CHAPTER 2 Water Demands This chapter provides an overview of the City’s water service area and describes the City’s historical annual water use. Subsequent sections of this chapter examine projected water conservation and describe the data and methodology used to develop future water demand projections. The key sections of the chapter are: • Service Area Description • Historical Annual Water Use • Water Conservation • Water Demand Projections A key objective of this water demand evaluation is to confirm the anticipated water demand requirement and its associated timing, particularly due to the recent significant demand reductions caused by a combination of droughts and poor economic conditions. Future water demands developed in this chapter will subsequently be allocated in the hydraulic model to evaluate system performance under projected 2035 demand conditions. The future water system evaluation will help update recommendations presented previously in the 2006 Water Master Plan Update and prioritize future water system facilities. 2.1 SERVICE AREA DESCRIPTION The City is located in Northern California approximately 50 miles north of San Francisco and 30 miles east of the Pacific Ocean, and is the county seat for Sonoma County. The City’s water service area is roughly coterminous with the City limits, but does extend slightly beyond the City limits in some areas, as shown on Figure 2-1. Land use within the City is primarily residential, but also includes some agricultural, industrial, commercial, and recreational land uses. The City obtains its water supply from two sources. The primary supply source is treated water purchased from the Sonoma County Water Agency (SCWA). The City also has five potable groundwater wells, two of which can be used to supplement water supply purchased from SCWA, and the remaining three wells are for emergency use only (only two of these emergency wells are currently operational). 2.2 HISTORICAL ANNUAL WATER USE This section summarizes the City’s historical water purchases from the SCWA and local groundwater production, water consumption, unaccounted for water, and water system peaking factors. 2.2.1 Water Purchases and Groundwater Production Prior to 1959, the City relied almost exclusively on groundwater to supply its customers. Then, beginning in June 1959, through 2006, with the availability of water from SCWA, the City began to rely exclusively on water purchased from SCWA. The City also maintains a local source of groundwater supply, which prior to 2007 (but after 1959), had only been used for emergency purposes. Since the introduction of potable groundwater supply in 2007 to supplement water purchased from SCWA, the City has received on average approximately 95 percent of its water 2-1 City of Santa Rosa August 2014 Water Master Plan Update o\c\405\02-13-36\wp\mp\071613_2Ch2 Chapter 2 Water Demands supply from SCWA. Table 2-1 summarizes the City’s historical annual water purchases from SCWA and groundwater production from 2006 to 2013. Table 2-1. Historical Annual Water Purchases and Groundwater Production, MG (AF) Year Purchased from SCWA Groundwater Total 2006(a) 7,756 (23,803) 0 (0) 7,756 (23,803) 2007(a) 7,397 (22,700) 271 (832) 7,668 (23,532) 2008(a) 7,137 (21,903) 489 (1,501) 7,626 (23,405) 2009(b) 6,157 (18,895) 440 (1,350) 6,597 (20,245) 2010(b) 6,033 (18,514) 298 (914) 6,331 (19,428) 2011(b) 5,598 (17,180) 410 (1,259) 6,008 (18,439) 2012(b) 6,306 (19,354) 258 (791) 6,564 (20,145) 2013(c) 6,743 (20,692) 369 (1,131) 7,111 (21,823) (a) Source: CSR_Use and Production Statistics_90-08. (b) Source: CSR_ProdandUse_2009-2012.xlsx, received from City staff on 8/29/13. (c) Source: 2013_Production and Use Statistics.pdf, received from City staff on 5/20/14. MG = Million gallons; AF = Acre-feet. Water use in the City significantly decreased in 2009 through 2011 and then increased in 2012 and 2013 with 2013 water use back above the 2009 level. It should be noted that this more recent, lower, water use is not representative of normal water use characteristics for the City as it has been significantly affected by the following factors: • Drought Conditions; • Water Shortage Conditions; and • Economic Conditions. Dry year conditions in 2007 and 2008 caused SCWA to request voluntary 15 percent reductions in water use from all of its water contractors. In 2009, further drought conditions caused the SCWA to implement the Water Shortage Allocation Methodology and provide monthly allocations to each of its water contractors. In response, the City adopted Stage 1 of the Urban Water Shortage Contingency Plan requesting customers to reduce their water use. The recent economic recession and high amounts of vacancy in existing residential and commercial customer accounts from 2007 to 2010 also had a significant effect on water usage. 2.2.2 Water Consumption The City tracks its water consumption through customer meter records. Table 2-2 summarizes the City’s historical annual water consumption by customer type. The predominant water use in the City is by residential customers, which accounts on average for approximately 73 percent of the total annual water consumption. 2-2 City of Santa Rosa August 2014 Water Master Plan Update o\c\405\02-13-36\wp\mp\071613_2Ch2 Chapter 2 Water Demands Table 2-2. Historical Annual Water Consumption by Customer Type, MG Year Customer Type 2006(a,b) 2007(a) 2008(a) 2009(c) 2010(c) 2011(c) 2012(c) 2013(d) Residential Single Family 4,107 3,996 4,020 3,424 3,215 3,202 3,458 3,565 Multi-Family 1,085 1,076 1,106 1,053 1,045 1,040 1,078 1,105 Subtotal Residential 5,192 5,072 5,126 4,477 4,260 4,242 4,536 4,670 Non-Residential Commercial 1,156 715 685 565 696 742 777 815 Industrial - 88 86 78 72 73 76 93 Institutional - 311 297 278 116 111 128 133 Irrigation 830 839 834 615 525 530 658 686 Other(e) - 50 34 168 45 25 25 19 Subtotal Non-Residential 1,986 2,003 1,936 1,704 1,454 1,481 1,664 1,746 Total 7,178 7,075 7,062 6,181 5,714 5,723 6,200 6,416 Percent Residential 72% 72% 73% 72% 75% 74% 73% 73% Percent Non-Residential 28% 28% 27% 28% 25% 26% 27% 27% (a) Source: CSR_Use and Production Statistics_90-08. (b) Water consumption from Industrial, Institutional, and Other customer types included in Commercial customer type. (c) Source: CSR_ProdandUse_2009-2012.xlsx, received from City staff on 8/29/13. (d) Source: 2013_Production and Use Statistics.pdf, received from City staff on 5/20/14 (e) Includes revenue (i.e., construction meters) and non-revenue water consumption. 2.2.3 Unaccounted for Water Unaccounted for water (UAFW) is the difference between the quantity of water purchased/produced and the quantity of water consumed or billed. UAFW typically includes all water not measured/metered within a system that is used for incidental purposes such as hydrant testing, fire-fighting, and water main flushing. UAFW also includes other unintended uses such as system leaks, unauthorized connections/water theft, water main breaks, and meter inaccuracies. The City’s annual water production, water consumption, and UAFW are summarized in Table 2-3. In the last eight years, the UAFW has ranged from 4.7 percent to 9.8 percent, with an average of 7.3 percent. West Yost recommends the use of this average UAFW factor of 7.3 percent for planning purposes in this Water Master Plan Update because this average accounts for some of the variability between the historical annual UAFW. This recommended UAFW factor of 7.3 percent is slightly higher than the UAFW factor (7.0 percent) used in the City’s 2006 Water Master Plan Update as it incorporates the more recent data (2006 to 2013), which documents that the UAFW was as high as 9.8 percent. However, this recommended UAFW factor is slightly lower than the UAFW factor (7.9 percent) used in the City’s 2010 Urban Water Management Plan (UWMP) based on the data available during that period. Future 2-3 City of Santa Rosa August 2014 Water Master Plan Update o\c\405\02-13-36\wp\mp\071613_2Ch2 Chapter 2 Water Demands specific City UAFW data should be used to re-calculate and update this UAFW value for the City’s water system to better reflect actual conditions. Table 2-3. Unaccounted For Water Total Water Total Water Percent of Total Year Production, MG(a) Consumption, MG(b) UAFW, MG Water Production 2006 7,756 7,178 578 7.5% 2007 7,668 7,075 593 7.7% 2008 7,626 7,062 564 7.4% 2009 6,597 6,181 416 6.3% 2010 6,331 5,714 617 9.7% 2011 6,008 5,723 285 4.7% 2012 6,564 6,200 364 5.6% 2013 7,111 6,416 695 9.8% Average 7.3% (a) Refer to Table 2-1. (b) Refer to Table 2-2. 2.2.4 Water System Peaking Factors Water system facilities are generally sized to meet peak demand periods. The peaking conditions of most concern for facility sizing are typically maximum month demand, maximum day demand with fire flow and peak hour demand. Peak water use is typically expressed as a ratio, or peaking factor, dividing the peak water use by the average daily water use. These peaking factors are then used to calculate maximum month, maximum day and peak hour water use conditions.