Mound measurements — quantifying medium-term soil erosion under olive trees in Northern Jordan S. Kraushaar a, ⁎, N. Herrmann b , G. Ollesch c , H.-J. Vogel a,d , C. Siebert e a Department of Soil Physics, Helmholtz Centre for Environmental Research — UFZ, 06120 Halle, Germany b Department of Geography, University of Hildesheim, 31141 Hildesheim, Germany c Elbe River Catchment Communities — Liaison Office, 39104 Magdeburg, Germany d Department of Soil Sciences, Martin Luther University of Halle-Wittenberg, 06120 Halle, Germany e Department of Catchment Hydrology, Helmholtz Centre for Environmental Research — UFZ, 06120 Halle, Germany abstract article info Article history: Received 20 November 2012 Received in revised form 15 December 2013 Accepted 20 December 2013 Available online xxxx Keywords: Erosion Soil degradation Olives Mediterranean Jordan Over the last few decades many quantitative erosion studies have revealed that olive orchard expansion and increased mechanization in southern European countries have led to increased soil erosion under olive trees. Consequently, these studies have suggested different methods of mitigation. In light of the 2014 European trad- ing zone expansion to countries east and south of the Mediterranean, a further intensification of olive plantations is postulated to meet market demands. To attain first medium-term estimates of erosion in Northern Jordan and its driving factors, a new method measuring olive mounds was implemented. Seven fields with clearly erosive structures were chosen throughout the Wadi Al-Arab catchment in Northern Jordan. Topographic measurements were used to reconstruct the historical and recent surface level and calculate the volume eroded since the plant- ing of the trees. A total of 81 bulk density measurements and 14 tree cores allowed the estimation of the soil loss in tons per hectare. The combination of modified land use map and slope information helped to identify similar olive fields with high erosive potential. Results show that the method provides medium-term quantitative estimates for averaged soil loss consistent with some existing results from similar research areas in the Mediterranean. They clearly indicate the significant potential for erosion in olive orchards with around 95 ± 8 t ha -1 yr -1 . Tillage practice and water erosion were identified as critical erosion processes, both depending on tillage characteristics, tillage timing, and soil parent material. The investigated fields represent about 19% of the catchment's surface area and are likely to contribute to the measured yearly sediment yield that fills up the Wadi Al-Arab reservoir with sediments. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The Mediterranean region is prone to land degradation caused by environmental factors and anthropogenic influences. Major drivers are land use with soil management techniques and land use changes as a result of the economic considerations by farmers following political boundary conditions. Among other factors, soil erosion, and hence, ac- celerated sediment loads in rivers, is still one of the most problematic forms of land degradation (García-Ruiz, 2010). In addition to local soil degradation, high rates of sediment loads lead to morphological impacts in riverbeds, sedimentation of reservoirs as well as eutrophication of surface waters (Boardman and Poesen, 2006). In the Mediterranean re- gion a substantial part of the water supply is often based on freshwater bodies and artificial reservoirs. Jordan, in particular, as one of the 10 most water-poor countries in the world (Nortcliff et al., 2008), has to increase its water storage capacities by harvesting rainfall and runoff in dams (Al-Ansari and Shatnawi, 2011). This is also the case in the Wadi Al-Arab catchment in Northern Jordan. The Wadi Al-Arab dam serves water for irrigation projects in the Jordan Valley as well as for households in the capital Amman in times of drought and therefore plays a key role in the water management of the Northern part of the Lower Jordan Valley (the Wadi Al-Arab dam director Hussein Al-Shurieki, personal communication). However, the reservoir is threat- ened by an increasing rate of sedimentation and by diminished water quality (Ghrefat and Yussuf, 2006; Al-Ansari and Shatnawi, 2011). Thus, although the offsite effects of erosion are known, Jordan has rarely been subject to studies identifying the sediment sources. For the north, Khresat et al. (1998) sketched different forms of soil degradation, men- tioning that water erosion and improper farming practices are two of the major causes. Both processes aggravate each other on olive planta- tions in the research area, where the total area of olive trees more than doubled between 1994 and 1999 and is still increasing (Venot, 2003; IOC, 2005; authors' observations), covering around 30% of the arable land (IOC, 2005, estimation for 2006). Many researchers have tried to demonstrate the vulnerability of olive orchards to soil erosion with the expansion of olive fields in European Mediterranean countries due to the EU Agrarian Policy and Geomorphology xxx (2014) xxx–xxx ⁎ Corresponding author. Tel.: +49 163 3348 420. E-mail address: sabine-kraushaar@gmx.de (S. Kraushaar). GEOMOR-04604; No of Pages 12 0169-555X/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.geomorph.2013.12.021 Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph Please cite this article as: Kraushaar, S., et al., Mound measurements — quantifying medium-term soil erosion under olive trees in Northern Jordan, Geomorphology (2014), http://dx.doi.org/10.1016/j.geomorph.2013.12.021