Your search found 16 records
1 Nill, D.; Schwertman, U.; Sabel-Koschella, U.; Bernhard, B.J. 1996. Soil erosion by water in Africa: Principles, prediction and protection. The Netherlands: Rodorf: TZ-Verlagsgesellschaft. 292p.: ill.: maps; 21 cm. (Schriftenreihe (Deutsche Gesellschaft fur Technische Zusammenarbeit) ; no.257)
(Location: IWMI-SEA Call no: 631.45 G100 NIL Record No: BKK-87)
2 Valentin, Christian. 2005. Surface crusts of semi-arid sandy soils: types, functions and management. Paper presented at the Conference on Management of Tropical Sandy Soils for Sustainable Agriculture: a holistic approach for sustainable development of problem soils in the tropics, Khon Kaen, Thailand, 27th November – 2nd December 2005
. 6p.
(Location: IWMI-HQ Call no: IWMI 631.4 G000 VAL Record No: H038703)
(Location: IWMI-HQ Call no: IWMI 631.45 G708 RUM Record No: H038783)
(Location: IWMI-HQ Call no: IWMI 631.45 G000 POE Record No: H038784)
(Location: IWMI-HQ Call no: IWMI 631.45 G000 POE Record No: H038785)
6 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.
(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.
(Location: IWMI HQ Call no: e-copy only Record No: H042653)
(0.24 MB)
In the Sahel, sandy soils are widespread and support not only most of the pearl millet production, the major staple crop in the region, but also grass production for livestock. Parent sediments of these soils have an aeolian origin and are hence prone to wind erosion. Still, their clay content, even though very low, allows physical crust formation during rainfall leading to runoff and water erosion. Squall lines, major rainfall events of the rainy season, are usually preceded by intense wind. Wind and water erosions are therefore closely associated in both time and space, but they are rarely studied simultaneously. Erosion measurements were performed for two years (2001, 2002) on a small catchment of grazing land (1,4 ha) at Katchari, Burkina Faso, a location typical of the Sahel area with under 500 mm annual rainfall. Wind erosion occurs at the onset of the rainy season, from May to 15th of July, when soil cover is the lowest and before the growth of vegetation. On this non-cultivated area, the same dynamic unfolds as that recorded in millet fields in other sahelian studies. Water erosion occurs throughout the rainy season, but certain intense events produce most of the total annual erosion. Wind causes the largest sediment fluxes leading to both erosion (up to 20 Mg/ha per year) and deposition (up to 30 Mg/ha per year) depending on the area in the catchment. Water erosion is one order of magnitude lower than wind erosion and is more intense where wind erosion is highest. Hence, the same area is eroded by both wind and water. Conversely, areas where aeolian deposition occurs are less affected by water erosion and correspond to fertile islands where vegetation grows. From this study, it comes out that there is on the whole no land degradation at the catchment scale, but an intense aeolian and water dynamic leading to substantial spatial variability typical of sahelian landscapes.
(Location: IWMI HQ Call no: e-copy only Record No: H042747)
(1.75 MB)
Soil erosion vulnerability and extreme rainfall characteristics over the Mediterranean semi-arid region of Tunisia are crucial input for estimation of siltation rate in artificial reservoirs. A comprehensive high resolution database on erosive rainfall, together with siltation records for 28 small reservoirs, were analysed for this region, the Tunisian Dorsal (the easternmost part of the Atlas Mountains). The general life-span of these reservoirs is only about 14 years. Depending on the soil degradation in the different catchments, the corresponding reservoirs display a wide range of soil erosion rates. The average soil loss was 14.5 t ha-1 year-1but some catchments display values of up to 36.4 t ha-1 year-1. The maximum 15-min duration rainfall intensity was used to determine the spatial distribution of rainfall erosivity. The northwestern parts of the Tunisian Dorsal display the most extreme rainfall erosivity. Spatial erosion patterns are to some extent similar; however, they vary greatly according to their location in the “soil degradation cycle”. This cycle determines the soil particle delivery potential of the catchment. In general, the northwestern parts of the Dorsal display modest soil erosion patterns due to the already severely degraded soil structure. Here, the soil surface is often the original bedrock. However, the greatest soil erosion occurs in the mid-eastern parts of the Dorsal, which represents the “degradation front”. The latter corresponds to the area with highest erosion, which is continuously progressing westward in the Dorsal. The large variation between the erosive rainfall events and the annual soil loss rates was explained by two important factors. The first relates to the soil degradation cycle. The second factor corresponds to the degradation front with the highest soil loss rates. At present this front is located at 300 m altitude and appears to be moving along an 80-km westward path starting from the east coast. A better understanding of the above can be used to better manage soils and soil covers in the Tunisian Dorsal area and, eventually, to decrease the soil erosion and reservoir siltation risk.
9 Wang, X.; Tuppad, P.; Williams, J. R. 2011. Modelling agricultural management systems with APEX [Agricultural Policy Environmental eXtender]. In Shukla, M. K. (Ed.) Soil hydrology, land use and agriculture: measurement and modelling. Wallingford, UK: CABI. pp.117-136.
(Location: IWMI HQ Call no: e-copy SF Record No: H045776)
10 Duiker, S. W. 2011. Effect of land use and soil management on soil properties and processes. In Shukla, M. K. (Ed.) Soil hydrology, land use and agriculture: measurement and modelling. Wallingford, UK: CABI. pp.291-311.
(Location: IWMI HQ Call no: e-copy SF Record No: H045785)
(Location: IWMI HQ Call no: 630 G000 INT Record No: H046693)
(16.90 MB) (16.9 MB)
12 Rajot, J.L.; Ribolzi, Olivier; Planchon, O.; Karambiri, H. 2005. Wind and water erosion of non cultivated sandy soils in the Sahel: a case study in northern Burkina Faso, Africa. In International Union of Soil Sciences (IUSS); Institut de Recherche pour le Developpement (IRD); Thailand. Land Development Department (LDD); International Water Management Institute (IWMI); FAO. Regional Office for Asia and the Pacific (FAO RAP); Khon Kaen University. Faculty of Agriculture. Management of tropical sandy soils for sustainable agriculture: a holistic approach for sustainable development of problem soils in the tropics. Proceedings of the First Symposium on Management of Tropical Sandy Soils for Sustainable Ariculture, Khon Kaen, Thailand, 27 November – 2 December 2005. Bangkok, Thailand: FAO Regional Office for Asia and the Pacific (FAO RAP). pp.175-181.
(Location: IWMI HQ Call no: 630 G000 INT Record No: H047326)
(0.60 MB) (16.9 MB)
In the Sahel, sandy soils are widespread and support not only most of pearl millet production, the major staple crop in the region, but also forage production for livestock. Parent sediments of these soils have an aeolian origin and hence are prone to wind erosion. However, the clay content, albeit very low, results in the formation of crusts during rainfall, thus leading to runoff and water erosion. Squall lines, major rainfall events of the rainy season, are usually preceded by intense wind. Wind and water erosion is thus closely associated both in time and in space, but they are rarely studied simultaneously. Erosion measurements were carried out during two years (2001, 2002) on a small catchment of grazing land (1.4 ha) at Katchari, Burkina Faso, typical of the Sahel area under 500 mm annual rainfall. Wind erosion occurred at the onset of the rainy season, when soil cover is the lowest, from May to 15th of July, before vegetation growth. Water erosion occurred throughout the rainy season, but some intense events produced most of the total annual erosion. Wind caused the largest sediment fluxes leading to both erosion (up to 20 Mg ha-1 yr-1) and deposits (up to 30 Mg ha-1 yr-1) according to the area of the catchment. Water erosion is one order of magnitude lower than wind erosion, and is more intense where wind erosion is the highest. Thus the same area is eroded both by wind and water. Conversely, in areas where there are aeolian deposits, water erosion is low and these areas correspond to fertile islands where vegetation grows. At this study scale, there is no land degradation, but intense dynamics leading to a high spatial variability typical of the Sahelian environment. On this uncultivated area, the dynamics were similar to those recorded in other Sahelian cultivated millet fields.
13 Tadesse, A.; Dagnew, D. C.; Belete, M. A.; Tilahun, S. A.; Mekuria, Wolde; Steenhuis, T. 2015. Impact of soil and water conservation practices on sediment losses and discharge in the headwaters of the Lake Tana Basin in the Ethiopian highlands [Abstract only] Paper presented at the 10th Alexander von Humboldt Conference 2015 on Water-Food-Energy River and Society in the Tropics. EGU Topical Conference Series, Addis Ababa, Ethiopia, 18-20 November 2015. 1p.
(Location: IWMI HQ Call no: e-copy only Record No: H047342)
(0.04 MB) (37.63 KB)
Donor and governmental sponsored soil and water conservation measures has been carried out in the last half century in the Lake Tana basin, Ethiopia. However, sediment loads in to the lake has never been reduced suggesting that the effectiveness of integrated soil and water conservation measures reducing soil loss needs to be investigated. The present study was conducted in two watersheds (Tikur-Wuha covers 500 ha and Guali covers190 ha) located in the headwaters of Lake Tana to investigate the impacts of soil and water conservation practices on discharge and sediment loads. In both watersheds different soil and water conservation technologies have been implemented since 2010 by the Tana Belese integrated watershed management project: gully treatment, stone buds, soil bunds, stone faced soil bunds, water ways, cut- off drains, hill side terracing, micro basins and area closures. Daily rainfall, runoff and sediment concentration were collected from 2010 – 2012. The results showed that average runoff volume was reduced by 13% in Tikur-wuha and by 7% in Guali from 2010-2012. The sediment load in Tikur-wuha watershed was reduced by 48% in 2011 and 30% in 2012, while sediment load in Guali watershed was reduced by 1% and 35% in 2011 and 2012 respectively. The results support that the implemented integrated SWC measures through government sponsored with full participation of the community and through incorporating different SWC technology options were effective in reducing runoff and sediment load. We recommend fortifying the government led SWC campaign with full participation of the local community to reduce soil erosion and siltation of Lake Tana.
14 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.
(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.
(Location: IWMI HQ Call no: e-copy only Record No: H050073)
(2.45 MB)
(Location: IWMI HQ Call no: e-copy only Record No: H052786)
(7.46 MB) (7.46 MB)
Soil loss by water erosion represents a key threat to land degradation worldwide. This study employs an integrated quantitative modelling approach to estimate its long-term global sustainability impacts. The global biophysical model estimates a mean increase of soil erosion rates of between 30 and 66% over the period 2015–2070 under alternative climate-economic scenarios, assuming different greenhouse gas concentration trajectories. In a subsequent step, projected soil erosion rates are converted into land productivity losses and inputted into an economic global simulation model to identify those regional hotspots where the greatest market tensions are expected to occur.
The headline result is that of a global economic contraction of up to 625 billion US$ by the year 2070. Moreover, soil erosion represents an acute challenge to food security in vulnerable regions (Africa and some tropical regions), where for certain crops (particularly oilseeds) the threat of shortages is potentially significant. Under the worst-case scenario, global primary agricultural production losses could amount to 352 million tonnes by 2070. Exploring different long-term socioeconomic-environmental pathways confirms the merits of sustainable management practises in coping with market and environmental stresses arising from soil erosion that limits the global increase of land used for food consumption to 115,000 km2 above the long run baseline. Finally, free (and fair) trade is essential to allow less affected regions to expand (marginally) their production, thereby cushioning the market tensions that are expected to occur in more acutely affected areas of the world.
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