Considering groundwater use to improve the assessment of groundwater pumping for irrigation in North Africa

Abstract

Groundwater resources in semi-arid areas and especially in the Mediterranean face a growing demand for irrigated agriculture and, to a lesser extent, for domestic uses. Consequently, groundwater reserves are affected and water-table drops are widely observed. This leads to strong constraints on groundwater access for farmers, while managers worry about the future evolution of the water resources. A common problem for building proper groundwater management plans is the difficulty in assessing individual groundwater withdrawals at regional scale. Predicting future trends of these groundwater withdrawals is even more challenging. The basic question is how to assess the water budget variables and their evolution when they are deeply linked to human activities, themselves driven by countless factors (access to natural resources, public policies, market, etc.). This study provides some possible answers by focusing on the assessment of groundwater withdrawals for irrigated agriculture at three sites in North Africa (Morocco, Tunisia and Algeria). Efforts were made to understand the different features that influence irrigation practices, and an adaptive user-oriented methodology was used to monitor groundwater withdrawals. For each site, different key factors affecting the regional groundwater abstraction and its past evolution were identified by involving farmers' knowledge. Factors such as farmer access to land and groundwater or development of public infrastructures (electrical distribution network) are crucial to decode the results of well inventories and assess the regional groundwater abstraction and its future trend. This leads one to look with caution at the number of wells cited in the literature, which could be oversimplified. (Résumé d'auteur

Inspiring a Broader Socio‐Hydrological Negotiation Approach With Interdisciplinary Field‐Based Experience

“…Let us consider, for example, the integration of hydroagricultural practices in a modeling framework based on the volumes of water applied to a given area. Determining such volumes is a challenge in itself and requires accounting for local farming systems and irrigation practices (Massuel et al, ). Faced with difficult quantification based on field measurements and field observations (the practices of irrigators are extremely variable), hydrologists often use theoretical values (e.g., FAO‐56) to calculate irrigation volumes on the basis of optimal practices from a technical point of view.…”

“…This resulted in the use of an interdisciplinary questionnaire concerning groundwater use, as well as a qualitative survey of the wells and their history. An initial finding was that understanding the diversity of methods used to access groundwater could reduce the uncertainty about the extrapolation of the number of pumping wells to be correlated with the volumes of pumped water (Massuel et al, ). The approach showed that the relationship between the number of wells and total groundwater use (flow) was governed by a set of nonhydrological determinants, i.e., other than the classic depth to the water table, type of well/borehole, type of pump, type of irrigation system, energy source, hydrodynamic properties of the aquifer, density of the wells in the vicinity, etc.…”

Time‐domain electromagnetic imaging of a clayey confining bed in a brackish environment: A case study in the Kairouan Plain Aquifer (Kelbia salt lake, Tunisia)

“…The Plio‐Quaternary aquifer of the KP is one of the largest aquifers in central Tunisia, with an area of 3,000 km 2 and a saturated thickness ranging from 200 to 500 m (Besbes & de Marsily, ; Jerbi et al, ). This vast aquifer is extensively used both for agricultural purposes and for the supply of drinking water (Leduc et al, ; Massuel et al, ). In this region, where the climate is semi‐arid, the mean annual rainfall is less than 300 mm/year, and the potential evapotranspiration is high, reaching approximately 1,700 mm/year during the summer (Massuel et al, ; Nazoumou & Besbes, ; Zribi, Paris Anguela, Duchemin, & Lili, ).…”

“…This vast aquifer is extensively used both for agricultural purposes and for the supply of drinking water (Leduc et al, ; Massuel et al, ). In this region, where the climate is semi‐arid, the mean annual rainfall is less than 300 mm/year, and the potential evapotranspiration is high, reaching approximately 1,700 mm/year during the summer (Massuel et al, ; Nazoumou & Besbes, ; Zribi, Paris Anguela, Duchemin, & Lili, ). This climate, combined with the intense and widespread use of the aquifer, is leading to a steady decrease in piezometric levels, at a rate of approximately 1,000 mm/year for the last 30 years (Leduc et al, ; Massuel & Riaux, ).…”

“…Large reservoirs have been built on the three main wadis, and they collect the run‐off from upstream, thereby modifying the groundwater recharge processes. The Plio‐Quaternary aquifer of the KP is intensively used for agriculture through private and public pumping wells (Massuel et al, ). As a result, groundwater levels have dropped by 30 m in the last 40 years (Leduc et al, ; Massuel & Riaux, ).…”