City of Morgan Hill Water System Master Plan 2017

Water use conditions that are of particular importance to water distribution systems include the average day demand (ADD), the maximum month demand (MMD), the maximum day demand (MDD), the peak hour demand (PHD), and the winter demand. The average day demand represents the annual water demand, divided by 365 days, since it is expressed in daily units. The winter demand typically represents the low month water demands and is used for simulating water quality analysis. The maximum month demand (MMD) is the highest demand that occurs within a calendar month during a year. The City’s MMD usually occurs in the summer months in either July or August. The MMD is used primarily in the evaluation of supply capabilities. Historical monthly water production records, obtained for the period between 1990 and 2015 ( Table 3.1 ), indicate the maximum month to average month ratio ranging between 1.30 and 1.73. Over the reviewed period, this ratio neither showed significant increasing or decreasing trends. Therefore, an MMD factor of 1.75 was deemed representative of City trends. This is the same peaking factor that was used in the 2002 master plan. The following equation is recommended for estimating the maximum month demand, given the average day demand: The maximum day demand (MDD) is the highest demand that occurs within a 24 hour day during a year. The City’s MDD, which usually occurs during the summer months, is typically used for the evaluation and design of storage facilities, distribution mains, pump stations, and pressure reducing valves. The MDD, when combined with fire flows, is one of the highest demands that these facilities should be able to service while maintaining acceptable pressures within the system. The maximum day demands were obtained from the City’s water production records. Groundwater well production records indicate the date of occurrence and magnitude of the maximum day demand for each calendar year, as listed in Table 3.1 . The maximum day to average day demand ratios for the period between 1990 and 2015 ranged from 1.40 to 1.94 and occurred in July or August. Through an analysis of these maximum day demands it was determined that a ratio of 2.0 would be used in this master plan, which is consistent with the peaking factor used in the 2002 WSMP. The following equation is then used to estimate the maximum day demand, given the average day demand: 3.6.1 Maximum Month Demand Maximum Month Demand = 1.75 x Average Day Demand 3.6.2 Maximum Day Demand

Maximum Day Demand = 2.0 x Average Day Demand

June 2017

3-11

City of Morgan Hill Water System Master Plan