Water volume calculated improperly in totals on right side of screen

I have noticed in many of my colonies that the volume of water calculated on the right side of the screen is too large. For example, in my current game I have about 100 thousand kg of fresh water available to me (determined by manually counting the squares), but the total says I have nearly 1 million kg.

The total was correct earlier in this game but it got fouled up when I gained access to larger amounts of fresh water. 

I just created a new game for the express purpose of testing this out, and opened up access to a large body of water containing about 47 thousand kg of fresh water (determined by manually counting it), but the total on the right side of the screen says I have access to about 94 thousand kg of fresh water (double what I actually have).