In the arid regions of Tunisia, considerable investments are being made to maintain the old water harvesting techniques and introduce new ones to capture the scarce amount of rainwater (100 mm to 230 mm annually) for agricultural and domestic purposes. However, no detailed assessment of the multiple effects and the costs and benefits of these techniques have been made so far. This paper summarizes the results of an in depth investigation of the multiple impacts (runoff mobilization, ground water recharge, agro-socio-economic impacts) of the water harvesting works undertaken in the watershed of oued Oum Zessar (southeastern Tunisia). The importance of interdisciplinary and integrated approaches was revealed through this detailed impact assessment and economic evaluation. In fact, the profitability of the water harvesting works depends largely on the criteria chosen. However, further refinements are needed to better include all possible impacts (positive and negative) that occur as a result of the installation of the water harvesting structures.

The objective of this study was to identify the different irrigators’ strategies and to analyze the economic profitability of irrigated production systems in relation to adaptations to the scarcity of groundwater resources in a context of climate change in the South east of Tunisian. Based on surveys of 190 irrigated farms, this research shows that eighty-five percent (85%) of respondents clearly perceive climate change in southeastern Tunisia. These changes result in a decrease and an increasing irregularity of the rains, a disruption of the winter season, a greater frequency of pockets of drought and the decrease of the piezometric level of the water tables. In response to these changes, irrigators have adopted adaptation strategies, the most common of which are: offensive strategy or “chasing”, defensive strategy and contractive strategy. These strategies include various adaptation measures such as annual cleaning and deepening of wells, the use of water saving, the change of the cropping system and the reduction of irrigated area. These readjustments for most of the measures adopted by the irrigators have an impact on the elements of their operating account. In addition, offensive and defensive strategies appear to be the most economically profitable types of adaptation at the 1% level. Knowledge of different adaptation strategies and their economic returns enables adaptation options to be identified that are both realistic in terms of implementation and ambitious in terms of their objectives, and help develop priorities for adaptation of water resources for irrigation.

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.

The objective of this study was to measure the efficiency level of Water Users Associations (WUAs) in the coastal oases of Gabès (South-Est of Tunisia) and assessing its main determinants. First, an input-oriented data envelopment analysis (DEA) was used to measure the relative efficiency scores of WUAs and to evaluate the management and maintenance costs sub-vectors efficiencies separately through a mathematical modification in the initial DEA specification. In a second stage, critical determinants of sub-vector efficiency are determined by applying a Tobit model. A key finding of the study is that WUAs are clearly inefficient. Results show that on average, 38% of the used inputs could be saved if the WUAs operated on the frontier. The inefficiency found can be mainly attributed to the number of water pumping stations managed, the ratio of water losses and WUAs' age. The results also show a discrepancy between the technical efficiency values calculated under the CRS and VRS assumptions, resulting in a 20% scale inefficiency. The study also revealed that the sub-vector inefficiency of WUAs is more linked with engineering inefficiencies than to their management inefficiencies.

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.