Introduction

Clean water is essential to Illinois' economy and quality of life.  Our forests play a vital role in purifying and maintaining clean lakes, rivers, streams, and groundwater.

Maintaining or restoring forest cover protects the site, preserves and improves the quality and integrity of stream waters flowing within and out of the area.  Forested lands are effective in maintaining erosional processes to normal, geological rates.  Forests are also effective in shading streams, thereby maintaining relatively cool waters in our forested streams.  Forests tend to act as a sink and take up and recycle nutrients.  Trees, associated vegetation, and the litter-covered forest floor absorbs the impact of rainfall and allows the rain to infiltrate without surface flow.  Sediments and debris carried in from other areas are usually trapped and held by the forest vegetation and leaf litter.

Forestry Best Management Practices (BMPs) are practices that protect our forest, soil, and water resources while allowing appropriate use of the resources.  The following voluntary guidelines for BMP's will help to ensure that Illinois' forested sites are not degraded, that the waters associated with these forests are of the highest quality compatible with natural processes, and that our forest resources are wisely utilized.  The Illinois Department of Natural Resources strongly encourages their use by everyone involved with growing, managing, and harvesting trees.

The actual cutting of trees has little impact on site degradation or stream water quality.  However, those activities associated with moving the product from the stump to the mill have the potential for causing substantial site and water quality degradation problems.  In general, the most serious problems involve erosion, the transport of the eroded material, and the deposition of this material.  Since site disturbance and site and water quality degradation may be directly related to erosion and sedimentation problems, the majority of the BMP's will focus on measures to minimize site disturbance.  The logger will benefit with lower costs through more efficient operations; the forest owner benefits by reducing the need for site reconditioning; and society benefits from less degradation of soil and water on the harvested area.
This manual can help guide you when making decisions about management activities on your land.  You can get professional advice on BMPs and all forest management activities from natural resource professionals.  See Appendix A.


Pollutant Types and Impacts from Forest Activities

Nonpoint source pollution occurs when rain and snowmelt runoff picks up and carries pollutants into streams and groundwater.  Soil, including the organic debris and nutrients in it, becomes a nonpoint source pollutant when it is exposed and unprotected.  Nationwide, three to nine percent of nonpoint source solution comes from forestry activities.  Because Illinois is relatively flat, only about three percent of the states' nonpoint source pollution comes from forestry practices.  While three percent sounds small, localized nonpoint source pollution can be significant, particularly in Illinois where many of our highest quality streams flow through forested watersheds.

Forest management activities can generate the following forms of nonpoint source pollution:

Sediment.  Forest floor vegetation and (organic matter) protect the soil from the erosive action of falling raindrops and runoff.  Forest activities, such as road building, can remove this protection. This can lead to erosion of the soil and movement of sediment.  When sediment is carried away in runoff and deposited elsewhere, sedimentation occurs.  Without using appropriate BMPs on exposed and sloping land, the soil may erode and wash into a body of water.  Sediment is the primary pollutant associated with forest activities, especially at stream crossings for forest roads and skid trails.

Sedimentation is a naturally occurring process.  However, human activities can speed it up.  The result can be large amounts of sediment accumulating in lakes, streams, and wetlands that speed up the aging of lakes and bury fish spawning grounds and impact habitat for fish, mussels, and other aquatic organisms.

Accumulating sediment also constricts naturally flowing channels, leading to increased stream bank erosion and possible flooding.  Suspended sediment clouds the water, making it difficult or impossible for sight-feeding fish to locate their prey.  It can also clog the gills of fish and have detrimental effects on aquatic life, literally suffocating them.  High sediment loads make it difficult for beneficial aquatic plants to grow, and silt deposited on a lake or stream bed can smother fish eggs and invertebrates important in the aquatic food chain.

Organic Debris.  Leaves and large woody debris that naturally fall into streams can benefit aquatic ecosystems.  Fallen trees 12" and larger with the root ball attached serve as prime fish habitat.  However, too much organic debris deposited in a short time can harm water quality.  This can occur during logging when tree tops and branches fall or wash into streams.  Too much decomposing matter in streams decreases dissolved oxygen in the water, which fish need to thrive and reproduce.  In extreme cases, logging waste can trap sediments and eventually interrupt streamflow and the movement of fish.

Nutrients.  Nutrients such as nitrogen and phosphorus exist naturally in forest soil and enter waterbodies if the soil erodes into water.  Also, if fertilizers are used in forest management, they can wash into runoff.  Excessive amounts of nutrients may cause algal blooms in lakes and streams, which can reduce levels of dissolved oxygen below what fish and other aquatic species need to survive.

Temperature.  Some sunlight filtering through trees is healthy for many streams.  It can promote plant growth (food) in the water and foster healthy ground vegetation along shorelines.  However, when trees and the shade they provide are removed along most small streams, peak mid-summer water temperatures climb as a result of increased sunlight.  This can accelerate harmful algae growth, reduce dissolved oxygen, and eliminate sensitive species of fish and other organisms.

Chemicals.  Fuel, oil, and coolants used in harvesting and road-building equipment must be handled carefully to avoid water pollution.  Pesticides (herbicides, insecticides, and fungicides) help control forest pests and undesirable plant species. But when applied improperly, pesticides can be toxic to aquatic organisms.  Read label directions before using these products.

Streamflow.  If timber harvesting equipment compacts forest soil, water infiltration into the soil is reduced and surface runoff into streams increases.  This also reduces water percolation through the soil to recharge groundwater.  Groundwater provides cool, clean water to lakes and streams, maintaining steady streamflows and lake levels throughout the summer.

Our purpose in this manual is to help you protect Illinois' water quality.  The Illinois Department of Natural Resources also encourages you to protect other natural resources on your forest land: wildlife, wetlands, endangered plants and animals, and timber.  Recreational opportunities and scenic beauty are also natural resources worthy of protection.  For information on financial incentive programs to manage and protect these resources, see Appendix A:  Sources of Assistance.