Managing Semi-Arid Watersheds: Training Course in Watershed Management

By Peter Ffolliott, professor of Watershed Management and of Renewable Natural Resources at The University of Arizona

1. Introduction
2. The Hydrologic Cycle
3. Water Resource Management
4. Effects of Watershed Management Practices on Water Resources
5. Development of Management Programs for Watershed Lands
6. Selected References
7. Study Questions

Introduction

Water and other natural resources on watershed lands play significant roles in satisfying human needs. A watershed can contribute forage for livestock and wildlife species, furnish a diversity of primary wood products, and yield water for municipal, agricultural, and industrial developments. It is urgent, therefore, for all concerned with management of watershed lands to understand the principles and concepts of watershed management and, more importantly, to develop ways of implementing land use practices that are compatible with watershed management principles.

Definitions of some terms are helpful in helping to understanding the roles of watersheds and watershed management in the development of natural resources. A watershed is a topographically delineated area that is drained by a stream system. It is considered to be a hydrologic-response unit, a physical-biological unit, or a socio-economic unit for management planning purposes. A river basin is defined similarly, but it is larger in scale than a watershed. For example, the Colorado River Basin, the Amazon River Basin, and the Congo River Basin comprise all lands that drain through these rivers and their tributaries into the ocean. In common usage, the term watershed refers to a smaller upstream catchment that is part of a river basin.

Watershed management is the process of organizing and guiding land and other resource use on a watershed to provide the desired goods and services without adversely affecting soil and water resources. Embedded in the concept of watershed management is the recognition of the interrelationships among land use, soil, and water, and the linkages between uplands and downstream areas. Watershed management practices are changes in land use and vegetative cover, and other non-structural and structural actions, carried out on a watershed to achieve watershed management objectives.

The Hydrologic Cycle

Managers of watershed lands must address specific questions in relation to land use. These questions include:

• What land use activities can take place without causing undesirable hydrologic effects, such as flash flooding, erosion and sedimentation, and water quality degradation?
• What land use alternatives might be implemented to change a hydrologic response for a beneficial purpose, such as increasing water yield, improving water quality by reducing sedimentation, and reducing flood damages?

To answer questions such as these, relationships between watershed management practices and resulting hydrologic responses can be analyzed by studying the hydrologic cycle (Figure 1). Importantly, the hydrologic processes of the biosphere, and the effects of vegetation and soil on these processes, must be understood. The hydrologic cycle is complex, but it can be simplified as a series of storage and flow components.

Permission to use illustration from Physics 161 Online granted by Greg Bothun, University of Oregon

Figure 1. The hydrologic cycle consists of a system of water-storage compartments, and solid, liquid, or gaseous flows of water within and between the storage points.

Water Budget Concept

The water budget is a concept in which components of the hydrologic cycle are categorized into input, output, and storage components. To illustrate this concept for a watershed and specified time interval:

I - O = S

The water budget represents an application of the "conservation of mass" principle to the hydrologic cycle. It is essentially an accounting procedure that quantifies and balances these hydrologic components for a watershed. Coupled with energy, precipitation is the primary input to a watershed system. A portion of this precipitation input is intercepted and evaporated, which represents a loss from the soil-moisture reserve or the water-flow process. Infiltration is the process of water entering the soil surface. Evapotranspiration, which represents the sum of all of the water evaporated and transpired from a watershed, is the most difficult of all of the components of a water budget to quantify. However, the evapotranspiration component and its linkage to soil water storage and the movement of water off of a watershed is one of the hydrologic processes most affected by vegetative manipulations. Relationships of precipitation, infiltration, and soil water storage affect volumes and rates of water movement downstream.

That part of the precipitation input that runs off a land surface and the part that drains from the soil and, as a consequence, is not consumed through evapotranspiration is the water-flow component of the hydrologic cycle. Some water flows quickly to produce streamflow, while other water flows (for example, the water that flows through groundwater aquifers) can take weeks or months to become streamflow. The streamflow response of a watershed is the integrated response of the various pathways by which "excess precipitation" moves.

The most direct pathway from precipitation to streamflow is that part of the precipitation that falls into stream channels, called channel interception. Channel interception causes the initial rise in a streamflow hydrography after which the hydrograph recedes soon after the precipitation stops. Surface runoff, also referred to as overland flow, occurs from impervious areas or areas on which the rate of precipitation exceeds the infiltration capacity of the soil. Some of the surface runoff is detained by the roughness of the soil surface, but, nevertheless, it represents a quick flow response to a precipitation input. Subsurface flow, also called interflow, is that part of the precipitation that infiltrates the soil, but it arrives in the stream channel over a short enough time period to be considered part of the stormflow hydrograph.

Watersheds in dryland environments frequently exhibit lower infiltration capacities and shallow soils with lower soil moisture storage capacities in contrast to watersheds in more humid regions. Surface runoff, therefore, is an important pathway of flow from these watershed lands. These watersheds generally respond more quickly, with relatively higher peak streamflows for a given amount of rainfall excess than watersheds in other regions. Furthermore, the streamflow is often ephemeral or intermittent, because of a lack of soil moisture storage, deep groundwater, and relatively low and frequently sporadic precipitation input.

A perennial stream, that is, a stream that flows throughout the year, is likely to be sustained by groundwater. This component sustains streamflow between periods of precipitation. Because of the long pathways involved and the slow movement of subsurface flow, groundwater flow does not respond quickly to rainfall.

One characteristic of stream channels in dryland regions is high transmission losses within the channels. When stream channels are dry most of the year, much of the water moving through the systems in a runoff event can infiltrate into the channel. This water is lost from surface streams and ends up as bank storage or percolates into lower soil storage or groundwater systems. As water moves farther downstream, the volumes of water in the channel can diminish until there no longer is flow in the channel at some point downstream.

Application of the Water Budget Concept

Application of the water budget concept to study the hydrologic behavior of a watershed is relatively simple. As mentioned above, if all but one component of the hydrologic cycle is measured or estimated accurately, it then is possible to solve directly for the unknown component.

An annual water budget for a watershed is often used in an analysis because of the simplifying assumption that changes in storage in the watershed system in a year generally are small. Water budget computations can be made, beginning and ending with "wet" months or "dry" months on the watershed. In either case, the difference in storage between the beginning and end of the year's period is relatively small and, as a result, can be ignored in the calculations. By measuring the precipitation input (P) and streamflow (Q) for a year, annual evapotranspiration (ET) can be estimated from:

ET = P - Q

Provided that an "acceptable" measurement of precipitation is obtained, a second assumption made in studying a water budget is that the total outflow of water from the watershed has been measured. It is often assumed that there is no loss of water by deep seepage to underground geological strata, and that all of the groundwater flow from the watershed is measured at a gauging station. However, transmission losses can be relatively high and, when geologic strata such as limestone underlie a watershed, the surface boundaries might not coincide with the boundaries governing the flow of groundwater. There are two unknowns in the water budget in such instances, ET and groundwater seepage (L), which result in:

ET + L = P - Q

When it is not appropriate to assume that the change in storage is small, the change must be estimated. This task is difficult, although changes in storage can often be estimated by periodical measurements of the soil water content on relatively small watersheds. Such measurements can be made gravimetrically, with neutron attenuation probes, or through the use of other methods.

Water Resource Management

Water limits much of what people can do. Stability of water supplies is critical to programs of development. Emphasis in water resource management in dryland regions generally is placed on developing or conserving water supplies. The usefulness of water supplies to people also depends largely upon their physical, chemical, and biological characteristics. It is important, therefore, that both quantity and quality be considered in the management of water resources.

Developing Water Supplies

Numerous methods have been used in developing water supplies in the dryland regions of the world. Water harvesting is one example of note. Water harvesting systems were used by people in the Negev Desert over 4,000 years ago, with applications of this technology continuing to the present. Not all of the systems have been successful, although some form of water harvesting has been necessary to sustain livestock and agricultural crop production and forestry, in many instances.

Water harvesting methods involve the collection and, in many instances, storage of rainfall until the water can be used beneficially. Components of water harvesting systems include:

• A catchment area, the surface of which is often treated to improve runoff efficiency.
• A storage facility for collected water, unless the water is to be utilized immediately, in which case a water spreading system is necessary.
• A distribution system when the stored water is to be used later for irrigation purposes.

Other methods of developing water supplies have little to do with the management of watershed lands directly. However, their applications in increasing the amounts of water available for irrigation, livestock production, or human use provide a means of increasing land productivity that, in turn, reduce the pressures of overgrazing by livestock, improper agricultural cultivation, and deforestation. Irrigation with saline water, reuse of irrigation and waste water, and construction of wells and development of springs are some of these methods. Still other methods, including cloud seeding, desalinization of sea and other saltwater, and transfers of water from water-rich areas to water-poor areas, have applications only under special conditions.

Conserving Water Supplies

Water conservation, where available water supplies are conserved for use at a later date, involves a variety of methods to reduce evaporation, transpiration, and seepage losses. Some of these methods pertain to treatments of water, soil, and plant surfaces, while others methods consist of manipulations of vegetative surfaces.

Reducing evaporation can lead to significant savings of water. Among the methods of reducing evaporation from small ponds and livestock tanks are covering these water bodies with blocks of wax, plastic, or rubber sheeting and floating blocks of concrete, polystyrene, or other materials. Liquid chemicals that form monomolecular layers on a water surface (for example, aliphatic alcohols) have been used on larger bodies of water, although their effectiveness can often be limited because of wind and deterioration in the sun. The use of evaporative retardants might be restricted by adverse environmental effects of aquatic organisms in natural lakes or reservoirs.

Transpiration losses from plants can be reduced in many ways, including:

• Replacing plant species that have high transpiration rates with species that have lower transpiration rates.
• Removing phreatophytes, plants with deep rooting systems that can extract water from shallow water tables, from stream banks.
• Planting windbreaks of trees or shrubs to reduce wind velocities.
• Applying antitranspirant compounds that either close stomata or form a film on leaf surfaces.

Antitranspirants, although effective in experimental investigations, have not been used widely on a large scale in natural vegetative communities.

Earthen canals and reservoirs that are constructed in pervious soils can lose considerable amounts of water through seepage. Methods of reducing the seepage losses from these structures include the compaction of the soil, treatment of the soil surfaces with sodium salts to break up aggregates, and lining canals and bottoms of small reservoirs with various impervious materials. This latter method is expensive for large reservoirs, although it usually is effective for a long period of time.

Water Quality

Water of low quality can present as much of a limitation to available water supplies as deficient quantities. In many instances, there can be an abundance of water, but its quality is such that it cannot be used safely for irrigation, domestic consumption, or other uses. Water supplies, therefore, must be considered in the context of usable water, or water that is suitable for a specified use.

The quality of water is affected by natural geologic-soil-plant-atmospheric systems and land uses practices. Water quality characteristics of concern to people can be grouped into physical, chemical, and biological characteristics.

Physical Characteristics

Physical characteristics that determine water quality include suspended sediments, turbidity, thermal pollution, dissolved oxygen, biochemical oxygen demand, pH, acidity, and alkalinity. Rainfall events frequently produce large amounts of runoff in short periods of time. These events often promote erosion and transportation of sediments. Streams in the dryland regions commonly transport high levels of suspended sediment and exhibit high turbidity, the latter indicating that light penetration into water is reduced severely.

Dissolved oxygen and biochemical oxygen demands are a concern in perennial streams, lakes, and reservoirs where biodegradable materials enter these bodies of water. The temperatures of water in dryland environments are usually high. In upland areas with cooler water temperatures, care is needed to prevent temperatures from increasing in water bodies where cold-water fish are found. In general, surface water and groundwater resources in dryland regions tend to be alkaline with high pH, due largely to the typically high levels of calcium and salts in the water.

Chemical Characteristics

Dissolved chemical constituents in surface water and groundwater systems reflect the characteristics of the drainage area. Processes such as the weathering of rock, physical-biological processes occurring on watershed lands, and atmospheric deposition all affect chemical compositions of water. Because it is an excellent solvent, when water comes into contact with rock surfaces and other soil materials, its chemical composition changes. The longer the contact is, the greater the change, such as the case with groundwater. Rock and soil substrates generally control ionic concentrations, including calcium, magnesium, potassium, and sodium, on watersheds with little human disturbance. Nitrogen and phosphorus concentrations are affected by biological activities, although much of the nitrate, chloride, and sulfate anions are added through atmospheric inputs.

High concentrations of dissolved solids (salts) can be one of the greatest limitations to the use of water. Salts tend to concentrate because of high evaporative rates and limited amounts of water in dryland environments. As a result, salinity frequently exceeds 100 parts per million (ppm). People can tolerate salinity levels of 2,500 to 4,000 ppm, at least temporarily. Livestock can tolerate 3,000 ppm. Irrigation with high salinity water, when feasible, is often restricted to salt tolerant plants, and it is necessary to flush salts through the soils so that levels of salt accumulations do not become toxic.

Biological Characteristics

Biological characteristics are determined largely by the organisms that impact the use of water for drinking and other forms of human contact. Disease organisms are associated with situations in which human and animal wastes are treated improperly, or the deposition of these wastes has been in close proximity to bodies of water.

Effects of Watershed Management Practices on Water Resources

Manipulation of vegetation that accompanies management of natural ecosystems can affect the long-term productivity of watershed lands. Of particular concern are impacts on quantities and qualities of water that originates from upland watersheds. It is important, therefore, to recognize the environmental effects that watershed management practices frequently have on the hydrology of watershed lands.

Environmental Effects

Many watershed lands are subjected to grazing by livestock and wild ungulates, harvesting of trees and shrubs for fuel and other wood products, agricultural cultivation, and other forms of human intervention. The harvesting of trees or shrubs or converting from one vegetative type to another can enhance water supplies if the watersheds are managed properly. However, when managed improperly, these manipulations can also lead to:

• Excessive surface runoff.
• Increased soil compaction and surface erosion.
• Increased gully erosion and mass soil movement.
• Increased sedimentation in downstream channels.
• Increased export of nutrients from upland watersheds.
• Increased temperature of stream waters.

If surface runoff and downstream sedimentation increase as a result of improper land practices, the prospects for downstream flooding are also increased. Soil erosion and the export of nutrients reduces the nutrient capital and, hence, the subsequent productivities of these watersheds. Stream water temperatures and increases in nitrate, phosphorus, and other nutrients adversely affect aquatic organisms. Introduction of residues from the harvesting of trees and shrubs into stream systems can lead to higher levels of biochemical oxygen demands and reduce dissolved oxygen, also adversely affecting aquatic ecosystems.

Detrimental impacts on watershed lands should be minimized with properly planned and implemented watershed management practices. Re-vegetation of deforested areas, for example, might return watershed lands to their former conditions, although the time for recovery is longer in dryland environments than in more humid ecosystems. "Best management practices" have been established in the United States and a number of other countries as guidelines for watershed management practices that help to avoid environmental problems.

Water Yield Increase

Water yields are often increased through manipulations of vegetative cover on watersheds when one or more of the following actions are taken:

• Plant species with high consumptive use are replaced with species with lower consumptive use.
• Forests or woodlands are clearcut or thinned.
• Species with high interception capacities are replaced with species with lower interception capacities.

Opportunities for water yield improvement from upland areas are best when deep-rooted plant species are replaced with shallow-rooted species. Clearcutting or thinning of trees and shrubs, often prescribed as part of wood harvesting operations, can also increase yields of water, although the effects of these silvicultural treatments diminishes as the trees and shrubs regenerate. Reductions in interceptive losses of vegetative cover alone normally do not result in significant changes in water yields unless these changes are accompanied by reductions in transpiration rates. These reductions are attributed to the fact that soil moisture tends to be at a level below field capacity of the soil much of the time. For the most part, differences in interception and, therefore, net rainfall simply are added to the soil and transpired at a later time.

Opportunities to increase water yield in upland areas through manipulation of vegetation are related directly to annual precipitation amounts. It has been suggested that the potential for increasing water yield in the southwestern United States is realized only on sites with annual precipitation in excess of 15 to 18 inches. The greatest increases are observed in regions of higher precipitation, and where precipitation is concentrated in the cool season of the year.

Increases in water yield on upland watersheds represent on-site effects. However, the net increases in water yield diminish as distance increases between upland areas and downstream reservoirs and other areas where the water is used. These reductions in streamflow result from transmission losses in channels, evaporation of water in route, and transpiration by vegetation along the stream bank. To illustrate the magnitude of these losses, increases in water yield attributed to vegetative changes on upland watersheds in the Verde River Basin of central Arizona are reduced to less than one-half by the time water has traveled 100 miles to downstream points of use.

Consumptive use of water by phreatophytes can be substantial in lowland areas. Opportunities for salvaging groundwater through eradication of phreatophytes has been attempted in parts of the western United States. One problem with such eradication practices is that these riparian systems also have values as wildlife habitats, which can be higher than the value of groundwater that is salvaged. However, where dense plant communities have developed, such as saltcedar stands in the southwestern United States, there can be opportunities to salvage groundwater to a limited extent and, at the same time, maintain a sufficient riparian ecosystem for wildlife habitats and other purposes.

Riparian Systems

Riparian systems are valuable components of dryland environments throughout the world. Riparian systems are found in the transition between aquatic and adjacent terrestrial ecosystems, and identified largely by soil characteristics and unique vegetative communities that require free or unbounded water. Standing water and running water habitats are found in riparian systems. As relatively small areas, riparian ecosystems are diverse and unique systems that are subjected to a number of uses and, as a frequent consequence, detrimental pressures.

Riparian systems are often the only sites on a landscape that have trees and shrubs. These systems represent areas of relatively high levels of forage production and, as a result, are attractive to livestock. Riparian systems are important wildlife habitats because of their abundance of food and cover, extensive edges between different forms of vegetation, and proximity to water. These ecosystems frequently are corridors of migration for animals. Riparian plant communities stabilize stream banks, and reduce soil erosion and delivery of sediments to aquatic ecosystems.

Special care is necessary to protect riparian systems from environmental degradation because of their frequent high use by people and their livestock. Cuttings of trees and shrubs, and grazing by livestock, must be controlled to maintain protective vegetative covers. Riparian sites can be fenced where excessive livestock grazing occurs. Water might be piped to tanks located outside of the enclosure to move livestock away from sites susceptible to compaction, erosion, or concentrations of animal wastes that can degrade water quality. Construction of water developments elsewhere, salting, and herding of livestock help in protection when fencing is not feasible. Activities such as road construction and intensive, unplanned outdoor recreational use should be minimized in riparian systems.

Degraded riparian systems can be returned to a more productive status by improving the conditions on upland watersheds. One objective of these improvements is to increase streamflow, although these flows should be more stable and less variable than when the systems are degraded. Increased streamflow is often accomplished by encouraging subsurface flow rather than overland flow. Measures that increase duration of flows in stream channels also promote re-establishment and maintenance of riparian vegetation.

Gully plugs, check dams, and other small engineering structures constructed in stream channels can be used to increase durations of flows and stabilize the channels to help in the re-establishment of riparian vegetation. These structures trap and store sediments, providing water retention systems. The stored sediments become saturated following storm events and, as drainage continues, the water is released more slowly and sustained for longer periods of time than in unobstructed channels.

Optimum management of riparian systems requires consideration of both the environmental factors and economic needs of the area. It is seldom that riparian areas are managed best for only a single use. A compromise form of management usually results in the greatest value to people. Riparian systems might have to be set aside as natural areas in some instances.

Development of Management Programs for Watershed Lands

There is clear evidence that a potential exists on earth to feed a much larger population than currently lives here. Despite this encouragement, it must also be remembered that the resources of individual regions and countries vary widely. Development of the resources on watershed lands also takes a long period of time before it yields benefits. Conversely, once degraded, watershed restoration also takes a long period of time. Unfortunately, political leaders often have short-term goals—they focus on immediate and popular concerns. Yet, the production and conservation of the resources on watershed lands are dependent upon long-term and extensive commitments. People must be ready to make this commitment to the development of the watershed lands if future land degradation is to be avoided.

It is important to recognize that the problems of managing resources on watershed lands do not arise necessarily from physical limitations nor from lack of technical knowledge. Wood harvesting practices, reforestation programs, and methods of livestock grazing have been developed to largely prevent adverse impacts on soil and water resources. Likewise, technology to solve many watershed problems is available. However, methods are needed to effectively demonstrate the benefits of instituting environmentally sound watershed management programs. The social and economic benefits from watershed management programs must be quantified and compared to the costs of not implementing these programs. Inhabitants of watersheds and their livelihoods must be considered as an integral part of any watershed management program, requiring integration of social, economic, and political factors in addition to biological and physical considerations.

Selected References

Anderson, H. W., M. D. Hoover, and K. G. Reinhart. 1976. Forests and water: Effects of forest management on floods, sedimentation, and water supply. USDA Forest Service, General Technical Report PSW18.

Blackburn, W. H. 1983. Livestock grazing impacts on watersheds. Rangelands 5:123-125.

Bosch, J. M., and J. D. Hewlett. 1982. A review of catchment experiments to determine the effect of vegetation changes on water yield and evapotranspiration. Journal of Hydrology 55:3-23.

Branson, F. A., G. F. Gifford, K. G. Renard, and R. F. Hadley. 1981. Rangeland hydrology. Kendall-Hunt Publishing Company, Dubuque, Iowa.

Brooks, K. N., P. F. Ffolliott, H. M. Gregersen, and L. F. DeBano. 1997. Hydrology and the management of watersheds. Iowa State University Press, Ames, Iowa.

DeBano, L. P., and L. J. Schmidt. 1990. Potential for enhancing riparian habitats in the southwestern United States with watershed practices. Forest Ecology and Management 33-34:385-403.

Heathcote, Fl L. 1983. The arid lands: Their use and abuse. Longman, London.

National Academy of Science. 1974. More water for arid lands. National Academy of Sciences, Washington, D.C.

Renard, K. G. 1970. The hydrology of semiarid rangeland watersheds. USDA ARS 41-162:26.

Study Questions

After completing this training module, and readings of the selected references, you should be able to answer the following study questions.

Precipitation and Interception

1. What are the conditions necessary for precipitation to occur?
2. What are the different precipitation and storm characteristics associated with frontal storm systems, orographic influences, and convective storms?
3. How does vegetation influence the deposition of precipitation?
4. What is the hydrologic importance of interception under different vegetative cover and climatic regimes?
5. What are the potential implications of precipitation chemistry patterns to watershed managers and other stakeholders in the region?

Evapotranspiration and Soil Water Storage

1. What are the different processes of evaporation from a water body, evaporation from a soil, and transpiration from a plant?
2. How can evapotranspiration be estimated by using either a water budget or energy budget method?
3. Under what conditions are potential evapotranspiration and actual evapotranspiration relationships similar? Under what conditions do they differ?
4. How does changes in vegetative cover affect evapotranspiration?

Infiltration, Runoff, and Streamflow

1. How do the soil moisture content, hydraulic conductivity of the soil, soil surface conditions, and presence of impeding layers in the soil profile affect infiltration rates?
2. How do land use activities affect infiltration capacities of a soil through each of the above?
3. How do changes in infiltration capacities result in different flow pathways through a watershed?
4. How can streamflow discharge be determined given velocity and cross-sectional area data?
5. What are the advantages and disadvantages of alternative ways in which streamflow can be measured?

Vegetation Management, Water Yield, Streamflow Patterns

1. What changes in vegetative cover usually result in an increase in the quantity of water yield?
2. What are the exceptions to the above?
3. What methods are available to estimate changes in water yield caused by changes in vegetative cover?
4. What factors are important in determining how much of a given change in water yield from an upstream watershed becomes realized downstream?
5. Does clearcutting of forests cause flooding to increase? If so, explain.
6. In what way do land use activities and environmental change affect hydrologic processes on watersheds, and the ultimate streamflow response? What is the relationship between processes on a watershed and cumulative watershed effects?

Surface Erosion and Control of Erosion on Upland Watersheds

1. What is the process of detachment of soil particles by raindrops and transport by surface runoff?
2. How do land management practices and changes in vegetative cover influence the process of soil detachment?
3. How can surface erosion be controlled, or at least maintained, at acceptable levels? What types of watershed management practices and guidelines are appropriate?

Gully Erosion and Soil Mass Movement

1. How are gullies formed?
2. What are the roles of structural and vegetative measures in controlling gully erosion?
3. What are the different types of soil mass movement and the causes of each?
4. How do different land use impacts, including road construction, timber harvesting, and conversion from deep-rooted to shallowrooted plants, affect both gully erosion and soil mass movement?
5. How would one prioritize the treatment of gullies?

Sediment Yield and Channel Processes

1. What are the different types of sediment transport?
2. What are the relationships between stream capacity and sedimentation?
3. Under what conditions will aggradation and degradation occur in a stream channel?
4. What are the relationships between upland erosion and downstream sediment delivery?
5. What is dynamic equilibrium, and why is it a useful concept when describing stream systems and their stages of development?

Water Quality

1. What is meant by the terms "water quality" and water pollution?"
2. What are the different physical, chemical, and biological pollutants associated with different types of land use that can occur on upland watersheds?
3. How does thermal pollution affect an aquatic ecosystem?
4. How do various silvicultural treatments, range management practices, and associated land use activities affect water quality?
5. Where should sampling locations be located in a water quality monitoring program?

Watershed Management and Multiple Use

1. What is the concept and what are the objectives of multiple use?
2. How can multiple use be implemented? What are the alternative approaches to this implementation?
3. What are the major constraints of implementing multiple use management?
4. What is the role of multiple use in the planning and implementation of a watershed management program?
5. What are the contributions of the concept of multiple use, and of the use of watersheds as systems of analysis, to ecosystem management?

Planning Watershed Management

1. Why is planning important?
2. What is involved in planning for watershed management?
3. What concrete steps need to be taken in the planning process?
4. How does one appraise watershed management plans and projects?

Assessing Economic Impacts of Watershed Management

1. What is the general nature of an economic analysis?
2. What are the specific ways in which an economic analysis is applied to watershed management practices, projects, and programs?
3. In what ways do economists go about the task of developing an economic evaluation?

Riparian Ecosystems

1. What are some of the ecological and hydrological roles that riparian ecosystems can play on a watershed?
2. What is the major function of riparian buffer strips, and how can they be used to manage non-point pollution?
3. In what ways can cumulative effects on a watershed result from losses and gains in riparian ecosystems?