Drink up: N.H. isn’t running out of water after all



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When state and federal officials recently looked at the history of water levels in New Hampshire wells, they found what appeared to be an alarming problem: In 2006, water in the average drilled well was 13 feet lower than it had been in 1984.That's a decline of about 7 inches a year, measured in almost 60,000 wells found in every part of the state.This leads to an obvious conclusion: New Hampshire is draining its underground aquifers dry. Obvious, but wrong."The water table isn't getting lower and lower ... despite how that seems," said Brandon Kernen of the state Department of Environmental Studies, who co-authored a report titled, "Preliminary Assessment of Trends in Static Water Levels in Bedrock Wells in New Hampshire, 1984 to 2007."The report analyzed data from the drilling of tens of thousands of water wells into bedrock at homes and businesses over two decades. It found that static water level - a measure of how far down you have to go in a well before getting to standing water - increased by an average of 13 feet during the period.Despite how that sounds, however, Kernen and co-author Joseph Ayotte of the U.S. Geological Survey said this doesn't mean groundwater levels have fallen 13 feet."It was pretty definitive: (The level) was lower over time," Kernen said. "Then the question became, why? Were lots of people using water? Is it that the growing season is increasing with the changing climate? Are people building houses on top of hills, which they used to not do ... so wells have to be deeper?"Technology, not less waterEventually, analysis indicated that the numbers actually reflect changes in well-drilling technology over the period, not changes in groundwater levels.For one thing, the authors said, wells can go down much farther than they used to, which means they regularly tap into deep aquifers that once would have been bypassed.For another, drillers line the upper portions of wells with more casing than they once did. This lining is encouraged or required because it can keep out surface contamination, but it has the side effect of sealing out some groundwater that would otherwise leak into the well.Combined, these factors seem to explain the apparent decline in water levels, Kernen and Ayotte said.They're confident partly because results from some monitoring wells installed in the last decade by large water users such as golf courses indicate that the groundwater table is in good shape.So, if the analysis of drilled wells doesn't say anything about groundwater levels, what good is it?The authors say it does cast some light on why certain wells do better than others and where new wells should be drilled, including the odd-sounding fact that wells on south-facing slopes are more likely to have problems than those on north-facing slopes.It also points to the way information may help planners deal with places that have a relatively high percentage of failed wells."This may help come up with guidelines for drilling, or locating wells," Kernen said.No long-term monitoringThe report was put together to answer a nagging question about the water supply."Over the years, well-drillers, laymen, people throw out comments like, 'New Hampshire is running out of water.' Yet, the state has very little dedicated monitoring of what long-term water level trends are," Kernen said.The only way to really know the state of hidden underground aquifers is to drill lots of wells in different conditions - in rural areas, amid development, near wetlands, atop hills - and keep track of their water level year in and year out.But New Hampshire has never paid the money needed to establish and maintain such a monitoring network. So Kernen and others decided to take a closer look at what New Hampshire does have: an extensive set of records filed by drilling companies each time they drill a new water well.Drilled wells collect water that oozes out of cracks in the bedrock, and can be anywhere from 100 to 1,000 feet deep. This is in contrast to traditional "dug wells," which are rarely deeper than 50 feet, and which collect water that oozes out of the sand and dirt above the bedrock.Drilled wells are more expensive than dug wells, but are less susceptible to surface contamination and usually have more dependable water flows.Virtually all new wells are drilled. They're almost everywhere, since more than half of all homes in New Hampshire get their water from private wells.Researchers had access to almost 60,000 well reports in digital form, meaning they're relatively easy to analyze in spreadsheet software, dating to 1984."It's actually a very nice data set," Ayotte said. "Not only does it cover a long time period, but these are by and large geo-located - we know where they are on the ground - so we can gather additional variables to look at. "The well-drilling community has gone to good efforts to provide the data that can help us."Lots of low-quality dataUnfortunately, the data lacks the main thing needed to monitor groundwater levels: results over time from the same location. Nobody went back and recorded water levels in wells after they were drilled.From planners' points of view, it was relatively low-quality data. Yet, there was enough of it that analysis could overcome the limitation.By plotting the depth of water in wells against the date it was drilled, they were able to show that the water depth in new wells has consistently fallen over time.Kernen is confident that this doesn't reflect falling aquifers largely because of a different set of data, from monitoring of businesses that remove large amounts of water (more than 57,600 gallons a day) from underground.Since 2000, the state has collected this information to ensure that major water users aren't hurting nearby wells or wetlands - in technical terms, are not "de-watering" the area.Kernen said the news from this monitoring is good: "We have not seen de-watering at those locations."Understanding the cause and effect of the well-drilling data took more analysis of variables in the reports filed by drilling companies. That led to the conclusions about well depth and use of casing.South-facing slopes It also points to other factors that might be involved, including the slope of the land.As Kernen explains it, south-facing slopes in the region are generally steeper than north-facing slopes because of the way the land was sculpted by glaciers as they retreated after the last ice age.This means that rainfall runs off south-facing slopes more quickly and is less likely to seep into the underground water table.Also, south-facing slopes have more plant life because of the extra sunlight, and plants remove a lot of water from underground.Those factors may explain why wells on or near south-facing slopes seem to have a longer way to go before they hit water.Their analysis also emphasized what's perhaps an obvious point: If you're on a hill, you're probably going to have to drill deeper to hit water.Finally, the report also shows something else: Old information can be useful, even if it doesn't meet all your needs."It's expensive to collect high-quality data, so if you can learn something from low-quality data, you're ahead of the game," Ayotte said. - DAVID BROOKS/THE TELEGRAPH

 

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