HRMS-based Innovative Monitoring of Grombalia Groundwater (Tunisia)

The growing number of inhabitants and anthropogenic activities in agricultural and industrial sectors in Grombalia coastal aquifer (Tunisia) is concretely affecting the quality and the quantity of the shallow aquifer. The conventional sampling used for the Grombalia groundwater quality monitoring seems to be inadequate (only 35 points in a study area of 372 Km2) to allow good understanding of the groundwater system. Indeed, 80 % of the total number points are dedicated to piezometric monitoring. Sampling representativeness, sampling procedures and time are significant determinants for efficient groundwater monitoring. This study highlighted the use of High-Resolution Monitoring Sensors (HRMS) in Grombalia coastal aquifer (Tunisia) as a‘green’ tool to reinforce and strengthen/or replace the existing aquifer monitoring network in the study area. Three “in-situ” HRMS (Aqua TROLL 500) were implemented in three identified hotspots points. They are equipped with interchangeable sensors measuring Temperature, Nitrate, and Water Depth delivering high-fidelity and high-frequency data in-sync with online remotely operated platform and provide the possibility to identify fleeting events that may not be detected by the low frequency of existing conventional monitoring system. The obtained results in June 2022 showed a significant drawdown of almost 2.5 m from the normal level recorded in the same period in 2020, in two among of three monitoring points. The excessive groundwater pumping rate and the increase of illicit pumping wells number have greatly affected the Grombalia groundwater reserves. It was noticed that the nitrate concentrations exceed the drinking water standard limit (50 mg/L), reaching 63 mg/L and 104 mg/L respectively in two among of three monitoring points. This increase could be due to the use of nitrate based chemical fertilizers by farmers during this period which increasingly degrades the quality of the groundwater. The HRMS implemented in the study area is proving great flexibility in collecting accurate and reliable data, with fewer resources and time need to be spent gathering data. The HRMS-based innovative monitoring system is used to control the groundwater withdrawals and quality and constitutes a solid demonstrative basis to propose remediation actions guaranteeing a sustainable, intelligent, and instantaneous management of the coastal aquifer of Grombalia.This research is supported by the PRIMA program under grant agreement No1923, project InTheMED. The PRIMA program is supported by the European Union