Abstract
A "Management by Watersheds" strategy is proposed for the Forest Service. The watershed is a basic ecosystem which can be managed so that its hydrologic function secures favorable conditions of water flows. Watershed analyses can diagnose watershed and stream health and help determine the type and schedule of management activities and restoration treatments in each watershed. Management by watersheds can resolve many water-related issues and achieve our goals of land stewardship and ecosystem management for watersheds and aquatic life.
Introduction
The purpose of this paper is to propose a "Management by Watersheds" strategy for the Forest Service. In recent years, conflicts over beneficial uses of water (in particular aquatic life), scheduled Forest Plan revisions, and increasing appeals and lawsuits directed at water issues have focused renewed attention on the vital importance of watershed management to the mission of the Forest Service.
Management by watersheds is grounded in the Organic Act and Clean Water Act. The Organic Act culminated more than 30 years of scientific concern and public debate over the exploitation of watersheds that led to creation of the National Forest System. The main intent of Congress was to secure "favorable conditions of water flows" by assuring healthy watersheds and streams. The Clean Water Act similarly aims to preserve and restore the physical, chemical, and biological integrity of the Nation's waters, including conditions such as substrate, cover, flow, depth, pools, and riffles (40 CFR 131.10).
The consequences of not managing by watersheds are serious and growing. In the Pacific Northwest, four salmon species have been listed as endangered, partly due to sediment loads caused by erosion in the headwaters. In Region 1, management of many watersheds has stopped as surveys have disclosed the poor condition of their streams due to excess sediment loads. In all areas, a growing number of appeals and lawsuits are based on watershed effects more than any other issue. State controls over water quality management are steadily tightening.
Through management by watersheds, the Forest Service will go a long way toward resolving such issues and preventing their recurrence by taking strong action. Management by watersheds is also at the core of the agency's goals of ecosystem management and land stewardship. By placing a major emphasis on a structured program that maintains healthy watersheds and restores ailing ones, the Forest Service can once again assume the high ground of being the champion for the wise and balanced use of land and resources for the good of future generations.
The Management by Watersheds Concept
Management by watersheds will promote the goals of the Organic Act and Clean Water Act by securing favorable conditions of water flows. Watersheds will be managed as ecosystems so that their hydrologic function sustains a balanced range of hydrologic conditions characteristic of healthy watersheds and streams.
The watershed is a basic ecosystem. It synthesizes inputs of water and energy with its physical, chemical, and biotic systems (geology, soils, terrain, and vegetation) to produce an array of landforms and stream channels and a range of streamflow and sediment yield characteristics. The balanced range of conditions sustained by the hydrologic function of a healthy watershed includes:
--Integrity of streamflow such that the magnitude and frequency of floods and base flows is not upset. Healthy watersheds behave like a "sponge" and exhibit high rates of infiltration that result in minimum surface runoff. Most precipitation soaks into the soil, which tends to retard flooding, recharge ground water, and regulate streamflow.
--Integrity of the fluvial system expressed as stable stream networks and channels and a balance between runoff and sediment yield. In healthy watersheds, the stream network is not expanding through gully erosion, streams are not aggrading nor degrading, channel form is maintained over time, and stream banks are well vegetated.
--Integrity of water quality and aquatic habitat. Healthy watersheds exhibit healthy streams that support productive, diverse, and stable populations of aquatic life and display a balanced range of habitat features such as depth of pools, composition of substrate, and sequence of pools and riffles.
Implementation of the Program
Management by watersheds IS ecosystem management for watersheds and fisheries on National Forest System lands. Its goals are to (1) maintain watershed health by preventing new problems through nonpoint source management, and (2) restore watershed health by correcting existing problems through watershed improvements. The program includes watershed analysis, watershed management, and watershed monitoring components.
Watershed Analysis
The first step in management by watersheds is to conduct a watershed analysis on all watersheds in the National Forest System, at a scale proper for scheduled Forest Plan revisions. A watershed condition analysis (WCA) and cumulative watershed effects analysis (CWE) will be done for each watershed to diagnose the health of the watershed in terms of its ability to provide favorable conditions of water flows.
The watershed analysis will clearly display relationships between the causative impacts of management and the values in the watershed and its streams and lakes that are being impacted. It will clearly address physical processes which are affected by management and which affect watershed and stream health.
The WCA and CWE are closely related. The WCA diagnoses watershed health at a given point in time. The CWE evaluates specific contributors to that condition. The intensity of analysis will vary depending on the values at risk and the level of risk to them. Many watersheds will only require a general examination for adequate diagnosis. Others may require a more detailed investigation. Examples of three levels of intensity already underway include:
Perceptual = Bitterroot NF, San Juan NF, Lake Tahoe Basin, Olympic NF;
Empirical = Shoshone NF, Megahan CWE Method;
Process = R1/R4 sediment model, R2 runoff model, R3 gully threshold model
The WCA will establish a DESIRED CONDITION for each watershed which reflects good watershed health. This desired condition is actually a RANGE OF CONDITIONS for certain land and stream attributes, typical of the dynamic equilibrium found in healthy watersheds and streams in the local physiographic area. The WCA will then diagnose the ACTUAL CONDITION, or health, of the watershed relative to the desired condition, using the same land and stream attributes. This approach defines a balanced range of conditions and assesses deviations from that range.
The CWE will evaluate specific contributors to existing watershed condition by analyzing the effects of management activities on the same land and stream attributes. This analysis will consider both inherent watershed hazards and the level of disturbance of activities in the watershed.
The WCA and CWE will include the concept of RISK, or the probability of a given hydrologic event exceeding our design standards. For example, the Shoshone NF uses a 10-year, 24-hour storm to evaluate effects. The WCA and CWE will need rigorous field validation to ensure accurate and defensible diagnoses.
Watershed Management
The results of WCA will help drive the management program for each watershed, which will be implemented through our Nonpoint Source Management Strategy. The general approach in each watershed will be as follows.
--If watershed health is good (within the balanced range of conditions) and trending flat or upward, land disturbing activities may be maintained or accelerated.
--If watershed health is good but trending downward, land disturbing activities must be slowed or adjusted through more rigorous application of watershed conservation practices.
--If watershed health is poor (outside the balanced range of conditions), only land disturbing activities which complement watershed recovery will be allowed, and a watershed restoration program may be implemented, until good watershed health is restored.
The results of CWE, by evaluating specific contributors to existing watershed condition and analyzing the effects of various management activities, will help schedule implementation of management activities, watershed conservation practices, and watershed restoration treatments in the watershed.
Specific projects will be designed to handle certain hydrologic events. If a larger event occurs that exceeds the project's design standards, the impact of such failure onsite would fall within the range of conditions of that larger event, so as to be undetectable and not cause chronic instability. This concept would implement our Nonpoint Source Management Strategy and comply with the principle of anti-degradation of water quality.
Watershed Monitoring
Each watershed will be monitored on a 5- to 10-year cycle to track progress in restoring and maintaining watershed health. Monitoring would focus on the same land and stream attributes as mentioned above. Monitoring results would be used to adjust the watershed management program as needed.
Dynamic Equilibrium and Watershed Health
In natural systems, catastrophic events periodically occur in the form of fires or floods. Such major "reset" events occur once every few decades or centuries. In between these events, a watershed little disturbed by humans operates in DYNAMIC EQUILIBRIUM. Conditions of streamflow and sediment yield, watershed and stream channel stability, water quality and aquatic habitat vary within some range about some average condition. The reset event temporarily throws the watershed out of equilibrium. The watershed then takes some years to recover to the prior, or a new, range of dynamic equilibrium conditions.
Healthy watersheds exhibit conditions within this range of dynamic equilibrium. The intent of management by watersheds is: to maintain this balanced range of conditions in between the major reset events, to avoid actions which would throw a watershed out of equilibrium or would increase the frequency or severity of major reset events, and to speed rather than impede a watershed's recovery from such events. Major reset events will occur, but we don't want to make any watershed more susceptible to damage or to further stress an unbalanced system.
A prudent level of land disturbing activities can occur in a watershed and still maintain watershed health within this balanced range of conditions. As long as floods or droughts are not worsened, sediment loads and bank erosion are not substantially increased, rills and gullies and landslides are not accelerated, and water quality and aquatic habitat features are maintained within a balanced range, a watershed will maintain good health.
Land and Stream Attributes of Watershed Health
The land and stream attributes of watershed health reflect the physical processes which are affected by climate, physiography, and management. They also reflect the values at risk in the watershed. Their balanced range of dynamic equilibrium conditions indicates good watershed health and enables deviations from this range to be discerned.
The balanced range of conditions for the LAND ATTRIBUTES will be defined for each land type within a physiographic area based on its geology, soil, landform, and vegetation. The range for the STREAM ATTRIBUTES will be defined for each stream type in a physiographic area based on its channel morphology, stream order, and flow regime. For example, in each physiographic area, the range of attributes for each stream type will be established by sampling minimally disturbed reaches of that stream type throughout the physiographic area.
Attributes of watershed health are listed below. The likely dimensions (units of measure) are defined for each. It will be possible to establish a balanced range of conditions for each, and to compare the existing condition with that range.
Land Indicators
1. VEGETATION TYPE: Vegetation type affects watershed response to hydrologic events. The dimension is acres or percent of watershed in major cover types (conifer, deciduous, woodland, grassland). Depending on the uses and values at risk, data on vegetation structure may also be needed.
2. VEGETATION AGE: Vegetation age reflects degree of hydrologic recovery. The dimension is acres or percent of watershed by age class for various forest and woodland cover types.
3. GROUND COVER: Ground cover controls infiltration and surface runoff. The dimension is percent of surface covered by plants and litter, rock, and bare soil. Both areal cover and depth of litter are important hydrologically.
4. COMPACTED OR IMPERVIOUS SURFACES: Compacted or impervious surfaces exhibit rapid runoff. The dimension is acres or percent of watershed with impaired infiltration. Connected impervious areas are important in routing runoff and sediment to streams.
5. LANDSLIDES: Landslides are affected by roads and vegetation treatment. The dimension is number or volume of landslides per square mile (and delivered to streams). Age of landslides (how many in a specified period) may often be useful to diagnose watershed condition and assess the role of management.
Stream Indicators
1. CHANNEL FORM: Channel form is controlled by the dynamic balance between the energy of streamflow and the supply of sediment and woody debris. Dimensions include width (feet), mean depth (feet), and sinuosity of the active channel, and water surface slope (percent).
2. SEDIMENT PARTICLE SIZE: Sediment particle size is affected by inputs of fine sediment due to land and channel erosion. The dimension is particle size distribution derived through a pebble count, Tarzwell substrate ratio, or riffle stability index.
3. BEDLOAD TRANSPORT: Bedload transport is affected by inputs of sediment due to channel and land erosion. Dimensions include a direct measure (lb/day) using a Helly-Smith sampler, or some measure of fine sediments deposited in pools during low flows as is being done by Tom Lisle.
4. BANK STABILITY: Bank stability is affected by the dynamic balance between the energy of streamflow and the supply of sediment and woody debris, and by vegetation management of riparian areas. Dimensions include bank erosion (feet) measured with erosion pins, or percent of bank in unstable condition above the active channel.
5. STREAM STRUCTURE: Stream structure includes such features as depth of pools, composition of substrate, and sequence of pools and riffles. These are controlled by the dynamic balance between the energy of streamflow and the supply of sediment and woody debris. Dimensions include mean depth of pools or number of pools exceeding a given depth, percent of channel length in woody debris deposits and mid-channel sediment bars, and pool-riffle ratio.
Implications to Management
Management by watersheds will require land and resource management programs to be changed. First, watersheds must be recognized as basic ecosystems and managed as ecosystems to secure favorable conditions of water flow. All programs must be conducted to achieve this goal.
Second, a truly interdisciplinary approach is crucial to the program's success. All employees must consider themselves to be watershed managers and must consider watershed management to be paramount. Watershed scientists must lead the way, but all others must be part of the watershed management team.
Third, the Chief must make a permanent commitment of policy, staffing and money to place Management by Watersheds at the heart of the Forest Service mission. This includes a continuing program of training for line officers, and a long-term commitment to monitoring in close cooperation with Research.
The Forest Service is at a crossroads in its history. We can either seize the day and regain the high ground of being the champion for the wise and balanced use of land and resources for the good of future generations, or we can allow the shifting winds of politics to control the future of the agency and of the lands we care for. Our challenge is to organize collectively to manage watershed systems as a whole, not just individual projects piecemeal. Our opportunity is to rediscover the purposes for which the Forest Service was created and to add substance to the form of Ecosystem Management.
* James Maxwell James Maxwell Paper Revised 2/19/93
