Summary of Key Findings
– Temperature was significantly correlated to water consumption. It was estimated that under current conditions water consumption will increase by an average of 34 liters per capita per day (LCD) for every 1 °C increase in average daily temperatures during July and August.
– Precipitation was significantly correlated to water consumption, and it was estimated that water consumption will increase by 1.75 LCD for every decrease in 1 mm of total precipitation during July and August, which during drought conditions could reach up to 57 LCD.
– The estimated decrease in water consumption from implementing watering restrictions is 12% for stage 2, 14% for stage 3, and 17% for stage 4.
Annual Water Consumption
Water demand is most often described in terms of liters per capita per day (LCD) and can represent the average amount of water used per capita for a specific water supply system or region. The average daily demand (ADD) in LCD represents the average water usage during the year and, for the Sunshine Coast, includes all water used by industrial, commercial, agricultural, institutional, and residential sectors (SCRD, 2013). Between 2003 and 2011, ADD on the Chapman water system averaged 653 LCD and the lowest annual average ADD was experienced in 2011 at 592 LCD. Since 2009, the average seasonal LCD on the Sunshine Coast varied throughout the year with late fall and winter experiencing the lowest and summer experiencing the highest (Figure 20). These results show that water consumption during July and August is nearly double the consumption during the winter season.
Figure 20: Average monthly daily water consumption in litres per capita per day in the Chapman water system from 2009 to 2013
Five Year Comparison of Water Consumption in Relation to Temperature and Precipitation
Since 2009, average daily summer (July and August) water consumption in the Chapman water system has varied between 865 LCD in 2011 and 1022 LCD in 2010 (Figure 21). Figure 18 below highlights the relationship between summer water consumption and temperature and precipitation from 2009 to 2013. Between 2009 and 2013, average daily temperature in July and August was positively correlated with daily water consumption (Spearman Rank Correlation, 1.49 x 10-19) and daily precipitation was negatively correlated (Spearman Rank Correlation, 5.38 x 10-17). A clear example of these relationships was demonstrated in early to mid-August 2009, where both water consumption and temperature dropped and precipitation increased (the relationship between water consumption and temperature and precipitation will be discussed in more detail below). Water consumption is also influenced by watering restrictions. Since 2009, the only years to not have watering restrictions above Stage 1 were 2010 and 2011. The clearest example on the impacts of watering restrictions in the figure below can be found in August of 2013, where on August 6th, stage 2 watering restrictions were implemented resulting in water use to drop despite steady temperatures and minimal precipitation for most of the month.
Figure 21: Daily water consumption, mean daily and average monthly temperature, and total daily precipitation in the Chapman Creek water system for the months of July and August from 2009 to 2013
Watering Restrictions
Watering restrictions above level 1, which automatically takes effect on May 1 (SCRD, 2014), have been implemented in 3 of the last 5 years as shown in the table below. The implementation of higher level watering restrictions is based on the discretion of the General Manager of Infrastructure Services at the SCRD (SCRD, 2014).
Table 4: Historic watering restriction levels and dates for the Regional Water Service Area (2009 to 2013)
| Year | Dates | Restriction Level |
| 2009 | July 23 to September 17 | 2 |
| 2012 | September 10 to 18 | 2 |
| 2012 | September 19 to October 4 | 3 |
| 2012 | October 5 to 12 | 4 |
| 2013 | August 6 to September 20 | 2 |
Calculating the effectiveness of watering restrictions was done by comparing water consumption from the years with stage 2 watering restrictions and higher to years with stage 1 watering restrictions for the same time period. Due to the typical drop in water consumption from August to September, July and August were calculated separately for the estimates on water savings during stage 2 watering restrictions.
Table 5: Estimated savings in water consumption from implementing watering restrictions in the Chapman Water system from 2009 to 2013
| Restriction level (year) | Date | Avg. LCD (Stage 1) | Avg. LCD (Stage 2 or higher) | Drop in consumption | Estimated Savings from Restrictions per stage | Comment |
| 2 (2009) | July 23 to Aug. 31 | 971 | 873 | 10% | 12% | Sept 10 to 18, 2012 was omitted |
| 2 (2009) | Sept 1 to 23 | 693 | 641 | 8% | ||
| 2 (2012) | Sept 10 to 18 | 644 | 768 | (16%) | ||
| 2 (2013) | Aug 6 to 31 | 954 | 817 | 14% | ||
| 2 (2013) | Sept 1 to 20 | 716 | 627 | 12% | ||
| 3 (2012) | Sept 19 to Oct 4 | 556 | 524 | 6% | 14% | Midpoint between Stage 2 and 4 |
| 4 (2012) | Oct 5 to 12 | 526 | 438 | 17% | 17% | Conservative estimate |
Water Consumption in Relation to Temperature and Precipitation
The results show that water consumption during July and August was significantly correlated with temperature from 2009 to 2013 (Spearman Rank Correlation, 1.31 x 10-19) and the estimated increase in LCD per increase in average daily temperature is 35 LCD (Figure 22). The months of July and August from 2009 to 2013 represent all of the factors that influence water consumption, including watering restrictions. When examining the years for July and August with no watering restrictions above Stage 2 (2010 to 2012), the increase in LCD per increase in average daily temperature is estimated to be 40 LCD (Spearman Rank Correlation, 1.46 x 10-14) (Figure 23). For precipitation, water consumption significantly correlated with total monthly precipitation from 2003 to 2013 (Spearman Rank Correlation, 0.043) (Figure 24). The results indicate that for every mm of rain, water consumption will decrease by 1.75 LCD.
Figure 22: Daily water consumption ( litres per capita per day) in the Chapman Water System in relation to mean daily temperatures collected at the Sechelt AUT climate station in Sechelt, BC (July and August 2009 to 2013) – Correlation is significant (Spearman Rank Correlation, 1.31 x 10-19)
Figure 23: Daily water consumption ( litres per capita per day) in the Chapman Water System in relation to mean daily temperatures collected at the Sechelt AUT climate station in Sechelt, BC (July and August 2010 to 2012) – Correlation is significant (Spearman Rank Correlation, 1.46 x 10-14)
Figure 24: Average monthly consumption (litres per capita per day) in the Chapman Water System in relation to total monthly precipitation collected in Gibsons, BC (July and August 2003 to 2013) – Correlation is significant (Spearman Rank Correlation, 0.043)