Drought Management:
OVERVIEW
Rhode Island is a wet state. On average we receive 44.1 inches of rain per year. Our last prolonged period of drought was in the mid 1960's, though we have had multiple short-term drought phases such as the late summer of 1999.
Drought is a tricky thing to define as it means many things to many people. According to Webster's Dictionary, drought is "a long period of low rainfall"--but rainfall is not the only indicator or cause of drought. The National Drought Policy Commission defines drought as "a persistent and abnormal moisture deficiency having adverse impacts on vegetation, animals, or people." Predicting and defining drought is both science and art-there is no universally accepted method for stating that a region is in or out of a drought state. Most scientists and policy makers base their assessments on indicators of drought such as streamflow, groundwater levels, precipitation and indices created to assist in determining the severity of dry spells.
Rhode Island is in the process of formalizing a Drought Management Plan. According to the current draft, "this Plan is being developed as part of the response to the period of precipitation deficiency beginning in the spring and summer of 1999. In some areas of the state, cumulative deficits in precipitation reached 8-12 inches below normal over an 12-month period. Streamflows across much of the state routinely fell below the 25th percentile of their historical flows [that] summer (within the lowest 25 percent on record for the month) and a coupled with long periods of record, set record low streamflow levels. Ground water levels were also below normal throughout the summer over much of the state."
The following pages will look closely at four indicators selected by the RI Water Resources Board. A total of seven indicators have been tentatively selected for use in drought management, but this website focuses on only four. This is due to data availability for two indices and, for the third, because the indicator was determined to be not sufficiently representative of drought conditions. A timeframe of 10 years was selected in keeping with the overall theme of this website; also, some data was unavailable in electronic form and had to be entered by hand--10 years was determined to be an acceptable amount of torture. Where historical data underlying the various charts and graphs are available for periods extending beyond 10 years I have tried to include it in table form.
NEXT PAGE: Indicators
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The discovery, if there is one, is that the indicators themselves respond to conditions very differently. Any attempt to quantify drought in numeric terms may be doomed to fail--the art of drought management may be more important than the science.