What happens to the conductivity of water when a base is dissolved in it

conductivity of water is increased

Explanation:

First to all, the conductivity of water is strongly relationed with the pH of it. In a solution, a current is carried by Ions, these ions can be positively charged (Cations) or negativily charged (Anions). The conductivity of a solution will depend on the concentration of all ions present on it. In the case of water, if we add a base, this will increase the pH of the water from 7 to a higher value. The greater their concentrations, the greater the conductivity will be.

Now, as it was stated before, these ions all have the electrical unit charges shown by their symbols, but they move at different velocities [mobilities] through the solution, so they contribute differently to the conductivity. The most mobile Anion is the [OH-] which is belonging to a base.

So in conclusion, the sums of all ions in concentrations will increase the conductivity of the solution (in this case water).