This report is a scoping study commissioned by the Bulk Water
Department. It is to assess whether a relationship exists between the
Southern Oscillation Index (SOI) and river flows in the Wellington
metropolitan water supply catchments.

If a relationship exists, the extent to which this can be used to predict low
river flows with a reasonable led in time will be assessed.
Based on the scoping study findings, recommendations for future work
and more comprehensive analyses will be given.

If forecasts of low rainfall/river flow periods can be issued, proactive
planning of the metropolitan bulk water supply system can be achieved.
This will allow the Bulk Water Department to:

- Decide on appropriate abstraction regimes from the various water
sources.
- More effectively manage the Te Marua lakes and Hutt aquifer storage.
- Implement timely conservation measures.
- Plan maintenance to ensure all supplies are operational during a
forecast drought.
- Include the forecast methodology into Phase I of the Bulk Water Drought
Strategy.