Water Cycle Study - East Devon District Council

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Ref EWCS April 2010 Exeter and East Devon Water Cycle Study Wimbleball SSA as a whole will decrease over the planning period due to an increasing number of properties. • We have assumed that baseline water consumption for existing metered and unmetered properties remains constant during the plan period. This differs from SWW assumption in the draft WRMP09 that PCC for metered properties decreases and then increases during the planning period and for unmetered properties increases due to increasing demand related to gardens and showering, which is a factor of climate change. • We have assumed that non-household demand remains the same during the planning period. SWW have assumed that both measured and unmeasured non-household consumption decreases over the planning period. • We have used SWW baseline and forecast occupancy rates for new properties provided in their draft WRMP09. We have assumed the occupancy rate in the existing housing remains constant throughout the planning period at the average baseline rate of 2.28. The SWW draft WRMP09 assumes that the occupancy rate for measured and unmeasured households increases and then decreases during the planning period. • We have used forecast dwelling numbers provided in the RSS up to 2026. These may differ from the values in the draft WRMP09. As mentioned earlier, the draft WRMP undergoes a rigorous testing and review process with Defra, Ofwat and the Environment Agency, as well as public consultation. One of the key areas for scrutiny in this process is the forecast dwelling and population assumptions; therefore we are not undertaking any additional review of the accuracy of SWW forecast population or dwelling numbers. 7.8.7 The list of scenarios below provides detail of the components of each scenario tested. These are summarised in Table 7.6. The outcomes of these demand management scenarios are shown in Figure 7.7 below. Scenario 1: Business as usual 7.8.8 This scenario looks at how potable demand would increase should the SWW draft WRMP09 forecast PCC rates be realised in the new development areas, assuming that all new properties are metered. The PCC for existing homes (metered and unmetered) is assumed to remain constant throughout the planning period at 140.24 l/h/d for existing metered homes and 166.94 l/h/d for existing unmetered homes. The meter penetration ratio of metered to unmetered homes is assumed to be in agreement with the SWW draft WRMP09 forecast. This scenario has been used as the basis against which all other scenarios have been derived. Scenario 2: New homes built to Code for Sustainable Homes Level 5, at 80 l/h/d. 7.8.9 This scenario looks at a hard lined approach to the implementation of CSH water efficiency targets for new developments to reduce demand, whereby all new homes built after 2009 will be required to achieve CSH level 5 (80 l/h/d). We have assumed that all other variables are as detailed in Scenario 1. 80
Exeter and East Devon Water Cycle Study Scenario 3: New homes built to Code for Sustainable Homes Level 3 and existing metered PCC reduced by 1 l/h/d/y 7.8.10 This scenario looks at how the implementation of CSH water efficiency targets to CHS level 3 and a decrease in existing metered PCC reduces the overall increase in demand. All new homes built after 2009 will be required to achieve CSH level 3 (105 l/h/d) and plans implemented to reduce the PCC for existing metered properties by 1 l/h/d, each year from 2009 to the end of the planning period. Scenario 4: Water Neutrality within WCS study area - New homes built to Code for Sustainable Homes Level 3 and existing metered PCC reduced by 1.5 l/h/d/y 7.8.11 This scenario looks at how the implementation of CSH water efficiency targets to CHS level 3 and a decrease in existing metered PCC reduces the overall increase in demand to baseline levels, and maintains a water neutral position. All new homes built after 2009 will be required to achieve CSH level 3 (105 l/h/d) and plans implemented to reduce the PCC for existing metered properties by 1.5 l/h/d, each year from 2009 to the end of the planning period. Scenario SWW Planned Metered Supply Ratio Other metering 1 Yes All new properties metered. 2 Yes All new properties metered. 3 Yes All new properties metered. 4 Yes All new properties metered CSH3 CSH5 Reduction in existing PCC Other measures No No No No No Yes No No Yes new properties from 2009 Yes new properties from 2009 Table 7.6 - Description of water resources scenarios assessed No Yes 1 l/h/d/y No Yes 1.5 l/h/d/y 81 Ref EWCS April 2010 No No
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