agenda city of watsonville city council/redevelopment agency meeting

The City will strictly follow the requirements established by federal and state regulatory agencies and
ensure that it continues to deliver high quality drinking water.
Climatalogical Considerations
#22. Describe the reliability of the water supply and vulnerability to seasonal or climatic
shortage, to the extent practicable, and provide data for each of the following: (A) an
average water year, (B) a single dry water year, (C) multiple dry water years
(10631(c)(1)).
Tables 5.6 and 5.7 show the effects of a single dry year and multiple dry weather years. Surface water
comprises only about 10% of the total water supply. In the event of a drought or breakdown of the
surface water filtration plant, such as occurred from 1989 through 1996, the City would depend more
heavily on groundwater. City wells are not currently run at full capacity, and can supply additional water
when needed. The maximum safe yield is the quantity of water that can be produced from the City
groundwater system, based on the historical production capacity of the aquifer and the pumping
capacity of the well equipment. Table 5.9 assumes no surface water is available in the dry water years,
and that groundwater wells produce at the maximum safe yield.
The City is able to supply its customers with adequate water through several years of drought.
However, during drought conditions, the City would also make significant increases in its water
conservation program. The City uses about 10% of the groundwater in the Pajaro Valley Basin, and
would take all possible action to reduce the demand on the already over-drafted groundwater basin.
The City will continue to work cooperatively with the PVWMA to find additional water supply options.
Using the guidelines of DWR, the City will reference Table 5.6 when determining drought conditions:
Average Year = 20.07” inches of rainfall.
- Year 2004 is considered the reference average year as it is the median year for rainfall over a 30
year period (from 1980 to 2010).
Single Dry Year = 10.66” inches of rainfall.
- Year 1976 is considered the reference single dry year as it is the lowest recorded year of rainfall
since 1903 (http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca9473).
Multiple Dry Year period = 14.79” average inches of rainfall.
- Years 1989-1992 is considered the reference multiple dry year period. This is the period
generally considered to be the lowest average runoff for a consecutive multiple year period
(three years or more) for a watershed since 1903. The two longest droughts in California history
are considered to be 1987-1992 and 1923-1935.
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