What is a carbon footprint and how is it measured?
A carbon footprint is the total CO2 and other greenhouse
gases produced by a home, business or government agency. To measure
its carbon footprint, SLVWD joined the California Climate Action
Registry (CCAR) in 2007 and the national Climate Action Registry
in 2008.
Using CCAR's established protocols, SLVWD inventoried
all of its greenhouse gas emissions in 2006 LINK
TO 2006 GHG EMISSIONS REPORT and 2007 LINK
TO 2007 GHG EMISSIONS REPORT. CCAR certified these results
in 2009, recognizing SLVWD as a "Climate Action Leader."
SLVWD is now working on its 2008 inventory.
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What are SLVWD's sources of greenhouse gas emissions?
As the chart below shows, SLVWD's largest source
of greenhouse gas emissions is electricity, which is used mostly
to operate our deep-water wells. SLVWD purchases our electricity
from PG & E, which includes both fossil-fuel and alternative
energy sources in its mix. Clearly, well-pumping is our largest
source of greenhouse gas emissions.
How does well-pumping emit greenhouse gases?
Because water is heavy, pumping water to the surface from underground
aquifers requires lots of energy.
SLVWD's Southern System, which serves some areas
in Scotts Valley, relies completely on wells. In dry years, the
level of groundwater drops, so more energy is required to pump
the water to the surface.
SLVWD's North System, which serves the northern
San Lorenzo Valley, is served by creeks on Ben Lomond Mountain,
and by a separate system of wells. Taking water from creeks high
in the watershed requires little energy, since gravity does the
work. In the dry season, SLVWD stops taking water from the creeks
and switches to its North system wells.
The chart above shows that SLVWD's greenhouse gas
emissions were lower in 2006 than in 2007. This is because 2006
was a wet year, and 2007 was a very dry year. In 2006, rains continued
into May. In 2007, rains stopped in January, and the North System
switched to wells early in the year. With more well-pumping, more
electricity was needed, and more greenhouse gases were emitted.
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