HRMS-Based Innovative Monitoring of Grombalia Groundwater (Tunisia)

The growing number of inhabitants and anthropogenic activities in agricultural and industrial sectors in the 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 to allow a good understanding of the groundwater system. 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 the 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. They are equipped with interchangeable sensors measuring Temperature, Nitrate, and Water Depth which were monitored continuously at hourly intervals from November 2021 to September 2022. The obtained results in June 2022 showed a significant drawdown of almost 2.5 m from the normal level recorded in June 2020, in two of the 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 exceeded the drinking water standard limit (50 mg/L), reaching 63 mg/L and 104 mg/L, respectively, in two of the three monitoring points. Since most of the study area is covered with citrus, this increase could be due to the spreading and fertilization activities which begin at the end of February and continue until the end of August-beginning of September which increasingly degrades the quality of the groundwater. The HRMS implemented in the study area are proving great flexibility in collecting accurate and reliable data, with fewer human resources and required time. 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 sustainable, intelligent, and instantaneous management of the coastal aquifer of Grombalia.