The pollution of the Rhine with salt
When the ICPR started working in 1950, the salt pollution of the Rhine had been a concern for downstream users for several decades. At the time, the potassium mines MDPA in Alsace north of Mulhouse alone annually discharged approximately 13 million tons of potassium into the Rhine. At the German-Dutch border this then led to a concentration of chlorides of more than 400 mg/l and posed a considerable problem for drinking water production and irrigation in agriculture.
The Salt Convention
In the 1960s the ICPR studied the different possibilities of disposing of the salt arising from potassium extraction. Apart from heaping and injecting even pipelines and transport by ship or train to the North Sea were considered.
In 1976, the so-called Salt Convention (only in German and French) (1983) was signed. This "Convention on the Protection of the Rhine against Pollution with Chlorides" aimed at reducing the salt load in three steps. Mainly, the sodium chloride was supposed to be injected into deeper subsoil layers. At the time, that was the most promising solution. Only the first phase, the reduction of the MDPA discharges by 20 kg/s into the Rhine during ten years took effect on 5 January 1987 and has been implemented.
In the second phase, a reduction of the salt discharges by 60 kg/s was planned. The implementation of this second phase was rejected by the 9th Conference of Rhine Ministers on 10 October 1988 as too inefficient and too costly. This slackened the further implementation of the Chloride Convention.
25 September 1991 the Additional Protocol to the Chlorides Convention (only in German andFrench) was signed, fixing the chlorides concentration at the German-Dutch border to 200 mg/l at maximum.
On the one hand, the additional protocol provided for a further reduction of the MDPA discharges in France during low discharge (beyond the 20 kg/s of the 1st phase) and, on the other hand, the surplus water from the polder Wieringermeer was to be bypassed into the Wadden Sea. The ICPR contracting parties Switzerland, Germany, France, Luxemburg and the Netherlands jointly financed both measures. The settlement of accounts was fixed to 31 December 1998. Round about the same time, the MDPA in Alsace completely stopped extracting potash.