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Maine's Water Resources
Overview
- Precipitation: Water that falls to the Earth’s surface from the atmosphere as rain, sleet, or snow. Average annual precipitation is 46 inches, or 28 trillion gallons.
- Maine Cooperative Snow Survey | Maine Geological Survey
- NOAA Meteorological Station Data: NOAA NCEI U.S. Climate Normals Quick Access
- Evapotranspiration: About 35% of precipitation, or 9.9 trillion gallons annually, is transferred from the land to the atmosphere by evaporation and plant transpiration.
- Run-off: About 50% of precipitation, 14.1 trillion gallons annually, runs-off the landscape to surface waters.
- Infiltration to groundwater: About 15% of precipitation, 4.2 trillion gallons annually, infiltrates the ground and recharges groundwater aquifers.
- Drought: Prolonged period of abnormally low rainfall, corresponding with dry soil, low groundwater levels, and low stream/lake levels.
- Drought monitor Maine | U.S. Drought Monitor
- Drought Task Force | Maine Emergency Management Agency
- Dry Well Survey | Maine Drought Task Force
Surface Water
Surface water refers to all water that is on the Earth’s surface, including rivers/streams, lakes, and wetlands.
- USGS Stream Data for Maine
- Maine Dept of Inland Fisheries and Wildlife Lake Survey Maps
- Maine Bureau of Parks and Lands Ice Out Dates
- Lake Stewards of Maine
- KnowledgeBase - Data sets for the Gulf of Maine Watershed
- USFWS Wetlands Mapper
- MGS publications
- Why is Sebago Lake so deep? by Robert A. Johnston
- Summary of Sebago Lake Shoreline Change Studies, 1990-1997 by Robert A. Johnston and Martha M. Mixon
- Songo Beach, Sebago Lake State Park by Robert A. Johnston
- Bottom Sediments of Sebago Lake by Robert A. Johnston
- Engineered Solutions to Stream Bank Erosion: A Case Study by Daniel B. Locke
- Measurement of Stream Discharge Using Weirs and Flumes by Daniel B. Locke
- Sandy River Bank Erosion, Avon, Maine - 2nd Update by Daniel B. Locke
- The Sunkhaze Peatland Complex by Daniel B. Locke
- Shoreline classification of Sebago Lake by Robert A. Johnston
Groundwater and Wells
Virtual Tour
- Our virtual tour is a series of photos which portray issues related to water supplies, wells, and environmental issues.
Field Localities
- Originally published on the web as the Survey's "Site of the Month," these sites include more detailed descriptions of geologic features, field trips, and localities.
Frequently Asked Questions
Fact Sheets
- Alkalinity: An Important Parameter in Assessing Water Chemistry
- Anatomy of a drilled bedrock well
- Corrosive Water – Facts, Common Questions, and Resources (PDF 0.1MB)
- Groundwater, Wells and the Summer of 1999
- Maine Springs
- Maine's Dug Wells
- Sand and gravel aquifer maps - A work in progress
- Sand and gravel aquifers
- Seismic refraction profiling: An important tool used in mapping sand and gravel aquifers
- Water resources in Maine
- Water well information
Geologic Maps and Digital Data
- Significant Sand and Gravel Aquifer Maps Online
- Bedrock Ground-Water Resources Basic Data Maps Online
- Water Well Database - Downloadable database of located water wells.
Related Reading
- Ground Water Handbook for the State of Maine
- Bibliography of Maine Geology - For those interested in more in-depth research, the Bibliography of Maine Geology contains more than 12,000 references related to Maine geology. The Bibliography is part of the Maps and Publications Search. The search results displayed will have links to online Maine Geological Survey maps and publications.
Water Resources Planning Committee
Groundwater Regulatory Issues
Residential wells
- Maine Department of Health and Human Services
- Private wells - information for homeowners - well types, hydrogeology, water treatments, water and well facts, arsenic facts and treatment, links for private wells, water testing
- Water testing
- National Groundwater Association
- Wellowner.org - information relating to private water well systems and groundwater
- Water Systems Council
- wellcare Information Sheets - fact sheets about wells, well components, water testing, and contamination
Groundwater
- Maine Municipal Planning Assistance Program
- Maine Emergency Management Agency
- U.S. Geological Survey
Ground-Water Contamination
- Groundwater | Maine Department of Environmental Protection
- Well water quality | Maine Department of Health and Human Services
- Citizen's Guide to Groundwater Protection (PDF) | U.S. Environmental Protection Agency
Natural Water Contaminants
- Radon
- Maine Radon | Maine Department of Health and Human Services
- Radon testing | Maine Health and Environmental Testing Laboratory
- The Geology of Radon | U.S. Geological Survey
- Indoor Air - Radon (Rn) | U.S. Environmental Protection Agency
- Radon-Specific Publications and Resources | U.S. Environmental Protection Agency
- Arsenic
- Arsenic in Drinking Water and Treatment Technologies | Maine Department of Health and Human Services
- Have you tested your well water for arsenic? (pdf) | Maine Department of Health and Human Services
- Arsenic in Drinking Water | U.S. Environmental Protection Agency
- Arsenic in Groundwater
- Uranium
- Uranium in my well water: Now what do I do? (pdf) | Maine Department of Health and Human Services
Last updated on September 29, 2025