Upstream-Downstream Savings
Researchers studying Bear Creek in central Oregon have determined that healthy, well-functioning water catchments can help boost water efficiency and protect water resources by keeping water on the land longer.
By
Wayne Elmore,
Dennis Doncaster
Introduction
Timing is a large part of using water efficiently. Humans have long recognized that it is much better to live in proximity to a steady water supply than one that delivers too much at some times and not enough at others. Knowing this, people have attempted to regulate the flow of water through the use of dams, reservoirs, and water systems. Such artificial water regulation systems are key aspects of civilization, but they are subject to failure and require large amounts of energy and direct maintenance. There is, however, another approach to managing water that relies not on artificial structures but on maintaining a healthy ecological system. A healthy, well-functioning water catchment (a much more descriptive term than watershed) will filter sediment, buffer high flows, and, most importantly keep water on the land longer.
Keeping water on the land longer has many benefits. The longer water remains on the land, the greater the potential growth of vegetation, and the more water is available for flow during dry seasons. This is especially evident in the arid areas of the world, including the western United States, where increasing populations and uses for water are making a predictable supply of fresh water an evermore-valuable commodity.
Healthy water catchments not only improve production, reduce floods, and ease droughts on their own, but also prolong the useful life of dams and reservoirs by reducing the volume of sediment (which can shorten the life of a reservoir by filling it in) and reducing the need for maintenance of facilities.
Critical to creating and maintaining healthy water catchments is recognition of the resilient and dynamic balance between soil, water, and vegetation throughout but especially in riparian areas. Fortunately, humans have been observing and studying streams and water catchments for a long time, and so the physical processes within water catchments are relatively well understood. The key is to manage so those physical processes are in a working order. The social aspects of creating and maintaining healthy water catchments are somewhat more complex. Humans have not always taken care of natural water systems to the best advantage. Ignorance, greed, and apathy have all played a role in creating less-than-ideal conditions along many of the world’s water systems. Fortunately, it is possible to change the way the land is treated and the land will respond accordingly. But to make such changes, people must be willing to cooperate with each other and believe that they can make a positive difference.
Riparian restoration and management has been a major issue in the arid West since the mid 1970’s. Early restoration efforts were mainly the responsibility of wildlife and fisheries biologists and concentrated on the exclusion of livestock for habitat improvement. Through experience and research it is now known that the restoration of riparian areas affects much more than just wildlife and fisheries habitat. The condition of riparian areas influences water quality, aquifer recharge, sediment filtering, energy dissipation, late season stream flows, the rate and volume of erosion, and stream bank stability. This is accomplished through what is often referred to as stream function, or the interaction of water, vegetation, soil, and landform. A stream is functioning properly when the stream morphology (shape), hydrology, and vegetation are able to dissipate the energy of normal high flows without excessive erosion, sediment transport, or channel adjustments. This is accomplished by a combination of dissipating energy within the stream channel and the floodplain.
Energy dissipation can be accomplished with large rocks and landform. But more often than not, vegetation is the linchpin to creating a dynamically stable and resilient stream channel and water catchments. This is especially true in areas of fine sediment.
An ideal riparian vegetative community will have sufficient numbers and varieties of vigorous plants of appropriate species to stabilize the soil with their roots and protect the soil surface by dissipating the energies of high flows. Vegetation is often superior to rock for stabilizing a stream channel, as it is able to adjust and fill in when there is a change in the channel. It not only helps to protect soil surfaces but it can help build and stabilize stream channels as well, by capturing and retaining sediment during high flows.
 |
Photo: Dennis Doncaster |
| August 1987—In the 10 years since the study began, vegetation has started to grow in the sediment deposits in the creek, with plant roots taking advantage of the nutrient-rich land. |
Given the history of manipulating water catchments, streams, and riparian areas, one might ask why it took so long to begin to understand these important processes and the consequences of those actions. One reason is that people were, and still are, driven by their values and opinions, and as someone once said, “Everyone is right from their point of view.” Another reason was not having a common language (terms and definitions) with which to communicate ideas so others could understand. There are many more reasons, but these two became large stumbling blocks toward progress. Recognition is now growing that to produce the values people desire from streams and associated riparian areas on a sustainable basis, these systems must be functioning on a certain level. Only when the basic physical attributes and processes are present and operable in streams and riparian areas are the desired values produced. When this is not the case, it is akin to using up the capital in the system and not producing any interest. The problem is not new. Plato wrote about water running off denuded hillsides into poor-condition streams in 400 BC. He said that water was no longer stored in the ground to be released as springs and streams, but instead ran quickly back to the ocean. He also said “the shrines of extinct water supplies serve as testimony to my hypothesis” In essence, riparian restoration and management is about keeping water on the land longer, and everything that is derived from streams and riparian areas results from this process.
Today there is a twofold problem facing riparian restoration and management efforts in the West. One is the perception of “instant success” and the other is the idea of “near natural rates of recovery.” The first arises partially from the early comparison of livestock grazing exclosures to areas that contained improper or poor grazing strategies for the stream. The grazed areas were usually adjacent to the exclosure, where there was a tendency to select sites that appeared to have the potential for a fast recovery. The exclosures commonly had some remnant vegetation, deep soils, or habitat values to protect. Some phenomenal changes were observed in stream recovery when “incompatible livestock use” was compared to “non-use.” However, it still took many years to begin to understand the true meaning of these changes. The notion of “near natural rates of recovery” arose out of these same observations and people began to expect all streams to display similar responses given the same management. This happened because differences in climate, soils, stream type, ecological condition, upland areas, valley gradient, and a multitude of other factors were not considered to the extent necessary to draw meaningful conclusions. For these reasons and others, an upward trend over time in stream condition is most often assumed to be producing a “near-natural rate of recovery” unless there is sound information that indicates something different.
The Bear Creek Example
Bear Creek in central Oregon gives us a unique opportunity to observe a stream during 30 years of change. As each of you look at the individual photos of this stream, analyze your own feelings about what you see. Assume, as you go from one photo to the other, you are arriving at this stream for the first time and you are required to rate it on its progress and condition. Think about what you would expect the stream to look like the next year, what changes will occur from certain climatic events or changes in management practices, and finally what you would expect the stream to look like in 2006.
Background
Bear Creek is located at an elevation of approximately 3,500 feet in the high desert of central Oregon. Precipitation averages 12 inches, per year with peak runoff occurring in mid- to late February. Summer thunderstorms are fairly frequent. Domestic livestock had grazed the area since the late 1800s and the licensed use in 1977 was 75 animal unit–months (AUMs) from April until September. Surveys during this year revealed that the riparian area totaled 2.5 acres per mile of stream and was producing approximately 200 pounds of forage per acre. That meant if livestock ate all the available forage and used 800 pounds per AUM, it took 1.4 miles of stream to support one cow/calf pair for one month. Stream banks were actively eroding, the channel was deeply incised, flows were frequently intermittent, and runoff events contained high volumes of sediment. The riparian area was storing less than 500,000 gallons of water per mile based on 30% porosity, channel cross-sections, and width of the wetted floodplain.
In 1976 to 1978, the Bureau of Land Management partially rested the area from grazing in an attempt to restore the productivity of the riparian area. In 1979 and 1980 the area was grazed for one week in September, and from 1981 to 1984 it was not grazed. Removal of juniper trees is also evident in the photographs. During 1985, the pasture was divided into three units, with money supplied from the county grazing board and labor provided by the permittee. The grazing was changed from season-long to a three-pasture late winter/early spring use period (mid-February to April 15). These dates normally follow the early runoff events for this stream system. This allowed vegetation to be present for bank protection and regrowth of vegetation during the critical summer months. This regrowth also provided bank protection from summer thunderstorm events and forage for the following year.
 |
Photos: Dennis Doncaster |
| November 1995—Beavers created a dam on the stream. |
 |
| August 1994—A drought period at the creek, allowing vegetation to grow in the channel and slow the water velocity as it travels, creating a moist sediment layer. |
Results
By 1992 the licensed use had increased to 300 AUMs. In 1995 the use was 327 AUMs, and in 1997 it was increased to 376 AUMs or five times the amount previously grazed from the area. The livestock permittee reportedly reduced his annual cost of hay by $10,000 because of the increased forage production that allowed for less winter hay. In 1996 the riparian area had almost doubled from 2.5 acres per mile to 4.9 acres per mile of stream, and the production had increased tenfold to approximately 2,000 pounds of forage per acre. The filtering of sediments by the vegetation had raised the streambed and frequent floodplain by 1 to 2 feet, and was now storing over 2 million gallons—over four times the original volume of water per mile. Stream length, sinuosity, had increased by one-third of a mile in the 3-mile stretch, also helping keep the water on the land longer by providing a longer path. The effects of improved riparian function were also evident in the timing and temperature of the water. Late-season flows had increased enough to provide open water throughout winter. During the hot season, the water stored in the riparian sponge maintained temperatures that were cool enough for temperature sensitive species to survive. This was evidenced by the fact that rainbow trout returned to areas of the stream that had previously been dry. Since 1996 Bear Creek and its riparian area has continued to improve. It has gone through six years of drought, two floods, and a significant rainfall event that washed out an ephemeral channel and formed a dam just downstream of the recovering reach. Photo points were frequently less than 5 feet of water or more. The dam finally eroded through during the spring runoff of 2006. A lot of sediment was deposited in the two years it was a small lake, but the vegetation immediately colonized the riparian area and the channel is now reforming.
A visit to the site in May 2007 (30 years after the first changes in management) showed a vastly different environment. Bear Creek is a stream again, but reed canary grass is now the dominant stabilizing species. It has changed a lot in 30 years, but primarily it has shown us that, given the opportunity to take advantage of droughts and floods, a stream can make miraculous improvement. If the prescribed management does not allow this to occur, streams will not recover. It is that simple.
Conclusions
Since the mid-1970s, much has been learned in the arid and semi-arid West about the compatibility of livestock grazing with the restoration and management of riparian areas. While there has been and still is dissention, anger, and myths surrounding this issue, people have not given up and have achieved a number of successes through applying some of these important guidelines:
- Values cannot be perpetuated until basic stream function is established.
- One grazing strategy does not fit all streams.
- Present riparian condition is very important in setting goals and objectives
- Timing, intensity, and duration are usually more important than number of livestock.
- The most important factor in success is commitment by the operator
- Upland condition must be included in any restoration program.
- Climate cycles dramatically affect restoration rates.
- Droughts are just as important as floods to riparian recovery.
- Restoration and sustainability of riparian resources occurs through using the interest produced and not the capital.
There is still a lot to learn and to do in order to restore the functionality of streams and riparian areas on a landscape scale over such a broad geographic area as the western United States. It can only occur through people working together over time on entire stream systems, which supports the need to foster ways to communicate thoughts and ideas more effectively, set biases aside to facilitate agreement on common goals and objectives, and to do this whether the stream flows through wild land, agricultural, urban, or industrial settings. An ongoing effort called “Creeks and Communities: A Continuing Strategy for Accelerating Cooperative Riparian Restoration and Management” is aimed at addressing this with an approach to building capacity for collaborative problem solving. The initiative is led by the interagency National Riparian Service Team and implemented by a network of individuals, organizations and institutions. To learn more about the Creeks and Communities strategy, go to: www.blm.gov/or/programs/nrst/.
Explanation of Terms
Riparian—The term for an area next to and near a water body where the vegetation type and amount is influenced by the presence of the water. Wetlands are a subset of riparian areas with specific legal definitions related to vegetation, soil, landform, and frequency of inundation by water. www.usace.army.mil/cw/cecwo/reg/rw-bro.htm. Some riparian areas may lack the frequency of inundation necessary to be classified as wetlands but still show the influence of nearby water in their vegetation. In short, all wetlands are riparian areas but not all riparian areas are wetlands.
Floodplain—An area immediately adjacent to a stream channel that is inundated during floods when water volumes are too great to be contained within the channel. Floodplains spread the flow of water and the energy associated with flowing water over larger areas than that associated with the channel itself. This slows the flow of water, reducing the potential for erosion and may even reduce the amount of sediment transported, as slower flowing water can carry less sediment than faster moving water. The human propensity to build on floodplains often makes this natural occurrence a disaster resulting in large expenditures of time, money, energy, materials, and effort with limited results.
Animal Unit Month—In the western United States ranchers are able to lease the privilege of harvesting a portion of the vegetation from public lands. This plant material is often referred to as forage. The most common way of harvesting forage is to use grazing animals such as cows and sheep. Efforts are made to graze at a level that will allow for both wildlife use and for the vegetation to regrow the following year. The base unit of this calculation is the animal unit month (AUM), which is calculated to be the amount that one cow and one calf would eat in a month. In much of the Western United States calculations are based on acres per AUM. In the more productive areas of the Eastern United States calculations may be made on the basis of AUMs per acre.
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Bureau of Land Management-the federal agency charged with maintaining land health while managing for multiple use (grazing, minerals, recreation, etc.) of much of the public lands in the western United States.
Permittee—refers to the person who has been given a permit to harvest a portion of the forage off of a specific area of public land.
January-February 2008
Upstream-Downstream Savings
Researchers studying Bear Creek in central Oregon have determined that healthy, well-functioning water catchments can help boost water efficiency and protect water resources by keeping water on the land longer.
By
Wayne Elmore,
Dennis Doncaster
Introduction
Timing is a large part of using water efficiently. Humans have long recognized that it is much better to live in proximity to a steady water supply than one that delivers too much at some times and not enough at others. Knowing this, people have attempted to regulate the flow of water through the use of dams, reservoirs, and water systems. Such artificial water regulation systems are key aspects of civilization, but they are subject to failure and require large amounts of energy and direct maintenance. There is, however, another approach to managing water that relies not on artificial structures but on maintaining a healthy ecological system. A healthy, well-functioning water catchment (a much more descriptive term than watershed) will filter sediment, buffer high flows, and, most importantly
keep water on the land longer.
Keeping water on the land longer has many benefits. The longer water remains on the land, the greater the potential growth of vegetation, and the more water is available for flow during dry seasons. This is especially evident in the arid areas of the world, including the western United States, where increasing populations and uses for water are making a predictable supply of fresh water an evermore-valuable commodity.
Healthy water catchments not only improve production, reduce floods, and ease droughts on their own, but also prolong the useful life of dams and reservoirs by reducing the volume of sediment (which can shorten the life of a reservoir by filling it in) and reducing the need for maintenance of facilities.
Critical to creating and maintaining healthy water catchments is recognition of the resilient and dynamic balance between soil, water, and vegetation throughout but especially in riparian areas. Fortunately, humans have been observing and studying streams and water catchments for a long time, and so the physical processes within water catchments are relatively well understood. The key is to manage so those physical processes are in a working order. The social aspects of creating and maintaining healthy water catchments are somewhat more complex. Humans have not always taken care of natural water systems to the best advantage. Ignorance, greed, and apathy have all played a role in creating less-than-ideal conditions along many of the world’s water systems. Fortunately, it is possible to change the way the land is treated and the land will respond accordingly. But to make such changes, people must be willing to cooperate with each other and believe that they can make a positive difference.
Riparian restoration and management has been a major issue in the arid West since the mid 1970’s. Early restoration efforts were mainly the responsibility of wildlife and fisheries biologists and concentrated on the exclusion of livestock for habitat improvement. Through experience and research it is now known that the restoration of riparian areas affects much more than just wildlife and fisheries habitat. The condition of riparian areas influences water quality, aquifer recharge, sediment filtering, energy dissipation, late season stream flows, the rate and volume of erosion, and stream bank stability. This is accomplished through what is often referred to as stream function, or the interaction of water, vegetation, soil, and landform. A stream is functioning properly when the stream morphology (shape), hydrology, and vegetation are able to dissipate the energy of normal high flows without excessive erosion, sediment transport, or channel adjustments. This is accomplished by a combination of dissipating energy within the stream channel and the floodplain.
Energy dissipation can be accomplished with large rocks and landform. But more often than not, vegetation is the linchpin to creating a dynamically stable and resilient stream channel and water catchments. This is especially true in areas of fine sediment.
An ideal riparian vegetative community will have sufficient numbers and varieties of vigorous plants of appropriate species to stabilize the soil with their roots and protect the soil surface by dissipating the energies of high flows. Vegetation is often superior to rock for stabilizing a stream channel, as it is able to adjust and fill in when there is a change in the channel. It not only helps to protect soil surfaces but it can help build and stabilize stream channels as well, by capturing and retaining sediment during high flows.
|
Photo: Dennis Doncaster |
| August 1987—In the 10 years since the study began, vegetation has started to grow in the sediment deposits in the creek, with plant roots taking advantage of the nutrient-rich land. |
Given the history of manipulating water catchments, streams, and riparian areas, one might ask why it took so long to begin to understand these important processes and the consequences of those actions. One reason is that people were, and still are, driven by their values and opinions, and as someone once said, “Everyone is right from their point of view.” Another reason was not having a common language (terms and definitions) with which to communicate ideas so others could understand. There are many more reasons, but these two became large stumbling blocks toward progress. Recognition is now growing that to produce the values people desire from streams and associated riparian areas on a sustainable basis, these systems must be functioning on a certain level. Only when the basic physical attributes and processes are present and operable in streams and riparian areas are the desired values produced. When this is not the case, it is akin to using up the capital in the system and not producing any interest. The problem is not new. Plato wrote about water running off denuded hillsides into poor-condition streams in 400 BC. He said that water was no longer stored in the ground to be released as springs and streams, but instead ran quickly back to the ocean. He also said “the shrines of extinct water supplies serve as testimony to my hypothesis” In essence, riparian restoration and management is about keeping water on the land longer, and everything that is derived from streams and riparian areas results from this process.
Today there is a twofold problem facing riparian restoration and management efforts in the West. One is the perception of “instant success” and the other is the idea of “near natural rates of recovery.” The first arises partially from the early comparison of livestock grazing exclosures to areas that contained improper or poor grazing strategies for the stream. The grazed areas were usually adjacent to the exclosure, where there was a tendency to select sites that appeared to have the potential for a fast recovery. The exclosures commonly had some remnant vegetation, deep soils, or habitat values to protect. Some phenomenal changes were observed in stream recovery when “incompatible livestock use” was compared to “non-use.” However, it still took many years to begin to understand the true meaning of these changes. The notion of “near natural rates of recovery” arose out of these same observations and people began to expect all streams to display similar responses given the same management. This happened because differences in climate, soils, stream type, ecological condition, upland areas, valley gradient, and a multitude of other factors were not considered to the extent necessary to draw meaningful conclusions. For these reasons and others, an upward trend over time in stream condition is most often assumed to be producing a “near-natural rate of recovery” unless there is sound information that indicates something different.
The Bear Creek Example
Bear Creek in central Oregon gives us a unique opportunity to observe a stream during 30 years of change. As each of you look at the individual photos of this stream, analyze your own feelings about what you see. Assume, as you go from one photo to the other, you are arriving at this stream for the first time and you are required to rate it on its progress and condition. Think about what you would expect the stream to look like the next year, what changes will occur from certain climatic events or changes in management practices, and finally what you would expect the stream to look like in 2006.
Background
Bear Creek is located at an elevation of approximately 3,500 feet in the high desert of central Oregon. Precipitation averages 12 inches, per year with peak runoff occurring in mid- to late February. Summer thunderstorms are fairly frequent. Domestic livestock had grazed the area since the late 1800s and the licensed use in 1977 was 75 animal unit–months (AUMs) from April until September. Surveys during this year revealed that the riparian area totaled 2.5 acres per mile of stream and was producing approximately 200 pounds of forage per acre. That meant if livestock ate all the available forage and used 800 pounds per AUM, it took 1.4 miles of stream to support one cow/calf pair for one month. Stream banks were actively eroding, the channel was deeply incised, flows were frequently intermittent, and runoff events contained high volumes of sediment. The riparian area was storing less than 500,000 gallons of water per mile based on 30% porosity, channel cross-sections, and width of the wetted floodplain.
In 1976 to 1978, the Bureau of Land Management partially rested the area from grazing in an attempt to restore the productivity of the riparian area. In 1979 and 1980 the area was grazed for one week in September, and from 1981 to 1984 it was not grazed. Removal of juniper trees is also evident in the photographs. During 1985, the pasture was divided into three units, with money supplied from the county grazing board and labor provided by the permittee. The grazing was changed from season-long to a three-pasture late winter/early spring use period (mid-February to April 15). These dates normally follow the early runoff events for this stream system. This allowed vegetation to be present for bank protection and regrowth of vegetation during the critical summer months. This regrowth also provided bank protection from summer thunderstorm events and forage for the following year.
|
Photos: Dennis Doncaster |
| November 1995—Beavers created a dam on the stream. |
|
| August 1994—A drought period at the creek, allowing vegetation to grow in the channel and slow the water velocity as it travels, creating a moist sediment layer. |
Results
By 1992 the licensed use had increased to 300 AUMs. In 1995 the use was 327 AUMs, and in 1997 it was increased to 376 AUMs or five times the amount previously grazed from the area. The livestock permittee reportedly reduced his annual cost of hay by $10,000 because of the increased forage production that allowed for less winter hay. In 1996 the riparian area had almost doubled from 2.5 acres per mile to 4.9 acres per mile of stream, and the production had increased tenfold to approximately 2,000 pounds of forage per acre. The filtering of sediments by the vegetation had raised the streambed and frequent floodplain by 1 to 2 feet, and was now storing over 2 million gallons—over four times the original volume of water per mile. Stream length, sinuosity, had increased by one-third of a mile in the 3-mile stretch, also helping keep the water on the land longer by providing a longer path. The effects of improved riparian function were also evident in the timing and temperature of the water. Late-season flows had increased enough to provide open water throughout winter. During the hot season, the water stored in the riparian sponge maintained temperatures that were cool enough for temperature sensitive species to survive. This was evidenced by the fact that rainbow trout returned to areas of the stream that had previously been dry. Since 1996 Bear Creek and its riparian area has continued to improve. It has gone through six years of drought, two floods, and a significant rainfall event that washed out an ephemeral channel and formed a dam just downstream of the recovering reach. Photo points were frequently less than 5 feet of water or more. The dam finally eroded through during the spring runoff of 2006. A lot of sediment was deposited in the two years it was a small lake, but the vegetation immediately colonized the riparian area and the channel is now reforming.
A visit to the site in May 2007 (30 years after the first changes in management) showed a vastly different environment. Bear Creek is a stream again, but reed canary grass is now the dominant stabilizing species. It has changed a lot in 30 years, but primarily it has shown us that, given the opportunity to take advantage of droughts and floods, a stream can make miraculous improvement. If the prescribed management does not allow this to occur, streams will not recover. It is that simple.
Conclusions
Since the mid-1970s, much has been learned in the arid and semi-arid West about the compatibility of livestock grazing with the restoration and management of riparian areas. While there has been and still is dissention, anger, and myths surrounding this issue, people have not given up and have achieved a number of successes through applying some of these important guidelines:
- Values cannot be perpetuated until basic stream function is established.
- One grazing strategy does not fit all streams.
- Present riparian condition is very important in setting goals and objectives
- Timing, intensity, and duration are usually more important than number of livestock.
- The most important factor in success is commitment by the operator
- Upland condition must be included in any restoration program.
- Climate cycles dramatically affect restoration rates.
- Droughts are just as important as floods to riparian recovery.
- Restoration and sustainability of riparian resources occurs through using the interest produced and not the capital.
There is still a lot to learn and to do in order to restore the functionality of streams and riparian areas on a landscape scale over such a broad geographic area as the western United States. It can only occur through people working together over time on entire stream systems, which supports the need to foster ways to communicate thoughts and ideas more effectively, set biases aside to facilitate agreement on common goals and objectives, and to do this whether the stream flows through wild land, agricultural, urban, or industrial settings. An ongoing effort called “Creeks and Communities: A Continuing Strategy for Accelerating Cooperative Riparian Restoration and Management” is aimed at addressing this with an approach to building capacity for collaborative problem solving. The initiative is led by the interagency National Riparian Service Team and implemented by a network of individuals, organizations and institutions. To learn more about the Creeks and Communities strategy, go to: www.blm.gov/or/programs/nrst/.
Explanation of Terms
Riparian—The term for an area next to and near a water body where the vegetation type and amount is influenced by the presence of the water. Wetlands are a subset of riparian areas with specific legal definitions related to vegetation, soil, landform, and frequency of inundation by water. www.usace.army.mil/cw/cecwo/reg/rw-bro.htm. Some riparian areas may lack the frequency of inundation necessary to be classified as wetlands but still show the influence of nearby water in their vegetation. In short, all wetlands are riparian areas but not all riparian areas are wetlands.
Floodplain—An area immediately adjacent to a stream channel that is inundated during floods when water volumes are too great to be contained within the channel. Floodplains spread the flow of water and the energy associated with flowing water over larger areas than that associated with the channel itself. This slows the flow of water, reducing the potential for erosion and may even reduce the amount of sediment transported, as slower flowing water can carry less sediment than faster moving water. The human propensity to build on floodplains often makes this natural occurrence a disaster resulting in large expenditures of time, money, energy, materials, and effort with limited results.
Animal Unit Month—In the western United States ranchers are able to lease the privilege of harvesting a portion of the vegetation from public lands. This plant material is often referred to as forage. The most common way of harvesting forage is to use grazing animals such as cows and sheep. Efforts are made to graze at a level that will allow for both wildlife use and for the vegetation to regrow the following year. The base unit of this calculation is the animal unit month (AUM), which is calculated to be the amount that one cow and one calf would eat in a month. In much of the Western United States calculations are based on acres per AUM. In the more productive areas of the Eastern United States calculations may be made on the basis of AUMs per acre.
Bureau of Land Management-the federal agency charged with maintaining land health while managing for multiple use (grazing, minerals, recreation, etc.) of much of the public lands in the western United States.
Permittee—refers to the person who has been given a permit to harvest a portion of the forage off of a specific area of public land.