Catchment advisor a step-change for the Karamū

It is a quintessential sunny winter’s morning as Andy McCall stands at the edge of the Karamū Stream flowing below Havelock North’s James Wattie Retirement Village.  

The stream’s water is dirty brown, slow moving and bathed in sunlight.  To its side the small Here Here Stream trickles down below the backyards of a row of houses.

“There’s a lot we could do to improve the water quality here,” says Andy, who is Hawke’s Bay Regional Council’s inaugural Urban Catchment Advisor for the Karamū.  

“If we could stop the erosion, plant up the sides of the stream and shade the water, we would lower the sediment and oxygen levels and stifle the aquatic weed growth. That in turn would increase the volume of water flow and help with flood mitigation. The riparian planting would improve the biodiversity of the area creating more macroinvertebrates, fish, and birdlife.”  

Sounds simple? But this is just one small part of the 238 kilometres of waterway, plus 514 square kilometres of land, that form the Karamū Catchment, and since his appointment in April, McCall has been doing a stocktake of everything happening within it.

In a bid to improve urban water quality, Hawkes’ Bay Regional Council (HBRC) created two new catchment positions earlier this year: one for Ahuriri and one for the Karamū.

Chris Dolley HBRC Group Asset Manager says the Ahuriri role is still in process with no one  yet appointed, while the focus of the Karamū role is to get a “a big picture view of the Karamū urban catchment. 

“Traditionally we have focused more on the rural catchment, but this is a step change for the Karamū,” he says. “We want to map all the things that are contributing to water quality issues in the catchment’s urban areas.

“That means getting very clear visibility on who is doing what on the stream and environs and eliminating as many contaminants as possible. We’ll be looking for illegal connections, stormwater run-off in dry conditions and cross-connections. (Out of interest there are currently 2149 consents within the Karamū Catchment, with 1057 discharging to water directly with the average age of these consents 6.7 years. Under HBRC’s TANK Plan existing consents will be subject to review, which may lead to tighter conditions being applied to current discharges.)  

But in the immediate future Dolley says an operational Urban Catchment Plan for the Karamū will be produced and will guide HBRC decision-making on how to invest to improve the main stream and intersecting drains’ water quality versus  “the things we can influence and the places where we can give guidance and support”. 

For Andy McCall, who has a Masters in Environmental Management from Massey University and was working for Northland Regional Council as a land management advisor  before he started in April, the Karamū Catchment is challenging – to say the least.

“It is one of the more polluted waterways I have looked at,” he admits. “It has a lot of contamination from excessive nutrients such as nitrogen, phosphorus and from sediment. It’s a highly modified and engineered water course and doesn’t have a natural flow path. 

“It also has a low fall in general,” he says. “There is roughly 10 metres or less fall across most of our network, so there is really very little gradient to the catchment and that makes it very challenging for flood mitigation and is why the stop banks and pump stations are needed – because things just don’t flow well.”

For McCall, working to improve the Karamū Catchment’s water quality will be a balancing act between what is needed to get water out during flood events and “what we can do to make the waterways – instead of just being open drains – nice recreational areas with high biodiversity and amenity values.”

He has already identified that shading is likely to be the most effective single tool for improving water quality in the immediate future with a longer-term focus on nutrient management in the upper and lower catchment, and stormwater management in the Hastings area. 

“Riparian planting has the potential to improve the biodiversity of the waterways while also reducing the need for spraying or weed boating to control aquatic weeds,” he says.

“But we will need to balance planting with understanding the hydrology of the area and looking at what effect the planting is going to have on the waterway.”

He would like to see future planting co-ordinated by HBRC with a focus on plants with good root structures such as dwarf harakeke and carrex that will hold steady in higher flows and not lean into the water and create turbulent flow or change the current.

The end goal is to improve the water quality of the Karamū and all the small streams and drains that intersect with it.  

“But there’s not a fixed time frame,” McCall cautions. “I am not  going to claim the stream will be swimmable in five years. 

“These problems were decades in the making and they’ll probably be decades in the fixing.”

More in-depth BayBuzz reporting on saving the Karamū here.