The Chalvet watershed observatory- a reliable monitoring to enhance understanding the hydrogeological functioning and pesticides transfers of pyroclastics aquifer. Martinique - FWI
Résumé
The Chalvet watershed observatory: a reliable monitoring to enhance understanding the hydrogeological functioning and pesticides transfers of pyroclastics aquifer. Martinique – FWI A.L. TAILAME
Martinique island drinking water supply, a tropical volcanic island located in the Lesser Antilles archipelago, is achieved predominantly by means of dams located on rivers (94% of drinking water). Considering the intensification of dry seasons during last years and the difficulties to maintain a minimal dry-weather flow in rivers, the water resource’s diversification become a key objective for the island environmental policy. Then groundwater is targeted as a suitable alternative resource.
However, the intensive agricultural practices on some parts of this small territory of 1024 km2 involve an improvement of pesticides transfers’ knowledge in order to better define the vulnerability of groundwater and for their adapted management and protection. In partnership with the water agency of Martinique (ODE), a hydrogeological observatory has been set up on the east flank of the Mount Pelée. Intensive agriculture predominates in this area, and groundwater’s, located within pyroclastics aquifers, suffers high pesticides pollution.
This observatory is composed by two mean boreholes. The water level monitoring started 10 years ago. A monthly monitoring of pesticides and majors and traces elements started in 2008 in the downstream borehole and in 2011 in the borehole located halfway up the mount flank. In March 2013, a helicopter-borne TDEM survey was conducted with SkyTEM 304 system to enhance the characterization of geological and hydrogeological structures of the volcanic edifice.
Geophysical data also allow building a conceptual geological and hydrogeological model and joint analysis of hydrogeological data, introduced in this poster, allows highlighting relationships between rainfall, groundwater levels variations and pesticides and major elements concentrations. Finally, our data help to improve understanding the hydrogeological functioning of this aquifer and pesticides transfers on volcanic islands, and confirm the effectiveness of this groundwater watershed observatory.