| 1. |
- Berndtsson, Ronny, et al.
(författare)
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Climate change and transboundary water management in the Tunisian Mellegue Catchment
- 2017
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Ingår i: Vatten: tidskrift för vattenvård /Journal of Water Management and research. - 0042-2886. ; :4, s. 131-144
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Human activities and climate change affect hydrological and sedimentological characteristics within catchments. For arid and semiarid areas this induces direct negative economic and environmental consequences on society. In fact, stability in the rainfall regime and less siltation trapped in reservoirs mean more water for irrigation, water supply, and better flood control. This is especially important in the Tunisian semiarid region where water needs are close to potential water resources and siltation is reducing the reservoir capacity rapidly. Wadi Mellegue was chosen in order to study trends of water resources availability. Linear regression modelling and Mann-Kendall tests were performed for trend analysis. The study dealt with rainfall, discharge, and sediment patterns in the catchment area during a 44-year period. The results display a common decline in rainfall depth at different time scales. However, a positive trend related to discharge and siltation process was found. An increase in vulnerability to the new climate conditions is described. Consequently, water resources and agricultural landscape management for the Mellegue catchment should be revised in order to ensure a sustainable up- and downstream catchment development.
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| 2. |
- Jebari, Sihem, et al.
(författare)
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Challenges of Traditional Rainwater Harvesting Systems in Tunisia
- 2015
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Ingår i: Middle East Critique. - : Informa UK Limited. - 1943-6157 .- 1943-6149. ; 24:3, s. 289-306
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of this article is to examine the relevance of traditional hydraulic systems in ensuring sustainable water supplies at the catchment level and to explore ways to involve farmers in rural development. The methodology we used is based on the analysis of the Tunisian experience with traditional hydraulic systems to conserve water and soil. We proceed with a description of new forms of small hydraulic structures, which, since 1960, have increased significantly throughout the arid and semiarid landscape of Tunisia. We present a strategic framework related to the mobilization of water and to the institutions operating in the field of hydro-agricultural business techniques. The findings can contribute to promoting efficient and sustainable hydro-agricultural structures among decision makers and agricultural stakeholders regarding their future projects. The conclusions we draw can also help to stimulate new thinking about current and future agricultural, social, and economic challenges not only within Tunisia but also in other arid countries in the MENA (Middle East and North Africa) region.
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| 3. |
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| 4. |
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| 5. |
- Jebari, Sihem, et al.
(författare)
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Exceptional rainfall characteristics related to erosion risk in semiarid Tunisia
- 2008
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Ingår i: Open Hydrology Journal. - : Bentham Science Publishers Ltd.. - 1874-3781. ; 1, s. 25-33
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- The Tunisian Dorsal area is representative of the semiarid Mediterranean region in terms of water resources availability as well as exceptional rainfall characteristics, runoff generation, and soil loss risk. In this context, soil properties, surface management practices together with highly intensive rainfall make the soils vulnerable to erosion. If the exceptional rainfall characteristics are linked to different erosion types, the erosion risk could be evaluated in a simple and straightforward way. In this regard, a short time-scale rainfall data base from the Dorsal area was analysed in the paper. The procedure used involves finding a representative duration between 1-60 min for the exceptional rainfall characteristics.Rainfall intensities of different return periods are then related to the different erosion types. The identified exceptional rainfall durations between 1-60 min were analyzed in terms of number of events, depth, average intensity and maximum intensity. Results show that the 15-min duration maximum intensity can be used to evaluate erosion risk based on soil erosion type. The developed methodology can be used to evaluate erosion risk in semiarid regions based on exceptional rainfall characteristics. In practical terms the results can be used to better manage catchments that are vulnerable to soil erosion.
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| 6. |
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| 7. |
- Jebari, Sihem, et al.
(författare)
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Historical aspects of soil erosion in the Mejerda catchment, Tunisia
- 2012
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 57:5, s. 901-912
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural use and related water erosion leads to significant changes in the sedimentological and hydrological characteristics of watersheds and thus means negative consequences for rural development. This research work aimed at putting present-day soil erosion of the important Mejerda catchment in to a historical context. The catchment of wadi Mejerda in northern Tunisia has experienced soil erosion due to weather and human impact during thousands of years. We used historical texts and results from archeological research that go back to 1000 B.C. as well as data collected during the last century. Soil erosion from different types of agricultural landscape management was analyzed together with information on the soils’ production potential, hydrographical network, and flood frequency. The results showed that water erosion has increased the hydrographic network by 65 km and increased the deltaic plain as much as 15 km2/century. The soil productivity has, however, also decreased significantly. Moreover, due to river choking, the number of overflowing occurrences has multiplied over the last century. Finally, it is shown that water erosion follows a specific cycle of degradation throughout the watershed. These findings could be considered for better water and soil management in the context of semiarid areas.
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| 13. |
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| 14. |
- Jebari, Sihem, et al.
(författare)
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Regionalizing short-term rainfall affected by topography in semiarid Tunisia
- 2007
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 52:6, s. 1199-1215
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of fine time-scale rainfall are important in many hydrological applications, such as infiltration, erosion and flooding. The spatial properties of such rainfall are, however, seldom known, especially for arid and semi-arid areas. A better knowledge of fine time-scale rainfall and also comparison with daily rainfall may yield possibilities for disaggregation. For this purpose, rainfall data of different time scales, from 1-min to daily, from 25 stations during four years (1995–1998), were spatially analysed by means of spatial correlation, empirical orthogonal function (EOF) and hierarchical clustering. The results show that the spatial correlation is typically non-isotropic and varying, depending on topography and local meteorological settings. Similarly, spatial patterns of EOF are closely related to main atmospheric synoptic situations as influenced by orography and spatial dependence regarding areas with predominant convective and frontal rainfall. The clustering displayed different homogeneous sub-groups over the Tunisian Dorsal Mountains that can be used to better manage the limited water resources that often depend on fine time-scale rainfall variability.
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| 15. |
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| 16. |
- Jebari, Sihem, et al.
(författare)
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Soil erosion estimation based on rainfall disaggregation
- 2012
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 436, s. 102-110
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedSoil loss estimation remains one of the most difficult research tasks all over the world. Current simulation tools are still not detailed enough to allow for realistic scenarios to handle soil erosion problems. A common problem is the lack of rainfall data at a sufficient level of detail. The present study uses a cascade disaggregation model to generate short time scale rainfall data, needed to calculate the erosivity index in erosion modeling. The model is used to determine the spatial soil loss rate by the Revised Universal Soil Loss Equation and a GIS approach. Comparison between observed and generated data in terms of erosive rainfall characteristics shows that the erosivity factor is over-estimated. This is caused by an overestimation of short rainfall events. Consequently, different duration limits beyond which erosive events could be considered within the generated series were used to estimate the model performance curve. This provided a suitable duration limit needed to reproduce the observed erosivity. The results showed that generated series only considering rainfall events superior than 90 min are appropriate. This procedure provides a soil loss rate less than 10% under-estimation. Moreover, using Masson, Wischmeier-Smith's and recent erosion limit intervals gave a realistic spatial erosion distribution. The results are promising and can be used to better manage erosion-prone soils.
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| 17. |
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| 18. |
- Jebari, Sihem, et al.
(författare)
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Spatial soil loss risk and reservoir siltation in semi-arid Tunisia
- 2010
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 55:1, s. 121-137
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Tidskriftsartikel (refereegranskat)abstract
- 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(-1) but 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.
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| 19. |
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| 20. |
- Jebari, Sihem
(författare)
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Water erosion modeling using fractal rainfall disaggregation- a study in semiarid Tunisia
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the Tunisian semiarid area, water erosion processes have led to negative economic and environmental consequences in a context of limited water resources. To characterize and predict these degradation phenomena, a comprehensive high-resolution data base on erosive rainfall, together with siltation records for 28 small reservoirs were analyzed. The studied small reservoir network displays a general life-span of about 14 years. The average soil loss is 14.5 tonnes/ha/year. The complex relationship between the erosive rainfall events and the annual soil loss rates can be explained by two important factors. The first factor is related to the soil “degradation cycle”. It determines the soil particle delivery potential of the catchment. The second factor corresponds to the “degradation front”. The latter presents a north-western/south-eastern direction. To investigate rainfall disaggregation possibilities, a regionalization of fine time-scale and daily rainfall was undertaken. The results showed that the spatial properties are typically non-isotropic. Clustering showed that two different homogeneous rainfall subgroups are closely related to the predominant convective and frontal rainfall types. The comparison illustrated important similarities between the maximum 15-min and the daily rainfall data. The above findings were an incentive to explore the multiplicative properties of a 4-year rainfall time series. The time series showed scaling behavior for time scales up to 100 min that coincides with the most active erosion process time scale. Moreover, the temporal structure of rainfall was reproduced using a disaggregation model (Olsson, 1998). The observed and generated rainfall time series displayed several similar characteristics. This allowed the reproduction of erosivity for erosive rainfall events longer than 45 minutes. The erosion modeling was performed using the USLE/GIS approach. Maps of observed and generated spatial erosion distribution were combined with the Masson’s and Wischmeier-Smith’s erosion limit intervals. According to the above, the potential of rainfall scaling-based approaches to predict water erosion levels in semiarid areas seems promising. Using this approach may help soil and water authorities in semiarid areas to better manage soil erosion problems.
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| 21. |
- Kadri, Nesrine, et al.
(författare)
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Analysis of Four Decades of Land Use and Land Cover Change in Semiarid Tunisia Using Google Earth Engine
- 2023
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Ingår i: Remote Sensing. - 2072-4292. ; 15:13
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Tidskriftsartikel (refereegranskat)abstract
- Semiarid Tunisia is characterized by agricultural production that is delimited by water availability and degraded soil. This situation is exacerbated by human pressure and the negative effects of climate change. To improve the knowledge of long-term (1980 to 2020) drivers for Land Use and Land Cover (LULC) changes, we investigated the semiarid Rihana region in central Tunisia. A new approach involving Google Earth Engine (GEE) was used to map LULC using Landsat imagery and vegetative indices (NDVI, MSAVI, and EVI) by applying a Random Forest (RF) classifier. A Rapid Participatory Systemic Diagnosis (RPSD) was used to consider the relation between LULC changes and their key drivers. The methodology relied on interviews with the local population and experts. Focus groups were conducted with practicians of the Regueb Agricultural Extension Services, followed by semi-structured interviews with 52 households. Results showed the following: (1) the RF classifier in Google Earth Engine had strong performance across diverse Landsat image types resulting in overall classification accuracy of ≥0.96 and a kappa coefficient ≥0.93; (2) rainfed olive land increased four times during the study period while irrigated agriculture increased substantially during the last decade; rangeland and rainfed annual crops decreased by 58 and 88%, respectively, between 1980 and 2021; (3) drivers of LULC changes are predominately local in nature, including topography, local climate, hydrology, strategies of household, effects of the 2010 revolution, associated increasing demand for natural resources, agricultural policy, population growth, high cost of agricultural input, and economic opportunities. To summarize, changes in LULC in Rihana are an adaptive response to these various factors. The findings are important to better understand ways towards sustainable management of natural resources in arid and semiarid regions as well as efficient methods to study these processes.
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| 22. |
- Kchaou, Rajia, et al.
(författare)
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Forage Potential of Cereal–Legume Mixtures as an Adaptive Climate Change Strategy under Low Input Systems
- 2023
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Ingår i: Sustainability (Switzerland). - : MDPI AG. - 2071-1050. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Mixed cropping systems can constitute important agroecological adaptation strategies for enhancing crop growth and productivity in view of climate change, while reducing the need for synthetic fertilizers and providing important ecosystem services. The aim of this study was to investigate growth, competitiveness, and productivity of two forage mixtures combining triticale (X triticosecale Wittmack) to common vetch (Vicia sativa L.), and to fenugreek (Trigonella fœnum-græcum L.) in different mixture combinations (40% T–60% V vs. 60% T–40% V and 40% T–60% F vs. 60% T–40% F). Field results showed that both forage legumes were higher inside the different crop mixtures (+225% for vetch, +94% for fenugreek) than in monocropping. In regard to the competition ration (CR), triticale was the more dominant and competitive species in three out of four studied mixtures. Forage yield was higher in crop mixtures than for corresponding sole crops. Yield gain was greater for common vetch-based mixtures than fenugreek ones (+60% vs. +30%). The results show that using cereal–legume mixtures can provide important productivity increase for fodder yield compared to conventional pure crops. The method is an important adaptive agricultural strategy in view of climate change.
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| 23. |
- Khemiri, Khaoula, et al.
(författare)
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Drivers of Long-Term Land-Use Pressure in the Merguellil Wadi, Tunisia, Using DPSIR Approach and Remote Sensing
- 2022
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Ingår i: Land. - : MDPI AG. - 2073-445X. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Increasing land use pressure is a primary force for degradation of agricultural areas. The drivers for these pressures are initiated by a series of interconnected processes. This study presents a novel methodology to analyze drivers of changing land use pressure and the effects on society and landscape. The focus was on characterizing these drivers and relate them to land use statistics obtained from geospatial data from the important semiarid Merguellil Wadi between 1976 and 2016. Cause-and-effect relationships between different drivers of land use change were analyzed using the DPSIR approach. Results show that during the 40-year period cultivated land increased and wetland areas decreased substantially. Drivers for change were pressure from economic development, cultivation practices, and hydro-agricultural techniques. This leads to stress on water and soil resulting in soil erosion, poverty increase, and rural exodus. We show that hydro-agricultural techniques adapted to the semiarid climate, allocation of land property rights, resource allocation, and improved marketing of agricultural products can help rural residents to diversify their economy, and thus better preserve the fragile semiarid landscape. Results of this study can be used to ensure sustainable management of water and soil resources in areas with similar climate and socio-economic conditions.
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| 24. |
- Khemiri, Khaoula, et al.
(författare)
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Is climate or direct human influence responsible for discharge decrease in the tunisian merguellil basin?
- 2021
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 13:19
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Tidskriftsartikel (refereegranskat)abstract
- Climate change and direct anthropogenic impact are recognized as two major factors affecting catchment runoff. This study investigated the separate effect of each of these factors for runoff from the important Tunisian Merguellil catchment. For this purpose, more than forty years of hydrological data were used. The methodology was based on hydrological characterization, NDVI index to monitor land use dynamics, and the Budyko approach to specify origin of change. The results show that hydrological change is much more important upstream than downstream. The last three decades display a 40% reduction in runoff. This is associated with the direct influence of humans, who are responsible for about 78% of the variation in flow. It appears that climate change contributes to less than about 22%. The combination of increased cultivated land and decreased annual rainfall is the main reason for reduced catchment runoff. Consequently, these effects threaten the sustainable runoff, water in reservoirs, and future water supply in general. Ultimately, the available runoff remains an important parameter and a key indicator to guide the choices of decision-makers and practitioners in current and future climatic conditions. This contributes to supporting sustainable management of remaining water resources.
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| 25. |
- Marzougui, Nidhal, et al.
(författare)
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How Can Sewage Sludge Use in Sustainable Tunisian Agriculture Be Increased?
- 2022
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Ingår i: Sustainability (Switzerland). - : MDPI AG. - 2071-1050. ; 14:21
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, farmers in Beja, an agricultural governorate in northwestern Tunisia, have expressed their willingness to use urban sewage sludge as agricultural fertilizer, especially with the unavailability of chemical fertilizers and the soil type of the region that is poor in organic matter. However, there is an imbalance between the important farmers’ demand versus the limited quantity of sludge produced by the Beja wastewater treatment plants (WWTPs). In the face of this, this study aims to identify the problems related to the agricultural reuse of sludge in Beja and propose solutions to solve them. The quality of the sludge produced by the five Beja WWTPs was assessed based on physicochemical and microbiological parameters. The data were collected using the Delphi method, with 15 experts representing different positions on the issue treated. The SWOT-AHP methodology was used to define the strategies promoting the sustainable use and management of urban sewage sludge for sustainable agricultural development in Beja. Results showed that there were no problems with compliance with the Tunisian standards NT 106.20 for the sludge produced. A set of twelve practical conclusions was identified, constituting the strategies of Strengths–Opportunities, Strengths–Threats, Weaknesses–Opportunities, and Weaknesses–Threats deduced from the SWOT-AHP.
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