Water and Forests
Water in the forest is often among the landowner's chief concerns, especially stream, ponds, and wetlands, and the wildlife that thrive in these areas. The following section describes some considerations that landowners may want to take into account. For information specific to your property, call the Maine Forest Service. Landowners should also take a look at the section on Laws and Regulations to see which might apply to their situation.
Forest areas in and around water bodies are complex systems, and provide habitat for a wide range of plants and animals. These forest areas and the waterbodies in them are the setting for different processes that provide food, water, shelter, breeding space, and other needs. "Water quality" refers to the characteristics of water in nature that support life. These include the natural chemical, physical, and biological aspects of streams, rivers, ponds, lakes, and non-forested wetlands. The chemical properties of water include things like pH, dissolved oxygen, nutrients, and the presence of chemical pollutants. The physical properties of water include such things as turbidity (how clear or cloudy the water is), and temperature. In addition, the physical characteristics and natural processes of water bodies that support life are important aspects of water quality. Examples include stable channels, the transport of nutrients, the volume and speed of the water, the streambed material, and sticks and logs that have fallen into streams naturally.
Forest streams, lakes, and wetlands typically have excellent water quality. Forestry operations that use Best Management Practices ("BMPs") can protect water quality. By preventing stream sedimentation, such operations can maintain streambed properties and clean water that allow fish - and the aquatic insects they depend on - to feed and spawn. Leaving trees that shade and provide leaf litter to water bodies limits changes in water temperature and chemical characteristics that could reduce the ability of some species to survive and reproduce. These are just the most commonly understood examples of how maintaining the properties of water in forests can protect the quality of aquatic habitats.
Water Movement in the Forest
Maine has a humid climate with thousands of lakes and ponds, large areas of forested and non-forested wetland, and thousands of miles of streams and rivers. All these forest waterbodies, and the areas that drain to them, are connected. Most of the water in the forest comes from rain or snowmelt which is either absorbed into the soil, flows over the ground, or enters stream channels, flowing downhill.
All these components are connected in a watershed, which includes all the land from which water drains to a given point. You can define a watershed for an entire lake, for a stream at a crossing site, or for a river where it reaches the ocean. Watersheds range in size from just a few acres (for a small stream), to thousands of acres (for a large river).
All land is part of some watershed. Understanding where water is coming from and draining to within the watershed will help you determine how much water flow to expect in the harvest area. This will help you locate roads and trails, and determine what types of BMPs will be needed. The amount of cutting or road construction at higher elevations in a watershed can affect the amount and timing of runoff at lower elevations, and may influence the BMPs needed to control water movement.
"Waterbodies" may include streams, rivers, lakes, ponds, and wetlands, as well as coastal areas. BMPs are recommended primarily for those areas where water is at or near the surface (streams, lakes, or wetlands), and where runoff can move directly into surface waterbodies. These waterbodies and related areas are defined and illustrated below.
Ephemeral Flow Areas: small drainage areas that flow into streams that have no defined, continuous channel. Examples are low-lying depressions or swales with an intact (or stabilized) forest floor. Soils in these areas may quickly become saturated during rainy periods, storms, or snowmelt. Surface water flows in these low areas over saturated soil without forming a channel. Water from ephemeral flow areas may carry sediment or other materials directly into streams. Ephemeral flow areas respond to soil and weather conditions, and are the immediate source of much of the water that enters small streams.
Streams are natural channels that:
- may flow year round or only part of the year,
- have a defined channel and banks,
- are relatively continuous and connected with larger surface waters, and
- have a streambed where flowing water has exposed the mineral bottom of soil, sand, gravel, ledge, or rock.
Forest streams in Maine vary widely in how much water they carry, how steep they are, the shape of the streambed or channel, how much area they drain, and when they flow.
Perennial streams usually flow year-round and range from small brooks to large rivers;
intermittent streams flow only a few months a year, and/or during wet seasons.
Wetlands are areas where soils are saturated or flooded a significant part of the year, and where water-loving plants are often found. Wetland soils usually have developed special characteristics, and often have a significant amount of water movement below the surface.
Forested wetlands are those that are dominated (or potentially dominated) by trees taller than 20 feet. Forested wetlands vary widely in their characteristics, often have relatively little water directly at the surface, have indistinct borders, and may require considerable expertise to identify. Forested wetlands are often managed for timber, with roads and trails crossing them.
Non-forested or open wetlands are not dominated by trees, though they may have some scattered trees, mostly less than 20 feet tall. They have water at or near the surface at least part of the year, and may have a more or less distinct border defined by the surrounding forest. The high water and organic content of wetland soils make them considerably weaker than upland soils and difficult to work in. Non-forested wetlands are not managed for timber, and should be crossed only when they cannot be avoided.
Normal High Water Mark: the place on the stream bank where the highest water levels typically occur, often during spring runoff. You can identify it from features like undercutting of the bank; a change in the type of vegetation; exposed roots that do not penetrate beyond a certain level; root scars; and water stains on stems, roots or other vegetation.
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How Harvesting Affects Water Quality
Forest harvests, especially road, trail, landing and drainage construction, can affect how water flows through an area or directly impact water quality by:
| Drainage system or structures: all the techniques used to get water off the road, trails, or landing. These can include the road crown, ditches, turnouts, cross-drainage culverts, water bars, etc. |
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- Reducing the soil's absorption of water. This can occur any time the forest floor is disturbed, removed, compacted, or otherwise damaged.
- Increasing soil erosion. When mineral soil is exposed, or fill is used, the opportunity for soil to be carried away by runoff is greatly increased.
- Diverting water flows. Roads and trails can block or intercept water moving over or through the soil. The more water that accumulates, the greater the chance that it will form a channel and start eroding soil. Sometimes logs or other debris fall into small streams and can block or alter the stream's flow, causing the stream to erode a new channel.
- Concentrating water flows. Roads, trails, and landings, and associated drainage structures can collect and funnel runoff, creating rills or gullies. In these situations, water erodes and transports exposed soil in its path.
- Reducing the benefits of stream-side vegetation. Harvesting may reduce shade on the water's surface, reduce natural woody debris, or eliminate leaf litter that is an important food source. Timber harvests that remove a significant percentage of the trees in a watershed can increase the amount of water moving through the soil into streams, though this effect is often temporary and limited to storm events or spring runoff.
Usually, it is impossible to avoid disturbing some soil or concentrating some flowing water during a harvest. The important point to remember is to avoid these disturbances as much as possible, and to use Best Management Practices (or BMPs) to prevent them from resulting in sedimentation or erosion.
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What Do Best Management Practices Do?
Forestry Best Management Practices, or BMPs, are designed to mimic or protect the natural functions of forests; they can: absorb runoff and soil nutrients, filter sediment, prevent large changes in water temperature, and contribute organic material to surface waters.
- BMPs minimize the risk of sediment and other pollutants getting into waterbodies. Sediment - soil, dirt, silt, sand, mud - is the primary type of pollution from forestry operations.
- BMPs maintain the natural flow of water in streams and wetlands. They avoid blockages, keep water flowing in its natural path, and prevent damage to the streambed and banks.
- BMPs protect shoreland vegetation. Some practices simply preserve enough of the forest so that it continues to function normally: shading the waterbody and stabilizing water temperatures, maintaining the soil's natural functions, and contributing organic matter that serves as habitat and a food source to aquatic plants and animals.
