The starting point in these cases is to say that if there is an easement to use water 'in common' then a 'downstream' water user is only entitled to the residue of the water after all 'upstream' users have taken the water that they need. Thus, the downstream user cannot insist that the upstream users moderate their use of water, so as to leave some water for him!

But, it all depends on the wording used. In a recent case, the downstream user had the right to use piped water 'in common' with the upstream user, but he was entitled to withdraw 'an amount of water as may be reasonably required for domestic and farm purposes'. Legally, those words made all the difference, with the CA deciding that they meant the upstream owner could only take water once the downstream owner had taken as much 'water as may be reasonably required for domestic and farm purposes'. Thus, if there was insufficient water, it followed that the downstream user would have priority over the upstream user (even though the natural spring and reservoir were on the upstream land!). Needless to say, this decision is likely to create enormous practical difficulties for the owner of the upstream land.

At the end of the day, this litigation was probably the result of sloppy wording by the person who drafted the original grant. That conveyancer should have thought through the implications of the wording he was using; with the benefit of hindsight, we can see that the correct approach would have been to spell out the priorities of the respective users of the water (and perhaps to have specified a maximum usage volume for the downstream owner). Certainly, the case should serve as a reminder to all conveyancers that it is not sufficient in these cases to assume that there will always be a sufficient supply of water to meet the needs of everybody – water is a finite source, and the well-drafted grant will anticipate the problems that might arise if there is an under-supply. Mitchell v Potter [2005] EWCA Civ 88. Source: www.practicallaw.com8-200-3446.