Improved integrated water resource management (IRWM) in the Mornag public irrigated schemes – Engineering component, aquifer recharge

Detailed description of project:

The Ministry of Agriculture, Hydraulic Resource and Fisheries aims to ensure integrated, efficient, ecological and sustainable management of water resource and the sustainable use of agricultural soils on the Mornag plain, southeast of the city of Tunis. Following the overexploitation of its groundwater table, the plain is threatened by the intrusion of sea water, while the dilapidation of the irrigation network hinders optimal water management.

The project consists of two components: the first is dedicated to the artificial recharge of the Mornag aquifer with treated wastewater from the “Sud Méliane II” water treatment plant. The second component addresses the rehabilitation of Mornag irrigated schemes on a total area of 6,812 ha. The total investment value (the two components, recharge of the water table and rehabilitation of the irrigation network together) is estimated at 22.1 million euros.

This technical component is accompanied by an accompanying measures component which aims to ensure sustainable and efficient management of water and land resources. The project is structured in three contracts A, B and C.

Contract B applies to the two components of the artificial recharge of the Mornag aquifer and rehabilitation of the Mornag irrigated schemes and is structured into six phases:

  1. Preliminary Design for the rehabilitation of the Mornag irrigated schemes (the Preliminary Design for the groundwater recharge of the Mornag aquifer had concluded that only the alternative of a hydraulic barrier seems, at the smallest recharge volume, to provide effective protection against water intrusion. The study also showed that the quality of treated wastewater produced by the “Sud Méliane II” WWTP does not meet the standards allowing groundwater recharge. Therefore, the barrier will be temporarily fed by conventional waters transferred from the Mejerdah Cap Bon Canal (CMCB))
  2. Detailed Design
  3. Tender Documents
  4. Support for the evaluation of the tender documents and contract award
  5. Implementation of performance studies
  6. Construction supervision and control of works

The rehabilitation component aims at rehabilitating the irrigation infrastructure of the Mornag public perimeters, which have been operational since 1982. The activities include the rehabilitation of 5 pumping stations (Total = 2,300 l/s with a TDH = 85 m), the rehabilitation of the existing irrigation system, the integration of extension zones and perimeters currently supplied with treated wastewater and the improvement of the irrigation hydrants. The pressure in the irrigation network will be increased to enable the introduction of water saving methods (such as drip and sprinkler irrigation). The management and the maintenance of the tertiary system and the water fee collection will be done by farmer’s organizations (groupements de développement agricoles).

Type of services provided:

For the groundwater recharge of the Mornag aquifer:

  • Additional tests and investigations for the hydrogeological study of the downstream zone of the water table: collection and analysis of groundwater data in wells, boreholes and piezometers in the coastal zone; geotechnical investigation by electromagnetic soundings, the construction of piezometers and test boreholes along two axes perpendicular to the sea in the coastal zone of the Mornag aquifer;
  • Updating of the regional hydrogeological model (i.e. covering the entire Mornag aquifer) and the development of two 2D sub-models representing the downstream zone to simulate the process of marine intrusion at each axis;
  • Analysis of treated wastewater produced by the El Attar wastewater treatment plant;
  • Detailed design study of the hydraulic barrier (phase 2): global concept; identification of the alignment and locations of the main structures, the pumping and filtration station, the infiltration boreholes and the groundwater and deep water table monitoring stations including a warning system for the advancement of the salt wedge; topographic survey; structural studies; study of forecasting management tools for the aquifer and the SCADA system and identification of maintenance and operation activities; cost estimate ; etc.
  • Preparation of the tender dossier for the realization of the hydraulic barrier and all its components (phase 3)
  • Support for the evaluation of proposals and the establishment of contracts for the realization of all components of the barrier (phase 4);
  • Elaboration of studies for the execution of the barrier components (phase 5);
  • Construction supervision and control of works relating to the hydraulic barrier (phase 6).

For the rehabilitation of the Mornag irrigation schemes:

  • Development of the Preliminary Design study for the rehabilitation of irrigation schemes (phase 1);
  • Detailed Design study for the rehabilitation of small irrigation schemes (rehabilitation of networks, creation of reservoirs and rehabilitation of pumping stations) (phase 2);
  • Preparation of bidding documents and support to the CRDA in formulating the agreements necessary for the implementation of the various project components (phase 3);
  • Support for the evaluation of offers and the establishment of Contracts (phase 4);
  • Elaboration of studies related to the execution of treatment plants and major structures required, in parallel with the execution of the works (phase 5);
  • Construction supervision and control of works to be carried out by companies on behalf of CRDA (phase 6);
  • Environmental impact studies for the two components.
CRDA Ben Arous
BMZ through KfW
10/2015 - 12/2020
Contract value: 2,647,518 €