Protecting a Vital Groundwater Resource
An in-depth study of the Northern Aquifer, a vitally important source of fresh water in Mauritius, is expected to provide comprehensive information about the groundwater resource and the twin risks of contamination and salt water intrusion. Improved understanding, by both engineers and local communities, will help the people of Mauritius to adopt integrated approaches to water management, with the goal of protecting precious groundwater resources and ensuring sustainable water supply.
The Northern Aquifer is one of five main underground water reserves on the island of Mauritius. It consists of about 30 domestic pumping stations, 56 industrial boreholes and 62 agricultural boreholes and plays a vitally important role in the social and economic life of Mauritius – particularly the northern plains where agriculture is the main economic activity. By 2025, the northern plains will require about 133 million cubic metres of water per year for the irrigation of agricultural crops; an expanding tourism industry, coupled with a burgeoning population, will also increase demand for water.
The Northern Aquifer currently contributes between 50 and 60 percent of water used for domestic purposes, such as washing and drinking, but it is susceptible to over-exploitation and pollution from agricultural chemicals, sewage and wastewater.
Moreover, a brackish saltwater intrusion has been detected up to two kilometres from the coast during the dry season.
With a view to improving knowledge of the complex geological structure of the Northern Aquifer (and the quality of its water) a partnership and co-finance arrangement has been established between the the Global Environment Facility, United Nations Development Programme and the government of Mauritius through its Ministry of Energy and Public Utilities/Water Resources Unit (WRU). A demonstration project was implemented with the objective of adopting Integrated Water Resources Management (IWRM) approaches to monitor and protect the aquifer. The demonstration project was structured around four components, each of which involves the implementation of a number of activities.
The first component consisted of an assessment of the freshwater/seawater interface and groundwater quality, and the establishment of a Geographical Information System (GIS). A specialist consultant undertook a study to determine the position of the interface. This required the drilling of five boreholes, each of which was fitted with multi-level piezometers, instruments that allow for the sampling of groundwater at different depths. The piezometers enabled the WRU to identify and monitor the position of the freshwater/seawater interface which shifts according to the seasons. Insodoing, the WRU was able to determine the extent to which the interface is moving in response to over-exploitation of groundwater resources, rainfall volumes (i.e. replenishment of the aquifer) and/or sea level rise.
The five boreholes, and others, also provided an ideal opportunity to assess groundwater quality and locate sources of contamination. A water quality monitoring programme was established to effect regular sampling and laboratory analysis. Recommendations were provided with regards to the state of the aquifer. The testing were used to establish a water quality baseline that will allow water authorities to continuously assess the vulnerability of groundwater resources against pollution and over abstraction, and provide information necessary for decision making.
The GIS activity allowed the mapping of the hydrogeological features of the Northern Aquifer and the capture, storage and analysis of information relating to its exploitation. One of the advantages of this exercise is that it will enable the WRU and the Central Water Authority of Mauritius to gauge more accurately the potential of the Northern Aquifer. This will assist the latter authority to more knowledgeably assess applications for the drilling of boreholes.
Components two and three were concerned with the assessment of improvements in wastewater collection and disposal, and water demand management, respectively. The use of injection boreholes for the disposal of treated wastewater was assessed by investigating impacts on the nearby lagoon. Laboratory equipment were purchased to more accurately assess these impacts.
Component four was focused on education and awareness raising. An awareness action plan was designed to encourage water users, local communities and other stakeholders to take ownership and responsibility for water saving, and protection of groundwater resources. Video and audio public service announcement were broacasted on national television and radio channels. This was supplemented by a series of formal, school-based seminars and talks in community centers aimed at encouraging the youth of Mauritius and the local communities to recognise the importance of freshwater resources and the need to use them responsibly.
Watch the videos produced about the demo project:
With its strong focus on improving understanding of the nature and potential of the Northern Aquifer, the IWRM demonstration project is contributing to efforts to manage water in a more integrated way, with the ultimate goal of securing water resources and the future health and well-being of the people of Mauritius.
“Based on the experience of this IWRM demonstration project, the government of Mauritius is currently looking at replicating the project to the 4 other aquifers of Mauritius with the ultimate goal of securing water resources and the future health and well-being of the people”, said Simon Springett, the UN Resident Coordinator in Mauritius.
As such the project addresses the paragraph 64 of the SAMOA Pathway on water and sanitation and directly feeds into the 2030 Agenda for Sustainable Development and its 17 Global Goals. In particular, it will help ensuring availability and sustainable management of water and sanitation for all (Goal 6). It also responds to the need to take urgent action to combat climate change and its impact particularly in Small Island Developing States (Goal 13). Finally the project should build on existing initiatives to develop measurements of progress on sustainable development that complement gross domestic product, and support statistical capacity-building in developing countries (Goal 17).