Drought of 1999-2002
So, how bad was the drought? Of course, depending on whom you talk to,
what element of drought you are talking about, or where you live, the drought
had varying effects on the people of
For instance, regarding stream flow, the central
section of the state bore the brunt of the drought…recording record low average
flows for several periods. In the north,
stream flows were not quite as low…until the very end of the drought, when a
record low flow was recorded at
Regarding groundwater, several of the USGS gauging
stations reported low to record low groundwater levels…especially in the most
populated regions. One item of note was
how the traditional tourist areas faired.
An interesting study of this issue was performed by Catherine Schmitt, a
candidate for a Master of Science degree in Ecology and Environmental Sciences
from The University of Maine.
Catherine’s Thesis is available at:
http://www.umaine.edu/waterresearch/research/pdfs/Schmitt%20thesis.pdf.
So again, how bad was the drought? Well, according to a report by the United
States Geological Survey (USGS), the drought of 1999-2002 was the worst
statewide drought in the past 50 years.
The measure used to determine this is what’s known as 7-day low flow. A 7-day low flow is a seven-day moving average of daily streamflow. This measure was done from January 1999 to September 2002, and was compared to average minimums, means, and maximums for the period of record at several long term (37 to 98 year) USGS stream- flow-gaging stations. The recurrence interval (a measure of how common a hydrologic condition is) was figured for each year of the drought.
The recurrence interval
of the 7-day low flow is a statistic commonly used to measure drought
severity. For example, a 7-day low flow
with a recurrence interval of 1 to 5 years would be a common condition, a
recurrence interval of 10 to 25 years would be more unusual, and a recurrence
interval of more than 50 years would be very unusual.
Recurrence intervals in
1999 showed streams in central Maine had unusual to very unusual low
flows. These low flows abated statewide
in 2000 to less than 10 years recurrance.
In 2001, low flows were extreme in central Maine and worsened northern
and western areas as well. In 2002,
central and western Maine recorded recurance levels greater than 100…that’s a
“hundred year drought”!
Overall, most of the
streams in the State experienced low flows with greater than 50-year recurrence
intervals at some time from 1999 to 2002.
See the USGS fact sheet
at http://water.usgs.gov/pubs/fs/2004/3021/
for more on the drought of 1999-2002.