Modelling water-harvesting systems in the arid south of Tunisia using SWAT

In many arid countries, runoff water-harvesting systems support the livelihood of the rural population. Little is known, however, about the effect of these systems on the water balance components of arid watersheds. The objective of this study was to adapt and evaluate the GIS-based watershed model SWAT (Soil Water Assessment Tool) for simulating the main hydrologic processes in arid environments. The model was applied to the 270-km(2) watershed of wadi Koutine in southeast Tunisia, which receives about 200 mm annual rain. The main adjustment for adapting the model to this dry Mediterranean environment was the inclusion of water-harvesting systems, which capture and use surface runoff for crop production in upstream subbasins, and a modification of the crop growth processes. The adjusted version of the model was named SWAT-WH. Model evaluation was performed based on 38 runoff events recorded at the Koutine station between 1973 and 1985. The model predicted that the average annual watershed rainfall of the 12-year evaluation period (209 mm) was split into ET (72%), groundwater recharge (22%) and outflow (6%). The evaluation coefficients for calibration and validation were, respectively, R-2 (coefficient of determination) 0.77 and 0.44; E (Nash-Sutcliffe coefficient) 0.73 and 0.43; and MAE (Mean Absolute Error) 2.6 mm and 3.0 mm, indicating that the model could reproduce the observed events reasonably well. However, the runoff record was dominated by two extreme events, which had a strong effect on the evaluation criteria. Discrepancies remained mainly due to uncertainties in the observed daily rainfall and runoff data. Recommendations for future research include the installation of additional rainfall and runoff gauges with continuous data logging and the collection of more field data to represent the soils and land use. In addition, crop growth and yield monitoring is needed for a proper evaluation of crop production, to allow an economic assessment of the different water uses in the watershed

Apport des données Landsat Thematic Mapper pour la cartographie des sols dans la région de Menzel Habib

Un essai de cartographie des sols a été réalisé au niveau de la zone de Menzel Habib, située en Tunisie présaharienne dans la région naturelle des basses plaines méridionales. Cette zone fait partie d’un Réseau d'Observatoires de Surveillance Écologique à Long Terme (ROSELT) mise en place par l’Observatoire du Sahel et du Sahara(OSS), dans le cadre d’un programme de suivi environnemental de la désertification. Ainsi, conformément aux objectifs généraux de ce programme insistant sur l’intérêt de la valorisation et l’exploitation des données anciennes pertinentes en relation avec le thème recherché par la présente étude. On a adopté une approche méthodologique reposant principalement sur la classification multispectrale d’une image satellite en ayant recours aux cartes des ressources en sols et pédologiques existantes. Il en ressort une carte pédologique couvrant toute la zone de Menzel Habib répartis en huit classes.Mots-clés : sols, cartographie, classification multispectrale, image satellite

Replicable Participatory Water Harvesting Selection Methodology

The developed methodology for the selection workshop can be summarized as shown in table 1. The developed methodology ensures that the stakeholder workshop are executed in similar fashion in all 4 study sites, which will make it easier to compare workshop results between study sites. It should be noted that study site partners do need to ensure that the methodology that is followed fits into the local context and circumstances; therefore the developed methodology may be adapted on details to better suit local conditions

Development of sustainable land management policies and practices in five selected countries from 1960 to 2010.

ABSTRACT Since the 1930s there has been worldwide concern about the effects of land degradation. After the problems experienced in the Dust Bowl in the USA, much attention was paid to soil and water conservation in both developed and developing countries. Initially Governments have stimulated the establishment of physical control measures, such as terraces and check dams, and reforestation. This was achieved through top-down regulations, and Forestry Departments were often in charge of the implementation. Subsequently the measures were implemented through more specialised agencies, and later with incentives, such as food aid. In some cases farmers were mobilised to work together on the establishment of the measures. Because of the low success rate of this top-down approach with line interventions, it was realised that a more participatory approach had to be followed. And the emphasis then shifted to area interventions such as cover crops, mulching and composting. In some countries voluntary ways of collaboration between farmers were developed. More recently Conservation Agriculture has been promoted, focusing on less soil disturbance, continuous land cover and crop rotations. This paper analyses whether and to what extent countries have followed such general trends in their soil and water conservation policies, since the 1990s often referred to as sustainable land management, or whether countries have also followed their own specific strategies. A historical (1960-2010) and comparative analysis of the development of these sustainable land management policies and practices is made in five selected countries (Indonesia, Ethiopia, Tunisia, Spain and Bolivia). Keywords: soil and water conservation, sustainable land management, policies, approaches, practice

Modification of the aggregate stability indices for wet sieving method and the water drop technique.

A