<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Effective watershed planning requires an understanding of the hydrology. In the humid tropical monsoon climates and especially in volcanic highland regions such as the Ethiopian Highlands, the understanding of watershed processes is incomplete. The objective is to better understand the hydrology of the volcanic regions in the humid highlands by linking the hillslope processes with the discharge at the outlet. The Ene-Chilala watershed was selected for this study. The infiltration rate, piezometric water levels and discharge from two nested sub watersheds and at the watershed outlet were measured during a four-year period. Infiltration rates on the hillsides exceeded the rainfall intensity most of the time. The excess rain recharged a perched hillside aquifer. Water flowed through the perched aquifer as interflow to rivers and outlet. In addition, saturation excess overland flow was generated in the valley bottoms. Perched water tables heights were predicted by summing up the recharge over the travel time from the watershed divide. Travel times ranged from a few days for piezometers close to the divide to 40 days near the outlet. River discharge was simulated by adding the interflow from the upland to overland flow from the saturated valley bottom lands. Overland flow accounted only for one-fourth of the total flow. There was good agreement between predicted and observed discharge during the rain phase therefore the hillslope hydrologically processes were successfully linked with the discharge at the outlet.</p></abstract>

Effective watershed planning requires an understanding of the hydrology. In the humid tropical monsoon climates and especially in volcanic highland regions such as the Ethiopian Highlands, the understanding of watershed processes is incomplete. The objective is to better understand the hydrology of the volcanic regions in the humid highlands by linking the hillslope processes with the discharge at the outlet. The Ene-Chilala watershed was selected for this study. The infiltration rate, piezometric water levels and discharge from two nested sub watersheds and at the watershed outlet were measured during a four-year period. Infiltration rates on the hillsides exceeded the rainfall intensity most of the time. The excess rain recharged a perched hillside aquifer. Water flowed through the perched aquifer as interflow to rivers and outlet. In addition, saturation excess overland flow was generated in the valley bottoms. Perched water tables heights were predicted by summing up the recharge over the travel time from the watershed divide. Travel times ranged from a few days for piezometers close to the divide to 40 days near the outlet. River discharge was simulated by adding the interflow from the upland to overland flow from the saturated valley bottom lands. Overland flow accounted only for one-fourth of the total flow. There was good agreement between predicted and observed discharge during the rain phase therefore the hillslope hydrologically processes were successfully linked with the discharge at the outlet.

Connecting hillslope and runoff generation processes in the Ethiopian Highlands: The Ene-Chilala watershed

Faculty of Civil and Water Resources Engineering

Agricultural Research Service, National Sedimentation Laboratory

International Water Management Institute (IWMI) East Africa Office

Department of Biological and Environmental Engineering

Journal of Hydrology and Hydromechanics

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Effective watershed planning requires an understanding of the hydrology. In the humid tropical monsoon climates and especially in volcanic highland regions...

Connecting hillslope and runoff generation processes in the Ethiopian Highlands: The Ene-Chilala watershed

Published Online: Oct 20, 2020

Page range: 313 - 327

Received: Feb 26, 2020

Accepted: Apr 22, 2020

DOI: https://doi.org/10.2478/johh-2020-0015

Keywords
Hillslope hydrology, Saturation, Rainfall intensity, Perched groundwater, Ethiopian Highlands

© 2020 Meseret B. Addisie et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Connecting hillslope and runoff generation processes in the Ethiopian Highlands: The Ene-Chilala watershed

Published Online: Oct 20, 2020

Page range: 313 - 327

Received: Feb 26, 2020

Accepted: Apr 22, 2020

DOI: https://doi.org/10.2478/johh-2020-0015

KeywordsHillslope hydrology, Saturation, Rainfall intensity, Perched groundwater, Ethiopian Highlands

© 2020 Meseret B. Addisie et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Keywords
Hillslope hydrology, Saturation, Rainfall intensity, Perched groundwater, Ethiopian Highlands