local patterns of childhood overweight and wasting in low- and middle-income countries between 2000 and 2017 (Nature Medicine, (2020), 26, 5, (750-759), 10.1038/s41591-020-0807-6)

An amendment to this paper has been published and can be accessed via a link at the top of the paper. © 2020, The Author(s)

Author Correction: Mapping local patterns of childhood overweight and wasting in low- and middle-income countries between 2000 and 2017 (Nature Medicine, (2020), 26, 5, (750-759), 10.1038/s41591-020-0807-6)

An amendment to this paper has been published and can be accessed via a link at the top of the paper. © 2020, The Author(s)

Die Verteilungsmuster von Sedimenten und Wasserqualität als Reaktion auf externe Einflussfaktoren im Becken des Abayasee, südäthiopisches Rift Valley

Abstract i Acknowledgment ii 1\. Introduction 1 2\. The Study Site 2 2.1. Climate 4 2.2. Hydrology 12 2.3. Lake water quality 15 2.4. Geology 16 2.5. Present day morphodynamics 18 2.6. Land use and land cover 19 3\. Water circulation and sediment dynamics of large shallow lakes 21 3.1. Dynamics of winds in the coastal regions 22 3.2. Response of lakes to wind stress forcing 25 3.3. Large scale motion in lakes 26 3.3.1. Effect of friction 28 3.3.2. Effect of water depth 28 3.3.3. Effect of surface waves 29 3.4. Sediment dynamics 30 3.5. Study Objectives 33 4\. Methods 34 4.1. Meteorology 34 4.2. Sedimentology 36 4.3. Water quality 38 5\. Results 42 5.1. Meteorology 42 5.1.1. The wind field 42 5.1.1.1. Diurnal variation of the wind 43 5.1.1.2. Monthly variability of wind field 48 5.1.1.3. Periodicity analysis 50 5.1.2. Temperature 52 5.1.2.1. Diurnal variability of temperature 56 5.1.2.2. Interdiurnal variability of temperature 56 5.1.3. Atmospheric pressure oscillation 60 5.1.3.1. Daily variation of mean atmospheric pressure 62 5.2. Sedimentology 63 5.2.1. Sediment distribution 63 5.2.2. Sediment composition 65 5.2.2.1. quartz 65 5.2.2.2. Feldspar 67 5.2.2.3. Clay 68 5.2.2.4. Calcite 69 5.2.2.5. Organic carbon 70 5.2.2.6. Carbonate carbon 71 5.2.2.7. Trace minerals 71 5.2.3. Interrelationships between variables 73 5.2.4. Cluster Analysis 76 5.3. Water Quality 77 5.3.1. Water temperature 77 5.3.2. pH 79 5.3.3. Conductivity 79 5.3.4. Dissolved oxygen 80 5.3.5. Suspended solids 81 5.3.6. Dissolved solids 83 5.3.7. Secchi depth distributions 84 5.3.8. Interrelationship between quality parameters 85 6\. Discussions 88 6.1. Meteorology 88 6.1.1. The wind Field 88 6.1.2. Temperature 89 6.1.3. Atmospheric pressure 90 6.2. Sedimentology 90 6.2.1. Texture 90 6.2.2. Mineral composition 92 6.3. Water quality 95 7\. Conclusions and recommendations 98 Appendix A. Mineralogical composition of surficial sediments in Lake Abaya (vol. %) 107 Appendix B. Contour plots of water quality parameters showing depth profiles at fixed monitoring stations vs. Julian days of sampling. 124 Appendix C. Variations in water quality parameters at fixed monitoring stations during sampling period. 136 References 141This study has attempted to investigate experimentally the distribution of surficial sediment and variation of water quality parameters under major influences of wind forcing and major rivers inflows in Lake Abaya, the largest Ethiopian Rift Valley Lake. A field study in Lake Abaya was conducted to understand and conceptualize better the lake dynamic process and functioning of main factors. Comprehensive field data consisting of water quality measurements, lake bed sediment grab samples and meteorological observations along the western shoreline have been obtained from Lake Abaya. Spatial and temporal variability of physical parameters are presented and the interrelationships between variables are discussed. Results indicate that the lake basin can be viewed as consisting of two main physiographic units, defined as sub basins, with behaviour defined by their response to external forcing over time. Distribution pattern of lake bottom sediments bears information about the interaction of physical processes and the resultant motion that controls the transport and distribution of suspended solids. The relationship between sediment texture and bottom topography was discussed. The distribution pattern of sediments was interpreted in the light of the different energy zones and major rivers loading. The spatial distribution diagrams of major minerals found in recent deposits on the lake bottom show that understanding of the sedimentary pattern is of vital importance for proper interpretation of the dynamic process operating on the lake. The downstream tendency of fine sediments suggested the general wind-controlled circulation pattern of the top layer to the north and the return flow in the bottom layer southwards. As well the inflow current of the tributary rivers as wind driven wave energies have an important influence on the spatial distribution of sediments. Persistent wind energy continuously mixes the lake water vertically and transports sediment in suspension horizontally resulting homogenous water column and extremely high turbidity throughout the whole open water zone. The intense wind mixing together with shallow depth apparently result an essentially homogenous water column. The observed spatial and temporal variability of physical variables allowed estimating general circulation pattern. The results were discussed in terms of the direction and magnitude of wind forcing, nature of sediment distribution, bathymetry (water depth and bottom slope), and major inflow that determine possible pattern and strength of circulation.Die Studie beschäftigt sich mit der Verteilung von Oberflächensedimenten und der Verteilung von Wasserqualitätsparametern unter den vornehmlichen Einflüssen des Windes und von Zuflüssen im Abayasee, dem größten See des äthiopischen Rift Valley. Zu diesem Zweck wurde am Abayasee ein Feldstudie durchgeführt, auf deren Grundlage ein konzeptionelles Modell der Prozesse und der Beziehungsgefüge der Hauptfaktoren erstellt werden konnte. Die im Gelände erhobenen Daten umfassen Wasserqualitätsmessungen, Seebodenproben und meteorologische Beobachtungen entlang des westlichen Seeufers. Die räumliche und zeitliche Variabilität der verschiedenen physikalischen Parameter wird präsentiert und das Beziehungsgefüge zwischen den verschiedenen Variabeln wird diskutiert. Die Ergebnisse deuten an, dass das Seebecken aus zwei physiographischen Haupteinheiten besteht, die als Teibecken zu definieren sind und die über ihre spezifischen Prozesse charakterisiert werden, angetrieben durch externe Kräfte. Das Verteilungsmuster der Seebodensedimente beinhaltet Informationen über die Interaktionen zwischen physikalischen Prozessen und daraus resultierenden Bewegungen, die den Transport und die Verteilung im Seewasser suspendierter Feststoffe steuern. So werden die Beziehungen zwischen Korngrößenzusammensetzung und der Topographie des Seebodenuntergrundes überprüft. Das Verteilungsmuster der Sedimente wird unter Berücksichtigung verschiedener Energiezonen des Sees und der Fracht der zuströmenden Tributäre betrachtet. Die flächendifferenzierte Betrachtung der Verteilungsmuster der Hauptmineralkomponenten der rezenten Seebodensedimente ergeben, dass ihrer Merkmale Rückschlüsse auf Strömungsprozesse im See zulassen. Die S-N-Verteilung der Tonund Schluffgehalte im Seebodensediment weist auf ein im Wesentlichen windkontrolliertes Strömungsmuster im See hin mit einer nordwärts gerichteten Oberflächenströmung und einer südwärts gerichteten Rückströmung am Seeboden. Sowohl die Strömungen der einmündenden Tributäre als auch die Energie der vom Wind angetriebenen Wellen beeinflussen die räumliche Verteilung der Seebodensedimente. Anhaltende Winde führen zu einer vertikalen Durchmischung des Seewassers und bewirken, dass in Suspension mitgeführtes Feinmaterial homogen über die gesamte Wassersäule verteilt bleibt und durchgehend in der Freiwasserzone zu einer starken Trübung des Wassers führt. Diese intensive Wind-Durchmischung führt durch die geringe Tiefe des Seebeckens zu insgesamt nur wenig räumlich und zeitlich differenzierten Eigenschaften des Seewassers. Die beobachtete zeitliche und räumliche Variabilität der physikalischen Parameter erlaubt eine Ableitung des allgemeinen Zirkulationsmusters. Dies umfasst sowohl die Windrichtung als auch die Stärke des Windes, den Charakter der räumlichen Sedimentverteilung, die Bathymetrie (Wassertiefe und Seebodengefälle) und die Hauptzuflüsse, die in unterschiedlicher Gewichtung Muster und Intensität der Seeströmungen beeinflussen

Effect of land use land cover dynamics on hydrological response of watershed: Case study of Tekeze Dam watershed, northern Ethiopia

Land use change is a very important issue considering global dynamics and their response to hydrologic characteristics of soil and water management in a catchment. A significant land use change has been observed in the Tekeze dam catchment. The main objective of this study was to estimate the potential impacts of the land use land cover (LULC) dynamics on hydrological response (stream flow and sediment yield). This was done by integrating SWAT model with GIS. The simulation and sensitivity analysis for each land use was done by dividing the catchment in to 47 sub-catchments and assigning HRUs based on multiple HRU definition. After a sensitivity analysis, calibration and validation of SWAT model, the impact of LULC dynamics on hydrological response were evaluated with three scenarios (climate of 2000s & 2008 LULC, climate of 2000s & 1986 LULC and climate of 1980s & 1986 LULC). In the Tekeze dam watershed, land cover change had a beneficial impact on modeled watershed response due to the transition from grass and shrub land to agricultural land. Simulation results for the Tekeze dam watershed indicates that increasing bare land and agricultural areas resulted in increased annual and seasonal stream flow and sediment yield in volumes. The mean annual stream flow was increased by 6.02% (129.20–137.74 m3/s) and the impact on sediment yield amounts to an increase of 17.39% (12.54–15.18 t/ha/yr) due to LULC dynamics. The hydrological response was more sensitive to LULC dynamics for the months of August to October than others in the year. These results demonstrate the usefulness of integrating remote sensing and distributed hydrologic models through the use of GIS for assessing watershed conditions and the relative impacts of land cover transitions on hydrologic response in a continuous manner