scholarly journals Review, impact of land use/cover change on soil erosion in the Lake Tana Basin, Upper Blue Nile, Ethiopia

2020 ◽  
Vol 10 (12) ◽  
Author(s):  
Alemsha Bogale
Keyword(s):  
Soil Erosion ◽  
Overland Flow ◽  
Agricultural Land ◽  
Base Flow ◽  
Nile River ◽  
Cultivated Land ◽  
Infiltration Capacity ◽  
Lake Tana ◽  
Blue Nile ◽  
Lake Tana Basin

AbstractLake Tana Basin is located in upper Blue Nile Basin which is comprises a total area of 15,096 km2 of which 3063 km2 is covered by the Lake which is the source of Blue Nile river. Lake Tana Basin and Blue Nile River provide various benefits also for downstream countries. The basin is highly degraded by different natural and manmade problems and it influence both Ethiopia and downstream countries. The main cause of basin degradation is inappropriate LULC. Huge area of cultivated land using without suitable management is the major basin problem. It is due to insure food security coming from unprecedented population growth rate. Forested land has encouraged the infiltration capacity and permeability of the land. It helps to increase the recharge capacity contribute to base flow whereas it is vice versa for cultivated land which is quick overland flow and significant soil erosion have observed. Besides, the soil erosion from agricultural land is the main source of nutrient enters to the lake which is the cause for eutrophication. To combat such problems both up and downstream countries should discuss together and design and implement appropriate basin management strategies to sustain the biodiversity and hydrological system of the basin.

Evaluation of satellite rainfall estimates over the Lake Tana basin at the source region of the Blue Nile River

2018 ◽  
Vol 212 ◽  
pp. 43-53 ◽  
Author(s):  
Ayele Almaw Fenta ◽  
Hiroshi Yasuda ◽  
Katsuyuki Shimizu ◽  
Yasuomi Ibaraki ◽  
Nigussie Haregeweyn ◽  
...  
Keyword(s):  
Source Region ◽  
Nile River ◽  
Lake Tana ◽  
Blue Nile ◽  
Satellite Rainfall ◽  
Rainfall Estimates ◽  
Lake Tana Basin

scholarly journals Application of HEC-HMS Model for Flow Simulation in the Lake Tana Basin: The Case of Gilgel Abay Catchment, Upper Blue Nile Basin, Ethiopia

Hydrology ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 21 ◽  
Author(s):  
Bitew G. Tassew ◽  
Mulugeta A. Belete ◽  
K. Miegel
Keyword(s):  
Sensitivity Analysis ◽  
Relative Error ◽  
Soil Conservation ◽  
Curve Number ◽  
Soil Conservation Service ◽  
Nile Basin ◽  
Lake Tana ◽  
Blue Nile ◽  
Blue Nile Basin ◽  
Lake Tana Basin

Understanding the complex relationships between rainfall and runoff processes is necessary for the proper estimation of the quantity of runoff generated in a watershed. The surface runoff was simulated using the Hydrologic Modelling System (HEC-HMS) for the Gilgel Abay Catchment (1609 km2), Upper Blue Nile Basin, Ethiopia. The catchment was delineated and its properties were extracted from a 30 m × 30 m Digital Elevation Model (DEM) of the Lake Tana Basin. The meteorological model was developed within HEC-HMS from rainfall data and the control specifications defined the period and time step of the simulation run. To account for the loss, runoff estimation, and flow routing, Soil Conservation Service Curve Number (SCS-CN), Soil Conservation Service Unit Hydrograph (SCS-UH) and Muskingum methods were used respectively. The rainfall-runoff simulation was conducted using six extreme daily time series events. Initial results showed that there is a clear difference between the observed and simulated peak flows and the total volume. Thereafter, a model calibration with an optimization method and sensitivity analysis was carried out. The result of the sensitivity analysis showed that the curve number is the sensitive parameter. In addition, the model validation results showed a reasonable difference in peak flow (Relative Error in peak, REP = 1.49%) and total volume (Relative Error in volume, REV = 2.38%). The comparison of the observed and simulated hydrographs and the model performance (NSE = 0.884) and their correlation (R2 = 0.925) showed that the model is appropriate for hydrological simulations in the Gilgel Abay Catchment.

Wildfire Impacts on Soil-Erosion and Hydrology in Wet Mediterranean Forest, Portugal

1993 ◽  
Vol 3 (2) ◽  
pp. 95 ◽  
Author(s):  
RA Shakesby ◽  
CDA Coelho ◽  
AD Ferreira ◽  
JP Terry ◽  
RPD Walsh
Keyword(s):  
Soil Erosion ◽  
Overland Flow ◽  
Ground Level ◽  
Fire Effects ◽  
Small Scale ◽  
Summer Drought ◽  
Mediterranean Environment ◽  
Infiltration Capacity ◽  
Order Of Magnitude ◽  
Autumn And Winter

The Agueda Basin, north-central Portugal is comparatively wet (rainfall, 1600-1800 mm/yr) with frequent, relatively large storms in autumn and winter yet the summer drought is sufficiently long and consistent for frequent forest wildfires. This paper discusses wildfire impacts in such a wet Mediterranean environment on soil hydrophobicity, infiltration capacity, overland flow coefficients, soil loss, rainsplash detachment and small-scale ground level changes for Eucalyptus globulus and Pinus pinaster forest: (1) 0-2 years after fire ('new' burn); (2) 3-4 years after fire ('old' burn); and (3) 'mature' (or long unburnt) sites. For 'new' burn sites, rainsplash detachment rates are an order of magnitude and soil losses two orders of magnitude higher than for 'old' burn sites and both are two orders of magnitude higher than for 'mature' sites. Soils are hydrophobic in all three categories of sites, but infiltration capacities are lower at 'new' burn and 'old' burn than at 'mature' sites. Overland flow coefficients on long unburnt sites were low while on burnt sites they were high and tended to be higher for summer and autumn than for winter and spring, implying enhanced hydrophobicity under summer drought conditions, causing decreased infiltration capacity and increased overland flow. The distinctiveness of fire effects on soil erosion and hydrology in this wet Mediterranean environment and implications for post-fire management are discussed.

scholarly journals An efficient semi-distributed hillslope erosion model for the sub humid Ethiopian Highlands

2012 ◽  
Vol 9 (2) ◽  
pp. 2121-2155 ◽  
Author(s):  
S. A. Tilahun ◽  
C. D. Guzman ◽  
A. D. Zegeye ◽  
T. A. Engda ◽  
A. S. Collick ◽  
...  
Keyword(s):  
Surface Runoff ◽  
Overland Flow ◽  
Sediment Concentration ◽  
Base Flow ◽  
Nile Basin ◽  
Erosion Model ◽  
Blue Nile ◽  
Ethiopian Highlands ◽  
Source Areas ◽  
Blue Nile Basin

Abstract. During the last two decades, saturated excess runoff has become accepted as the main source for overland flow in humid regions. Erosion modeling has generally not kept up with this new reality and predictions are often not based on landscape topographic position, which is a main variable in saturation excess runoff. In addition, predicting sediment loss in Africa has been hampered by using models that have been developed in western countries and do not perform as well in the monsoon climate prevailing in most of the continent. The objective of this paper is to develop a simple erosion model that can be used in the Ethiopian highlands in Africa. We base our sediment prediction on a simple distributed saturated excess hydrology model that predicts surface runoff from severely degraded lands and from bottom lands that become saturated during the rainy season and estimates interflow and base flow from the remaining portions of the landscape. By developing an equation that relates surface runoff to sediment concentration generated from runoff source areas, assuming that base flow and interflow are sediment free, we were able to predict daily sediment concentrations from the Anjeni Watershed and Blue Nile Basin with a Nash Sutcliffe efficiency ranging from 0.64 to 0.77 using only two calibrated sediment parameters. Anjeni is a 113 ha watershed in the 17.4 million ha Blue Nile Basin in the Ethiopian Highlands. The daily flows were predicted with Nash Sutcliffe efficiency values ranging from 0.80 to 0.93 if degraded areas were assumed the major sediment source areas and covered 14% of the Anjeni watershed and 20% of the Blue Nile basin. The analysis suggests that identifying the runoff source areas and predicting the surface runoff correctly is an important step in predicting the sediment concentration.

scholarly journals Rainfall Variability over Mountainous and Adjacent Lake Areas: The Case of Lake Tana Basin at the Source of the Blue Nile River

2009 ◽  
Vol 48 (8) ◽  
pp. 1696-1717 ◽  
Author(s):  
Alemseged T. Haile ◽  
Tom Rientjes ◽  
Ambro Gieske ◽  
Mekonnen Gebremichael
Keyword(s):  
Rainfall Variability ◽  
Temporal Patterns ◽  
Time Variability ◽  
Nile River ◽  
Mountainous Area ◽  
Spatial And Temporal Patterns ◽  
Lake Tana ◽  
Blue Nile ◽  
Spatial Correlation Structure ◽  
Hourly Rainfall

Abstract The water resource of the Blue Nile River is of key regional importance to the northeastern African countries. However, little is known about the characteristics of the rainfall in the basin. In this paper, the authors presented the space–time variability of the rainfall in the vicinity of Lake Tana, which is the source of the Blue Nile River. The analysis was based on hourly rainfall data from a network of newly installed rain gauges, and cloud temperature indices from the Meteosat Second Generation (MSG–2) Spinning Enhanced Visible and Infrared Imager (SEVIRI) satellite sensor. The spatial and temporal patterns of rainfall were examined using not only statistical techniques such as exceedance probabilities, spatial correlation structure, harmonic analysis, and fractal analysis but also marginal statistics such as mean and standard deviation. In addition, a convective index was calculated from remote sensing images to infer the spatial and temporal patterns of rainfall. Heavy rainfall is frequent at stations that are relatively close to the lake. The correlation distances for the hourly and the daily rainfall are found at about 8 and 18 km, respectively. The rainfall shows a strong spatially varying diurnal cycle. The nocturnal rainfall was found to be higher over the southern shore of Lake Tana than over the mountainous area farther to the south. The maximum convection occurs between 1600 and 1700 local standard time (LST) over the Gilgel Abbay, Ribb, and Gumara catchments, and between 2200 and 2300 LST over Lake Tana and the Megech catchments. In addition, the hourly rainfall of the station with the highest elevation is relatively closely clustered as compared to those stations at lower elevation. The study provides relevant information for understanding rainfall variation with elevation and distance from a lake. This understanding benefits climate and hydrological studies, water resources management, and energy development in the region.

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