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Open AccessArticle

Impact of Soil Conservation and Eucalyptus on Hydrology and Soil Loss in the Ethiopian Highlands

1
Faculty of Civil and Water Resources Engineering, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia
2
Blue Nile Water Institute, Bahir Dar University, Bahir Dar, Ethiopia
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Institute of Disaster Risk Management and Food Security Studies, Bahir Dar University, Bahir Dar, Ethiopia
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Amhara Regional Agricultural Research Institute, Bahir Dar, Ethiopia
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Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003, USA
6
Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
7
Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA
*
Author to whom correspondence should be addressed.
Water 2019, 11(11), 2299; https://doi.org/10.3390/w11112299
Received: 25 September 2019 / Revised: 29 October 2019 / Accepted: 30 October 2019 / Published: 2 November 2019
(This article belongs to the Special Issue The Effect of Hydrology on Soil Erosion)
The Ethiopian highlands suffer from severe land degradation, including erosion. In response, the Ethiopian government has implemented soil and water conservation practices (SWCPs). At the same time, due to its economic value, the acreage of eucalyptus has expanded, with croplands and pastures converted to eucalyptus plantations. The impact of these changes on soil loss has not been investigated experimentally. The objective of this study, therefore, is to examine the impacts of these changes on stream discharge and sediment load in a sub-humid watershed. The study covers a nine-year period that included installation of SWCPs, a three-fold increase from 1.5 ha in 2010 to 5 ha in 2018 in eucalyptus, and the upgrading of an unpaved to the paved road. Precipitation, runoff, and sediment concentration were monitored by installing weirs at the outlets of the main and four nested watersheds. A total of 867 storm events were collected in the nine years. Runoff and sediment concentration decreased by more than half in nine years. In the main watershed W5, we estimated that evapotranspiration by eucalyptus during the dry phase (November to May) increased approximately from 30 mm a−1 in 2010 to 100 mm a−1 in 2018. In watershed W3 it increased from 2 mm a−1 to 400 mm a−1, requiring more rainfall before saturation excess runoff began in the rain phase. The reduction in runoff led to a decreased sediment load from 70 Mg ha−1 a−1 in 2010 to 2.8 Mg ha−1 a−1 in 2018, though the reduction in discharge may have negative impacts on ecology and downstream water resources. SWCPs became sediment-filled and minimally effective by 2018. This indicates that these techniques are either inappropriate for this sub-humid watershed or require improved design and maintenance. View Full-Text
Keywords: Ethiopian highlands; eucalyptus; gully; soil loss; soil and water conservation practices Ethiopian highlands; eucalyptus; gully; soil loss; soil and water conservation practices
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MDPI and ACS Style

Mhiret, D.A.; Dagnew, D.C.; Alemie, T.C.; Guzman, C.D.; Tilahun, S.A.; Zaitchik, B.F.; Steenhuis, T.S. Impact of Soil Conservation and Eucalyptus on Hydrology and Soil Loss in the Ethiopian Highlands. Water 2019, 11, 2299.

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