You are here

Water quality on forest lands

Status: 
Complete
Dates: 
February, 1993 to December, 2000

The Importance of Water Quality

The quality of water draining forested watersheds is typically the best in the nation.
The quality of water draining forested watersheds is typically the best in the nation.
No other resource serves as many purposes as water. It is widely used in industry, in electric energy production, in farming and ranching, and, of course, by households for drinking, washing, and gardening. Water is essential to the health of ecological systems, supports numerous forms of recreation, and provides important amenity values. In addition, water is valuable in flushing and treating wastes, both from contained sites such as industrial plants, commercial establishments, and houses, and from land areas such as lawns, farms, and forests.

Water is essential to the viability of forests, farms, pastures, and other land areas, but, as it runs off, water carries soil from the land. Excess soil reaching streams impairs fish habitat, accumulates in reservoirs and other water management facilities, and increases costs of water treatment. In addition, pesticides, nutrients, and other contaminants attached to soil particles often leave the site.

This research aims to summarize the state of knowledge regarding the effects of forest management on water quality and the value to society of maintaining high quality runoff from forest lands. The work includes detailed cataloging of effects of forest management on water quality based on experiments in more than 40 experimental forest areas in the United States and Canada. Economic costs and benefits of water-quality control was also explored.

Sources of Water Pollution

Pollutant concentrations at the reception point (such as a city water facility) are the result of many upstream management actions and natural events.
Pollutant concentrations at the reception point (such as a city water facility) are the result of many upstream management actions and natural events.
Stream water quality is a function of a variety of parameters, including temperature, sediment loads, inorganic chemistry, and toxic metals and organic compounds. Sources of water pollution are usually grouped into point and nonpoint categories. Point sources, which emit from pipes or canals, include municipal wastewater treatment plants and industrial facilities. Nonpoint sources, which are diffuse and difficult to monitor, include runoff from farms, pastures, forests, cities, and highways, as well as rural septic systems and landfills. Watershed management is, in large part, the management of nonpoint sources of water pollution.

The quality of water draining forested watersheds is typically the best in the nation; however, some forest management practices can seriously impair stream water quality. Forest management activities (e.g., timber harvesting, construction of forest roads) may substantially alter the quality of water draining forests, and are regulated as nonpoint sources of pollution. 

Important impacts of forest management activities on water quality have been documented, in some cases, for undesirable changes in stream temperature and concetnrations of dissolved oxygen, nitrage-N, and suspended seimdnets. Sediment is the main concern, although nitrate and water temperature impacts are also of concern in some locations. Best management practices, such as stream buffers, can avoid most of these effects.

The Economics of Water-Quality Control

The costs of water-quality control in the United States are substantial and rising. A survey by the Environmental Protection Agency from the mid-1990’s indicated that community water systems in the United States would need to invest $138 billion over the next 20 years. Additional expenditures will be necessary by industry, agriculture, and other sectors to protect water quality. These costs highlight the importance of considering the economics of water quality.

Perhaps the most fundamental economic question regarding drinking water quality is whether the benefits of drinking water standards exceed the costs. The benefits of water-quality standard consist of averted losses of two general kinds:

  1. Losses from drinking unclean water, including human health losses and associated health care costs; and

  2. Losses between the pollution source and the drinking water diversion, including fish population losses, costs of removing sediment from canals and reservoirs, and decreases in recreation quality and use, especially where meeting the standard involves controlling upstream sources of pollution.

The costs to be compared with such benefits include those at water treatment plants or by rural households that must treat their own water, and costs of controlling pollution emissions upstream of the drinking water diversion. Potential upstream pollution control costs include, for example, crop losses from decreased pesticide use; costs of controlling erosion from fields, forests, and roads; reduced beef production associated with fencing cattle out of riparian areas; and costs at upstream wastewater treatment plants.

Despite serious efforts to estimate the benefits of drinking water standards and other water-quality controls, the estimates remain rough. Because of imprecise benefit estimates and reluctance to compromise on the safety of public drinking water, drinking water standards are often set without definitive economic analysis of costs and benefits, efficiency, and equity.

To avoid waste of resources, standards should be met efficiently. A drinking water standard may be met solely by treating existing water prior to use, or by a combination of water treatment at points of use and pollution control upstream where the water-quality problems originate. Because pollution may occur at various points in the watershed, corrective action may involve many different costs. And because the costs of alternative actions can differ considerably, opportunities for inefficiencies (or conversely for cost savings) abound.

A related economic issue is the equity of options for implementing the efficient cost allocation. Expecting each actor to bear the cost of any change required to minimize the total cost of reaching the downstream water-quality standard may unfairly allocate the costs. If so, options for cost sharing, including the use of economic subsidies, should be explored.

Minimizing the cost of meeting drinking water-quality goals will require considering the full range of options for controlling pollution at the source. However, the complexities and uncertainties of nonpoint-source pollution seriously constrain efforts to utilize traditional economic incentives to reach cost-efficiency goals.

Nevertheless, real opportunities exist for cost savings, which are most likely to be realized by a combination of limited pollution control regulations to provide a baseline of control and watershed-based negotiations that emphasize subsidies to encourage use of practices thought to reduce nonpoint-source emissions. Initial efforts will focus on the most obvious cost saving opportunities, where the benefits of nonpoint-source pollution controls are clear and the transaction costs are limited. Careful monitoring will then hopefully allow fine-tuning of existing control efforts and addition of new ones where warranted.

Key Findings

Water Quality and Forest Management

  • Stream water quality is a function of a variety of parameters, including temperature, sediment loads, inorganic chemistry, and toxic metals and organic compounds.

  • Current forest management practices do not typically involve addition of large quantities of fine organic material to streams, and depletion of streamwater oxygen is not a problem; however, sedimentation of gravel streambeds may reduce oxygen diffusion into spawning beds in some cases.

  • Concentrations of nitrate-N typically increase substantially after forest harvesting and fertilization, but only a few cases have resulted in concentrations approaching the drinking-water standard of 10 mg of nitrage-N / liter.

  • Road construction and timber harvesting increase suspeneded sediment concentrations in streamwater, with highly variable results among regions in North America.

  • The use of best management practices usually prevents unacceptable increases in sediment concentrations, but exceptionally large responses (especially in relation to intense storms) are not unusual.

  • In most cases, retention of forested buffer strips along streams prevents unacceptable increases in stream temperature.

Economics of Water-Quality Control

  • To avoid waste of resources, water-quality standards should be met efficiently. Equitable allocation of costs is also an important consideration.

  • Real opportunities exist for cost savings, which are most likely to be realized by a combination of limited pollution control regulations to provide a baseline of control and watershed-based negotiations that emphasize subsidies to encourage use of practices thought to reduce nonpoint-source emissions.

Related Publications

Brown, T.C. 2000. Economic issues for watersheds supplying drinking water. Pp 42-51 in G.E. Dissmeyer (ed.). Drinking Water from Forests and Grasslands - A Synthesis of the Scientific Literature. General Technical Report SRS-GTR-39. Asheville, NC: USDA Forest Service, Southern Research Station. 246 pp.

Brown, T.C., and D. Binkley. 1994. Effect of management on water quality in North American forests. General Technical Report RM-GTR-248. Fort Collins, CO: USDA Forest Service, Rocky Mountain Forest and Range Experiment Station. 27 pp. 

Binkley, D., and T.C. Brown. 1993. Forest practices as nonpoint sources of pollution in North America. Water Resources Bulletin 29(5):720-729.

Binkley, D., and T.C. Brown. 1993. Management impacts on water quality of forests and rangelands. General Technical Report RM-GTR-239. Fort Collins, CO: USDA Forest Service, Rocky Mountain Forest and Range Experiment Station. 114 pp.

Brown, T.C., D. Brown, and D. Binkley. 1993. Laws and programs for controlling nonpoint source pollution in forest areas. Water Resources Bulletin 29(1):1-13.



Principal Investigators:
Co-Investigators:
Dan Binkley - Colorado State University
Douglas Brown - Rocky Mountain Forest and Range Experiment Station