Soil erosion is a serious threat in Ethiopian highlands. Continuous land degradation resulted in loss of fertile top soil leading to low agricultural productivity. In addition, excessive soil erosion from Koga Watershed in upper catchment to an artificial reservoir (Koga Dam reservoir) is substantially reducing its service life. Community participatory based effective watershed management strategies may have tremendous potential to reduce soil erosion. However, it is not practical to implement management interventions in the entire basin. This study aims to identify and map erosion hotspot areas in Koga Watershed to assist local government decision towards implementing watershed management strategies. Multi Criteria Evaluation (MCE) technique was integrated with Geographic Information System (GIS). For these analysis four major factors: Topography, soil, land use and potential location of gullies were considered. Each of these was processed and analyzed for its potential contribution to erosion on a pixel by pixel basis. The factors were weighted using pair-wise comparison matrix and weights were combined using Weighted Overlay Tool of ArcGIS Spatial Analyst Toolbox to obtain the final erosion hotspot map. The results found that 2% (440 ha) to be highly sensitive, 43% (9,460 ha) to be moderately sensitive, 16% (3,520 ha) to be marginally sensitive and 32% (7,040 ha) currently not sensitive. The remaining 7% of the watershed area (22,000 ha) was constraint to erosion. The lowland area near the dam was found to be found most sensitive for erosion and sedimentation.
Estimating reference evapotranspiration (ET ) at 24 h
timesteps has been considered sufficiently accurate for a long time.
However, recent advances in weather data acquisition have made it
feasible to apply hourly procedures in ET computation.
Hourly timesteps can improve the accuracy of ET
estimates, as data averaged daily may misrepresent evaporative power
during parts of the day. The objective of the present study is to assess
the differences between daily ET computations
performed on 24 h (ET ) and hourly (ET
) timesteps for rice-wheat cropping systems in the
Ganga Basin, India. The meteorological data for computing reference
evapotranspiration were collected from an automatic weather station
located in an experimental plot at IIT Kanpur, India. Daily and hourly
ET computations were performed according to the FAO-PM
(Allen et al, 1998) equation for rice and wheat cropping seasons.
Diurnal variations of meteorological parameters resulted in
underestimation of ET when the daily time step is
considered. No significant difference was observed during wet periods.
It is also observed that the hourly estimates of ET
were able to capture the abrupt changes in climate variables, while the
daily ET fails to get it as it considers the average
values only. As a result, the sums of hourly values are more reliable
for ET estimates in the Ganga Plains.
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