how do i replace water pump drive belt on nissan micra?

You really need access to underneath the car - either a pit or lift - very difficult if not impossible to do from above, especially if it has power steering as the pump takes up space which might have given access.
Remove undershield - the plastic guard under the engine bay.
Slacken power steering pump mounting bracket pivot bolt. Slacken adjustment screw - hard to get at - and remove belt from pulleys. Fit new belt and tension by measuring deflection of belt.

JD
October 2010

get a copy of the haynes manual, full details in there.

hope it helps
October 2010