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.
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
= Inflow of water to the watershed
= Outflow of water from the watershed
= Change in storage of the volume of water in the watershed,
that is, storage at the end of a period (S2) minus storage at the
beginning of a period (S1).
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
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
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 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
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
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
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 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 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.
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 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.
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.
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
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 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.
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 goalsthey
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.
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,
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,
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.
After completing this training module, and readings of the selected references,
you should be able to answer the following study questions.
Precipitation and Interception
What are the conditions necessary for precipitation to occur?
What are the different precipitation and storm characteristics associated
with frontal storm systems, orographic influences, and convective storms?
How does vegetation influence the deposition of precipitation?
What is the hydrologic importance of interception under different
vegetative cover and climatic regimes?
What are the potential implications of precipitation chemistry patterns
to watershed managers and other stakeholders in the region?
Evapotranspiration and Soil Water Storage
What are the different processes of evaporation from a water body,
evaporation from a soil, and transpiration from a plant?
How can evapotranspiration be estimated by using either a water budget
or energy budget method?
Under what conditions are potential evapotranspiration and actual
evapotranspiration relationships similar? Under what conditions do they
How does changes in vegetative cover affect evapotranspiration?
Infiltration, Runoff, and Streamflow
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?
How do land use activities affect infiltration capacities of a soil
through each of the above?
How do changes in infiltration capacities result in different flow
pathways through a watershed?
How can streamflow discharge be determined given velocity and cross-sectional
What are the advantages and disadvantages of alternative ways in which
streamflow can be measured?
Vegetation Management, Water Yield, Streamflow Patterns
What changes in vegetative cover usually result in an increase in
the quantity of water yield?
What are the exceptions to the above?
What methods are available to estimate changes in water yield caused
by changes in vegetative cover?
What factors are important in determining how much of a given change
in water yield from an upstream watershed becomes realized downstream?
Does clearcutting of forests cause flooding to increase? If so, explain.
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
Surface Erosion and Control of Erosion on Upland Watersheds
What is the process of detachment of soil particles by raindrops and
transport by surface runoff?
How do land management practices and changes in vegetative cover influence
the process of soil detachment?
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
How are gullies formed?
What are the roles of structural and vegetative measures in controlling
What are the different types of soil mass movement and the causes
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?
How would one prioritize the treatment of gullies?
Sediment Yield and Channel Processes
What are the different types of sediment transport?
What are the relationships between stream capacity and sedimentation?
Under what conditions will aggradation and degradation occur in a
What are the relationships between upland erosion and downstream sediment
What is dynamic equilibrium, and why is it a useful concept when describing
stream systems and their stages of development?
What is meant by the terms "water quality" and water pollution?"
What are the different physical, chemical, and biological pollutants
associated with different types of land use that can occur on upland
How does thermal pollution affect an aquatic ecosystem?
How do various silvicultural treatments, range management practices,
and associated land use activities affect water quality?
Where should sampling locations be located in a water quality monitoring
Watershed Management and Multiple Use
What is the concept and what are the objectives of multiple use?
How can multiple use be implemented? What are the alternative approaches
to this implementation?
What are the major constraints of implementing multiple use management?
What is the role of multiple use in the planning and implementation
of a watershed management program?
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
Why is planning important?
What is involved in planning for watershed management?
What concrete steps need to be taken in the planning process?
How does one appraise watershed management plans and projects?
Assessing Economic Impacts of Watershed Management
What is the general nature of an economic analysis?
What are the specific ways in which an economic analysis is applied
to watershed management practices, projects, and programs?
In what ways do economists go about the task of developing an economic
What are some of the ecological and hydrological roles that riparian
ecosystems can play on a watershed?
What is the major function of riparian buffer strips, and how can
they be used to manage non-point pollution?
In what ways can cumulative effects on a watershed result from losses
and gains in riparian ecosystems?
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