Your search found 4 records
1 Zegeye, A. D.; Tebebu, T. Y.; Abiy, A. Z.; Dahlke, H. E.; White, E. D.; Collick, A. S.; Kidnau, S.; Dadgari, F.; McCartney, Matthew; Steenhuis, T. S. 2009. Assessment of hydrological and landscape controls on gully formation and upland erosion near Lake Tana. In Awulachew, Seleshi Bekele; Erkossa, Teklu; Smakhtin, Vladimir; Fernando, Ashra (Comps.). Improved water and land management in the Ethiopian highlands: its impact on downstream stakeholders dependent on the Blue Nile. Intermediate Results Dissemination Workshop held at the International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia, 5-6 February 2009. Colombo, Sri Lanka: International Water Management Institute (IWMI). pp.162-169.
Hydrology ; Water erosion ; Highlands ; Watersheds ; Simulation models / Africa / Ethiopia / Gilgil Abay Basin / Debre-Mewi Watershed / Lake Tana
(Location: IWMI HQ Call no: IWMI 333.9162 G100 AWU Record No: H042516)
(0.62 MB)
Gully formation and upland erosion were studied in the Debre-Mewi Watershed in the Gilgil Abay Basin south of Lake Tana. Gully erosion rates were found to be equivalent to over 500 tonnes/ha/year for the 2008 rainy season when averaged over the contributing watershed. Upland erosion rates were twentyfold less. Gully formation is accelerated when the soils are saturated with water as indicated by water table readings above bottom of the gully. Similarly, upland erosion was accelerated when the fields were close to saturation during the occurrence of a rainfall event. Height of the water table is an important parameter determining the amount of erosion and should, therefore, be included in simulation models.
2 Dagnew, D. C.; Guzman, C. D.; Tebebu, T. Y.; Zegeye, A. D.; Akal, A. T.; Mekuria, Wolde M.; Ayana, E. K.; Tilahun, S. A.; Steenhuis, T. S. 2015. Contributions of peak sediment events to annual loads and the effects of best management practices on peak loads in the sub-humid Ethiopian highlands: the Debre Mawi watershed [Abstract only] In Nyssen J., Enyew A., Poesen J et al. (Eds.). International Conference on Tropical Lakes in a Changing Environment: Water, Land, Biology, Climate and Humans (TropiLakes), Bahir Dar, Ethiopia, 23-29 September 2015. Book of Abstracts. Bahir Dar, Ethiopia: Bahir Dar University. pp.94.
Sedimentation ; Watersheds ; Highlands ; Management techniques ; Soil conservation ; Water conservation ; Water erosion / Ethiopia / Ethiopian Highlands
(Location: IWMI HQ Call no: e-copy only Record No: H047344)
(0.66 MB)
Intense rainfall/runoff events produce large proportion of suspended sediment concentrations and sediment load responses. With an aim to mitigate land degradation problems in Ethiopia, soil and water conservation projects are being massively implemented. The effect of these conservation measures in reducing sediment in streams have never been quantified due to unavailability of sediment data. In a quantitative evaluation to quantify the contribution of intense event/daily sediment loads to annual sediment loads and effect of conservation measures in reducing erosion, we monitored three nested experimental sub-watersheds and a 95 ha main watershed in the sub-humid Ethiopian highlands, Debre Mawi watershed for four consecutive years. The contribution of the largest 10–minute events and peak daily sediment loads to annual sediment loads and the effect of Best Management Practices (BMPs) on peak sediment transport processes were evaluated. The contribution of the largest event loads reached up to 22% of the total annual sediment loads. The peak event sediment loads reached up to 11 t ha-1. The contribution of the largest daily sediment load events to annual loads is up to 86%. For the two largest daily sediment load events, the contribution reached up to 95%. The total sediment loads of the two largest daily sediment load events ranged from 40-68 t ha-1day-1 indicating that most of the annual sediment loads are transported with in one or two intense daily sediment load events in the (sub) humid Ethiopian highlands. Comparison of peak sediment loads before and after the implementation of BMPs indicates that conservation practices such as soil bunds, stone faced soil bunds and stone bunds substantially reduced the contribution and magnitude of peak sediment loads. The sediment trap efficiency of the BMPs can be further improved by making ditches deeper than existing practice of 50 cm depth in the Ethiopian highlands.
3 Dagnew, D. C.; Guzman, C. D.; Zegeye, A. D.; Akal, A. T.; Moges, M. A.; Tebebu, T. Y.; Mekuria, Wolde; Ayana, E. K.; Tilahun, S. A.; Steenhuis, T. S. 2017. Sediment loss patterns in the sub-humid Ethiopian Highlands. Land Degradation and Development, 28(6):1795-1805. [doi: https://doi.org/10.1002/ldr.2643]
Sediment ; Erosion ; Gully erosion ; Humid zones ; Highlands ; Watersheds ; Catchment areas ; Rainfall-runoff relationships ; Infiltration ; Precipitation / Ethiopia / Debre Mawi Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H047878)
Controlling soil erosion is important for maintaining land productivity and reducing sedimentation of reservoirs in the Ethiopian highlands. To gain insights on sediment loss patterns, magnitude of peak sediment events, and their contribution to annual loads, hydrometric and sediment concentration data were collected for five years (2010 – 2014) from the 95 ha Debre Mawi and four nested catchments (located 30 km south of Lake Tana). Soil and water conservation practices (SWCPs) consisting of soil bunds with 50 cm deep furrows were implemented in the third year, which made it possible to examine the effects of SWCPs on peak sediment loads. The results show that a 10-minute event causes soil loss of up to 11.4 Mg ha-1, which is 22% of the annual sediment yield. Thirty to seventy-five percent (up to 30 Mg ha-1day-1) of the sediment yield was contributed by the greatest daily flow in each year. The contribution increases to 86% for the two largest daily flows. SWCP interventions reduced sediment loss by half but did not affect the relative contribution of peak events to annual loads. Due to gully erosion, peak sediment loads at the outlet of the entire catchment were greater (up to 30 Mg ha-1day-1) as compared to the nested catchments without gullies (0.5 to 8 Mg ha-1day-1). Consequently, to reduce sediment loss, conservation measures should be designed to decrease runoff during large storms. This can be attained by deepening furrows on unsaturated hillsides and reducing the entrainment of unconsolidated sediment from failed gully banks.
4 Dagnew, D. C.; Guzman, C. D.; Akale, A. T.; Tebebu, T. Y.; Zegeye, A. D.; Mekuria, Wolde; Tilahun, S. A.; Steenhuis, T. S. 2017. Effects of land use on catchment runoff and soil loss in the sub-humid Ethiopian highlands. Ecohydrology and Hydrobiology, 17:274-282. [doi: https://doi.org/10.1016/j.ecohyd.2017.07.004]
Land use ; Land management ; Catchment areas ; Runoff ; Soil properties ; Soil organic matter ; Soil disturbance ; Erosion ; Subhumid zones ; Hydrology ; Highlands ; Sedimentation ; Grasslands ; Cultivated land ; Tillage ; Watersheds / Ethiopia / Ethiopian Highlands
(Location: IWMI HQ Call no: e-copy only Record No: H048463)
Land use and management affects runoff and soil loss from a catchment. The present study investigated the effects of land use on runoff and suspended sediment concentration and yield in the northwestern Ethiopia. We selected two small catchments: cultivated land and grassland dominated catchments within the 95 ha Debre Mawi catchment. Hydrometric and sediment concentration data were collected for five years (i.e., 2010–2014). Significant (p < 0.05) differences in daily, monthly and annual runoff, as well as suspended sediment concentrations were observed between cultivated land and grassland dominated catchments. The greater runoff, suspended sediment concentration and yield in the cultivated catchment could be attributed to repeated tillage and low soil organic matter. Repeated tillage in the cultivated land lead to soil disturbance and the low organic matter lead to aggregate instability, both of which consequently increase the detachment of soil particles and transport by generated runoff. Our results support that land management practices that involve lower soil disturbance and increase ground cover on degraded highland areas such as the Ethiopian highlands could help reduce runoff and soil loss.
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