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August 2016
7-3
City of Morgan Hill
2015 Urban Water Management Plan
minimum historical yields for a running average of three years. The period between 2013
and 2015 was selected to represent the multiple dry years. The percent of average supply
for the third multiple-dry year does not include additional water transfers that may be
obtained by SCVWD during extreme droughts for the Llagas subbasin.
Table 7-1 Basis of Water Data
Year Type
Base
Year
Volume
Available
Percent of Average
Supply
(AF)
(%)
Average Year
63,900
100%
Single-Dry Year
1977
60,705
95%
Multiple-Dry Years 1st Year
2013
60,705
95%
Multiple-Dry Years 2nd Year
2014
54,315
85%
Multiple-Dry Years 3rd Year
2015
41,535
65%
Notes:
1.
Available volume for single dry and multiple dry year periods based on estimated
percent of average supply, per SCVWD 2015 UWMP.
7.2.2
Sources for Water Data
To establish a basis of normal, single dry, and multiple dry hydrologic water year’s, historical
rainfall data available from DWR was analyzed, as it relates to the City.
7.3 SUPPLY AND DEMAND ASSESEMENT
Law
During prolonged years of drought, City-wide water use patterns are expected to change.
Typically, outdoor water use will initially increase as irrigation is used to offset decreased rainfall.
10635 (a) Every urban water supplier shall include, as part of its urban water management plan, an
assessment of the reliability of its water service to its customers during normal, dry, and
multiple dry water years. This water supply and demand assessment shall compare the
total water supply sources available to the water supplier with the total projected water
use over the next 20 years, in five-year increments, for a normal water year, a single dry
water year, and multiple dry water years. The water service reliability assessment shall
be based upon the information compiled pursuant to Section 10631, including available
data from state, regional or local agency population projections within the service area of
the urban water supplier.