There is a close relationship between our water resources and the surrounding land. How land is used whether it is forested, used for agriculture, or developed with buildings and roads is a critical factor in determining the quality and quantity of groundwater and surface water. Forests provide remarkable benefits, helping to ensure clean water in sufficient quantities for aquatic habitat, safe drinking water, and recreational opportunities.
Forest vegetation occurs in several layers trees, shrubs, and smaller plants. This vegetation provides a tremendous amount of surface area that can collect water during storms, much more than a farm field or developed area. During storms, water adheres to leaves, twigs, and branches, intercepting as much as 25 percent of total rainfall in a dense forest. Rather than flowing into streams and rivers where it would increase flooding, much of this water returns to the atmosphere by evaporation (Figure 1).
In addition to the water intercepted by vegetation, rainfall also collects and forms puddles in depressions in the ground. Forests generally have a greater capacity to store water in this way than agricultural or developed areas because of their irregular ground surface. This water can evaporate or filter into the soil to recharge underground aquifers. These aquifers provide much of our drinking water and also recharge rivers, streams, wetlands, and lakes during dry periods.
Conversely, the roads, parking lots, and rooftops associated with development do not store rainfall, resulting in concentrated flows that are channeled and quickly discharged to rivers and streams. Loss of forest land to development contributes to flooding by increasing the amount of water that flows directly to streams and rivers during storms.
The thick vegetation in many of Vermonts forests helps prevent erosion. Ground vegetation, litter (leaves and twigs), and plant roots protect the soil from erosion during periods of heavy rainfall, keeping sediment out of lakes and rivers. Vegetation also stabilizes streambanks and shorelines.
Not only is the volume of run-off from developed land vastly greater than run-off from forest land, run-off in urban or suburban settings is often turbid and laden with pesticides from lawns and metals, gasoline, and solvents from vehicles. On agricultural lands, run-off often carries sediment, fertilizer, and pesticides. These pollutants are rarely found in run-off in forested areas. In addition, forested buffers along streams and lakes filter pollutants from run-off before it enters surface waters and jeopardizes water quality.
Development converts forests to buildings, roads, parking lots, and lawns, increasing the possibility of flooding and reducing the recharge of groundwater. Removing too many trees, especially in high-elevation watersheds, can change a streams hydrology and result in higher flood flows, movement of stream channels, and excessive erosion. Logging too close to surface waters or skidding across streams can deposit sediment that degrades habitat for plants and animals that live in our waters.
In Vermont, a cooperative agreement between the Vermont Forest Products Association, the Department of Forests, Parks and Recreation, and the Agency of Natural Resources Enforcement Division is helping prevent negative logging impacts on water quality. Since 1987, this agreement has provided training and technical assistance for hundreds of loggers and foresters. Assistance is provided through a technical team approach involving volunteers from the Forests Products Association and Agency personnel. More than 500 field visits have been made to monitor and ensure proper application of water quality protection measures. When necessary, enforcement actions are taken.
Fortunately, a growing number of forest practitioners in Vermont adhere to the states Acceptable Management Practices for Maintaining Water Quality on Logging Jobs in Vermont, an important means of keeping stream protection practices in place.
Land Use and Drinking Water
Historically, Vermonters have benefitted from an abundance of high-quality drinking water. Protection of this resource is becoming more difficult, however, as competing land uses threaten both its quantity and quality. Protection of this precious resource is most effective through a pollution prevention approach, such as a source protection plan (SPP).
An SPP is a land management tool that contains specific information regarding a water system. Drinking water sources are identified and the corresponding recharge area or source protection area is mapped or delineated. (A recharge area is an area into which water naturally flows or is pumped to serve as a drinking water supply; a source protection area is a recharge area with an emphasis on limiting certain types of land uses which could contaminate the water supply.) For systems that attain their drinking water from lakes, reservoirs, or rivers, understanding the character of the watershed is important. Drinking water systems served by groundwater sources should identify the nature of the aquifer. Both surface water and groundwater systems should pay particular attention to soils, slope, hydrology, and land use.
Concerns about how land is used within the source protection area should focus on activities which are potential sources of contamination, such as septic systems and fuel tanks. SPPs provide land use management tools which reduce the threats of contamination and foster drinking water protection by mapping the recharge area of a water source, recommending measures to control potential sources of contamination, and identifying alternative drinking water sources in the event of contamination.
For more permanent drinking water protection, the nature of land use and land ownership need to be taken into account. Purchase of the source protection area an be a viable approach for protecting drinking water. Although acquisition is a more costly approach for protecting a drinking water supply, the expense can be reduced by taking advantage of the Vermont Drinking Water State Revolving Fund. Source protection funds can provide low-interest loans to municipalities for purchasing land or development rights. Funding is provided on a priority basis, and water systems must have a delineated source protection area and source protection plan to be eligible. Currently, more than 300 water systems (about half of our schools and public community water systems) have SPPs in place meaning theyre eligible to seek revolving loan funds to help buy and conserve land adjacent to their water sources.
Sustaining safe drinking water is an expensive proposition but may save money in the long-term. If contamination occurs, cleanup costs follow. A knowledge of land use, geology, and the hydrologic features of a watershed or aquifer provide the scientific basis needed to protect drinking water supplies effectively. With sound information, water suppliers can continue to deliver high-quality drinking water.
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