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South Carolina Drought Forecasting
Greg Carbone and Kirstin Dow
Department of Geography
University of South Carolina
Outline
Community water systems managers in South Carolina
Resampling methodology applied to drought forecasting
Sample products
Investigating CWS Managers
• 3 Focus groups
• 4 meetings with key informants
• Survey results from 269 managers (52%)
5 - Day Forecasts
0
10
20
30
40
50
60
70
1 -
No
tco
nfid
en
t
2 -
3 -
So
me
wh
at
4 -
5 -
Ve
ryC
on
fide
nt
SC
SRB
0
10
20
30
40
50
60
70
1 - N
otco
nfid
ent
at a
ll 2 -
3 -
Som
ewha
tco
nfid
ent 4
-
5 - V
ery
Con
fiden
t
SC
SRB
3-Month Forecasts
Per
cent
age
Confidence in…
Survey Questions Included in Use of Forecasts for Planning
Percentage of “Yes” responses SC PAPlan future water storage needs for finished water? 16.8 13.1
Plan expanded distribution capability? 16.7 7.4
Plan when to bring new water supplies on line? 15.6 16.3
Adjust existing reservoir levels or back-up storage? 24.4 24.2
Anticipate inventory supply needs or guide purchasing decisions?
19.2 16.5
Schedule personnel, maintenance, or construction? 59.0 52.1
Schedule additional testing for water quality? 29.3 28.7
Help make budget projections? 22.2 10.8
Justify increased infrastructure investments? 18.9 11.7
Start a public information campaign to conserve water? 57.5 65.9
Summary of CWS Managers Views
• CWS managers’ have some confidence in climate forecasts, but……
• Confidence does not increase the likelihood that CWS managers will use forecasts
• Level of concern over risks and severity of consequences offers greater insight into uses of forecasts
Drought Stage
(SC Drought Response
Committee)
Palmer Drought Severity Index
(PDSI)
Standardized Precipitation Index (SPI)
Keetch-Byram Index
1 Incipient -0.50 to -1.49 0 to -0.99 300 to 399
2 Moderate -1.50 to -2.99 -1.00 to -1.49 400-499
3 Severe -3.00 to –3.99 -1.50 to -1.99 500-699
4 Extreme ≤ -4.00 ≤ -2.00 ≥ 700
South Carolina Drought Stages
Anticipating future drought indices
• Resample from climatology• Incorporate long-lead forecasts
Using Climatology (“equal chances”)
1/9 1/9 1/9
1/9 1/9 1/9
1/9 1/9 1/9
AboveNormalBelow
Temperature
Above
Normal
Below
Pre
cip
itatio
n
1934,1943,1960,1965,1975,1980,1993,1998
1944,1951,1952,
1964,1979,1983,
2003
1946,1948,1963,1973,1976,1977,1990,1997
1940,1942,1958,1962,1971,1984,1996,2001
1950,1954,1959,
1970,1972,1978,
1992,1994,2002
1935,1936,1938,1945,1953,1961,1968,1974,1997,2000
1931,1932,1933,1937,1941,1947,1969,1987,1999
1939,1949,1956,
1957,1966,1981,
1986,1988
1955,1967,1982,1985,1989,1995
AboveNormalBelow
Temperature
Above
Normal
Below
Pre
cip
itatio
n
1934,1943,1960,1965,1975,1980,1993,1998
1944,1951,1952,
1964,1979,1983,
2003
1946,1948,1963,1973,1976,1977,1990,1997
1940,1942,1958,1962,1971,1984,1996,2001
1950,1954,1959,
1970,1972,1978,
1992,1994,2002
1935,1936,1938,1945,1953,1961,1968,1974,1997,2000
1931,1932,1933,1937,1941,1947,1969,1987,1999
1939,1949,1956,
1957,1966,1981,
1986,1988
1955,1967,1982,1985,1989,1995
AboveNormalBelow
Temperature
Above
Normal
Below
Pre
cip
itatio
n
May 2002 drought prediction(made on January 1, 2002)
“El Nino Projections”(made 1 June 2002)
“El Nino Projections”
Final Thoughts• Seasonal temperature and precipitation
forecasts can be used for “secondary products” that address particular concerns and awareness– Risk aversion, past experience
• Since interannual variability swamps marginal probability shifts, exploit the historical climate record
• Purveyors need regional-scale appreciation for user knowledge base and requirements
Community Water Systems
• Provide water to at least 25 people or 15 service connections year round (EPA)
• Variety of water sizes, water sources
• Risk aversion: reliability/resilience built into management and systems
• Other management criteria: profitability, competitiveness, politically influenced
Drought Stage
(SC Drought Response
Committee)
Palmer Drought Severity Index
(PDSI)
Standardized Precipitation Index (SPI)
Keetch-Byram Index
1 Incipient -0.50 to -1.49 0 to -0.99 300 to 399
2 Moderate -1.50 to -2.99 -1.00 to -1.49 400-499
3 Severe -3.00 to –3.99 -1.50 to -1.99 500-699
4 Extreme ≤ -4.00 ≤ -2.00 ≥ 700
July Mean TemperatureGreenwood SC, 1895-2000
July Mean Temperature (°F)
70 72 74 76 78 80 82 84
July PrecipitationGreenwood SC, 1895-2000
July Precipitation (inches)
0 2 4 6 8 10 12
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