Those living around rivers Naivasha and Nyandarua will face water rationing starting immediately.
The Water Resources Authority (WRA) said this had been occasioned by drought that has seen water levels in the two rivers, which drain into Lake Naivasha and Lake Elementaita, fall sharply.
"The rationing will continue until all the rivers start flowing again," said WRA Naivasha sub-county manager Geoffrey Mworia.
This has raised fears of an increase in disputes over water points. Other rivers that have been affected by the drought are Kinja, Upper Malewa and Wanjohi, which all flow into Lake Naivasha.
River Gilgil, whose water ends up in Lake Elementaita is also affected. "We are engaging residents to ensure that the rationing does not catch them unawares. We will not allow anyone to divert water from these rivers. Any blockage will be removed," said Mr Mworia.
"A rationing timetable will be worked out with the affected communities so that all those who rely on the (river) water do not suffer. We have a situation where those in the upper areas have water while those downstream are facing an acute shortage."