Key Points:

Experts are working on a proposal for a spruce up of a popular Bay of Plenty estuary and the Kaituna River which has the highest commercially white water-rafted waterfall in the world, attracting thousands of international tourists a year.

Local councils will today wade through public feedback on a proposal to clean up the Maketu Estuary - a 2.3km2 shallow tidal inlet which currently receives 4 per cent of the Kaituna River flow each tidal cycle through the man-made Fords Cut. The 50km river starts at Okere Falls at Lake Rotoiti and flows to sea at Te Tumu in the Western Bay of Plenty.

The Kaituna Maketu Joint Council Committee has suggested diverting more of the river into the estuary to increase waterflow, improve water quality and protect declining aquatic and bird life in both waterways.

When the river reaches the sea about half of its water has come from lakes Rotorua and Rotoiti. The rest comes from run-off and tributaries in the lower river which water experts say is the source of most pollutants.

Environment Bay of Plenty manager for rivers and drainage Ken Tarboton said about 2.7 million cubic metres (96 per cent) of Kaituna River water goes out to sea per tidal cycle with the remaining 100,000 cubic metres going into the estuary. The committee is hoping to increase the flow to the estuary to about 448,000 cubic metres (16 per cent).

The level of nitrogen into the Kaituna River at Te Tumu has increased by about 70 per cent since 1975. The Affco freezing plant at Rangiuru and a wastewater treatment plant at Te Puke send discharge into the water and run-off from farms and seepage from septic tanks have contributed to nutrients and bacteria in the river.

Wetlands in the area, home to threatened species such as the matata/fernbird and the natuku/bittern, have declined. In 1840 there was 6100ha of freshwater wetland compared with 92ha in 2001.

Officials are also worried about development around the river and reduced buffers between the land and the water. They say stock grazing can affect salt marsh and nesting grounds for birds and fish spawning, and silt washing into the river changes the way the water traps pollutants.

The erosion of sand dunes around the estuary is also a concern.

One of the options to divert the river includes installing one-way floodgated culverts at the Te Tumu end of the Papahikakawai Channel to divert some river water and tidal flow back into the estuary.

The estimated cost is close to $1 million.

The idea of the committee - a combination of focus groups, community organisations and local council and iwi representatives - is to improve sustainable management of the river and estuary by 2018.

The committee has also suggested developing a regional park in the lower Kaituna area and creating at least 100ha more wetlands by 2018.

Information days for the public about the Kaituna Maketu Estuary strategy and proposed diversion scheme have been held over the last couple of weeks. Feedback for the strategy closes at 5pm today and those who submitted will have a chance to present their argument orally on April 1 or 2.

* A 2.3km shallow tidal inlet in the Western Bay of Plenty.
* Popular eeling and whitebaiting spot. Fishing for kahawai and snapper is also common in the area.
* Currently receives 4 per cent (100,000 cubic metres) of the Kaituna River flow per tidal cycle via the man-made Fords Cut.
* Has had a decline in plant and aquatic species.
* Is heavily polluted by a freezing works, wastewater plant and farm run-off going into the Kaituna River.
* Development around the river, reduced buffers between the land and the water, stock grazing and silt have also contributed to pollution, reduced wetlands and fish spawning.
* A working group is proposing more water be diverted from the river to improve water quality.