Tracking hidden groundwater with radar technology

The aim of this study is to investigate whether a technique developed to measure the basal meltrate of ice shelves can be used to monitor groundwater in arid and semi-arid regions.

Groundwater is the most exploited of all the Earth’s raw materials, with a world-wide per capita extraction of over 350 litres per day.  Particularly in the developing world, groundwater extraction has been growing at a near-exponential rate, leading to unsustainable exploitation of many aquifers. A key technical challenge for the management of groundwater is to increase the visibility of the resource: how can you manage a resource that you can’t see?

ApRES (Autonomous phase-sensitive Radio Echo Sounder) is a downward-looking radar that has been developed in a collaboration between BAS and UCL to monitor very precisely an ice shelf’s changing thickness. By precisely measuring the change in the thickness of the ice, it’s possible to see how fast the ice shelf is being melted by the ocean. The instrument is relatively low cost, and is capable of being left to monitor the ice shelf over a period of a year or more, surviving the harsh Antarctic winter with low power requirements.

The water table in arid and semi-arid regions is marked by a change from unsaturated to saturated material.  From the point of view of radar, that surface has many properties similar to the transition between ice and water at the bottom of an ice shelf.

Working with our Moroccan partners, the aim of this project is to see whether the ApRES concept can be exploited to monitor the changing depth of the water table and therefore provide a robust, low cost method to monitor the state of charge of aquifers supplying groundwater in developing nations – to convert an invisible resource to one that is visible and therefore more readily manageable.

We are pleased to be working with partners Fatima El Khalifa from the Moroccan Climate Innovation Center, Mohammed Slimani from the Bouregreg and Chaouia Water Basin Agency, and Namira El Amrani from Hassan 1^st University, Settat.

Carlos Martin deploying ApRES in Morocco where it can be used to detect changes in groundwater level