Onema

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  • VIEWPOINT OF PARTNER

    -Martin Guespereau \ RMC water agency
    "Karst aquifers contain large quantities of water that are not extensively used in the Rhone-Mediterranean basin..."

Better knowledge for better management

Effective implementation of the reference network for low-water monitoring confirmed that the situation has worsened over the past 40 years, particularly in Southern France. Onema also financed the drafting of two guides on assessing and protecting groundwater in karst aquifers.

A monitoring network for low-water situations

The national reference network for low-water monitoring is now up and running, with 250 stations, including 14 in the overseas territories. The goal is to measure significant variations in low-water flow rates, i.e. small flow rates, and to identify climate-change impacts on the hydrological regimes of rivers. The network is not definitive and new stations may become eligible over time, given however that at least 40 years of data (duration of low-water periods, severity, seasonality) represent one of the selection criteria. The stations are grouped in geographic zones to facilitate detection of regional trends and, if they exist, determine their significance. This approach is particularly innovative. Trends in low-water and snow regimes over the past 40 years have been confirmed and regional aspects revealed. Over the period, low-water situations worsened, particularly in Southern France. Onema contributes to funding the programme run by Cemagref and provides management on the national level.

A new national database on draw-offs

The project for a national draw-off database was launched in 2010. The purpose is twofold, first to validate and store data on water draw-offs and uses, second to provide a framework for efforts to rationalise water draw-offs. Onema ensures the operational management of the project under the auspices of the Ecology ministry and the Adour-Garonne water agency.

Evaluate and protect karst groundwater

How can groundwater reserves and their future flow rates be evaluated in karst formations? How can the resource be protected? Because traditional methods for the study of groundwater cannot be used in these very particular environments, Onema funded two step-by-step guides, drafted by BRGM, corresponding to the needs of the Water agencies. They are intended for hydrogeologists at the Water agencies, local governments and design offices. The first presents the tools used to characterise how karst formations operate in order to assess water resources and predict future flow rates, the second provides the means required to evaluate the vulnerability of karst systems and to improve the design of protection perimeters for water abstractions.