Modelling aeolian sediment transport in the Badia of Jordan
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Despite wind erosion processes are well described in literature many vul- nerable wind erosion areas as the steppe (Badia) of Jordan have not been studied extensively. The International Center of Agricultural Research in the Dry Areas (ICARDA) has an interest in estimating wind erosion for different agricultural plots in Jordan. A wind erosion research was car- ried out on a experimental Barley, Water harvesting and Natural grazing plot at Al-Majidyya, (45 km South-East from Amman) Jordan. A mea- surement campaign consisting of a wind tower with five cup anemometers, three Saltation Detectors, a wind vane and 30 Modified Wilson and Cook (MWAC) sediment catchers were established during summer (June-Sept) 2011. No wind erosion storms were recorded by the anemometers (Max wind velocity = 7.37 m/s) and no saltation was recorded by the Saltation Detectors. The sediment of the MWAC catchers were insufficient for data analysis. The cover and roughness characteristics of the three experimental plots were different, whereby the Water harvesting plot had a higher aero- dynamic roughness (Z0 ≈ 17 cm) compared to the other two plots (Z0 ≈ 10 cm) due to the presence of vegetation lines consisting of ridges and shrubs planted in furrows. The ridges on the Barley plot were parallel with the predominant wind direction (West) and therefore no obstacle for the wind. Three datasets were obtained, besides wind and soil data of Al-Majidyya (UU dataset) also weather data from the past of the Al-Muwaqar and Queen Alia Airport (Amman) stations were provided. A detailed historical wind analysis in combination with wind velocity comparisons were made. Accord- ing to ICARDA and The National Center for Agricultural Research and Ex- tension (NCARE),the wind erosion storm season was from June-September, however the historical wind analysis showed a potential wind erosion season from October-March. The Revised Wind Erosion Equation (RWEQ) model was used to estimate mass transport and soil losses for each experimental plot. Four periods of the translated Al-Muwaqar dataset were selected and used in the RWEQ Model. These selected periods were based on the number of potential wind erosion days whereby U2 > Uthreshold . This resulted in four periods from January- March of the years 2002,2003,2004 and 2011. The Barley and Natural graz- ing plot showed the highest mass transport rates, Q(x)barley = 0−3.0 (kg/m) and Q(x)Naturalgrazing = 0 − 1.0 (kg/m) for the potential wind erosion pe- riod of ≈ 10 days in 2002. However the Jan-March period of 2004 showed the highest average mass transport rate per 10 minute timestep, meaning that for a valid period of 5 days already a Q(x)barley = 0 − 1.86 (kg/m) was obtained. The Barley plot was the most erodible plot followed by the Natu- ral grazing plot which was a third of the wind erosion quantities compared to the Barley plot due to lower erodible soil factors. However the Water harvesting plot showed almost no wind erosion due to the low Combined Crop factor caused by the vegetation lines. The wind erosion quantities of the Water harvesting plot were > 90% reduced compared to the quantities of the Barley and Natural grazing plot.