At the recent Braid Conference at Lincoln University, a retired hydrologist of 60 years’ experience recently summed up the reason why Ecan is unable to manage Canterbury’s freshwater;
It is necessary to understand that braided rivers, their riparian margins and the Canterbury plains are all part of the same system, and are all connected. The plains should be considered an extension of the riparian margins with underground braids beneath connected to the gravels and groundwater that lie under the braided rivers themselves.
The principle of the Resource Management Act 1991 of dividing and trading off the region’s freshwater resource in a piecemeal fashion is simply inappropriate.
Each human intervention of taking water from one part of this system will have consequences for another.
- Ecan (falsely) claims it can take “alpine” water for irrigation and to restore the environment. Integrated Catchment Management ICM management of a river system from the Alps to the sea has become accepted as the most appropriate way to manage rivers.
- Over allocation of water from braided rivers for irrigation creates problems of sediment building up in the flood plains and the subsequent invasion of woody plants. Ecan’s river engineers attempt to mitigate this by annually aerially spraying the braids with high concentrations of glyphosate together with toxic wetting agents. This wipes out the cover, pool structures, and soil ecology to the detriment of the fish and birds that inhabit braided rivers.
- Over allocation of river water combined with agricultural encroachment causes the loss of secondary, tertiary braids, and wetlands. Essential components of braided rivers as nursery areas and for recruitment of algae, juvenile fish, and macroinvertebrates following major floods.
- Over allocation of groundwater for irrigation results in the loss of groundwater sourced rivers and streams
- Constraining braided rivers into fairways or channels works against the nature of braided rives where lateral accretion and degradation at the margins is a feature. The recent flood damage in the Rangitata and Ashburton Rivers is a consequence of such intervention. (Inappropriate law allows adjoining landowners to take recently accreted land once grass is able to become established).
- The coarse porous soils of the Canterbury Plains are vulnerable to nitrate leaching. Ecan has allowed intensive dairying to ramp up beyond the capacity of natural processes to accommodate the excess nitrate. Ecan has added to high levels of groundwater pollution by issuing consents for landlocked processing plants to apply high loadings of nitrate enriched factory waste onto farmland.
- Precision irrigation which attempts to reduce nitrate leaching beyond the root zone of plants has proved to be more harmful than flood irrigation. Not only are groundwater levels dropping, but nitrate pollution of groundwater has increased.
- “Aquifer enhancement” is simply robbing Peter to pay Paul
“Group think” is not understanding
The centrepiece of the Canterbury Water Management Strategy is a selective version of “community collaboration” where committees composed primarily of water users determine the fate of Canterbury’s freshwater.
Models are not reality
Models are frequently used as a cost effective means of explaining complex issues at a conceptual level. Unfortunately they do not provide answers of sufficient accuracy on which to base regulations or to allocate resources.
RHYHABSIM – The River Hydraulic Habitat Simulation model has been much abused in water allocation hearings in New Zealand. RYHABSIM combines simple hydrological measurements with simplistic biological observations to predict how 2 dimensional physical habitat changes with changing flows. Where habitat or space in a river is not limiting the results are meaningless. This is the case for braided rivers which have low productivity yet the Lake Coleridge Project Hearing used evidence from this model to alter the “protected” flows of the Rakaia River
AquiferSim – the model Ecan uses to assist the allocation of groundwater (and managing groundwater pollution) is too coarse grained to be meaningful.
Ecan’s director of science Tim Davie may claim it takes 30 to 60 years for pollution to clear from groundwater in parts of the plains but it takes as little as 2 to 40 days for groundwater to connect the upper and lower reaches of the Selwyn River.
OVERSEER – a model developed to sell fertilizer to farmers, has been the primary tool used by Ecan to develop Farm Environment Plans since 2010.
Despite multiple iterations and $50 million dollars invested attempting to validate OVERSEER as a regulatory tool, the model remains under review by the Ministry for the Environment.
Around 70% of the rates received by Ecan are invested in attempting to manage nitrate pollution using this model that has never been verified nor validated.
When the NZFFA reported the degraded state of the Selwyn River to Ecan, the compliance manager said he would increase the auditing frequency of nearby farm environment plans – really!
A precautionary approach is appropriate when evidence is unreliable, uncertain or incomplete. The Water Rights Trust and many other informed and concerned water advocates pleaded with Ecan to take a precautionary approach to managing Canterbury’s freshwater. Unfortunately greed has taken precedence.