Murang'a Governor Mwangi wa Iria wants the spillover water from Ndakaini Dam channelled into locals' homes.
He said it is a shame that so much water is going to waste when so many homes, even those surrounding the dam, go without water.
The dam that has the capacity to hold 70 million cubic metres of water, filled up on Monday. It is now spilling 15,000 cubic metres of water per second.
The spillover is being channelled into Chania and Thika rivers and it is feared that it might cause floods downstream in areas bordering the two rivers, especially the low-lying Ithanga.
The county disaster management team has been sensitising residents on the looming danger and preparing them for any eventualities.
But Wa Iria said the water could have been harnessed and channelled into homes for use during the forthcoming dry season.
The governor said the fact that the dam has filled up during the short rains indicates that the situation may be worse during the long rains in April.
"We should now be preparing to conserve excess water to help homes that do not have the commodity instead of letting it go to waste," he said.
He urged the Water ministry to put measures in place that will benefit residents in the face of excess rains being experienced through the dam.
The dam located in Gatanga supplies over 82 per cent of the water consumed in Nairobi county yet the majority of the people living in the neighbourhood do not have tap water.
Sources in the management of the dam said it has the capacity to supply water for three consecutive months without any intake.
"The Murang'a community has not benefited from the dam, but it can at least benefit from the spillover water," he said.
The governor also wondered why some areas of Nairobi still have dry taps even after the dam filled up.
He said Nairobi Water and Sanitation Company rations water due to insufficiency and wondered why the situation had not been remedied by the rains.
"We have been made to understand that the reason we cannot share the dam water with Nairobi is because it is not enough, but now the dam is releasing water and it is still not enough. Something is clearly going on, and we need to sit down and have an open talk," he said.
Only 45 per cent of homes in the county have access to clean water.
He said Water PS Joseph Wairagu, who is from the county, should help residents get access to the dam water.
