Bristol City Council’s target is to reduce water consumption by 3% year on year and has managed to achieve a reduction of around 37% since 2009 (Figure 2). In the last two years there has been the additional positive benefit of a carbon saving of 23 tCO2 (using UK government carbon factors for mains supply and sewerage) and a financial saving. Other indirect benefits include reduced sewerage loads, reduced demands on mains drainage and reduced demand for chemical treatment of supplied water.
In terms of office buildings, in 2012/13, water consumption was equivalent to 5.7m3/employee compared to 6.02m3/employee in 2011/12 (Bristol City Council, 2014).
Figure 1: Water consumption of top 50 sites, Bristol City Council (Ransom, 2014)
Bristol Council, working closely in partnership with Bristol Water, monitors all high consuming sites for water consumption to provide accurate data analysis and identify trends and leaks for further work or resolution. Leaks have been dealt with and the highest consuming sites have been identified and as a result a number of initiatives to reduce its water consumption have been undertaken.
This includes:
- Installing waterless urinals at the larger offices
- Installation of rainwater harvesting at key sites including the City Hall and the Create Centre.
- 100 Save-A-Flush devices installed in older council buildings
Bristol City Council has also managed to reduce water use in outdoor areas. Water used in horticultural operations was minimised by selecting drought tolerant flowers and replacing annual plants with perennials that are less water intense. There is a plan to replace water thirsty trees with those which only require watering in a very dry summer, instead of weekly, thus making further water savings.
Additionally, new horticultural features have been planted close to newly planted trees to benefit from shared resources, promoting better germination and establishment with less watering. The Council has also fitted drainage reservoirs in hanging baskets which better retain the water and again reduce the level of watering requirement (Ransom, 2012).
Figure 2: Mains and rainwater use (m3 per month)(Worsfold, 2014, pers.comm., 14 August)
Rainwater harvesting from a large roof feeds a 70m3 underground storage facility. Rather than a conventional storage tank, a system of 1350mm diameter pipes was used, which avoids the need for deep excavations. Combined with water saving appliances, potable water consumption has been reduced by 40%[1].
The water using devices include push button taps, dual flush WCs and low flow showers.
[1] Sometimes large volumes of harvested water are also used for the washing on site of archaeological finds.