The water’s conductivity is determined by the quality and amount of ions dissolved in the water. It can be used to estimate the leaching of the gypsum from the fields, as the calcium and sulphate in the gypsum dramatically increase the conductivity of the runoff. Conductivity increases after gypsum application, and then begins to gradually decrease. Once the conductivity of the water has permanently dropped to the original level, the gypsum can be said to have been washed away. However, the quality of the water in the Savijoki river varies greatly with the amount of rain, and short-term changes to the water quality do not reliably indicate the extent or duration of the effects of the gypsum.