Municipalities owe South Africa's water boards almost R2.3 billion, Water Affairs Minister Edna Molewa said on Thursday.

In a written reply to a parliamentary question, she said the "in arrears" portion of this debt, on April 31 this year, was R1.4 billion.

This figure is R300 million more than the arrears total Molewa gave three months ago. At a parliamentary media briefing on May 16 this year, she told reporters that the arrears debt -- that older than 60 days -- was "about R1.1bn".

In her written reply, tabled on Thursday, she said the total amount owed by municipalities to the country's 12 water boards -- including "current" debt of R860 million -- was R2,261,372,566.

Molewa said her department was finalising an institutional reform and realignment project, aimed at "improving financial viability for all institutions by merging marginal viable institutions with those with [a] stronger economic base".

Once this was completed, economies of scale would make institutions stronger and better able "to deliver on their mandate and also to support local government".