North rivers dirtiest in NZ

Northland's freshwater swimming spots are the dirtiest in New Zealand, an environmental report shows.
The Ministry of Environment's report showing compliance of monitored freshwater swimming spots for the  past two summers shows Northland had the worst overall results in the country - with eight out 20 spots consistently too polluted to swim in.
Environmental groups  point the finger at dairy farmers but those who test the water say cows aren't the only creatures to blame.
Forest and Bird Society spokesman Kevin Hackwell  wasn't surprised swimming spots were polluted, because the region's dairy farms had one of the highest national rates  of not complying with effluent discharge rules.
However, Northland Regional Council environmental monitoring officer Emma Simpson said blaming  farmers failed to explain two of the worst results: Langs Stream and Whangarei Falls. Ecoli bacteria was not only produced by cows but also by septic tanks, pigs, possums, and birds, she said.
Northland's climate and geography "results in heavier downfalls and more contamination running into rivers and lakes".
The region's large size,   combined with a comparatively small  regional council,  meant the ministry's report was "comparing apples with oranges".
While the  regional council had the ability to  identify ecoli, water samples needed to be sent to Christchurch to  find the  source of pollution. The cost was high and budget limited, Ms Simpson said.
Northland Fish and Game Council manager Rudi Hoetjes said the problems started in Northland with  hills  being cleared for farming. Trees on the hills  traditionally absorbed water but now it ran straight down a lot faster, collecting fertiliser on the way.
"Wetlands and swamps around the hills acted like a big sponge or filter - but because these areas have been converted to farmland, towns and roads, the rainwater and fertiliser runs straight into rivers and lakes."
 Aquatic weeds  then flourished, slowing water flow and elevating temperatures, he said. Urea from cow  effluent also landed there.
Mr Hoetjes said the   council was "not moving at a great speed of knots" in terms of compliance.
NRC farm dairy and effluent monitoring officer Dennis Wright said the maximum  fine for a farmer  who  illegally discharged  farm and dairy effluent was  $750.
"Once we've tried every other avenue we could take a prosecution to the Environment Court which could hand down a maximum fine of $200,000."
NRC's compliance rates were "not where they should be", Mr Wright admitted. "But we're making really good progress."
Our of 100 points
THE GOOD:
Hikurangi Lake: 100
Waipapa River, Puketi Forest:  92.0
Waipoua River, Hokianga: 88.1
Waipapa Basin, Kerikeri: 87.8
Omamari Beach Stream, Kaipara: 84.6
THE BAD:
Otamure Bay Stream, Whananaki:  24.7
Langs Stream Middle Beach, Langs Beach: 35.9
Whangarei Falls: 53.2
Otaua Stream, Hokianga: 66.7
Kerikeri Stone Store: 71.8