The United States Geological Survey (USGS), the New Hampshire Department of Environmental Services (DES) and the New Hampshire Geological Survey at DES (NHGS) have completed a study to assess why ground water levels measured in wells constructed in bedrock aquifers declined by more than 13 feet on average from 1984 to 2006.
of the study indicate that there are multiple factors that are related to the
lowering of observed water levels in newly constructed wells in New Hampshire. “Over 50
percent of the citizens in New
Hampshire obtain their drinking water supply from
wells drilled in bedrock. Yet, the depth of water in bedrock aquifers has not
been adequately monitored in the State,” according to Brandon Kernen,
Hydrologist with DES.
of reported water levels, measured during well construction, was conducted as a
preliminary effort to assess bedrock water level trends across New Hampshire. “Land
development, water use and climate trends all can affect the availability of
ground water,” according to Brandon Kernen at DES. “The study was conducted
because observed average annual water levels in new wells have shown a steady
decline over the past two decades, and we need to identify the reasons for this
trend so that the State can make well-informed decisions about managing ground water.”
found that primary factors related to trends of deeper average water levels are
concurrent increases in overall well depths and the use of new well
construction practices,” according to Joseph Ayotte, hydrologist with the USGS.
“These changes may result from homeowners needing more water or from
improvements in drilling technology – allowing wells to be drilled deeper more
quickly and using longer casing to protect the well. The result of these
practices is that the amount of available water in wells has increased due
largely to the increased well depths.”
also found that wells located on hillsides or steep slopes, especially those
that are south-facing, are more likely to experience deeper water levels than
wells not in these areas. The reasons for these results are unclear. The study
also notes that a lack of information on changes in water use over time meant
that it was not possible to determine whether potential increased water demand
and use impacted water levels state-wide.
NHGS and DES have developed and are implementing a strategy to improve routine
monitoring of water levels in bedrock aquifers. Representative bedrock wells
throughout New Hampshire are being equipped with water-level monitoring devices
to measure current water-level trends, utilizing automated equipment on
long-term loan from other federal agencies and grants obtained from state and
federal agencies. The data will used to assess whether available ground water
supplies are being affected by changes in factors such as climate, land use or
water use. The data also should improve our understanding drought conditions
and of the timing and degree to which precipitation replenishes the drinking water
supplies of the majority of the residents in New Hampshire.
and data from existing ground water monitoring wells may be found on USGS’ New Hampshire Web site.
Investigating the Changing Ground Water Levels in N.H. Wells
January 13, 2011