OPEN ACCESS
When sustainability limits for resource use or adverse effects from multiple users are reached, there is a need to manage for the cumulative impacts of all users as well as the impacts of individual users. Ir- rigation expansion in Canterbury led to sustainability limits for water availability for further irrigation and water quality decline from land use intensification. This paper illustrates some of the key lessons for management of cumulative impacts from Canterbury examples. In the Rakaia-Selwyn Groundwater Zone, the spatial scale of management shifted from managing the drawdown impacts on adjacent bores to managing the total extraction from the groundwater zone and the effects on flows in groundwater-fed streams. The management of nitrate contamination from land use intensification across the Canterbury Plains required analysis of the cumulative effects of current and future developments on drinking wa- ter quality: this also led to requirements for increased controls on existing users and raised the issue of affordability of additional controls. As illustrated in water quality management for Lake Benmore, modelling of cumulative effects is more complex than modelling the effects of individual projects. Uncertainties in predicting cumulative effects can be greater than the contributions of individual projects. This creates difficulties not only in setting overall limits for managing cumulative effects but also in determining whether impacts from project proposals can be accommodated. The setting of nitrogen discharge limits on land users in the catchment of Wainono Lagoon demonstrates the issue of equity considerations in allocation of discharge allowances. This is not only for the allocation among existing users but also between existing dischargers and potential new dischargers. The management of salinisa- tion of the Woolston-Heathcote groundwater supply is an example of the need to manage the collective contributions of those responsible for adverse effects not just the individual users. The greater complexity of monitoring for the management of cumulative impacts is illustrated in the management of environmental flows in the Te Ngawai River. This required integrating the measurements of individual extractions and the combined effect on river flow in real time.
complex models, cumulative effects, equitable allocation, monitoring, sustainability limits, water management
[1] Jenkins, B., Challenges in Cumulative Impact Assessment: Case Studies from Canterbury, New Zealand. Environmental Impact IV, WIT Transactions on Ecology and the Environment. Vol. 215, WITPress: Southampton, pp. 25–36, 2018. ISBN 978-1-78466-281-3.
[2] Environment Canterbury, Canterbury Land and Water Regional Plan December 2015. Environment Canterbury: Christchurch, 2015.
[3] Scott, D., Groundwater allocation limits: land-based recharge estimates. Report U04/97, Environment Canterbury: Christchurch, 2004.
[4] Environment Canterbury, Decision of the Commissioners regarding 69 groundwater takes in the Rakaia-Selwyn Groundwater Allocation Zone. Environment Canterbury: Christchurch, 2007.
[5] Bidwell, V., Lilburne, L., Thorley, M. & Scott, D., Nitrate discharge to groundwater from agricultural land use: an initial assessment for the Canterbury Plains. Prepared for Steering Group of the CWMS, Environment Canterbury: Christchurch, 2009.
[6] Environment Canterbury, Annual Groundwater Quality Survey 2012. Environment Canterbury: Christchurch, 2012.
[7] Foundation for Arable Research (FAR), New Zealand Pork, DairyNZ, Beef+Lamb New Zealand, Horticulture New Zealand, Deer Industry New Zealand, Industry-agreed Good Management Practices relating to water quality. Environment Canterbury: Christchurch, 2015.
[8] Jenkins, B., Water Management in New Zealand’s Canterbury Region: A Sustainability Framework. Global Issues in Water Policy Vol. 19, Springer: Dordrecht, 2018. DOI: 10.1007/978-94-024-1213-0.
[9] Norton, N., Spigel, B., Sutherland, D., Trolle, D. & Plew, D., Lake Benmore Water Quality: a modelling method to assist with assessments of nutrient loadings. Report R09/70 prepared by NIWA for Environment Canterbury: Christchurch, 2009.
[10] Spigel, B., Plew, D., Hamilton, D., Sutherland, D. & Howard-Williams, C., Updated model assessment of the effects of increased loads into Lake Benmore. NIWA: Christchurch, 2015.
[11] Robson, B. & Hamilton, D., Three-dimensional modelling in the Swan Estuary, Western Australia. Ecological Modelling, 174, pp. 203–222, 2004.
[12] Norton, N. & Robson, M., South Canterbury Coastal Streams (SCCS) limit setting process – predicting consequences of future scenarios: Overview Report, Report R15/29, Environment Canterbury: Christchurch, 2015.
[13] Canterbury Water, South Coastal Canterbury ZIP Addendum. Environment Canterbury: Christchurch, 2014.
[14] Norton, N., Revised Working Draft Nitrogen Load Limit and Allocation Framework. Environment Canterbury: Christchurch, 2013.
[15] Norton, N., Harris, S., Scott, M., Lilburne, L., Robson, M., Stapleton, J., MacDonald, M., Newman, N. & Whitehouse, W., Process and outcomes of the Nitrogen Allocation Reference Group (NARG) for the South Canterbury Coastal Streams area. Report R14/110, Environment Canterbury: Christchurch, 2014.
[16] Norton, N., Harris, S., Scott, M., Lilburne, L., Robson, M., Stapleton, J., MacDonald, M., Newman, N. & Whitehouse, W., Process and outcomes of the Nitrogen Allocation Reference Group (NARG) for the South Canterbury Coastal Streams area. R14/110, Environment Canterbury: Christchurch, 2014.
[17] Environment Canterbury, Proposed Variation 3 to the Proposed Canterbury Land and Water Regional Plan. Environment Canterbury: Christchurch, 2015.
[18] Whiting, G., Ellison, E. & Fenemor, A., Minute 2 (Minute and directions on expert caucusing): proposed Plan Change 3 (South Canterbury Coastal Streams). Canterbury Regional Council: Christchurch, 2015.
[19] Environment Canterbury, Caucusing statement in relation to Nutrient Management provisions: Plan Change 3 to the partially operative Land and Water Regional Plan. Environment Canterbury: Christchurch, 2015.
[20] Hertel, I., Groundwater contamination in the Heathcote/Woolston area, Christchurch, New Zealand. University of Canterbury: Christchurch, 1998.
[21] Scott, M. & Wilson, N., Seawater intrusion network review. Environment Canterbury: Christchurch, 2012.
[22] Glubb, R. & Miller, B., Te Ngawai Water Use Telemetry Project. Report U06/65, Environment Canterbury: Christchurch, 2006.