Cawthron Institute
As part of a larger project studying the Motueka river catchment, the Cawthron Institute has looked at the effects of water quality and supply on river health and its ability to provide adequate habitat for aquatic fauna.
Faecal contamination of streams made many parts of the catchment unsuitable for swimming. Significant contamination was tracked down to dairy cattle crossing rivers four times daily to and from milkings, which quadrupled the levels of faecal contamination. Farmers agreed to install bridges and other crossings, and faecal bacteria levels have fallen considerably. As well as the benefit to the environment, crossings mean easier stock management and less lameness.
Using brown trout as the indicator species, Cawthron also modelled the river and predicted the effects on flow, depth and width of removing quantities of water for irrigation. This information was used by the Tasman District Council, Fish & Game NZ and farmer representatives to agree on an acceptable level of water extraction that would meet irrigators needs and still allow trout to thrive and anglers to have something to catch.
The Cawthron Institute is a private, independent, not-for-profit research centre that has been operating in Nelson for 85 years. Activities include basic research, specialist scientific advice for commercial clients, and high-volume routine laboratory testing. Specialist fields include the aquaculture of shellfish and seaweeds, biosecurity issues, marine and freshwater science, and analytical chemistry and microbiology.
The work described here is part of a larger programme called Integrated Catchment Management, which looks at the whole Motueka catchment and examines issues like water allocation and water quality. It involves scientists from the Cawthron Institute, Landcare Research, NIWA, Forest Research, Otago University. Studies include effects of soil erosion, forestry, water allocation and river health, water quality and its effects downstream and out to sea on the shellfish industry; social scientists work with the community on decision-making within the council and how science can be used in decisions; working with iwi; economists trying to work out how decisions on future resource use may affect the viability of industries, and so on.
Farming vs fishing
The Motueka catchment has a long history of irrigation. In the early 90s the Fish & Game Council applied for water conservation order on the Motueka river, aiming to protect its salmon characteristics. That caused great consternation in the agricultural and horticultural industries in the area. One side wanted water left in the river and the other side wanted to take water out.
Negotiations took place and Cawthron was asked to provide some scientific input to give guidance on what sorts of impacts on the health of the river system could be expected if varying amounts of water were removed. They used a special modelling technique that works out how depths and velocities in the river will change with changing flow rates, and that can then be related to the preferences of particular species brown trout or eels or aquatic invertebrates living in the river.
Brown trout have the highest flow demand, they like the fast flowing water, so the reasoning is if you can provide a suitable habitat for adult brown trout then there will be sufficient habitat for other species.
The irrigators looked at the amount of land that could be irrigated in the catchment, application rates and potential requirements in terms of cu-mecs of water. Cawthron looked at what would be the impact of removing that amount water taking into account the mean annual low (summer) flow in the river. The irrigators wanted about 12% of the natural low flow, and Cawthron worked out the reduction in velocity, depth and width of the river and therefore the fish habitat that was likely to take place, and the impact on fish numbers.
With that information both sides were able to negotiate an acceptable compromise. It involved the local fish and game manager, management of the irrigation company and the local council. Eventually the conservation order went to the Environment Court and because of the successful negotiations the order was agreed to by all parties prior to going to court, so the hearing was over quickly.
Cawthron have also using radio tagged brown trout to try to understand fish movement around the whole catchment. They worked out low-cost ways of estimating changes in smaller streams, and found out what happens if you take water out of the tributaries how this affects the rearing of young fish and how important that is for the main fishery down in the river.
Cattle crossings
The second project began with a survey of water quality around the Motueka river catchment. In one particular area Cawtron identified a problem of high faecal contamination of water. They met with their community reference group (members of the community that live throughout the catchment that they consult quite frequently), and subsequently presented the results to some farmers in the catchment.
One farm in particular was monitored, and they videoed cows going to and from the milking shed through the river, monitoring water quality upstream and downstream from the crossing Results showed that cattle were about 20 times more likely to defecate or urinate in the water as they walked through water rather than in the paddock, and as a result of this traffic through the river four times a day the background load of indicator bacteria quadrupled.
A meeting with local farmers produced agreement that the problem needed to be addressed. They built a series of bridges and also found that there were benefits for them and the stock as well for the environment ease of moving stock independent of river flows (if the river flooded access could be cut off to the rest of the farm), and no problem of stock damaging their feet as they walked through the river gravel.
Other farmers have learnt from this and either built bridges or re-routed races so that stock would cross existing bridges. These results found their way eventually into the Fonterra accord.
Follow-up work at four sites on the river has shown a definite improvement in water quality even though not all of the stock crossings have been fixed up yet. The original levels were well above the guidelines for recreational swimming and certainly well above any drinking water guidelines. They have now come down and generally meet the swimming guidelines.
Faecal contamination of streams made many parts of the catchment unsuitable for swimming. Significant contamination was tracked down to dairy cattle crossing rivers four times daily to and from milkings, which quadrupled the levels of faecal contamination. Farmers agreed to install bridges and other crossings, and faecal bacteria levels have fallen considerably. As well as the benefit to the environment, crossings mean easier stock management and less lameness.
Using brown trout as the indicator species, Cawthron also modelled the river and predicted the effects on flow, depth and width of removing quantities of water for irrigation. This information was used by the Tasman District Council, Fish & Game NZ and farmer representatives to agree on an acceptable level of water extraction that would meet irrigators needs and still allow trout to thrive and anglers to have something to catch.
The Cawthron Institute is a private, independent, not-for-profit research centre that has been operating in Nelson for 85 years. Activities include basic research, specialist scientific advice for commercial clients, and high-volume routine laboratory testing. Specialist fields include the aquaculture of shellfish and seaweeds, biosecurity issues, marine and freshwater science, and analytical chemistry and microbiology.
The work described here is part of a larger programme called Integrated Catchment Management, which looks at the whole Motueka catchment and examines issues like water allocation and water quality. It involves scientists from the Cawthron Institute, Landcare Research, NIWA, Forest Research, Otago University. Studies include effects of soil erosion, forestry, water allocation and river health, water quality and its effects downstream and out to sea on the shellfish industry; social scientists work with the community on decision-making within the council and how science can be used in decisions; working with iwi; economists trying to work out how decisions on future resource use may affect the viability of industries, and so on.
Farming vs fishing
The Motueka catchment has a long history of irrigation. In the early 90s the Fish & Game Council applied for water conservation order on the Motueka river, aiming to protect its salmon characteristics. That caused great consternation in the agricultural and horticultural industries in the area. One side wanted water left in the river and the other side wanted to take water out.
Negotiations took place and Cawthron was asked to provide some scientific input to give guidance on what sorts of impacts on the health of the river system could be expected if varying amounts of water were removed. They used a special modelling technique that works out how depths and velocities in the river will change with changing flow rates, and that can then be related to the preferences of particular species brown trout or eels or aquatic invertebrates living in the river.
Brown trout have the highest flow demand, they like the fast flowing water, so the reasoning is if you can provide a suitable habitat for adult brown trout then there will be sufficient habitat for other species.
The irrigators looked at the amount of land that could be irrigated in the catchment, application rates and potential requirements in terms of cu-mecs of water. Cawthron looked at what would be the impact of removing that amount water taking into account the mean annual low (summer) flow in the river. The irrigators wanted about 12% of the natural low flow, and Cawthron worked out the reduction in velocity, depth and width of the river and therefore the fish habitat that was likely to take place, and the impact on fish numbers.
With that information both sides were able to negotiate an acceptable compromise. It involved the local fish and game manager, management of the irrigation company and the local council. Eventually the conservation order went to the Environment Court and because of the successful negotiations the order was agreed to by all parties prior to going to court, so the hearing was over quickly.
Cawthron have also using radio tagged brown trout to try to understand fish movement around the whole catchment. They worked out low-cost ways of estimating changes in smaller streams, and found out what happens if you take water out of the tributaries how this affects the rearing of young fish and how important that is for the main fishery down in the river.
Cattle crossings
The second project began with a survey of water quality around the Motueka river catchment. In one particular area Cawtron identified a problem of high faecal contamination of water. They met with their community reference group (members of the community that live throughout the catchment that they consult quite frequently), and subsequently presented the results to some farmers in the catchment.
One farm in particular was monitored, and they videoed cows going to and from the milking shed through the river, monitoring water quality upstream and downstream from the crossing Results showed that cattle were about 20 times more likely to defecate or urinate in the water as they walked through water rather than in the paddock, and as a result of this traffic through the river four times a day the background load of indicator bacteria quadrupled.
A meeting with local farmers produced agreement that the problem needed to be addressed. They built a series of bridges and also found that there were benefits for them and the stock as well for the environment ease of moving stock independent of river flows (if the river flooded access could be cut off to the rest of the farm), and no problem of stock damaging their feet as they walked through the river gravel.
Other farmers have learnt from this and either built bridges or re-routed races so that stock would cross existing bridges. These results found their way eventually into the Fonterra accord.
Follow-up work at four sites on the river has shown a definite improvement in water quality even though not all of the stock crossings have been fixed up yet. The original levels were well above the guidelines for recreational swimming and certainly well above any drinking water guidelines. They have now come down and generally meet the swimming guidelines.