Climate
Historic climate data were investigated to determine if any significant trends in temperature and precipitation have been experienced at the climate stations between 1962 and 2013. Although there is variability in seasonal weather patterns, all of the climate data were examined based on monthly data and then the months were grouped into seasons based on seasonal factors that influence water supply and water consumption in the region. The seasonal analysis on climate included examining winter season months (November to February) in order to determine if trends in winter temperature and precipitation patterns have changed in a manner that affects winter snowpack conditions. The summer season (July to September) was examined to determine if historic temperatures and precipitation patterns have changed in a manner that may influence water availability and water consumption during this time of the year. Analyzing the data in this manner allowed the climate data to act as an indicator for determining potential changes to annual water supply.
Discharge (indicator of water supply)
All of the data were adjusted to represent the water year (October to September) in order to accurately represent discharge on an annual basis. As outlined by Fleming et. al. (2007), water years are preferable to calendar years for studying hydroclimatology in the Pacific Northwest. The annual hydrological cycle is better represented from October to September as this time frame encapsulates both the winter and spring freshets (Fleming et al., 2007).
Historical monthly discharge during the spring season (April to June) was examined to determine if the timing of spring peak flows are occurring earlier in the year. The shift in the hydrograph was also examined by comparing discharge patterns by decade to determine if annual discharge has experienced a significant shift in mean monthly flow.
It was recognized that Chapman Creek is regulated during the summer season when creek flows are augmented from the control structures at Chapman and Edwards Lake; however, as water flows under natural conditions for the fall, winter, spring, and early summer, changes to historic streamflow patterns from climate change can provide insight on changes in the water supply.
Water Consumption
Water consumption was analyzed based on annual, monthly and daily consumption data from the available records. Liters per capita per day (LCD) was calculated for all years in order to compare water consumption between years.
Summer (July and August) water consumption was examined in relation to temperature and precipitation as these two months experienced the highest water consumption throughout the entire year and also represent the time of year when water supplies can be the most limited.
A comparison of water consumption over the last 5 years was done to identify the relationship between average daily water consumption and average daily temperature and total daily precipitation.
Watering restrictions for the Region apply to all municipal customers of the Sunshine Coast and are implemented by the SCRD. There are four levels of restrictions (Table 5) and Stage 1 watering restrictions are always in effect May 1 to September 30 unless higher level restrictions are implemented.
Table 5: All stages of watering restrictions for the entire Sunshine Coast, BC
| Stage 1 (Normal) | Stage 2 (Moderate) | Stage 3 (Acute) | Stage 4 (Severe) |
| Sprinkling of lawns, trees, shrubs, flowers or vegetables three times a week for four hours per day (two hours in the morning and two in the evening) | Sprinkling of lawns, trees, shrubs, flowers or vegetables two times a week for two hours per day (two hours in the morning) | No lawn sprinkling allowed and sprinkling of trees, shrubs, flowers, and vegetables is only allowed by hand-held container at any time | Complete ban on all outdoor water use |
The effectiveness of watering restrictions was estimated by calculating the average consumption for years with watering restrictions (stage 2 and higher) against years without watering restrictions (stage 1) for the same time periods.
Seasonal Classification
Based on the seasonal climate factors influencing water supply and water consumption, three seasonal groupings were identified to describe climate, supply, and consumption for the Chapman water system on the Sunshine Coast, BC. The three seasons influencing water supply and/or consumption that were examined include:
- Winter (November to February): The winter season builds the snow pack to provide water supply in the summer and is influenced by winter temperature and precipitation.
- Spring (April to June): The spring season experiences snow melt that influences water supply in the summer and is characterized by the timing of peak flows in Chapman Creek. The factors examined include annual hydrographs by PDO/ENSO event and by decade.
- Summer (July to September): July and August are the months that experience the highest water consumption throughout the year. During this time of year climate can impact water availability into the fall season because water supply is most susceptible to drought conditions. The factors examined included temperature and precipitation trends from July to September and water consumption in relation to temperature and precipitation during July and August.
Although there are some differences in the climate, consumption and discharge dynamics among these seasonal groupings, these groupings have been established to identify the impacts that climate change may have on water supply and water consumption on the Sunshine Coast.
Sensitivity Analysis
An analysis was conducted to determine the sensitivity of the capacity at the SCRD’s water treatment plant and the equivalent to total available lake storage in relation to water consumption patterns influenced by climate change. The relationships between summer consumption, climate and watering restrictions over the last 5 years were used to provide the basis for developing the scenarios for the sensitivity analysis. The scenarios were developed for average daily water consumption, total water consumption during July and August, and maximum daily demand under average summer temperature increases of 1,2,and 3 °C with and without drought conditions (periods where the region experiences no rainfall).