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This digest is a publication of the
Senator George J. Mitchell Center for Environmental and
Watershed Research and the
Maine Drinking Water Program.
THE EFFECTS OF THE 2001-2002 DROUGHT ON MAINE DRINKING WATER
SUPPLIES
Summary
Maine's Drinking Water Supply
Public Water Supply and Drought
How Did the Drought Affect Public Water Supplies?
The Drought in Perspective
What Did the Affected Systems Have in Common?
What Steps Can Managers Take to Prepare for Drought?
Predicting Water Shortages During Future Droughts
References
Additional Information
Water
level declines in Adams Pond, supply for Boothbay Region Water
District, during the drought of 2001.
Photograph courtesy of J. Ziegra.
SUMMARY
Maine experienced the worst drought in over thirty years during 2001
and 2002. Water in streams, lakes, and groundwater dropped to
record-low levels.1 Thousands of private wells went dry,
and many public water systems were forced to implement water use
restrictions and tap into back-up supplies. The drought exposed
vulnerabilities in the state's public water supply, highlighting a
need for water use planning and management even in a "water-rich"
state like Maine.
Not all public surface water systems experienced problems, even in
areas where the drought was severe. Small, shallow lakes that were
already being pumped close to their safe yield were the most
vulnerable surface water supplies. These systems were located in the
coastal region and other areas where seasonal tourism and
residential development increase water demand, suggesting that
surface water systems with these characteristics are most likely to
be affected by future droughts.2
This document highlights the effects of the drought on Maine surface
water supplies and discusses ways that managers of vulnerable
systems can prepare for future drought and climate variability.
MAINE'S DRINKING WATER SUPPLY
Thanks to a history of glaciation and a humid climate, Maine has
abundant freshwater resources that supply clean drinking water. The
majority of Maine residents are served by public water supplies.
Rivers, lakes, and ponds supply 75 % of the volume of public water
withdrawals, providing drinking water to half a million people
(although there are more groundwater systems).
Drinking
water withdrawals, in million gallons per day (mgd).3
Public water systems are governed by the
Maine Drinking Water Program, which enforces the Safe Drinking Water
Act, and the Maine Public Utilities Commission, which regulates
community, non-transient public water systems. These systems are
defined as having 15 connections or serving 25 or more people
year-round.
PUBLIC WATER SUPPLY AND DROUGHT
A public water supplier needs adequate volume of water to
satisfy customer demand, maintain viability of the public water
system, and to provide for sanitary and fire protection needs.
Anything that affects water quality is a serious concern because
public health may be affected. In addition, changes in water quality
require adjustments in water treatment that can be costly for water
suppliers, and these costs are passed on to consumers.
Defining Drought
A public water supplier is concerned with two aspects of drought.
The first is the physical effect on water quantity and water quality
(supply). The second is how the drought affects consumers (demand).
A drinking water system will be affected by drought when decreasing
supply intersects increasing demand. For the purposes of this
assessment, drought is defined as a deficit of precipitation
sufficient to create stress on and competition for otherwise
adequate drinking water supplies.
HOW DID THE DROUGHT AFFECT PUBLIC WATER SUPPLIES?
A total of 53 public water supplies were affected by the
drought: 45 of approximately 400 community groundwater systems and
eight of 68 surface water systems. While more groundwater systems
were affected, 70% of surface water systems reported below normal
water levels in the summer of 2001.
Number
of affected systems by county
THE DROUGHT IN PERSPECTIVE
Although New England is considered to be "water-rich," Maine has
experienced several significant drought periods, the most recent in
2001, the driest year since records began in 1895. The severity of
the drought varied across the state, with northern Maine
experiencing the driest conditions. Lakes, streams, and groundwater
were at record low levels.1
Public
water supplies affected by the 2001-2002 drought, based on a survey
of surface water systems and reports to the Maine Drinking Water
Program and Public Utilities Commission. A system was considered
affected by the drought if: 1) water quantity was reduced enough for
the system to impose voluntary or mandatory conservation; 2) the
system manager utilized or explored additional or alternative
supplies; and/or 3) the manager expressed concern about the
drought's effects on water quantity or quality. Squares represent
surface water systems;
circles are groundwater systems.
Map created by S. Nelson based on data from Maine Office of GIS.
WHAT DID THE AFFECTED SYSTEMS HAVE IN COMMON?
How a particular water supply responds to drought will depend on
its size and watershed characteristics, and the relative
contributions of precipitation, surface runoff, and groundwater to
the overall water budget. Water levels in 2001 were below normal in
the majority of public water supply lakes and streams, in some cases
at record low levels. Yet only eight surface water systems were
considered "affected," meaning they had problems as a result of
decreased water volumes. Climate and hydrologic conditions alone
were not enough to drive a system to implement water use
restrictions.
Ratios of water use to safe yield for affected (red) and
unaffected (white) surface water supplies. A ratio above the
threshold of one suggests vulnerability to drought.
The response of water supplies is strongly influenced by the timing
of drought relative to the seasonal demand patterns of a specific
system. A closer look at the affected systems revealed that they
operate close to their safe yield during times of high demand, even
in a non-drought year. (Safe yield is the maximum quantity of water
that can be withdrawn during an extended dry period. The more often
a system pumps over the safe yield, the greater the risk of a water
shortage.) During the summer of 2001, drought conditions and
increased seasonal demand combined to push vulnerable systems "over
the edge", forcing them to implement water use restrictions.
Predicted population increases for coastal (blue) and inland
(brown) counties, 1990-2015.4
Drought conditions were mildest along
the coast, yet the majority of public water systems affected by the
drought were located in coastal counties. Population increases,
tourism, seasonal housing pressure and accompanying land use changes
increase the demand for water in coastal areas, where freshwater
supplies are limited. Over six million people visit the coast each
year, and future population and development increases are predicted
to be greater for coastal counties. Conflicts over water use are not
likely to subside in the near future.
WHAT STEPS CAN MANAGERS TAKE TO PREPARE FOR DROUGHT?
The 2001-2002 drought revealed that small water supplies in
populated coastal areas are most at risk for water shortages.
Because drought occurs infrequently in Maine, there is little
institutional memory among water managers. Lessons learned from
dealing with the 2001-02 drought can be used to make recommendations
for future drought preparedness.
1. Enforcing Water Use Restrictions
Four surface water systems implemented voluntary conservation
measures and one system imposed mandatory restrictions in 2001. The
most common strategy was to target the large users of water while
asking all customers for voluntary conservation via newspapers or
direct mailings. This approach was successful for all of the systems
except one. Most managers cited good cooperation with towns and
customers in reducing water demand. Cooperation coupled with the end
of the summer tourist season (not the end of the drought) eased the
pressure on systems so they could avoid mandatory restrictions.
Successful water conservation efforts involve everyone in a
community, from seasonal visitors to summer homeowners to local
businesses. Regular communication with water users develops
relationships that will prove beneficial for public water system
managers in the event of a drought.
2. Securing back-up supplies
Minimizing system leaks, developing watershed management plans,
coordinating with large water users, and metering water usage are
all important conservation tools. Yet balancing supply and demand
with back-up sources remains the best insurance against drought
problems. Surface water systems affected by the 2001-2002 drought
were more reliant on supplemental or alternative water supplies.
With increases in seasonal demand related to residential and tourism
development growth, managers will look farther afield for additional
supplies at the same time that environmental or health regulations
limit the availability of suitable water sources.5
3. Monitoring
The point when managers implemented conservation measures in 2001
might coincide with parameters which could serve as threshold or
action levels when planning for drought. Dry conditions (as measured
by precipitation, water levels, streamflows, and drought indices)
had been building for five or more months before water restrictions
were implemented, and yet the worst of the drought did not occur
until later.
The affected systems implemented conservation when water withdrawals
approached or reached the estimated safe yield. Monthly water usage
as a percentage of safe yield can be used to predict whether or not
a system has reached a point of intersecting supply and demand and
will begin to experience drought stress. In general, systems that
were affected by the drought were withdrawing volumes close to or
exceeding their safe yield prior to the drought.
Monthly water usage as a percentage of safe yield for affected
(red) and unaffected (gray) surface water supplies, 2001-2002. Water
use above the threshold is a characteristic of drought-affected
systems.
PREDICTING WATER SHORTAGES DURING FUTURE DROUGHTS
The 2001-2002 drought revealed that conflicts over water use are
likely to be greatest in areas served by small surface water systems
where seasonal demand exceeds available supply. Water systems in
coastal Maine, where predicted increases in residential development
and tourism will raise the demand for water, are most likely to
encounter difficulties in the uncertain climate of the future.
Preserving the integrity of ecosystems that supply drinking water
will help to protect public water systems from the effects of a
variable climate. Current efforts in source water protection, such
as acquiring and protecting undeveloped land in the watershed,
improving security, and enhancing system flexibility, recognize that
drinking water supplies are parts of larger watersheds. Future water
use management that views drinking water supplies as aquatic
ecosystems requires integration with other environmental and
planning strategies.
A dock extends on dry ground in Ambejejus Lake during the drought
of 2001.
REFERENCES
- Lombard, P.J. 2004. Drought conditions in Maine, 1999-2002: A
Historical Perspective. U.S. Geological Survey Water-Resources
Investigations Report 03-4310.
- Schmitt, C. 2003. The effects of the 2001-2002 drought on
Maine water supplies. M.S. Thesis. University of Maine, Orono, ME.
- Hutson, S.S., N.L. Barber, J.F. Kenny, K.S. Linsey, D.S. Lumia,
and M.A. Maupin. 2004. Estimated Use of Water in the United States
in 2000. USGS Circular 1268.
http://water.usgs.gov/pubs/circ/2004/circ1268
- Maine State Planning Office. 2002. Population forecasts for
Maine counties.
http://www.state.me.us/spo/economics/economics/forecasts.php
- Schmitt, C., J.L. McNelly, and J.B. Storer. 2004. Surface
water supplies and the environmental permitting process: Is human
consumption being appropriately considered? Maine Water Utilities
Association Journal, October 2004.
SOURCES OF ADDITIONAL INFORMATION
Maine Drinking Water Program
Dept. of Health & Human Services
286 Water Street, Key Bank Building, 3rd Floor
Augusta, ME 04333-0011
tel: 207/287-6196
tty: 207/287-5550
fax: 207/287-4172
http://www.medwp.com
Senator George J. Mitchell Center
5710 Norman Smith Hall, Orono, ME 04469
tel: 207/581-3244
fx: 207/581-3320
email: umgmc@maine.edu
Prepared by: Catherine Schmitt
January 2005
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