AgdaPkt 2002-07-01 - Laserfiche WebLink

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3.1 Weather In water use forecasting, it is typical to "weather normalize" base year water use. Water use tends to increase with hot, dry weather and decrease with cool, wet weather. Hence, it is important to adjust for abnormal weather patterns in order to establish an unbiased starting point for the forecasts. We collected monthly rain and daily maximum temperature data from the National Atmospheric and Oceanic Administration for the Redwood City weather station over the period 1948 to date. Our analysis of this data shows that weather during the calendar year 2000 was closer to normal than any other year in the series. This simplifies the weather normalization task as the 2000 water use data are already effectively weather normalized. The annual weather values for 2000 and normal are shown in Exhibit 4. Exhibit 4. Weather for Year 2000 Description 2000 Normal Annual Rain (inches) 19.57 20.21 Annual Average of Daily Max Temperature (°F) 71.0 71.3 3.2 Water Prices Changes in water prices are also known to change customers' behavioral decisions regarding water use. Following the first law in economic demand theory, as the real price of a commodity increases, the quantity demanded by consumers decreases. A review of RWC water prices shows they have remained relatively stable over recent years after adjusting for inflation. This finding of rate stability again simplifies the analysis as there is no need to make water price adjustments to base year water use. Appendix E contains the 2002 water price schedule. 3.3 Water Conservation Technologies Water fixtures have tended to become more water efficient over time because of improvements in water conservation technologies. In this study, we specifically account for known water using efficiencies occurring with toilets and clothes washers. These are the two largest end uses of indoor residential water use, making up about half of total use. Toilet manufactures came out with 1.6 gallon per flush toilets, known as ultra-low flush toilets or ULFTs, in 1989. Toilets before this time used 3.5 gallon per flush or more. In January 1992, a California Plumbing Code change required all new toilets to be ULFTs. Many older, less-efficient toilets were still being sold, however, at this time. A Federal plumbing code change effective January 1994 mandated ULFTs be used in all new Page 5