Freshwater Update 63, November 2014

River water temperatures and Visual clarity of rivers (JAS).

New Zealand’s freshwater resources are under increasing pressure. NIWA has investigated how differences in implementation of minimum flow and allocation rate limits can lead to vastly different outcomes for both water users and the downstream flow regime.

As limits on nutrient loads from farms tighten, Enhanced Pond Systems hold great potential for storing and treating effluent and recovering resources.

The increasing demands on New Zealand’s freshwater resources, and the complexities of planning, regulating and evaluating the impacts of water use, underpin a new GIS modelling tool.

Intensification of agriculture within a catchment is often associated with increases in the trophic state (biological productivity) of waterways, known as eutrophication. NIWA reports on the relative roles of landscape and local factors on the trophic state of 21 Canterbury streams.

Better management of farm dairy effluent is a high priority for New Zealanders. NIWA is working to improve understanding of effluent volume and quality, to aid industry planning and practices.

Information on the effects of human-induced disturbances on sediment yields and sediment sources from catchments is limited. Such information could be used to guide decisions on the application of catchment rehabilitation measures.

In New Zealand, planning for freshwater quality and quantity management is being delegated increasingly to collaborative stakeholder groups (CSGs), as encouraged by the Government’s recent freshwater reforms.

Constructed wetlands treating agricultural drainage waters are expected to show some removal of the faecal indicator bacterium, Escherichia coli (E. coli).

NIWA is leading a collaborative project to improve water quality in Lake Wairarapa by restoring the pollutant attenuation function of lakeshore wetlands.

Compound-specific stable isotopes and radioisotopes hold the key to identifying and apportioning major sources of eroded soils, and their persistence, in the Bay of Islands.

Wetlands are important habitats for wildlife and provide critical ecosystem services, such as buffering of floods and removal of sediments, nutrients and other pollutants

Wood is a key component in most pristine New Zealand streams.

Monitoring water quality and aquatic biota can actively engage communities with their local streams, but is that where the benefits end?

Mean annual budget-based watershed models offer benefits of robustness and simplicity, but they do not provide information on seasonal or storm event loadings that are of more ecological relevance.

Models can be used to represent changes or potential variations in regional climate in response to broader scale (national or global) climate change scenarios. Based on these models the local environmental impacts of climate change can then be assessed.

The Catchment Land Use for Environmental Sustainability model system (CLUES) was used to simulate E. coli loads in the upper Waikato River catchment.

NIWA recently used the Catchment Land Use for Environmental Sustainability model system (CLUES) to evaluate the potential catchment-scale efficacy of two mitigation strategies at reducing annual loads of sediment and nutrients to the Kaipara Harbour.