Hydrologist seeks to mitigate flooding, recharge groundwater

A research project led by a consortium of interested parties is seeking the possibility of creating a system by which rainwater runoff from rooftops of buildings is diverted into the ground.

A second project, known as the GEO-INF system, seeks to meet the dual objectives of flood mitigation and groundwater charge.

Hydrologist Marco Cremona, together with Solid Base Ltd, the University of Malta, the Malta Resources Authority and St Theresa College, have dedicated the past two years researching how this innovative idea could be implemented at minimum costs and requiring minimum space.

The research will focus on deriving raw data on the permeability and water-filtration characteristics of geological formations, the development of a low-cost filtration - recharge system - and a methodology for the drilling of the cores.

So far, the consortium has dedicated its efforts to determining the quality of runoff generated from roofs in different localities.

"The idea is simple but with great potential," Cremona said. "Rainwater is a free resource lacking two pollutants: salt and nitrate. This makes it the ideal resource to replenish ground water."

Cremona described the system as compact, innovative, reliable and cost-effective. Overflow from the roofs would be collected, filtered and passed through the ground through a drilled hole.

"It is unfortunate that water awareness has decreased over the years. The lack of water reservoirs and wells is also causing sewage to overflow. Obviously, this water would be too polluted to be reused as it would pose a danger for public health," he said.

The project's methodology included comprehensive laboratory water analysis of runoff generated from five roofs. Then samples were gathered between January and April from three sites.

One of the sites also happens to be Cremona's home in Mosta.

Geologist Adrian Mifsud said that to assess the permeability of geological formations, separate tests were carried out. The tests were carried out on the lower globigerina limestone.

The consortium is also focusing its tests on the centre and south of Malta - from Mosta downwards.

"Moreover, the high density of dwellings and properties are built on the lower globigerina limestone formation," Mifsud said.

The geology team also carried out an extensive site assessment study to select 15 drilling sites on the basis of geology, expected variance in permeability, accessibility for drilling rig and size of roof area. 

"A total of 15 'infiltration boreholes' have been drilled, detailed logs drawn up and in-situ permeability tests carried out in each," Mifsud added.

The second party of the project constitutes the development of a computer model that computes the 'best fit' GEO-INF system for a given size of roof.

This programme produces the optimal installation to suit the particular situation, such as satisfactory water-dissipating performance, lowest cost and smallest footprint.

But one problem that this project might attract is popularity. Cremona conceded that government intervention would be required if households were to be convinced to make use of such a project.

"Admittedly, this project is not for direct personal gain... it's for the benefit of society as a whole. At the end of the day, we all make use of groundwater and we all suffer when our roads flood," he said.

Cremona said that ideally, this system would be utilised by schools, factories, hotels and other large buildings.

"If implemented, this system could be an alternative to the lack of wells," he said.