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 Forecasts3-Month Forecasts Percentage Confidence in…

Survey Questions Included in Use of Forecasts for Planning Percentage of “Yes” responsesSCPA Plan future water storage needs for finished water? Plan expanded distribution capability? Plan when to bring new water supplies on line? Adjust existing reservoir levels or back-up storage? Anticipate inventory supply needs or guide purchasing decisions? Schedule personnel, maintenance, or construction? Schedule additional testing for water quality? Help make budget projections? Justify increased infrastructure investments? Start a public information campaign to conserve water?

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 to to Moderate-1.50 to to Severe-3.00 to – to 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 AboveNormalBelow Temperature AboveAbove NormalNormal BelowBelow Precipitation

1934,1943,1960, 1965,1975,1980, 1993, ,1951,1952, 1964,1979,1983, ,1948,1963, 1973,1976,1977, 1990, ,1942,1958, 1962,1971,1984, 1996, ,1954,1959, 1970,1972,1978, 1992,1994, ,1936,1938, 1945,1953,1961, 1968,1974,1997, ,1932,1933, 1937,1941,1947, 1969,1987, ,1949,1956, 1957,1966,1981, 1986, ,1967,1982, 1985,1989,1995 AboveNormalBelow Temperature AboveAbove NormalNormal BelowBelow Precipitation

1934,1943,1960, 1965,1975,1980, 1993, ,1951,1952, 1964,1979,1983, ,1948,1963, 1973,1976,1977, 1990, ,1942,1958, 1962,1971,1984, 1996, ,1954,1959, 1970,1972,1978, 1992,1994, ,1936,1938, 1945,1953,1961, 1968,1974,1997, ,1932,1933, 1937,1941,1947, 1969,1987, ,1949,1956, 1957,1966,1981, 1986, ,1967,1982, 1985,1989,1995 AboveNormalBelow Temperature AboveAbove NormalNormal BelowBelow Precipitation

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 to to Moderate-1.50 to to Severe-3.00 to – to Extreme≤ -4.00≤ -2.00≥ 700