South Carolina Drought Forecasting

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South Carolina Drought Forecasting

• Greg Carbone and Kirstin Dow
• Department of Geography
• University of South Carolina

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• Outline
• Community water systems managers in South
  Carolina
• Resampling methodology applied to drought
  forecasting
• Sample products

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Investigating CWS Managers

• 3 Focus groups
• 4 meetings with key informants
• Survey results from 269 managers (52)

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5 - Day Forecasts
Confidence in
3-Month Forecasts
Percentage
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Survey Questions Included in Use of Forecasts
for Planning
Percentage of Yes responses SC PA
Plan 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
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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

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South Carolina Drought Stages
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
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Anticipating future drought indices

• Resample from climatology
• Incorporate long-lead forecasts

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Using Climatology (equal chances)
1/9 1/9 1/9
1/9 1/9 1/9
1/9 1/9 1/9
Above
Normal
Precipitation
Below
Above
Normal
Below
Temperature
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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
Above
Normal
Precipitation
Below
Above
Normal
Below
Temperature
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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
Above
Normal
Precipitation
Below
Above
Normal
Below
Temperature
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May 2002 drought prediction (made on January 1,
2002)
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El Nino Projections (made 1 June 2002)
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El Nino Projections
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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

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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

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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
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