Valorization of return water from agricultural greenhouses heated by geothermal water in southern Tunisia

Abstract

The sector of protected crops under heated greenhouses in southern Tunisia has continued to develop with the availability of geothermal resources. The poor management of these resources leads to their degradation in terms of quantity and quality. This situation is worsening with the demand for water in the agricultural sector. Therefore, the development of these geothermal potentials is necessary to ensure their sustainability. The present work aims at characterizing the return water and assessing its impact on greenhouse crops and oasis systems. The study was based on physico-chemical analyses of return water collected from nine geothermal poles spread over the three governorates (Gabes, Kebili and Tozeur), field visits and surveys conducted with farmers. These physico-chemical analyses indicate a poor to average water quality with a very high saline risk and a medium alkaline risk. Indeed, the salinity of the water varies from 2.6 to 11.9 g/l and the SAR from 5.1 to 8.8. In addition, the salinity management techniques adopted by farmers are still limited due to their low financial capacity.