The lack of rain in May led to wilted and stunted plants in this Chestnut Hill garden. Credit: Brian Rademaekers.
This May was an extremely dry one for Philadelphia, with the city recording just .59 inches of rain before a sizeable downpour last week. The rain that fell May 27 was by far the heaviest of the month, more than doubling the total. Still, rain totals for the month were below normal by 2.51 inches. As Inquirer weather columnist Tony Wood pointed out, before that rain, we were on pace for the driest start to the year since 1986 and the 14th driest May since records dating to 1872.
Other local news reports have expressed concern from area farmers, like Bucks County’s Shang-Ri-La Sod Farm, which irrigated during May for the first time in 48 years.
Here at Philadelphia Water, we’ve been getting questions from residents concerned about the lack of rain. While the situation is far from ideal and river flows were noticeably low in May, there are some bright spots. For one thing, we are nowhere near the sort of lows seen during the record year of 1965, which came at the tail end of a period that has been called “Philadelphia’s Dustbowl.” Between 1963-65, we missed out on over 40 inches–that’s an entire year’s worth–of precipitation.
Chris Crockett, deputy commissioner of planning and environmental services with Philadelphia Water, says the department is keeping an eye on water levels and that a few strong rains, like the May 27 downpour and the heavy rain that marked the first few hours of June, could straighten out the imbalances we’re seeing from the dry start to 2015.
“I’d say we are looking more like 1999 and 2002 than 1965 at this point,” says Crockett.
The other good news, Crockett says, is that reservoir storage in New York City is around 97 percent, and lower basin reservoirs like Beltzville and Blue Marsh are at 100 percent storage. If our local flows get too low, those reservoirs are required to release more water and help boost our supply.
Talking about drought concerns on a day when we’re getting flash flood warnings from the National Weather Service might seem counterintuitive, but the two worries aren’t entirely unrelated.
“The Schuylkill River and our local streams are what you call ‘stressed,’” says Crockett. “They have too much runoff when it rains and not enough base flow (groundwater from non-wastewater sources) when it hasn’t rained. They will drop in flow very quickly without rain over relatively short periods of time, but if it rains they are back to normal or flood very quickly.”
Right now, the Pennsylvania Dept. of Environmental Protection has no plans to issue drought warnings, in large part because they’re monitoring many factors beyond the low river flows and parched garden beds that sparked concern among residents in May.
“The real indicator of drought and drought risk are the groundwater levels, precipitation, stream flows, and reservoir storage, which would suggest a prolonged impact on the overall flow for a period of time that would extend beyond the next rain,” says Crockett. “It’s when many things get low that a few good rains won’t alleviate drought worries.”
The human body, he says, can provide a good metaphor.
“Think of it like your blood pressure. It goes down and up over the course of the day, and you can have it higher when you are in pain or sick for a period of time, or even drop when you stand up too quickly, but when something serious happens and you lose blood and it can’t come back up without help, then you have big problems,” says Crockett. “The same goes for rivers.”
Weather forecasters are calling for a fairly wet week to kick off June*, and experts at Philadelphia Water are keeping a close eye on water levels and other indicators.
“We’re continuing to watch the situation, and if anything changes we will share with everyone,” says Crockett.
*UPDATE: The 24-hour period marking June 1 smashed the precipitation record set in 1881, with more rain falling yesterday alone than was recorded at the Philadelphia International Airport weather station during the entire month of May. Philly.com has more on the stunningly wet start to June here. Please be careful and heed any flood warnings.
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