My MRI was at Mayo and I asked about extra water and was told not with that particular contrast agent.

From your suggested search.

""It is important that you drink plenty of fluids after your examination to flush the gadolinium out in the urine. Although there is not a set recommended amount, ...''

""Yes, you should drink plenty of water after an MRI with contrast to help your kidneys flush the chemical from your body. While the contrast is naturally filtered out, drinking extra fluids accelerates the process and is one of the most helpful steps to protect your kidneys. Aim for at least an extra liter (about two pints or three cups) over the next 24 hours, unless your doctor has advised you to limit fluids for other medical reasons. ""

I consumed quite a bit more than that over the next 24 hours.