The scope and business case for guidelines that direct rainfall, runoff and flow modelling across all New Zealand catchments is under development.
3 waters infrastructure service delivery relies on flow information to; manage water within quantity and quality limits set under the National Policy Statement on Freshwater Management, make regional and local resource, land use planning decisions and consent decisions and invest in infrastructure (including in flood protection, drainage, contaminant management and irrigation).
INDUSTRY NEEDS
Currently there is no nationally agreed or standardised approach to the maintenance of rainfall statistics or the application of runoff models to determine flow volumes. The industry needs rainfall and runoff guidelines because:
- The statistical analysis of rainfall events is required regularly, and especially after major storm events, and is not currently carried out uniformly across the country.
- There are many different models that can be applied to determine the volume of runoff, and each has different pros and cons. The most appropriate runoff model for use in one region might be different from that in another region.
- One of the key parameters for runoff is the soil type, and there are parts of the country which have no soil data appropriate for use in runoff modelling.
- The continuous modelling of rainfall events is important in understanding contaminant loads. Work is required to develop better models for this purpose.
POTENTIAL BENEFITS
Rainfall and runoff guidelines would develop a standard set of data and modelling approaches for all New Zealand catchments. This means that the best available data will be used in all situations and applied in models that are widely regarded as best practice.
BETTER DECISIONS WHEN MANAGING CATCHMENTS AND INVESTING IN INFRASTRUCTURE
- Better environmental outcomes - more accurate measurement and understanding of water flows impacts all aspects of freshwater management, including consenting processes, managing allocation and managing discharges of contaminants
- More resilient infrastructure - a reduction in underbuilds reduces the risk of failures (inaccurate modelling might lead decisions makers to believe that the infrastructure is capable of more protection than it actually provides)
- More cost-effective infrastructure - a reduction in overbuilds reduces costs (inaccurate modelling might lead decision makers to build more infrastructure than is necessary for a given level of service)
DECISIONS ARE FASTER AND MADE AT LOWER COST
- An agreed standard reduces rework within consent applications
- An agreed standard reduces debate on model parameters and appraisal within all processes that use water flow modelling
- Lower administrative costs (such as the time spent building models)
- A more certain planning environment gives developers greater confidence in investing in communities (including a clear understanding of the costs early in the process).
Other benefits of collaboration
- The dispersed nature of the agencies involved leads to a greater understanding of different perspectives in water management
- The expected development of a single platform for successful implementation (such as the platform developed in Australia) can lead to a range of other possible initiatives and improves processes for using flow information across agencies.
- This initiative is a collaborative process that will bring together agencies to establish a common best practice to improve decisions which rely on rainfall and runoff modelling. These agencies include regional councils, territorial local authorities (TLAs), transport agencies, and central agencies in the Natural Resources Sector (MfE, MPI, MBIE, DoC, LINZ, TPK, DIA and MoT) as well as MCDEM
PROCESS
The first stage in realising these benefits is to develop a business case and implementation plan to identify what the guidelines need to cover, what guidance should be determined, and how to ensure the guidelines are implemented well. A funding application has been submitted to the Better Public Services Seed Fund to develop this. If funding is successful the business case will be presented to Ministers for approval in November 2017.
STAKEHOLDERS
This initiative is a collaborative effort, and several parties will be involved to take the initiative from concept to implementation.
The Ministry for Environment will be the lead central agency involved in developing the Better Business Case, with Land Information New Zealand actively supporting the initiative where it links to data platforms. Water New Zealand is providing co-ordination and project management, technical resource and strategic direction to develop the funding bid.
A large number of councils, specialist water groups and central government agencies have indicated support for this initiative. Ultimately, the use of the guidelines will include all TLAs and Regional Councils along with other infrastructure builders and owners.