Insaf Mekki

Management of groundwater resources in relation to oasis sustainability: the case of the Nefzawa region in Tunisia.

In Southern Tunisia Nefzawa region, the deep fossil aquifers have been used intensively to support agricultural activities and economic development. This resulted in the degradation of groundwater resources as well as in their conflicting uses. Efficient management strategies that allow for compromises between economic development and water resource preservation are needed. Such strategies require initial understanding of the interactions between stakeholders and water related processes. This paper aims to conceptualize the causalities between the management of deep fossil aquifers and the functioning of oasian agrosystems. By merging biophysical and socioeconomic issues, we propose an integrated assessment of public policies devoted to the management of groundwater resources. The failure of public policies emphasizes both the lack of consideration for individual initiatives and the long-term uncertainties on such policies, where farmer practices have been driven by economic and cultural factors. A set of indicators is next proposed for assessing the preservation of deep fossil aquifers that support agricultural and economic development. Further methodological improvements are needed to evaluate the long-term effects of constraints and incentives on the management of deep fossil aquifers.

Measuring Crop Evapotranspiration Over Hilly Areas

Agricultural production systems around the Mediterranean basin rely mostly on rainfed agriculture in hilly watersheds, although some irrigation is sustained downstream of water reservoirs. With climate change and increasing demand for water, most commonly cultivated species, particularly cereals, are exposed to high risks of water shortages during the growing season. Under such threats, managing agricultural activities, for optimum water use, requires a good assessment of crop actual evapotranspiration (ET), a major term of both land surface energy and water balances.

Evapotranspiration of Wheat in a Hilly Topography: Results from Measurements Using a Set of Eddy Covariance Stations

Several methods allow the determination of evapotranspiration (ET), either by direct measurement or by estimation from weather data. The most used estimation method is the FAO56 (FAO-PM), based on the concept of reference evapotranspiration (ETo) and crop coefficient (Kc). The eddy covariance technique (EC) developed for measurement of convective fluxes between land surface and the atmosphere is commonly used to estimate ET. However, these methods were established under standard conditions in flat terrain, and their use in hilly areas is questionable. In this work, the variability of ETo and ET measured by EC and energy balance (EB) in a hilly area of northern Tunisia is studied for different relief configurations. The experiment was conducted using a meteorological (M), and three EC-EB measurement stations in three wheat fields. Two stations were installed on opposite slopes of a ridge with apposing aspects and moderate slopes (A, B), and one station was installed in a flat site (C). Results of monitoring during the mid-season of wheat growth showed similar ETo levels in all sites for hourly and daily time steps with relative RMSE in the range 0.03–0.08 compared to M. Average ET values in sloping fields (A, B) were, respectively, 15% and 10% lower than in (C). However, hourly values of ET/ETo obtained from EC measurements were smaller than FAO-Kc, contrarily to those based on the EB method.