Situated in the centre of the Mediterranean Sea, the Maltese archipelago comprises three main islands - Malta, Gozo and Comino. On these islands ground water aquifers are the main source of fresh water.
Malta is one of the most densely populated countries in the world, placing immense pressure on these aquifer systems. As part of an initiative to better understand the characteristics of this resource, the Sustainable Energy and Water Conservation Unit (part of Malta’s Ministry for Energy and Health) contracted Fugro to undertake a thermographic aerial survey to locate areas of coastal discharge and help manage water resources more effectively.
The annual total ground water inflow to the islands’ aquifer systems is approximately 57 million cubic metres, of which an estimated 23 million cubic metres is lost annually through natural discharge at coastal areas. In addition, the intrusion of saline waters into the fresh water is a problem that offers significant challenges due to the disparity between demand for fresh water and the naturally occurring fresh water resources. In order to ensure that intrusion of saline water is managed effectively, a number of measures are being implemented by the Maltese Government.
Airborne thermography measures the temperature of the earth’s surface based on the amount of energy it is emitting, using an aircraft-mounted sensor that is sensitive to thermal infrared energy. In this project, the technology enabled Fugro to clearly delineate between the temperature variations of seawater versus fresh ground water. Ground water in Malta is estimated to have a stable temperate of about 19-20 degrees Celsius, whereas the seawater during the winter time is about 15 degrees Celsius. Taking into account this variation in temperature, airborne thermography made delineation of sites where the two waters meet a relatively simple task. Thermographic imagery provided sufficient detail to pinpoint thermal variations in the sea surface and relate these to freshwater or seawater areas.
Technological advancements in thermographic remote sensing have played a key role in improving management of available water resources.
Technical experts analysed the imagery and generated reports highlighting the location and extent of the hot spots where water (mainly brackish) with a different temperature to that of ground water was discharging into the sea. A total of 51 sites were identified along the coastline; some were hot spots identified in a previous survey in 1990 and Fugro’s analysis identified 23 new sites. Having access to a study conducted 25 years previously, helped establish and confirm the hot spots where water with a different temperature to ground water was consistently being discharged into the sea. These sites are to be the subject of further field investigations to characterise the flows and nature of the water and, where applicable, adopt water retention technologies
"Technological advancements in thermographic remote sensing have played a key role in improving management of available water resources," explains Arjun Sheoran, Technical Sales Manager at Fugro. "The results and analysis provided by Fugro allowed for better characterisation of the coastal ground water discharge within the Maltese islands and highlight Fugro’s world class remote sensing solutions and their application across a broad range of domains."
The thermographic aerial survey was undertaken in 2015 under the European Regional Development Fund (ERDF) 346 Project - Assessment of subsurface ground water discharge in the Maltese islands - which is co-financed by the ERDF.
An estimated 23 million m³ of ground water is lost each year through natural discharge at Maltese coastal areas.