Study Shows State Getting More Rain
Scientists at the University say the state is getting more rain.
David Miller, a professor of natural resources management and engineering, together with other researchers, has updated Connecticut’s rainfall statistics for the Department of Environmental Protection. The state uses the statistics on the frequency of storms in setting standards for the design of structures including storm drains, culverts, roads and bridges, he says.
“The statistics that were being used in the state were old, based on 30 years of rainfall records from before the 1940’s,” Miller says.
The statistics show the probability that more than a specific amount of precipitation will fall during any particular amount of time.
Miller conducted a statistical analysis of 100 years of rainfall data in the state, from 1896 to 1996. “We calculated what we call ‘return frequencies’ for certain size storms, which was our primary reason for conducting the study,” he says. “Culverts and gutters, anything that carries rainwater or storm water, are designed to withstand a certain size storm. For large structures it’s a ‘one in 100-year, 24-hour storm.’ That means there’s a one percent chance that it will happen in any year.”
Miller was surprised at what his study revealed. “The average rainfall is increasing,” he says. “It’s about 12 percent higher now than it was 100 years ago, and that’s a significant change. It means that when we have a given frequency storm, there will be more water in it than we previously expected. When we have a drought period, it’s not going to be as dry as previous droughts with the same frequency.”
Increased rainfall in the state has many implications. “Floods will be higher, culverts won’t be big enough, and roads might wash out,” he says. “All kinds of things can happen. We hope the data will be useful to environmental consultants and to researchers studying trends in precipitation.”
Miller notes that a “24-hour, 100-year storm” along the Connecticut coast would yield at least 9.2 inches of rainfall. Storrs would receive about 8 inches of precipitation.
He notes that global warming models predict that it should be getting wetter in the Northeast and drier in the Midwest. “One hundred years is a very short time on the climate scale,” he says. “But it is getting wetter, and we’ll have to deal with that in the future.”
The study also examined the probability of the number of consecutive dry days. These statistics will be useful to the recreation, sports, and green industries, and even the average person with weather concerns, he says: “So if you are planning a wedding in May, we can give you the odds of having good weekend weather.”
Other researchers involved in the project are UConn faculty members Glenn Warner, associate professor of natural resources management and engineering, and Fred Ogden, associate professor of civil and environmental engineering, and Arthur DeGaetano, director of the Northeast Regional Climate Center at Cornell University.
A written report, “Precipitation in Connecticut,” which includes maps, graphs, and tables of the rainfall statistics, is available as Special Report 38 on the Connecticut Institute of Water Resources website: http://www.ctiwr.uconn.edu.