Your search found 11 records
1 Beven, K. J. 2006. Streamflow generation processes. Wallingford, UK: International Association of Hydrological Sciences (IAHS). 431p. (IAHS Benchmark Papers in Hydrology 1)
Hydrological cycle ; Groundwater table ; Runoff ; Watersheds ; Precipitation ; Hydrology ; Catchment areas ; Humid zones ; Stream flow ; Infiltration / USA / New Zealand / Alaska / New England Watershed
(Location: IWMI HQ Call no: 551.48 G000 BEV Record No: H043507)
(0.39 MB)
2 Addisie, M. B.; Ayele, G. K.; Gessess, A. A.; Tilahun, S. A.; Moges, M. M.; Schmitter, Petra S.; Steenhuis, T. S. 2015. Hydro-geomorphological features at gully heads in the humid northern Ethiopian Highlands, Birr Watershed. Paper presented at the 3rd International Conference on the Advancements of Science and Technology [ICAST], Bahir Dar, Ethiopia, 8-9 May 2015. 7p.
Hydrogeology ; Geomorphology ; Morphology ; Humid zones ; Highlands ; Watersheds ; Water table ; Soil properties ; Gully erosion ; Landscape ; Case studies / Ethiopia / Ethiopian Highlands / Birr Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H047312)
(0.36 MB)
The study was conducted in the Birr watershed at twelve gully heads located close to each other. The survey includes measurements of morphological features, soil properties, water table elevations and catchment characteristics including erosion at each gully head. The analysis showed that gully head morphology could be explained by the role of different gully head controlling factors. The result suggested the maximum rate of head cut retreat reaches from 0 to 22.5m. There was no head retreat recorded from the arrested heads relative to unprotected heads. Compared to semiarid highlands of northern Ethiopia, the average short term head cut retreat was 12 fold greater. From the direct shear test, angle of internal friction by far greater than the slope of gully heads which are located at flat lands. The width depth ratio showed that the shallow depth heads were controlled by fluvial erosion whereas for the deep gully heads both fluvial and mass wasting due tension cracks are operating. In this study a significant power relationship established between the volume of the gully head and the length of retreat at the active gullies with V = 4.85 L1.05 (R2 = 0.91 and P= 0.042) which is different from the relation obtained from the entire gully system as a result of varies controlling factors.
3 Addisie, M. B.; Ayele, G. K.; Gessesse, A. A.; Tilahun, S. A.; Moges, M. M.; Zegeye, A. D.; Mekuria, Wolde; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2016. Rehabilitating gullies with low cost methods, in the sub humid Ethiopian highlands. Paper presented at the International Conference of the Advancement of Science and Technology, Bahir Dar, Ethiopia, 17-18 July 2016. 10p.
Gully erosion ; Humid zones ; Highlands ; Environmental degradation ; Ecosystems ; Watersheds ; Riverbank protection ; Vegetation ; Plantations ; Sedimentation
(Location: IWMI HQ Call no: e-copy only Record No: H047636)
(691 KB)
Gully erosion in the highlands of Ethiopia has reduced agricultural productivity and degraded ecosystem services. To better understand the processes controlling gully erosion and design effective control measures, a study was conducted in the headwaters of the Birr watershed for three consecutive years (2013-2015). Fourteen gullies with similar morphology were studied in three adjacent sub-watersheds. Stabilization measures were applied to 5 of the 14 gully heads. Three gully control measures were compared: a) reshaping gully banks and head to a 45 degree slope with stone rip rap on the gully heads, b) controlling gully bed grade, and c) planting grasses and trees on shallow gullies (i.e., < 3 m deep). Results demonstrated that gully control measures were effective in controlling the expansion of gullies as no further retreat was observed for the 5 treated gully heads, whereas the average retreat was 3 meters with a maximum of 22.5 m for the 9 untreated gullies. The migration of untreated gully heads produced an average soil loss of 38 tons per gully. Compared with simple reshaping of gully heads, the additional integration with stone rip rap was an effective and low cost measure. Vegetative treatment by itself could not stop the upslope migration of gully heads, though it had the potential to trap sediments. Re-vegetation at gully heads stabilized with stone rip rap occurred faster than at unprotected, reshaped heads and banks. From the fourteen rehabilitation treatments, gully head protection integrated with plantation showed the largest potential in decreasing gully development in terms of labor, time and material it requires.
4 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.
5 Addisie, M. B.; Ayele, G. K.; Gessess, A. A.; Tilahun, S. A.; Zegeye, A. D.; Moges, M. M.; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2017. Gully head retreat in the sub-humid Ethiopian Highlands: the Ene-Chilala Catchment. Land Degradation and Development, 28(5):1579-1588. [doi: https://doi.org/10.1002/ldr.2688]
Gully erosion ; Erosion control ; Humid zones ; Highlands ; Catchment areas ; Sedimentation ; Wet season ; Monitoring ; Soil texture / East Africa / Ethiopia / Ene-Chilala Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H048152)
In the northern highlands of Ethiopia, gully erosion is severe. Despite many efforts to implement gully prevention measures, controlling gully erosion remains a challenge. The objective is to better understand the regional gully erosion processes and to prevent gully head retreat. The study was conducted in the Ene-Chilala catchment in the sub-humid headwaters of the Birr River located southwest of Bahir Dar, Ethiopia. Twelve gully heads were monitored during the 2014 and 2015 rainy monsoon phase. We measured gully head morphology and retreat length, soil shear strength, ground water table levels, and catchment physical characteristics. Two active gully head cuts were treated in 2014 and an additional three head cuts in 2015 by regrading their slope to 45° and covering them with stone riprap. These treatments halted the gully head advance. The untreated gullies were actively eroding due to groundwater at shallow depths. The largest head retreat was 22.5 m, of which about half occurred in August of the first year when the surrounding soil was fully saturated. Lowering both the water table and protecting the gully heads can play a key role in reducing gully expansion and soil loss due to gully erosion in the Ethiopian highlands.
6 Asadi Zarch, M. A.; Sivakumar, B.; Malekinezhad, H.; Sharma, A. 2017. Future aridity under conditions of global climate change. Journal of Hydrology, 554:451-469. [doi: https://doi.org/10.1016/j.jhydrol.2017.08.043]
Climate change ; Arid climate ; Forecasting ; Climatic data ; Models ; Precipitation ; Evapotranspiration ; Assessment ; Time series analysis ; Simulation ; Humid zones
(Location: IWMI HQ Call no: e-copy only Record No: H048417)
(9.97 MB)
Global climate change is anticipated to cause some major changes in hydroclimatic conditions around the world. As aridity is a reliable indicator of potential available water, assessment of its changes under future climatic conditions is important for proper management of water. This study employs the UNESCO aridity/humidity index, which is a derivative of precipitation (P) and potential evapotranspiration (PET), for assessment of aridity. Historical (1901–2005) simulations and future (2006–2100) projections of 22 global climate models (GCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) are studied. The Nested Bias Correction (NBC) approach is used to correct possible biases of precipitation (simulated directly by the GCMs) and PET (estimated by applying FAO56-Penman-Monteith model on simulated parameters of the GCMs). To detect future aridity changes, the areal extents of the aridity zones in the past and future periods as well as through four sub-periods (2006–2025, 2026–2050, 2051–2075, and 2076–2100) of the future are compared. The results indicate that changes in climate will alter the areal extents of aridity zones in the future. In general, from the first sub-period towards the last one, the area covered by hyper-arid, arid, semi-arid, and sub-humid zones will increase (by 7.46%, 7.01%, 5.80%, and 2.78%, respectively), while the area of the humid regions will decrease (by 4.76%), suggesting that there will be less water over the global land area in the future. To understand the cause of these changes, precipitation and PET are also separately assumed to be stationary throughout the four future sub-periods and the resulting aridity changes are then analyzed. The results reveal that the aridity changes are mostly caused by the positive PET trends, even though the slight precipitation increase lessens the magnitude of the changes.
7 Akale, A. T.; Dagnew, D. C.; Giri, S.; Belete, M. A.; Tilahun, S. A.; Mekuria, Wolde; Steenhuis, T. S. 2017. Groundwater quality in an upland agricultural watershed in the sub-humid Ethiopian Highlands. Journal of Water Resource and Protection, 9(10):1199-1212. [doi: https://doi.org/10.4236/jwarp.2017.910078]
Groundwater ; Water quality ; Water pollution ; Sampling ; Highlands ; Agriculture ; Intensification ; Watershed management ; Humid zones ; Surface water ; Drinking water ; Contamination ; Wells ; Electrical conductivity ; Elements / Ethiopia / Lake Tana / Tikur-Wuha Watershed / Ribb Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H048459)
(3.75 MB)
Agricultural intensification to meet the food needs of the rapidly growing population in developing countries is negatively affecting the water quality. In most of these countries such as Ethiopia, information on surface and especially groundwater quality is lacking. This limits the measure that can be taken to stop pollution. We, therefore, investigated the spatial and temporal variation of groundwater quality in the upland watershed. Tikur-Wuha watershed was selected because it is located in the Lake Tana watershed, which is seeing the first signs of eutrophication. Groundwater samples were collected from July 2014 to June 2015 from 19 shallow wells located throughout the watershed. Collected water samples were analyzed both in situ and in the laboratory to determine pH, electric conductivity (EC) and total dissolved solid (TDS), concentration of chemicals (nitrate, dissolved phosphorus, calcium, magnesium, aluminum and iron) and Escherichia coli (E. coli). We found that shallow groundwater had greater chemical concentrations and E. coli level in the monsoon rain phase than in the dry phase. Wells located down slope exhibited greater concentrations than mid- and upper-slope positions, with the exception of the nitrate concentration that was less down slope, due to denitrification in the shallow groundwater. Only E. coli level was above the WHO drinking water quality standards. Further studies on groundwater quality should be carried out to understand the extent of groundwater contamination.
8 Zegeye, A. D.; Steenhuis, T. S.; Mekuria, Wolde; Dagnaw, D. C.; Addisse, M. B.; Tilahun, S. A.; Kasse, T. A. 2017. Effect of gully headcut treatment on sediment load and gully expansion in the sub humid Ethiopian Highlands. Environment and Ecology Research, 5(2):138-144. [doi: https://doi.org/10.13189/eer.2017.050208]
Gully erosion ; Sedimentation ; Humid zones ; Highlands ; River banks ; Lakes ; Soil conservation ; Water conservation ; Water resources ; Watershed management ; Concentrating / East Africa / Ethiopia / Ethiopian Highlands / Lake Tana
(Location: IWMI HQ Call no: e-copy only Record No: H048461)
The Ethiopian government has been implementing a land restoration program that aimed to restore degraded ecosystems and double agricultural productivity throughout the country since 2010. However, the success of the restoration program has been limited due to the lack of integrating gully erosion control measures. Consequently, many reservoirs in Ethiopia and downstream riparian countries have lost their storage capacity due to sedimentation, and studies demonstrated that gully erosion is one of the degradation hotspots within watersheds and contribute considerable proportion of the total sediment loads from a particular watershed. This study was conducted in one of large gullies in the Debre-Mawi watershed, northwestern Ethiopia to quantify the effect of gully head treatment in reducing the amount of sediment load generated from uplands and from the gully itself. We measured discharge, and sediment load and concentration in 2013 and 2014 at the upstream (inlet) and downstream ends (outlet) of the studied gully. Before the 2014 rainy phase, a gully headcut was stabilized with gabions at the bed and the gully bank was regarded to 45o. The gully head retreated 12 m in 2013 but gully head retreat was stopped following the implementation of the treatment in 2014. The total sediment load and sediment concentration at the outlet was reduced by 42% and 30% respectively, in 2014 (i.e., after treatment) when compared to 2013 (i.e., before treatment). The result of this study support that controlling the upward retreat of gully head is effective in reducing sediment load and concentration as well as upward movement and expansion of gullies. However, maintenance of gully head control measures is the key to sustain the benefits.
9 Adimassu, Zenebe; Alemu, G.; Tamene, L. 2019. Effects of tillage and crop residue management on runoff, soil loss and crop yield in the humid highlands of Ethiopia. Agricultural Systems, 168:11-18. [doi: https://doi.org/10.1016/j.agsy.2018.10.007]
Conservation tillage ; Crop production ; Crop yield ; Crop residues ; Crop management ; Productivity ; Ecosystem services ; Mulching ; Soil conservation ; Soil degradation ; Erosion ; Runoff ; Humid zones ; Highlands / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H048973)
(1.08 MB)
This study was conducted on Eutric Nitisols of Holeta Agricultural Research Center (HARC) in the humid highlands of Ethiopia. The main objective was to assess the effect of tillage and crop residue management on runoff, soil loss and wheat (Triticum aestivum L.) yield over three years (2009–2011). Nine treatments combining three tillage practices (zero, minimum and conventional tillage) and three rates of crop residue (0, 1 and 2 t ha-1 yr-1) were used. The experiment was laid out in a Randomized Complete Block Design with three replications. The result showed that average runoff was significantly higher (332 mm) in zero tillage without crop residue (T0C0) and lower (198 mm) in conventional tillage with 2 t ha-1 yr-1 crop residue (T2C2). The average soil loss was lower (16 t ha-1 yr-1) in zero tillage with 2 t ha-1 yr-1 crop residue (T0C2) and higher (30 t ha-1 yr-1) in conventional tillage without crop residue (T2C0). Although, zero and minimum tillage treatments reduced soil loss significantly as compared with conventional tillage practices, the annual soil loss (16 t ha-1 yr-1) is still much higher than the tolerable soil loss for the Ethiopian highlands (2–10 t ha-1 yr-1). This suggests the need to complement zero and minimum tillage practices with physical soil and water conservation practices. On average, highest grain (2 t ha-1) and biomass (6 t ha-1) yields of wheat were recorded in T2C2 while the lowest grain and biomass yields were recorded in T0C0. Based on the above observation, we argue that conventional tillage combined with sufficient crop residue is the most appropriate approach to reduce runoff and increase wheat yield in the short-term. However, zero tillage practices with crop residue are effective to reduce soil loss. As this study was based on results of three years data, long-term study is needed to figure out the long-term impacts of tillage and crop residue management in Ethiopia.
10 Hussein, M. A.; Muche, H.; Schmitter, Petra; Nakawuka, P.; Tilahun, S. A.; Langan, Simon; Barron, Jennie; Steenhuis, T. S. 2019. Deep tillage improves degraded soils in the (sub) humid Ethiopian highlands. Land, 8(11):1-15. [doi: https://doi.org/10.3390/land8110159]
Agricultural production ; Deep tillage ; Soil degradation ; Humid zones ; Highlands ; Watersheds ; Conventional tillage ; Hardpans ; Sediment ; Rain ; Runoff ; Soil loss ; Soil moisture ; Infiltration ; Maize ; Crop yield / Ethiopia / Robit-Bata Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H049375)
(2.40 MB) (2.40 MB)
Intensification of rainfed agriculture in the Ethiopian highlands has resulted in soil degradation and hardpan formation, which has reduced rooting depth, decreased deep percolation, and increased direct runoff and sediment transport. The main objective of this study was to assess the potential impact of subsoiling on surface runoff, sediment loss, soil water content, infiltration rate, and maize yield. Three tillage treatments were replicated at five locations: (i) no tillage (zero tillage), (ii) conventional tillage (ox-driven Maresha plow, up to a depth of 15 cm), and (iii) manual deep ripping of the soil’s restrictive layers down to a depth of 60 cm (deep till). Results show that the posttreatment bulk density and penetration resistance of deep tillage was significantly less than in the traditional tillage and zero-tillage systems. In addition, the posttreatment infiltration rate for deep tillage was significantly greater, which resulted in significantly smaller runoff and sedimentation rates compared to conventional tillage and zero tillage. Maize yields were improved by 6% under deep tillage compared to conventional tillage and by 29% compared to no tillage. Overall, our findings show that deep tillage can be effective in overcoming some of the detrimental effects of hardpans in degraded soils.
11 Natarajan, N.; Vasudevan, M.; Raja, S. A.; Mohanpradaap, K.; Sneha, G.; Shanu, S. J. 2023. An assessment methodology for drought severity and vulnerability using precipitation-based indices for the arid, semi-arid and humid districts of Tamil Nadu, India. Water Supply, 23(1):54-79. [doi: https://doi.org/10.2166/ws.2022.415]
Drought ; Vulnerability ; Precipitation ; Humid zones ; Semiarid zones ; Assessment ; Agroclimatic zones ; Climate change ; Risk ; Rain / India / Tamil Nadu / Karur / Cuddalore / Kanyakumari / Coimbatore
(Location: IWMI HQ Call no: e-copy only Record No: H051622)
https://iwaponline.com/ws/article-pdf/23/1/54/1169584/ws023010054.pdf
https://vlibrary.iwmi.org/pdf/H051622.pdf
https://vlibrary.iwmi.org/pdf/H051622.pdf
(2.08 MB) (2.08 MB)
As the short- and long-term impacts of climate change are becoming more visible at smaller regional scales, frequent occurrence (absence) of erratic precipitation as well as water scarcity issues can be identified as reliable indicators for predicting meteorological droughts. A supervised declaration of meteorological drought based on available precipitation data requires an understanding of reliability and consistency of drought indices for appropriate severity classification. An attempt has been made in this study to critically evaluate the performance of six popular drought indices namely, Standardized Precipitation Index (SPI), China Z Index (CZI), Modified China Z Index (MCZI), Deciles Index (DI), Rainfall Anomaly Index (RAI), and Z-Score Index (ZSI) for four districts in Tamil Nadu falling under arid (Karur), semi-arid (Cuddalore), dry sub-humid (Kanyakumari) and moist sub-humid (Coimbatore) conditions based on 120 years of precipitation records. Results showed that the SPI and CZI provided similar quantification of drought events (about 18% of the total months) irrespective of their climatic considerations while ZSI and RAI resulted in overestimation of drought severity (about 30–47%). Based on the classification strategy adopted for the selected indices, a framework for drought vulnerability assessment is proposed in conjunction with the estimated drought severity classifications.
Powered by DB/Text WebPublisher, from
