Water Committee Agenda and Packet 2015 04 03

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2 WATER DEMAND AND HISTORICAL DEMAND MANAGEMENT 2.4.1.1 Climate Variability Impact on Water Supply and Demand Climate variability has the potential to impact water supply patterns and water demand. Recent climate forecasts indicate the potential for a future warming trend in the region. For example, in 2012 the Water Research Foundation completed a Joint Front Range Climate Change Vulnerability Study. All of the scenarios simulated as part of the study showed an increase in annual average temperature ranging from 1 degree to 6 degrees Fahrenheit for 2040. However, the annual percent change in precipitation ranged from -15 percent to +17 percent for 2040. While it is becoming more common to consider the impacts of climate variability on water supply planning the potential impact on water demands are less understood because of the variability of temperature and precipitation forecasts. Because recent water demands were used as the basis for forecasting future water demands, the demand forecasts in this plan already reflect some impact on water demand based on current climate conditions. A sensible approach to water demand forecasting is to regularly update demand projections based on actual current conditions. The purpose and goal of this document was to prepare a water conservation plan to improve water efficiency under current supply and demand conditions. In order to plan for potential climate variability it is recommended the City complete an analysis of water supply and demand under climate change conditions to determine the adequacy of the City's water supply under a variety of future climate scenarios; such an effort was outside of the scope of work for this water conservation planning effort. 2.4.2 Forecast Development As part of the preparation of the Water Efficiency Plan, three separate demand forecasts were prepared: • Baseline forecast (without conservation) • Passive savings forecast • Passive and active savings forecast The baseline forecasting method used historic demand patterns to establish the baseline per capita demand and then increase these demands with population out to 2032 as if the 2014 per capita water -use patterns continue without change to 2032. This is a standard approach to demand forecasting, but it does not take into account the expected impacts of water efficiency. The second and third forecasts were developed using a more robust approach in which demands were separated out by water -use sector or customer category (for example, residential, commercial, irrigation, etc.), with seasonal and non - seasonal demands (outdoor and indoor) disaggregated for each category. Then a separate demand forecast out to 2032 was prepared for indoor and outdoor demand in each customer category. This allowed the impacts of specific water efficiency measures like high- efficiency toilets and clothes washers to be considered. 2.4.2.1 Population Planning Projections The population served with potable water by the City of Louisville in 2013 was approximately 18,584. Staff have indicated that the City plans to achieve a build out population of 22,145 by 2032. This suggests an average annual growth rate of between 0.75 to 1.0 percent per year. Table 10 shows the population forecast for Louisville from 2015 to 2032. The year 2032 was chosen as a demand forecasting horizon. These data are shown graphically in Figure 5. WBG071714052946BSO 2 -13