This update has taken some time to get to, but we have published the latest hydrological modelling dataset (HMD) including flow data to the end of 2017. The 2017 year was noteworthy with very low late winter inflows contributing to controlled storage crossing the one and two per cent risk curves

The HMD includes:

infrastructure and hydro constraint attributes (including access to contingent storage)

flows (including inflows, outflows, tributary flows, and some river flows)

storage and spill information

Due to the high proportion of hydro generation in the New Zealand electricity system, a good understanding of hydrology is required for many functions.

1. Operationally, this data is used within the industry to inform planning and decision making related to the inherent uncertainty of hydrology, i.e. describing the timing and volume of energy supply from inflows to the broader electricity system. The information may be used as inputs into studies employing tools such as DOASA, a hydro-thermal scheduling model, which seeks to optimally dispatch hydro resources.

2. The dataset holds an accurate record of hydro data that assists with monitoring market outcomes as well as providing important historical context to observed market responses. In addition, this information plays a key role in the calculation of the security standards for energy and capacity.

3. Broader studies around possible future scenarios for the New Zealand electricity system are also enabled through the use of this data.

We continue to improve the organisation of the dataset to avoid confusion and errors in the use of this data. These changes mean that file names, descriptions, or formats may have changed slightly from the previous dataset. We’ve again included index files in each folder, and this year have published derived tributary inflows for the key reservoirs in each modelled hydro scheme.

This publication is a full update of the dataset and has revisited rating changes and historical correlations. For more discussion of the differences please see the accompanying reports: Report 2a Flows comparison, and Report 3a Storage and spill comparison.

Users of the dataset are encouraged to post feedback - especially if they believe there is an error, a better method for accomplishing the same end, or if something has been missed in the infrastructure and hydro constraints file.

The Authority appreciates the cooperation of the hydro generators and other data providers in compiling and publishing this dataset. At this time we are unsure if we’ll get to an HMD update for 2018 flow data, although we will maintain the infrastructure attributes as we are made aware of changes.