Decision support experiments and evaluations using seasonal to ...

The U.S. Climate Change Science Program Chapter 3
Interest in the effects
of climate variability
on water supplies
in the Southwest
has been limited
by dependence on
seemingly unlimited
groundwater
resources, which
are largely buffered
from interannual
climate fluctuations.
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December 23, 2003
interannual and multi-decadal climate variations,
forced by persistent patterns of oceanatmosphere
interaction, lead to sustained wet
periods and severe sustained drought (Andrade
and Sellers, 1988; D’Arrigo and Jacoby, 1991;
Cayan and Webb, 1992; Meko et al., 1995; Mantua
et al., 1997; Dettinger et al., 1998).
Sources of vulnerability
Despite this wealth of information, interest
in the effects of climate variability on water
supplies in the Southwest has been limited by
dependence on seemingly unlimited groundwater
resources, which are largely buffered from
interannual climate fluctuations. Evidence of
extensive groundwater depletion in Arizona and
New Mexico, from a combination of rapid urban
expansion and sustained pumping for irrigated
agriculture, has forced changes in water policy,
resulting in a greater reliance on renewable surface
water supplies (Holway, 2007; Anderson
and Woosley, Jr., 2005; Jacobs and Holway,
2004). The distance between the Southwest’s
urban water users and the sparsely-populated
mountain sources of their surface water in Wyoming,
Utah, and Colorado, reinforces a lack of
interest in the impacts of climate variations on
water supplies (Rango, 2006; Redmond, 2003).
Until Southwest surface water supplies were
substantially affected by sustained drought,
beginning in the late 1990s, water manage-
ment interest in climate variability seemed to
be focused on the increased potential for flood
damage during El Niño episodes (Rhodes et al.,
1984; Pagano et al., 2001).
Observed vulnerability of Colorado River and
Rio Grande water supplies to recent sustained
drought, has generated profound interest in the
effects of climate variability on water supplies
and management (e.g., Sonnett et al., 2006).
In addition, extensive drought-driven standreplacing
fires in Arizona and New Mexico
watersheds have brought to light indirect impacts
of climate variability on water quality and
erosion (Neary et al., 2005; Garcia et al., 2005;
Moody and Martin, 2001). Prompted by these
recent dry spells and their impacts, New Mexico
and Arizona developed their first drought plans
(NMDTF, 2006; GDTF, 2004); in fact, repeated
drought episodes, combined with lack of effective
response, compelled New Mexico to twice
revise its drought plan (NMDTF, 2006; these
workshops are discussed in Chapter 4 in Case
Study H). Colorado River Basin water managers
have commissioned tree ring reconstructions
of streamflow, in order to revise estimates of
record droughts, and to improve streamflow
forecast performance (Woodhouse and Lukas,
2006; Hirschboeck and Meko, 2005). These
reconstructions and others (Woodhouse et al.,
2006; Meko et al., 2007) reinforce concerns
over surface water supply vulnerability, and
the effects of climate variability and trends
(e.g., Cayan et al., 2001; Stewart et al., 2005)
on streamflow.
Decision-support tools
Diagnostic studies of the associations between
ENSO teleconnections, multi-decadal
variations in the Pacific Ocean-atmosphere
system, and Southwest climate demonstrate
the potential predictability of seasonal climate
and hydrology in the Southwest (Cayan et al.,
1999; Gutzler, et al., 2002; Hartmann et al.,
2002; Hawkins et al., 2002; Clark et al., 2003;
Brown and Comrie, 2004; Pool, 2005). ENSO
teleconnections currently provide an additional
source of information for ensemble streamflow
predictions by the National Weather Service
(NWS) Colorado Basin River Forecast Center
(Brandon et al., 2005). The operational use of
ENSO teleconnections as a primary driver in
Rio Grande and Colorado River streamflow