Conclusions

The results from this study show that climate patterns on the Sunshine Coast have changed over the last 50 years.  Annual average temperatures have increased by approximately 2 °C and average total annual precipitation has decreased by 24 mm.  Climate trends during the winter season are impacting the available water supply as temperatures are increasing, which is increasing the elevation where snowpack starts to hold significant snow water equivalent, and precipitation is occurring more frequently as rain at higher elevations.  The increasing temperatures with diminishing snow pack is causing the snow to melt earlier and more rapidly during the spring season, as reflected in the historic discharge trends for Chapman Creek.  The existing streamflow regime in Chapman Creek is showing signs of shifting towards a more rain dominated regime, which would change the entire water holding dynamic of the watershed.  The discharge data further showed that peak discharge occurs earlier in the spring particularly when warm PDO is in phase with El Nino and this affects summer base flows when demand for domestic distribution and environmental services is highest.  Climate conditions during the summer season are also impacting supply as the increasing temperatures can reasonably be assumed to cause the snowpack to be completely gone earlier into the summer season and the decreasing trends in precipitation would result in less recharge to storage reservoirs.  The impacts of climate change on water supply have been shown to be enhanced from climate variability during PDO and ENSO events.  The warm PDO in phase with El Nino events further indicated the sensitivity that a warming climate may have on water supply.

The increases in temperature and decreases in precipitation trends were shown to be correlated to water consumption during the summer season when water supplies are the most limited.  The significant correlation between water consumption and temperature and precipitation identifies how climate change may impact water consumption behaviors on the Sunshine Coast.  If average summer temperatures continue to increase with population growth and the Sunshine Coast remains a popular tourist destination, regular water scarcity issues could occur more frequently in the near future.  These realities of low water supplies and high water consumption could be more serious if the Sunshine Coast experiences a prolonged drought.

The sensitivity analysis revealed two key findings: (1) the current capacity of the existing water treatment plant could be exceeded regularly in the next 5 years and (2) total water consumption during the summer could regularly exceed the equivalent to the available water supply in the next 10 years if water demand is business as usual, snow pack continues to decrease in the winter, the summer temperatures increase by an average 1 or 2 °C, and prolonged droughts become more common.