Seifu A TilahunSeifu A TilahunSchool of Civil & Water Resources Engineering,BDUSchool of Civil & Water Resources Engineering,BDU

Storm Runoff and soil erosion Storm Runoff and soil erosion processes on the Ethiopian processes on the Ethiopian

highlandhighland

IntroductionIntroductionField Experiments on the Field Experiments on the hydrologyhydrology

Field Experiments on ErosionField Experiments on ErosionPEER Science project at BDUPEER Science project at BDU

OutlineOutline

river sediment concentrations have not declined

runoff and erosion processes are not fully understood

investigating where they takes place in the landscape

used this information to model erosion

IntroductionIntroduction

IntroductionIntroduction • 1 Automatic Rain Gauge

• 4 weirs installed & measured storm runoff (40 -50 events)

• 1 weir at the outlet (Adet Research Center)

• 19 piezometers to measure ground Water level

• 14 infiltration test• Sediment concentration

from 5 weirs (40 -50 events)

• Rill measurement from 10 agricultural fields

• 4 gully profile measurement

Infiltration Rate vs. Infiltration Rate vs. Rainfall IntensityRainfall Intensity

Debre Mawi

Bayabil et al. 2010 Ecohydrology

Saturated AreasSaturated Areas

As = 10%

Saturation

Weir-1

RunoffRunoff

RunoffRunoff1

2

3

4

5

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ErosionErosion

Sediment ConcentrationSediment Concentration

8 Aug 2010

Sediment Sediment ConcentrationConcentration

Rill & Gully Rill & Gully erosionerosion

– 120 ton ha -1 yr-1 in 2010

81m2 in 2005

321m2 in 2010

625m2 in 2011

Soil erosion with Soil erosion with wetnesswetness

1.1. Saturated hydraulic conductivity Saturated hydraulic conductivity generally greater than rainfall generally greater than rainfall intensity for well vegetated intensity for well vegetated watershedswatersheds

2.2. After a precipitation threshold is After a precipitation threshold is exceeded, discharge at outlet of exceeded, discharge at outlet of watershed is linearly related to watershed is linearly related to total precipitation total precipitation

3.3. soil erosion was related to wetness soil erosion was related to wetness through landscape position through landscape position

4.4. Modelling should incorporate the Modelling should incorporate the above processesabove processes

ConclusionConclusion

To propose more effective soil and To propose more effective soil and water conservation practices by water conservation practices by identifying those parts in the identifying those parts in the landscape that contributes most of landscape that contributes most of the sediment and nutrients at the the sediment and nutrients at the outlet.outlet.

Project goalProject goal

Measure stream flow and sediment Measure stream flow and sediment concentrationsconcentrations

Measure shallow ground water levelMeasure shallow ground water level Employ sediment tracers to locate Employ sediment tracers to locate

sediment source areassediment source areas Focus group discussion and transect Focus group discussion and transect

walkwalk Soil nutrient analysisSoil nutrient analysis Modeling of runoff and sediment Modeling of runoff and sediment

ActivitiesActivities

Thank You!!Thank You!!