In this Ideas hour we look at the pressure on our rivers. The big issue is water quality – the impact of urban wastewater and agricultural runoff on waterways – but there are quantity issues too. How much can be taken from a water course without compromising its ecological viability?

We talk to Sue Millar about the Silverstream river restoration project; Hera Smith, director on the board of Te Wai Maori Trust; Dr Clive Howard-Williams, Chief Scientist Freshwater and Estuaries, at Niwa; and Professor Gary Jones, former chairman of the International River Foundation.