Anglers worried about algal issues in their favourite Hawke's Bay rivers and streams could find an answer to their dreams kilometres away in the Ruataniwha water storage scheme.
Hawke's Bay Regional Council group manager resource management Iain Maxwell says that while other steps are in place to control the problem, an answer may come from the "flushing flows" from the dam project.
"This would in effect create artificial freshes or floods that mother nature may not have provided," he said, after concerns were raised by angler Dick Bradshaw, whose home overlooks the Tukituki River, near Havelock North.
The river provides some of the best fishing spots imaginable, says Mr Bradshaw, who with wife Val splits his time between the hillside home and the lifestyle of his native Canada, where he grew up with the lakes and streams of Quebec.
Although aware of algal issues in the river from time to time, he was stunned by the sight which greeted him a fortnight ago near the Patangata Bridge, where the filamentous (stringy) algae had clogged the river, and could be dragged clear in clumps resembling sodden wool.
Mr Maxwell says it is proposed that one of the functions of the water storage scheme will be to release water four times every summer to scour the algae off the rocks. "This benefit is only possible with storage at the scale that the RWSS would bring.
"It appears that many of the region's rivers (Tukituki and Ngaruroro) have had high levels of filamentous (stringy) algae in them.
"The Ngaruroro where it leaves the Forest Park has high levels and parts of the Tukituki. It appears from an initial look at the data that the levels of the potentially toxin-producing phormidium are lower than last year."
Mr Maxwell says the growth of algae is controlled by numerous factors, including water temperature, nutrient, sunlight and flow.
"The two factors that we can often most readily manage are flow and nutrient," he says.
"In the Tukituki, the phosphorus is the key nutrient that grows algae.
"The new planning framework for this catchment is intended to reduce the load of phosphorus entering the river, so reducing the growth rate of algae.
"This summer, despite being wet early on, has progressively dried up and so allowed the algae in the river to continue to grow unchecked.
"Normally, we would have had some small freshes or floods to flush the river clean by now."
Mr Bradshaw said what he saw recently was the worst he had seen in the river, and it was time to raise his concerns.