Agreements to manage individual agricultural groundwater withdrawals. What lessons can be learned from three case studies of diffuse pollution management?

Arrangements between polluters and third parties are sometimes mobilised as tools to fight against soil and groundwater pollution. This article aims at: i) presenting three of these arrangements (New York City in the United States, Munich in Germany, and Vittel in France), ii) discussing their advantages and drawbacks and iii) studying their ability to be used for unregulated diffuse groundwater withdrawals. Indeed, many farmers withdraw water individually. When no management tools are in place, this practice can lead to groundwater overexploitation. Arrangements present various advantages to manage water, in particular: to be more easily acceptable than regulatory tools, to accelerate change in behaviour toward sustainable practices on water withdrawals and to be adapted to local constraints. Arrangements can successfully manage groundwater, especially if farmers are financially incited to adhere, if society accepts to pay the cost of these arrangements, and if they are only temporary measures, which help farmers to change their behaviour. The absence (or the limited number) of arrangements organized up to now on groundwater does not allow us to draw any conclusion as to their relevance. This absence can be explained by: the difficulty of identifying liabilities and defining what we understand by overexploitation, the absence of water rights and the limited economic interests of an overexploited for which the consequences will appear only after a very long period of time.