Synthesis of Design Guidelines and Experimental Data for Water Quality 

Function in Agricultural Landscapes 

in the Intermountain West

Susan Buffler

2005

Thesis Committee

Craig Johnson, John Nicholson and Nancy Mesner

Utah State University

Photo credit: Susan Buffler

Appendix C 
Table of Contents

Table of Contents......................................................................................................................................i

Abstract....................................................................................................................................................ii

Preface...................................................................................................................................................... 1

Background.............................................................................................................................................. 2

Project Goal ............................................................................................................................................. 3

Methods.................................................................................................................................................... 4

Characteristics of the Study Area............................................................................................................. 4

Buffer Complexity and Dynamics........................................................................................................... 5

Nutrient Cycling .......................................................................................7

Landscape Attributes Influencing the Effectiveness of Riparian Buffers;

Implications for the Intermountain West .................................................................................................7

Primary Attributes.............................................................................................................7

Buffer Width.............................................................................................7

Slope Gradient..........................................................................................7

Soil Infiltration .........................................................................................8

Surface Roughness...................................................................................8

Slope Length (Discussion) .......................................................................8

Adjacent Land Use Practices....................................................................8

Secondary Attributes..........................................................................................................8

Differences Between Arid and Non-Arid Riparian Systems ..................................................................9

Climate .....................................................................................................9

Hydrology.................................................................................................9

Soils........................................................................................................10

Topography.............................................................................................10

Vegetation...............................................................................................10

Wildlife...................................................................................................11

Sources and Causes of Impairment........................................................................................................11

Contaminants and Buffer Effects...........................................................................................................13

Particulate Contaminants -Sediment......................................................................................................13

Reasons for Concern ...............................................................................13

How Buffers Affect Sediment .................................................................14

i
Particulate Bound Phosphorus (P)................................................................................. 14

Reasons for Concern...............................................................................14

How Buffers Influence P Dynamics .......................................................14

Pesticides........................................................................................................................ 15

Reasons for Concern...............................................................................15

How Buffers Affect Pesticides................................................................15

Pathogens .......................................................................................................................15

Reasons for Concern ..............................................................................16

How Buffers Affect Pathogens...............................................................16

Dissolved Contaminants........................................................................................................................16

Nitrogen (N)...................................................................................................................16

Reasons for Concern..............................................................................16

How Buffers Influence N Dynamics......................................................17

Dissolved Phosphorus............................................................................18

Reasons for Concern..............................................................................18

How Buffers Influence P Dynamics.......................................................18

Buffer Design Guidelines......................................................................................................................19

Summary ...............................................................................................................................................21

Attributes........................................................................................................................21

Primary Attributes...................................................................................21

Secondary Attributes...............................................................................21

Planning Protocol...........................................................................................................22

Matrix A - Sediment...............................................................................................................................23

Matrix B - Pesticides..............................................................................................................................29

Matrix C - Phosphorus...........................................................................................................................33

Matrix D - Pathogens.............................................................................................................................39

Matrix E - Nitrogen................................................................................................................................41

References..............................................................................................................................................50

 Abstract

Currently, there is no scientific literature examining appropriate riparian buffer widths for water quality for streams on private agriculturally dominated lands in arid regions of the Intermountain West. The 

initial step in this research effort was a review of buffer research as documented in the literature in other 

physiographic regions of the United States. Research findings on appropriate buffer widths for water 

quality parameters were synthesized using a matrix format. Differences between arid and non-arid 

landscape characteristics, soil, topography, vegetation, climate and hydrology and their effect on buffers 

for water quality were also researched. The combined research findings in this document (Appendix C) 

were then used to develop Buffer Design Guidelines for Water Quality and Wildlife Habitat Functions 

on Agricultural Landcapes in the Intermountain West. ii
Preface

Water quality is a major global issue. It is 

estimated that over 1 billion people worldwide do 

not have access to safe, clean drinking water. Just 

3% of all water on earth is fresh water but only 

0.003% is usable (Leopold 1997; Mason 2002). 

Although many of the issues regarding water are 

political and economic, the importance of clean 

water for human, aquatic, and riparian health 

cannot be understated.

The Clean Water Act (CWA) of 1972 was passed 

by the U.S. Congress in response to increasing 

concerns about water pollution. The Clean Water 

Act’s mission is to “restore and maintain the 

chemical, physical, and biological integrity of 

the Nation’s Waters” (EPA 2005b). This statute 

uses a number of regulatory and non-regulatory 

tools to implement reduction of pollutants into 

waterbodies and provides for financing of water 

treatment facilities and management of polluted 

runoff.

Water quality, however, is a social value imposed 

by humans for some existing or potential 

beneficial use (Fry et al. 1994). The CWA directs 

states and tribes to protect water quality for 

specific beneficial uses including clean drinking 

water (public water supply) and recreation 

(primary and secondary contact), aquatic and 

wildlife habitat and fish consumption, agriculture, 

and other uses (EPA 2005a).

The Safe Drinking Water Act (1974) established 

public drinking water standards, enforceable 

by law, for various contaminants detrimental to 

human health. Primary contaminants include a 

wide variety of classes: disinfection byproducts, 

disinfectants, inorganic chemicals such as heavy 

metals and nitrate, organic chemicals such 

as herbicides and industrial discharges, and 

radionuclides such as uranium (EPA 2005a). 

Acceptable levels were developed and are 

published for each contaminant. 

Water quantity and water quality are rapidly 

becoming a serious problem in the Intermountain 

West and other arid regions of the western 

United States. Over one hundred years of 

riparian degradation by livestock, dams and 

water diversions, and irrigation return flows have 

contributed to degradation of the region’s streams 

and rivers. Increasing urbanization accompanying 

unprecedented population growth are pushing 

water resources to their limits in many 

communities. In conjunction with these issues, 

a prolonged drought (1998-2004) has created 

an immediate need for management practices to 

address these water problems. 

There is substantial research data to suggest that 

riparian buffers (linear vegetated areas along 

rivers, streams and other water bodies) are a 

cost effective tool in mitigating water quality 

problems. However, most of the research on 

riparian buffer effectiveness has been done in 

landscape regions beyond the Intermountain 

West. Intermountain West resource managers 

have expressed a need for a buffer planning 

protocol and design guides that meet the unique 

characteristics of this region (Johnson and Buffler 

2005). 

The data synthesized in the literature review 

and identification of unique Intermountain 

West landscape characteristics affecting buffer 

functions provided the foundation upon which 

Buffer Design Guidelines for Water Quality 

and Wildlife Habitat Functions on Agricultural 

Landscapes in the Intermountain West (Riparian 

Buffer Handbook) was developed. 

The Riparian Buffer Handbook is a resource for:

● assessing the functional condition of 

existing riparian buffers and the off-site 

conditions to be buffered

● determining the applicability of buffers to 

address these conditions

● determining buffer 

appropriateness, general buffer design 

guidelines and management strategies, 

buffer configuration and structural 

characteristics to meet water quality and 

wildlife objectives

Every riparian buffer and adjacent upland site 

condition will have unique aspects making 

it difficult to develop universally applicable 

planning and design guidelines, however, many 

site characteristics and adjacent land uses are 

1
similar throughout the region and are familiar 

to area resource managers. In these settings the 

riparian buffer design protocol and guidelines 

presented in the Riparian Buffer Handbook can be 

used by resource managers. Inevitably, atypical 

buffer situations will be encountered; expert 

advice from conservation partners, extension 

water quality specialists, Natural Resource 

Conservation Service (NRCS) personnel and 

other state and county agencies should be 

solicited.

Currently, the Conservation Security Program 

(CSP) administered by the NRCS, provides 

funding and assistance on agricultural lands 

for practices that promote or maintain the 

“conservation and improvement of soil, water, 

air, energy, plant and animal life, and other 

conservation purposes on Tribal and private 

working lands. Working lands include cropland, 

grassland, prairie land, improved pasture, and 

range land, as well as forested land that is an 

incidental part of an agriculture operation” 

(NRCS 2005). Water quality practices funded 

by the CSP include conservation tillage, filter 

strips, terraces, grassed waterways, managed 

access to water courses, nutrient and pesticide 

management, prescribed grazing, and irrigation 

water management. 

Protection of riparian areas (buffers) on private 

cropland and mixed cattle / crop systems in the 

sagebrush steppe region of the Intermountain 

West can be fiscally feasible for many private 

landowners. They have access to cost-share for 

planning and implementation programs such 

as the Conservation Reserve Program (CRP), 

Wildlife Habitat Improvement Program (WHIP) 

and Environmental Quality Improvement 

Program (EQIP). In addition, the NRCS offers 

technical assistance to landowners and frequently 

helps build funding partnerships with Non 

governmental organizations (NGOs) (NRCS 

2005). Partnerships will be key to implementing 

riparian buffer projects.

Background

Historically, waterways and riparian areas have 

always attracted humans (Busch and Scott 2004). 

Hunting, fishing, the development of agriculture, 

cities, transportation networks, and recreation, 

has traditionally occurred in these areas. Human 

impacts on riparian systems, particularly in the 

Western United States, have been considerable. 

It is estimated that over 70 percent of western 

riparian habitat has been significantly altered 

or eliminated by draining, clearing, permanent 

flooding, diverting and damming (Gardner et al. 

1999; NRC 2002). 

In the western United States, cattle grazing alone 

accounts for 80% of damaged stream and riparian 

systems (Belsky et al. 1999). Cattle tend to 

congregate in cool, shady riparian habitat where 

forage availability and quality is high (Clary and 

Medin 1992). In many cases, exclusion from 

riparian areas has been successful in restoring 

riparian areas to proper functioning condition 

(BLM 1997). Other low impact rotational grazing 

management systems such as Holistic Resource 

Management (Savory and Butterfield 1999) and 

seasonal rest rotation of cattle and sheep have 

been shown to improve riparian function (BLM 

1997). However, Belsky et al. (1999) in their 

review of livestock influences on stream and 

riparian ecosystems argue that nothing short of 

complete exclusion will return riparian areas to 

their proper functioning condition. 

Agricultural land uses contribute the majority 

of non-point sources of pollution leading to 

degradation of surface and subsurface waters 

2

Photo credit: Susan Buffler

Canoeing on the Bear River, Cache Valley, UT
(EPA 2000 Chapter 10). Contaminants originating 

in agricultural landscapes include sediment, 

fertilizers, herbicides and pesticides, organic 

and inorganic compounds, bacteria and viruses, 

hormones and antibiotics (Barfield et al. 1998; 

Belt et al. 1992; Dillaha and Inamdar 1997).

Riparian areas function in maintaining ecological 

processes such as: regulating stream temperature, 

stream flow, cycling nutrients, providing organic 

matter, filtering chemicals and other pollutants, 

trapping and redistributing sediments, stabilizing 

stream channels and banks, absorbing and 

detaining floodwaters, maintaining fish habitats, 

and supporting the food web for a variety of biota, 

and regulating stream temperature (Wenger 1999; 

Fischer et al. 2000; Obedzinski 2000; CRA 2001; 

NRC 2002: Chambers and Miller 2004). Thus 

protection of existing functional riparian systems 

and restoration of degraded systems can be one 

tool employed to address water quality issues.

Unfortunately, unlike wetlands, riparian areas 

are not protected under Section 404B1 of the 

Clean Water Act mainly because there is no 

currently agreed on definition for a riparian 

area (NRC 2002). The definition used by the 

National Research Council (NRC) is a first step 

in initiating a process to define riparian areas 

by their function and ecological processes. The 

definition used by the NRC is appropriate for the 

Intermountain West since it is comprehensive 

but also general enough to be used for different 

physiographic regions.

“Riparian areas are transitional 

between terrestrial and aquatic 

ecosystems and are distinguished 

by gradients in biophysical 

conditions, ecological processes, 

and biota. They are areas through 

which surface and subsurface 

hydrology connect water bodies 

with their adjacent uplands. They 

include those portions of terrestrial 

ecosystems that significantly 

influence exchanges of energy and 

matter with aquatic ecosystems 

(i.e. zone of influence). Riparian 

areas are adjacent to perennial, 

intermittent, and ephemeral 

streams, lakes, and estuarinemarine shorelines.” (NRC 2002)

Although riparian buffers have been shown to be 

effective in improving water quality, the current 

state and federal buffer width recommendations 

are generally not based on scientific consensus but 

on political acceptability (Dillaha and Inamdar 

1997; Fischer et al. 2000; Fischer and Fischenich 

2000) and ease of conservation program delivery. 

Developing buffer width guidelines based on 

scientific data that are responsive to regional 

landscpae characteristics is essential to long 

term enhancement of water quality in the region. 

Buffers are particularly effective when combined 

with other conservation practices. 

Project Goal 

The goal of this document was to synthesize the 

riparian buffer literature into a format that:

● identified the most important landscape 

attributes affecting buffer width and 

design

● identified unique Intermountain West 

landscape characteristics that will affect 

buffer width

● identified a planning protocol that 

could be adapted to western landscpape 

conditions, utilizes readily available or 

easily measured data, is scientifically 

defensible, easily replicated and is easily 

implemented in the field

3

Cattle grazing on a remnant riparian area. 

Bear River, southeastern Idaho. Photo credit: 

Susan Buffler
To accomplish this goal, a buffer planning 

protocol, must respond to those Intermountain 

West landscape characteristics most important 

in resolving water quality issues. These include: 

hydrological characteristics of the watershed, 

adjacent land use and land management practices, 

general soil characteristics, slope gradients, 

vegetation and surface roughness, climate, 

runoff characteristics, fish and wildlife species 

needs, and recreation activities (Buffler 2005). 

The planning protocol and guidelines must also 

be flexible enough to respond to atypical site 

conditions that may be encountered in the field. 

Specific intended riparian buffer functions 

addressed in the water quality portion of the 

proposed planning protocol are to reduce impacts 

to water quality from adjacent land uses by 

reducing sedimentation and pollution of surface 

water and contamination of shallow ground water. 

The Riparian Buffer Handbook should be used as 

a tool by land managers in conjunction with other 

Best Management Practices (BMP) to improve 

water quality. Buffers in and of themselves are not 

a panacea for all water quality improvements.

The NRCS and resource planning professionals 

are increasingly involved in watershed scale 

planning of which buffers are a small part. The 

reality, however, is that funding for buffer projects 

tends to be allocated one landowner initiated 

buffer at a time making contiguous buffering 

problematic but not impossible.

Methods

Several tasks were required to achieve the broad 

goals outlined above. The first was to delineate 

an appropriate study area. Delineation of a 

study area within the Interior Western states was 

determined through identification of regions with 

general similarity in: soils, climate, vegetation, 

hydrology wildlife, and cropping and grazing 

systems. 

The second step, the largest task, was to review 

literature relevant to riparian buffers. This 

review included books, journal articles, technical 

publications and gray literature. In addition 

soil scientists, range scientists, ecologists and 

wildlife biologists from the Intermountain West 

with expertise in conservation buffers were 

interviewed. Several protocols for estimating the 

general condition of riparian habitat ecosystem 

function, and structure were reviewed.

In order to identify appropriate buffer widths and 

design guidelines for riparian buffers on private 

lands in the Intermountain West, these steps were 

followed.

1. Delineate the region of interest 

2. Review, inventory and catalog available 

relevant riparian buffer literature

3. Focus on:

a. Buffer retention of sediment, nitrogen, 

phosphorus, pesticides, and pathogens. 

Each of these is described and a matrix of 

relevant research compiled.

b. Unique characteristics of riparian 

ecosystems in the Intermountain West.

4. Query major professional societies, nongovernmental organizations (NGOs), and 

government agencies about riparian buffer 

guidelines

5. Review findings with the National 

Agroforestry partners

6. Review of guidelines prepared in this research 

by outside experts

Research results from the literature reviewed were

organized into a series of tables. A table was

prepared for each type of contaminant. An

additional table displays research findings on

buffer effects on surface and subsurface flows.

Characteristics of the Study Area

The study area is large and complex; a 

picturesque landscape with valleys of varying 

sizes and broad plains enclosed or edged by tall 

mountains. Elevations range from over 13,000 

foot mountain peaks to valleys at 3,000 feet. 

Precipitation varies from more than 50 inches in 

upper watersheds to less than six inches at lower 

elevations and in mountain rain shadow areas. 

Desiccating winds are strong and persistent. 

Wind and runoff generated soil erosion is 

prevalent on open exposed landscapes throughout 

the study area.

4
Forest and range land, most in public ownership, 

predominate in the upper reaches of area 

watersheds. Range land is also dominant in 

the broad lower elevation plains and drier 

southern and western sections of the study area. 

Rolling foothills and relatively flat valleys often 

with fertile soils, a sufficient growing season 

and access to water for irrigation are typical 

of cropped lands in lower reaches of most 

watersheds.

These more agriculturally productive lower 

elevation landscapes support row crops, orchards, 

dairy and ranching activities. Riparian buffers 

in these working landscapes are the focus of 

this project. Working landscapes in the study 

area are populated by scattered farms and 

ranches supported by small rural communities. 

Historically agriculture, ranching and tourism 

have been the mainstays of the Intermountain 

West economy. However a transformation is in 

progress fueled by a declining farm and ranch 

economy. Regional economies are diversifying. 

Unprecedented urban and exurban growth, 

much of it occurring along riparian corridors, 

is consuming farm and ranch land, and wildlife 

habitat, and converting it to suburban tracts and 

upscale ranchettes. This new land use dynamic 

combined with old riparian resource issues 

(grazing, logging, mining, and recreation) present 

planners and resource managers with complex 

challenges.

Riparian Buffer Complexity and 

Dynamics

Riverine systems are multidimentional 

(longitudinal, lateral and vertical) complex and 

change over time. Climate influences the entire 

system. Geologic and topographic features define 

the watershed. Watershed hydrology, surface, 

subsurface and stream flows affect and are 

affected by riparian buffer plant communities. 

All of these factors are subject to modification 

by human activity. The following discussion 

highlights several key riparian buffer structural 

and functional characteristics that affect riparian 

buffer vegetation and water quality. 

At the stream reach (buffer project scale), 

bank storage, or channel water moving into 

the riparian zone influences not only water 

storage, chemical transformations, and surface 

water temperature but may also greatly 

affect the composition and extent of plant 

communities (NRC 2002). Alteration of the 

flow regime by water impoundment, diversion, 

or groundwater withdrawals has significantly 

reduced native riparian vegetation in many 

parts of the West. Once this occurs, salinity may 

increase (Stromberg 2001) and weedy species, 

particularly mesic and often non-native trees, 

gain a foothold and are difficult to remove (Busch 

and Scott 2004). Decline in groundwater may 

isolate patches of native vegetation leading to 

their disappearance (Busch and Scott 2004). 

Restoration becomes more difficult; native 

cottonwoods, for example, require specific peak 

flows for establishment and reproduction and 

higher water tables for long-term survival.

A riparian vegetation study done on the Snake 

River, Idaho revealed that approximately 30% 

of the flora and 60% of the tree basal area and 

density was composed of exotic species. Only 

two regionally native tree species were found. 

Adjacent agricultural uses had eradicated or 

severely reduced native species in the upland 

areas of the downstream section of the river 

(Dixon and Johnson 1999). An increase in 

woody vegetation over time, mainly on in-stream 

islands, was observed. It was speculated that 

reduced low flows from damming over a period 

of about 80 years and increased sedimentation 

5

Map of the study area. Adapted from West 

1988. Cambridge Press
Benefit Grass Shrub Tree

Stabilize 

bank erosion

low1 high high

Filter 

sediment 

 

high low low

Filter 

sedimentbound 

nutrients, 

pesticides, 

microbes

high low low

Filter soluble 

nutrients, 

pesticides, 

microbes

medium low medium

Aquatic 

habitat 

 

low medium high

Wildlife 

habitat

range/

pasture/

prairie 

wildlife

high medium low

Forest 

wildlife 

 

low medium high

Economic 

products 

 

medium medium2 medium

Visual

diversity 

 

low medium high

Flood 

protection

 

low medium high

from agricultural practices created larger island 

and mainland riparian areas. Introduction of 

exotic trees with different reproduction and 

establishment requirements may also have 

contributed to the increase of exotic species 

(Dixon and Johnson 1999). This pattern was also 

found on rivers and streams in Arizona that have 

not been diverted but where flooding has been 

controlled (Stromberg 2001).

Riparian vegetation from the canopy, woody 

debris, roots and leaf litter, helps stabilize stream 

banks by protecting the soil surface from impacts 

of rain and increases infiltration through soil 

macropore formation (NRC 2002). However, 

once vegetation is removed, surface cover and 

root strength are reduced, increasing erosion and 

often concentrating overland flow; surface erosion 

may occur during storm events, particularly with 

increasing slope (NRC 2002). 

Deep rooted plants have better soil holding 

capacity than shallow rooted plants (Schultz 

et al. 1994), however, historically occurring 

native grassed riparian zones on streams in the 

Great Plains, may have greater bank holding 

properties on streambanks with low slopes, 

due to their fibrous root systems (Lyons et al. 

2000). Streambanks with steeper slopes are 

better stabilized by woody vegetation. Grass and 

wooded riparian areas have different structures 

(Table 1). For instance, grassed streambanks 

store significantly more sediment than wooded 

streambanks, are narrower, and tend to produce 

undercut banks favored by fish. Wooded 

riparian areas provide fish habitat and energy 

inputs through debris falls and may have lower 

summer baseflows due to higher water uptake by 

vegetation (Lyons et al. 2000; Cushing and Allan 

2001).

Naturally meandering streams with adequate 

vegetation for bank stabilization are more 

effective for flood control than channelized 

streams because stream flow is reduced (Fry 

et al. 1994). Natural inputs of woody debris 

to the stream can cause localized flooding but 

downstream flooding may be reduced (Lyons et 

al. 2000). Natural streams are also more capable 

of initiating and sustaining communities of native 

riparian plants and wildlife.

Nutrient cycling

Complex cycling of nutrients between soil 

minerals, microbial components, and plants is also 

characteristic of riparian areas. Major nutrients 

such as nitrogen, carbon, and phosphorus are the 

most important in the function of natural riparian 

ecosystems (Baker et al. 2004). 

6

Table 1. Relative effectiveness of different 

vegetation types for providing specific buffer 

benefits.

1 slope dependent

2

 includes decorative woody floral industry

NRCS 2005
Riparian vegetation strongly affects nutrient 

cycling in aquatic systems. Plant litterfall and 

large woody debris is broken down by physical 

action and by in-stream organisms providing 

a carbon energy source in the form of coarse 

particulate organic matter (Cushing and Allen 

2001; Baker et al. 2004). Plant roots release 

carbon and decaying cells to supply an energy 

source to soil microbes, thereby increasing 

mineralization activity. Release of nitrogen from 

decaying plant tissues through mineralization 

is lower in arid areas except where irrigation is 

practiced and large quantities of vegetation are 

available (Brady and Weil, 2000). Riparian areas 

may act as a source or a sink, releasing or holding 

nutrients depending on riparian management 

(phosphorus and sediment) as well as seasonal 

factors (nitrogen) (Wenger 1999). 

Properly functioning riparian buffers are more 

effective at maintaining or enhancing water 

quality than impaired buffers (Buffler 2005).

Landscape Attributes Influencing the 

Effectiveness of Riparian Buffers; 

Implication for Intermountain West 

Buffers

Although general and brief, the previous 

discussion makes an important point; numerous 

site attributes affect riparian buffer function. 

Each attribute could therefore affect decisions 

regarding appropriate buffer widths to protect 

water quality. 

Literature reviews as cited in Kleinschmidt 

Associates (2000) and completed by Buffler 

(2005) suggest there are several landscape 

attributes (primary attributes) that have the 

most significant influence on riparian buffer 

effectiveness and width. They are introduced 

briefly below. 

Primary Attributes

Buffer Width

Developing a protocol for determining 

appropriate buffer widths for water quality is 

the primary goal of this project. Because of its 

importance, width and its relationship to reducing 

sediments, nitrogen, phosphorus, pathogens, and 

pesticides is mentioned here and discussed in 

greater detail later in this chapter.

According to Gilliam et al. (1997), buffer width 

is the most important controllable variable in 

determining effectiveness of buffers in reducing 

pollutants and protecting stream health with most 

of the beneficial effects of buffers occuring within 

the top upslope half of the buffer (Peterjohn and 

Correll 1984; Lowrance 1992; Jordan et al. 1993; 

Robinson et al. 1996; Lim et al. 1998; Schmitt et 

al. 1999; Jin and Römkens 2001; Syversen et al. 

2001). 

Buffer widths for streams in more arid areas may 

need to be wider due to the different nature of 

western stream systems. For example, higher 

order valley streams typical of the study area tend 

to be wider with less vegetation overhanging the 

stream, therefore, a different stream ecosystem 

results (Gilliam et al 1997; Lyons et al. 2000). 

Fry et al. (1994) suggests that since arid rivers 

move more freely throughout their floodplains 

than those in wetter regions, buffer widths should 

range from 23m to 35m. This is particularly 

relevant where streams are intermittent and 

summer storms are short and intense. 

Slope Gradient

Few studies reviewed compared different slope 

gradients with levels of contaminant removal. A 

6m (19.7’) buffer on a Montana riparian pasture 

reduced sediment at 3m (9.8’) on slopes ranging 

from 2 to 20% (Hook 2003). Jin and Römkens 

(2001) found no increased trapping efficiency on 

a simulated buffer beyond 3m on a 4 or 6% slope. 

Davies and Nelson (1994) found that in logged 

forests effects on sedimentation depended on 

buffer width, not on slope, erodability, or time. 

However, on sites where nitrogen, dissolved 

phosphorus, pathogens, and pesticides need to 

be attenuated wider buffers may be required on 

steeper slopes, although Jones (2001) found weak 

correlations between slope and nitrogen removal 

in three California riparian buffers. Other studies 

show a less clear trend with some contaminants 

decreasing with decreasing slope (Patty et al., 

1997). Sites with slopes steeper than 25% with 

7
little surface roughness or infiltration capacity 

probably need wider buffers (Kleinschmidt 1999).

Soil Infiltration

 Soil infiltration is important in removing fine 

sediment, nitrogen, and certain pesticides and 

pathogens (Kloppel et al.1997; Barfield et al. 

1998; Arora et al. 2003; Boyd et al. 2003). 

Antecedent conditions also affect runoff 

rates. Water flowing over saturated soils 

will more likely bypass potential subsurface 

transformational processes (Daniels and Gilliam 

1996; Hill 1996). 

Soil texture and structure influence infiltration. 

Many of the soils in valleys of the Intermountain 

West have a strong clay component. Clay 

soils, comprised of small particles, have lower 

infiltration rates, but higher water holding 

capacity than gravelly, sandy, or loamy soils 

(Leopold 1997; Brady and Weil 2000; NRC 2004) 

thus reducing buffer effectiveness. 

Surface Roughness

Surface features such as coarse woody debris, 

rocks and boulders, vegetation, and other 

microtopographic features, reduce overland 

flow in woody and mixed vegetation buffers 

(Kleinschmidt 1999). Sites with high levels of 

surface roughness increase infiltration of surface 

runoff reducing overland flow and thus decreasing 

the amount of contaminants to the stream. 

Reduced overland flow can, therefore, reduce 

buffer width required for water quality functions. 

Slope Length (Discussion)

Slope length was not considered to have as 

important an effect on buffer width as slope 

gradient. As noted above and elsewhere in this 

appendix, most attenuation of contaminants with 

the exception of nitrogen, occurs within the first 

20m (60’) of the buffer. The minimum buffer 

width recommended in the Riparian Buffer 

Handbook based on the literature review and 

assessment of Intermountain conditions is 70’ 

(21.3m) or top of stream bank plus 35’(10.7m), 

whichever is greater, thus slope length was not 

considered a primary attribute for determining 

buffer width because attenuation occurs within 

the minimum length recommended. 

Adjacent Land Use Practices

Adjacent land use and management practices 

can have a significant effect on the quantity of 

pollutants that reach the buffer (Kleinschmidt 

Associates 1999). Planting perpendicular to the 

slope as opposed to conventional vertical tillage 

has been shown to reduce herbicide runoff from 

cultivated fields (Patty et al. 1997). Implementing 

NRCS in-field and range conservation practices 

such as terraces, in-field buffers, grassed 

waterways, and rotational grazing have proved 

effective at reducing contaminants before they 

reach riparian buffers (Buffler 2005). Minimizing 

the application of fertilizers, and pesticides 

adjacent to buffers (especially phosphorus) is 

preferable since buffer function may decline over 

time if they become overloaded with chemicals 

(Wenger 1999). Wider buffers may be required 

where in-field conservation practices are not 

implemented. 

Secondary Attributes

Secondary attributes are landscape features that 

affect buffer effectiveness and width but to a 

lesser degree than Primary Attributes. Secondary 

Attributes identified in the literature include:

• surface water features

• sand and gravel aquifers

• seeps and springs

• floodplains

• wetlands

Secondary attributes are frequently used to 

modify (expand) preliminary widths delineated 

using primary attributes alone (Kleinschmidt 

1999). 

Differences Between Arid and Non-Arid 

Riparian Systems - Effects on Buffer 

Attributes and Width

The functional characteristics of site attributes are 

different in arid and non-arid environments. These 

differences must be understood when interpreting 

buffer width research findings from non-arid 

environments and assessing their applicability to 

riparian buffers in the arid Intermountain West. 

8
Climate

The major differences between riparian areas 

in arid and mesic regions are driven by climate. 

Arid regions of the United States are found 

approximately between the 100th parallel and the 

Cascade and Sierra Nevada Ranges of the coastal 

states of California, Oregon, and Washington. 

Low precipitation, cold winters, and hot windy 

summers characterize the high desert regions 

of the Intermountain West and are generally 

dominated by high pressure (Obedzinski et al. 

2001; Malanson 1993). 

Amount and seasonal distribution of precipitation 

differs between arid and mesic regions. 

Precipitation in the arid Intermountain region 

ranges from less than 5 inches (127mm) to greater 

than 60 inches (1,524mm) in the higher elevations 

with evapotranspiration exceeding transpiration 

(WRCC 2004). 

Many of the water sources in the west originate 

in the mountains as snowmelt and from summer 

monsoons (Fry et al. 1994; Cushing and Allan 

2001). Biomass production tends to be lower in 

arid than in mesic regions and short-term effects 

such as summer rains can further influence 

biomass production and cover (Malanson 1993; 

Stromberg 2001). Long-term drought and 

moisture cycles of several hundred years have 

also been documented, altering flow regimes and 

vegetation patterns over time (Obedzinski et al. 

2001). 

Lower precipitation and periodic drought in 

the west coupled with lower stream flows 

and modified flood cycles due to damming or 

diversion makes recovery of damaged riparian 

systems more difficult due to increased stress 

from lowered water tables. Restoration of uplands 

damaged by grazing and other detrimental land 

use practices is critical for restoration of riparian 

areas as well (Stromberg 2001). Irrigation 

return flows are common in arid regions and are 

often contaminated with herbicides and excess 

nutrients. This source of water can be used for 

restoration, however, if these inputs are reduced 

or eliminated. 

Hydrology

Hydrology is the largest factor controlling 

effectiveness of buffer function (Gilliam et 

al. 1997). Overland flow is the predominant 

hydrological characteristic in buffers in the 

Intermountain West. Attempts should be made 

to eliminate the effects of channelization which 

increase flow velocity and reduce or negate buffer 

effectiveness. Long-term effects of overland flow 

such as sediment build up along field edges may 

cause flow to migrate around the edge creating 

channels through the buffered area (NRC 2002) 

while periods of intense rainfall, common in 

the Intermountain region, may quickly create 

channels due to the heterogeneity of the terrain 

(Dosskey 2002). To increase buffer effectiveness, 

design criteria should include methods for 

promoting sheet flow through the buffer (Gillliam 

et al. 1997). 

Riparian areas provide important connections 

between surface and subsurface waters (NRC 

2002) which profoundly affect the transformation, 

infiltration, and / or containment of contaminants. 

Interactions between the stream channel and 

groundwater, however, are not the same along the 

channel length (NRC 2002).

Water movement into streams in the 

Intermountain regions is more likely to come 

from overland flow because of lower levels of 

vegetative cover and soils high in clay content 

(Baker et al. 2004). In low order mountain 

streams water moves into the channel through 

groundwater but out of the channel in higher 

order valley streams (effluent or losing stream). 

In more mesic areas, water moves into the 

stream channel (influent or gaining stream) 

mainly through groundwater. Maintenance of 

streams in the Intermountain West is dependent 

on snowmelt supplies (NRC 2002). Groundwater 

flow contributes more than overland flow in mesic 

areas with their greater vegetative biomass and 

more consistent precipitation (Malanson 1993; 

Baker et al.2004).

9
Figure 2. Comparison of mesic (A) and arid (B) 

stream hydrology.

(Susan Buffler: adapted from Malanson 1993 and 

Baker et al. 2004).

Soils

Valley soils tend to be shallow and more saline 

in arid regions, particularly where irrigation in 

riparian floodplains is practiced (Fry et al. 1994; 

Stromberg 2001). They are high in clay content 

and have low infiltration rates. Soils in general 

tend to be nitrogen limited, since denitrifying 

bacteria rarely have adequate conditions for 

optimal function (Mee et al. 2003). 

Topography

Much of the Intermountain West is characterized 

by high elevation mountain ranges interspersed 

with broad, flat valleys. Riparian buffer plant 

communities vary with elevation and topographic 

aspect due to temperature change, increased 

soil moisture at higher elevations and shaded 

topographic aspects (Grimm et al. 1997; Mee 

et al. 2003). Lateral stream bank slopes are 

frequently steep, a product of channel inclusion.

Vegetation

Hydrology and geomorphology play a major role 

in the development and maintenance of vegetation 

types in arid regions (Gardner 1999; Stromberg 

2001). Vegetative cover is typically less dense in 

arid and semi-arid regions, reducing infiltration 

and increasing the likelihood for faster overland 

flow, particularly with increasing slope and other 

topographic features. 

A strong increase in the depth to water table 

with increasing distance from the stream 

dictates which vegetation types will occur in the 

riparian zone (Stringham et al. 2001), therefore, 

vegetation is often taller in riparian areas than 

in the surrounding matrix (Malanson 1993). 

Woody vegetation surrounds riparian areas and 

other water supplies such as lakes and cold desert 

springs (Malanson 1993; Cushing and Allan 2001; 

CRA 2001). 

Riparian vegetation, however, is composed of 

narrow bands of trees and shrubs competing for 

the relatively large water supply (Malanson 1993: 

Baker et al. 2002; NRC 2004). Large woody 

vegetation tends to decline rapidly with increasing 

distance from the stream following the pattern of 

the water table (Malanson 1993).

Vegetation in these regions tends to be more 

distinct than in other regions of the United States 

with stronger delineations between riparian and 

upland zones (Malanson 1993). 

Plant density is lower in the Intermountain 

West, due to the lack of rainfall. Soils in the 

Intermountain West are often shallow and coarse 

and unable to hold much moisture, and therefore, 

vegetation is sparse supporting drought tolerant 

shrubs, grasses, and herbaceous species in the 

plant community (Mee et al. 2003). Shrub 

steppe is the predominant plant community in 

the study area. The shrub steppe region of the 

Intermountain West ranges from 4,000 to 6,000 

feet (1219 to 1828m) with no dominant tree 

species. Plant cover ranges from about 50 to 75% 

(Mee et al. 2003). Few studies have been done on 

riparian ecophysiology in the Intermountain West 

(Dawson and Ehleringer 1991). Plant species 

diversity tends to be lower in intermittent and 

ephemeral than in perennial channels in riparian 

areas in arid lands (Stromberg 2001) leading to 

greater fragility when groundwater is reduced. 

Species richness is also more heterogeneous due 

to moisture limitations and variability (Tabachhi 

et at. 1998). 

Plants in the Intermountain West are more 

commonly dieoceous, having male and female 

individuals (Dawson and Ehleringer 1993). 

Female trees were disproportionately found in 

non-stressful sites closer to the stream but had 

lower water use efficiencies than male trees. 

Dawson and Ehleringer (1991) also found that 

10
mature Boxelder (Acer negundo) trees used deep 

groundwater instead of stream water even when 

close to the stream. Youngest trees near the stream 

used stream water but young trees farthest from 

the stream used water from precipitation. Possible 

explanations include wide ranging stream channel 

movement and undependable stream water flows.

Wildlife

Riparian systems in arid regions account for less 

than 1% of the land area but 70% of wildlife 

species (Fry 1994; Belsky 1999; CRA 2001). 

Over 80% percent of all bird species in the Great 

Basin are either dependent or partially dependent 

on riparian areas while 51% of bird species in 

the Southwest are totally dependent on these 

areas (Gardner et al 1999). Species diversity in 

the western U.S. can be as great as that in the 

east. Herbivory by deer, elk, moose, and beaver 

can have significant adverse effects on riparian 

vegetation and consequently buffer effectiveness. 

Table 2. Summary of the main differences of 

riparian areas between arid and non-arid regions.

Climate

• low precipitation levels occurring mainly in 

winter and summer monsoons

• short duration, high intensity rainfall

• evapotranspiration exceeds precipitation

• hot, dry, windy summers

• cold winters

• dominated by high pressure in summer

• long and short term drought cycles

Hydrology

 • regulated stream flows and diversions

• maintenance of streamflow dependent on 

snowmelt

• higher order valley streams tend to be effluent 

(water moves out of the stream channel)

• overland flow predominates 

 Soils

 • shallow saline soils

 • high clay fraction

 • low infiltration 

Topography

• mountain ranges interspersed with broad flat 

valleys

• frequent steep gradients

Vegetation

• low biomass production 

• low plant density (cover ranges from 50 to 75%)

• plant communities vary with elevation

• vegetation decreases with increasing water table 

depth

• woody vegetation predominates in riparian areas 

along lower elevation higher order streams 

• low surface roughness is common 

Wildlife

• riparian areas account for 70% of wildlife 

species 

• over 80% of birds are dependent or partially 

dependent on riparian areas

• high species diversity

• herbivory can be high and adversely affect 

riparian vegetation 

The conclusions drawn from comparing 

riparian buffer attributes in arid and non-arid 

environments is that in the Intermountain West:

 • overland flows are higher, more intense 

 and shorter lived

• infiltration rates are lower

• plant density and surface roughness are 

slower

The buffer width implications of these differences 

is that riparian buffers in the Intermountain West 

need to be wider to meet water quality objectives. 

Sources and Causes of Impairment

Nationwide, approximately 19% of total stream 

miles have been assessed by states and tribes in 

their 2000 305b reports (EPA 2000a), 39% of 

these streams were considered impaired. Fifty 

percent of the streams in the Great Basin are 

impaired to some extent (Chambers et al. 2004). 

Losses in Utah are undocumented (Gardner 

1999). Significant numbers of stream miles in 

the study area are impaired for one or more 

beneficial uses (Table 3, 4).Agriculture, stream 

modifications and habitat alteration are the top 

three contributors to impairment of surface and 

subsurface waters. Agriculture accounts for 48% 

of the impairment to streams (EPA 2005). Leading 

contaminants from these agricultural sources 

include pathogens (bacteria), sedimentation, 

habitat alterations, oxygen-depleting substances, 

11
nutrients, thermal modifications, metals, and flow 

alterations. Pathogen contamination accounts for 

35% of water quality impairment. 

Loss of riparian areas and thus their buffering 

and bank stabilizing functions are difficult 

to determine but it is estimated that 85% to 

95% percent of riparian habitat in Arizona, 

New Mexico, and California have been lost 

(NRC 2002). Agricultural practices such as 

inappropriate grazing, fertilizer treatments, 

irrigation return flows and recreation associated 

impacts are the main sources of riparian habitat 

degradation in the study area (EPA 2000b). 

Invasive exotic plants, such as tamarisk (Tamarix 

ramosissima Deneb.) have also influenced the 

distribution of native riparian vegetation and 

degraded riparian habitat. 

Table 3. Major causes of stream impairment in the 

study area by state.

ID MT OR UT WA WY

Pathogens 

(Bacteria)

X X X X

Flow alterations X X

Nutrients X X X

Siltation X X

Thermal 

modifications

X X X

Habitat alteration X X X

Metals X X X

Total dissolved 

solids

X

pH X

Low dissolved 

oxygen

X

Adapted from EPA 2000b

ID - Idaho, MT - Montana, OR - Oregon, UT - 

Utah, WA - Washington, WY - Wyoming

 State

 Stream 

miles 

assessed 

 Designated

 use*

 %

 impaired 

 Impairment 

 source

ID 17,333 Aquatic/

wildlife

47% Not 

determined

MT 8,714 Aquatic/

wildlife

3% Agriculture 

Resource 

extraction

7,066 Recreation 49%

OR 114,823 Aquatic/

wildlife

26% Agriculture, 

silviculture, 

habitat and 

hydrologic 

modifications, 

hazardous 

waste sites, 

urban runoff

5,062 Recreation 44%

984 Fish 

consumption

81%

UT 10,465 Aquatic/

wildlife

16% Agriculture, 

nutrients, 

sediment

518 Recreation 2%

WA 70,439 Aquatic/

wildlife

40% Agriculture, 

hydrologic, 

habitat 

modification, 

natural 

sources, and 

septic tanks

70,439 Recreation 16%

58,990 Fish 

consumption

74%

WY 2,640 Aquatic/

wildlife

7% Unknown 

sources, 

agriculture, 

and natural 

sources 252 Recreation 100%

*fish, shellfish, and wildlife protection and 

propagation. (adapted from EPA 2000b)

12

Table 4. Percent of impairment for designated use 

per stream miles assessed by state.

Irrigation operation on the Bear River, Cache 

Valley, UT. Photo credit: Susan Buffler
Contaminants and Buffer Effects

Contaminants can be classified generally as either 

dissolved or particulate. The major dissolved 

contaminant from agricultural lands is nitrogen 

(N) while the major particulate contaminant is 

sediment and sediment-bound chemicals and 

nutrients. Phosphorus (P) is found in particulate 

and dissolved form while pesticides are mainly 

associated with sediment and are dependent on 

their adsorption capacity to sediment particles. 

Pathogens are mainly associated with sediment 

and are dependent on retention in the soil, 

infiltration and water flow. 

Buffer designs are tailored to address nonpoint source pollution that include nutrients, 

agricultural chemicals, pathogens from animal 

waste and sediment, however, a continuing 

concern is the bypass of contaminants through 

the buffer either directly or through naturally 

occurring hydrological characteristics of 

the buffer. In some cases, riparian buffers 

are ineffective in reducing contaminants 

from adjacent land uses and alternative best 

management practices should be implemented. 

For example, a ten year study on Rock Creek, 

Twin Falls, Idaho (Maret et al. 1991) documented 

significant improvement in water quality 

when BMPs including riparian buffers were 

implemented. However, irrigation bypass and tail 

waters laden with pollutants (an estimated 14% of 

the water diverted) returned to the stream at some 

point below the diversion. This is an important 

area not covered in this document that requires 

further study.

Particulate Contaminants - Sediment

Sediment entering rivers and streams is a natural 

phenomenon critical to buffer function and 

structure and stream morphology. However, when 

quantities of sediment entering the stream exceed 

the normal range, buffer function and structure, 

and water quality can become impaired. Buffer 

function and structure are also impaired and 

stream channel dynamics altered when normal 

sediment loads in the stream channel are reduced 

or eliminated by dams or diversions. 

Reasons for concern

Sediment is a leading contaminant of streams in 

the Intermountain West (EPA 2005). Sediment 

often originates from upland land management 

practices and, if not altered or buffered, can 

have significant impacts on stream water quality. 

Excess amounts of sediment in streams physically 

reduces light infiltration and thus algae production 

and habitat and food for other aquatic organisms 

(Wenger 1999; Mason 2000). Some pesticides 

and phosphorus can adsorb to soil particles and 

be carried into streams through erosion and runoff 

(Harris and Forster 1997). Sedimentation is also a 

significant factor in reducing the storage capacity 

of reservoirs.

Livestock damage to stream banks accounts 

for a significant amount of riparian and stream 

bank damage in consequent sediments entering 

the stream (Belskey 1999). Livestock trample 

vegetation and physically damage stream banks 

due to pressure from hooves. Excessive trampling 

breaks down stream banks resulting in flattened 

bank angles, a reduction in bank undercutting 

and accelerated erosion (NRC 2002; Baker 

et al. 2004). Vegetation is damaged or killed 

causing root loss destabilizing stream banks and 

accelerating stream widening (NRC 2002). 

Improper grazing also contributes to soil 

compaction, destruction of biological crusts, 

and introduction and distribution of exotic plant 

species. Indirect impacts include, alteration of fire 

regimes, increased erosion, changes in infiltration 

rates, runoff and water holding capacity, changes 

in plant competition patterns and reproductive 

success (NRC 2002). These in turn may lead 

to changes in stream width, depth, bank water 

depth and the composition of bed material. Water 

quality is reduced through increased suspended 

sediments and in-channel deposition (Stromberg 

2001). 

Other factors that influence sediment dynamics 

of the stream include watershed management 

(Wenger 1999; Rhodes et al. 2004), damming 

and diverting streams, mining, construction sites, 

road construction, and forestry practices (Wenger 

1999; Baker et al. 2004; NAC 2004). Peak flows, 

sediment, and channel migration are reduced 

downstream of dams. This leads to decreases 

13
in vegetation structural complexity, decreased 

biodiversity, and unwanted plant and animal 

species (Baker et al. 2004). 

 

How buffers affect sediment

Riparian buffers can be effective for trapping 

or displacing sediment (Dillaha and Inamadar 

1997) and stabilizing stream banks to reduce 

erosion, and providing large woody debris in the 

stream channel for sediment trapping (Wenger 

1999). Both grass and forest buffers are useful for 

trapping sediment. The processes of deposition 

and infiltration act to remove sediment; with 

smaller clay particles removed by infiltration. 

Factors influencing buffer effectiveness include, 

width, length, sediment load, flow rate, slope, 

grass height and density, surface roughness, and 

degree of vegetative submergence (Belt et al. 

1992; Dillaha and Inamadar 1997). 

Most studies (Matrix A) found that larger particle 

sizes in sediment are deposited in the first 3 to 

10m of the buffer while smaller sized particles 

may be transported and deposited or infiltrated 

farther overland into the buffer (Chaubey et 

al. 1994, 1995; Robinson et al. 1996; Barfield 

et al. 1998; Mendez et al. 1999; Schmitt et al. 

1999; Sheridan et al. 1999; Lee, Kye-Han et 

al. 2000; Syversen et al. 2001; Hook 2003). 

Dosskey et al. (2002), however, found that areas 

with heterogeneous topography may not reduce 

sedimentation significantly due to increased 

channelized flow. Sediment can build up at the 

field / buffer interface and create a dam or berm. 

Overland flow is then diverted around the berm, 

creating channelized flow through the buffer 

(Wenger 1999). Daniels and Gilliam (1996) also 

found that buffers were overwhelmed by high 

flows. In these cases, buffers inappropriately 

designed or maintained can become a source 

of sediment. Long-term trapping may not be 

feasible without periodic sediment removal. Grass 

buffers, although more likely to be inundated 

by exceptionally high levels of sediment, are 

useful in maintaining sheet flow and preventing 

rill and gully erosion. Forest buffers have other 

advantages and a combination of grass and forest 

is usually recommended (Wenger 1999). 

Particulate Bound Phosphorus (P)

Phosphorus is essential for energy transfer, 

protein synthesis and other metabolic processes 

and is a component of deoxyribonucleic acid 

(DNA) (Brady and Weil 2000). Phosphorus, 

although generally occurring in adequate amounts 

in the Intermountain West, tends to fix to soil 

particles when applied to crops in soluble form. 

Over-application of synthetic fertilizers and 

manure tends to occur leading to a buildup of 

phosphorus in the soil (Brady and Weil 2000; Hart 

et al. 2004). 

Phosphorus is found in both organic and inorganic 

forms and is either sediment bound or dissolved 

(Hart et al. 2004). Since most P is readily 

adsorbed to mineral and organic soil particles, 

its removal in buffers tends to follow the same 

patterns as sediment (Uusi-Kamppa 1997; Zheng 

2004). Factors affecting retention of P are: kinetic 

factors, particle size, adsorption capacity of the 

soil, contact time, and temperature (Uusi-Kamppa 

1997). 

Reasons for Concern

Phosphorus can contribute to eutrophication or 

“the enrichment of waters by inorganic plant 

nutrients” (Mason 2002; Zheng et al. 2004). 

Increased algal blooms create low oxygen 

conditions due to decay of organic material and 

reduce fish and plant diversity (Hart et al. 2004).

How buffers influence P dynamics

Riparian buffers can be effective in reducing the 

amount of sediment bound P (Gilliam 1994). 

Increasing buffer width, in general, reduces 

particulate P (Chaubey et al. 1994, 1995: Daniels 

and Gilliam 1996: Lee et al. 2000). Because P 

is stored in buffers and is not transformed, it 

is susceptible to being remobilized, therefore, 

where high flows may overwhelm filters, (Daniels 

and Gilliam 1996) (Matrix C), additional best 

management practices to reduce P before it enters 

the buffer are recommended. Sediment traps or 

retention basins, constructed wetlands, terraces, 

and on farm water and nutrient management can 

reduce P impacts to waterways (NRCS 2005).

14
Pesticides

Pesticides are a broad range of chemicals used 

for the control of undesirable plants, animals, 

insects and fungi. These include herbicides, 

insecticides, fungicides, and rodenticides. Runoff 

from pesticides is estimated to be 1 to 5% of the 

amount applied (Arora et al. 2003). Retention 

of pesticides in the soil depends on its ability to 

adsorb to soil particles. Pesticides losses from 

agricultural fields are mainly due to timing of 

application, slope, and tillage practices (Arora et 

al. 2003; Boyd 2003). 

Reasons for concern

Excess runoff can result in pesticide 

contamination of drinking water and aquatic 

habitats. Toxic effects can be lethal or sublethal. 

Sublethal doses can cause impairments such as 

slowed reflexes, impaired learning behavior, 

lower reproductive success (Mason 2002) and 

loss of biodiversity (Harris and Forster 1997). 

Many pesticides can concentrate in animal fats 

causing death or sterility. Concentrations of DDT 

and DDE have been found in human breast milk 

(Mason 2002), although these rates are declining 

in Japan and the U.S.

How buffers affect pesticides

Pesticides may be weakly or strongly adsorbed 

to soil particles (Arora et al 2003; Boyd 

2003) and losses from water transport can 

be rapid (Harris and Forster 1997) with peak 

concentrations occurring soon after application. 

The mechanisms of pesticide transport, however, 

are not well understood (Harris and Forster 1997; 

Wenger 1999). Pesticides may enter the stream 

channel either through surface or subsurface 

flow, and particle transport. Saturation of soil or 

compaction promotes excess pesticide movement 

in surface flow (Harris and Forster 1997).

Riparian buffers can reduce the amount of 

pesticide runoff from cropland by adsorption, 

infiltration, and microbial breakdown (Arora et 

al. 1997; Barfield et al. 1998; Lowrance et al. 

1998; Arora et al. 2003). Research has shown 

that the area ratio, or the ratio of the contributing 

surface runoff area to the filter strip area, has 

a significant effect on runoff infiltration and 

sediment, nutrient and pesticide retention rate of 

vegetated filter strips (Arora et al. 2003; Boyd et 

al. 2003). Arora et al. (2003) found that buffers 

reduced the concentrations of two herbicides 

but not an insecticide in outflow. All three 

pesticides, however, were more highly retained 

in the 15:1 ratio plots than in the 30:1 plots. They 

concluded that herbicide reduction was through 

infiltration; while the insecticide was reduced 

through adsorption and that the 30:1 plot had 

higher runoff rates. Boyd et al. (2003) also found 

that infiltration and adsorption played a key role 

in chemical retention. They found that sediment, 

and therefore insecticide reduction, was higher in 

the 15:1 ratio plots compared with 45:1 plots due 

to adsorbtion while there was no difference for 

the herbicides. Higher amounts of pesticides are 

found with increasing concentration and flow rate 

(Kloppel et al. 1997). Buffer widths of 8 to 20m 

were shown to decrease pesticides by up to 100% 

in some cases with trapping efficiency increasing 

with width (Patty et al. 1997; Verdilis et al. 2002) 

(Matrix B).

Pathogens

Pathogens include a variety of organisms such 

as bacteria, viruses, protozoa, and helminths 

(parasitic worms). Of particular concern in 

the Intermountain West are those organisms 

associated with livestock. Concentrated animal 

feeding operations may contribute substantial 

amounts of pathenogenic contaminants to 

waterways. Direct access by livestock and 

wildlife to streams and rivers can also introduce 

these contaminants to waterways. Spreading 

contaminated manure and sewage wastewater 

though irrigation increases the risk of spreading 

disease in surface water (Mason 2002).

Reasons for concern

Worldwide, waterborne pathogens kill 25 million 

people per year and disable millions more. 

Children are the most frequent victims through 

dehydration caused by diarrhea. Birds, livestock, 

and other animals often transmit these diseases 

(Mason 2002). In Egypt and other parts of Africa, 

the removal of natural flood regimes has led to a 

buildup of a permanent population of snail hosts 

of Schistosoma spp., a parasitic worm causing 

anemia and reduced immunity to other diseases. 

15
In the U.S., the recommended standard for the 

pathogen fecal coliforms for direct human contact 

with water is 200 colonies forming units (CFU) 

per 100 ml (Coyne et al. 1998; Wenger 1999); 

however, for drinking water the EPA (2005) 

has set a goal of zero. No more than 5% of the 

samples in the public water supply taken in each 

month may have coliforms. 

How buffers affect pathogens 

Trapping efficiencies for pathogens in grass 

buffers tend to be high, amounts of bacteria in 

grass buffers were often found to be significantly 

greater than the standard of 200 CFU per 100ml 

(Chaubey 1994; Coyne et al. 1998). Entry et 

al. (2000a) found no decline in total and fecal 

coliforms in applied wastewater through an 8m 

(26.25ft) buffer regardless of season or vegetation 

type. They did, however, see a decrease in total 

and fecal coliforms with depth to 30cm (11.8in) 

and over time. Ninety to 120 days following 

application, concentrations of fecal coliforms in 

treated filter strips were similar to those in non 

treated riparian filter strips (Entry et al. 2000b). 

Lim et al. (1998), however, found that a 6.1m 

(20.01ft) tall fescue (Festuca arundinaceae) 

buffer removed 100% of the fecal coliforms 

but Young et al. (1980) concluded that a 36m 

(118.1ft) buffer would be required to reduce total 

and fecal coliforms to below 1,000 organisms 

per 100ml (Matrix D). Most of the studies of 

coliforms looked at the effects of grass buffers. It 

is unclear whether a multi-species buffer would 

have greater total coliform removal capacity.

Escherichia coli survival in water tends to be 

about 24 hours and 2 to 4 hours in soil and 

sediments. There is evidence, however, that 

E. coli can survive and proliferate in warm, 

moist soil conditions with appropriate nutrient 

concentrations (Source Molecular 2004). 

Although this is more common in tropical areas, 

it occurs in temperate riparian areas as well 

(Byappanahalli et al. 2003; Whitman et al. 2003). 

Appropriate riparian buffer widths may help 

to slow down transport of certain pathogens. 

If bacteria reach areas where conditions are 

appropriate for proliferation, such as moist 

riparian zones, total elimination may not be 

possible by using buffers alone. Using BMPs 

for manure and limiting livestock access to 

streams would be more appropriate in reducing 

concentrations to the buffer. 

Studies investigating concentrations of 

Cryptosporidium parvum, a microbe transmitted 

from livestock to humans, found that slope, soil 

type, and rainfall intensity affected infiltration 

rates (Atwill et al. 2002; Tate et al. 2004; Trask 

et al. 2004). Clay soils were less effective in 

removing of oocysts from the buffer but greater 

amounts were found in subsurface flow in sandy 

and loam soils (Atwill et al. 2002). As with E. 

coli, it is unclear how effective grass buffers 

would be since studies of C. parvum were 

conducted only in 1m (3.3’) trial boxes with 

simulated rainfall with or without grass (Atwill et 

al 2004; Tate et al. 2004; Trask et al. 2004).

Dissolved Contaminants 

Nitrogen (N) 

Nitrogen is an important nutrient for plant and 

animal growth and function. Nitrogen is also an 

important component of amino acids, the building 

blocks of proteins, and plays a role in plant 

carbohydrate use and root development. Nitrogen 

fertilizer application can increase plant growth 

and therefore; it is widely used in agricultural 

production (Brady and Weil 2000).

Nitrogen is available in organic and inorganic 

forms. Most of the N in soil is in organic forms 

associated with humus. Inorganic nitrogen, found 

mainly in fertilizer nitrogen, is highly soluble 

therefore readily leached. Nitrate (NO3

-

) and 

ammonium (NH4

+

) forms of nitrogen are readily 

taken up by plants but available typically in 

relatively small amounts (Brady and Weil 2000). 

Reasons for concern

The largest sources of N to streams are through 

N fertilizer and concentrated livestock feedlots 

and manure application to lands adjacent to 

riparian areas. Up to 90% of hog waste can 

volatilize as ammonia (NH3

) (Phelps 1997). 

Atmospheric deposition and septic systems are 

also significant sources of NO3

-

. Approximately 

25% of the total Chesapeake Bay N load comes 

from atmospheric deposition (NOAA 2005). 

Some of the excess NO3

-

 has been implicated in 

16
methaemoglobinaemia in infants less than six 

months old where ingestion of NO3

-

 above 100 

mg per L of water results in reduction of red 

blood cells to carry oxygen and is often fatal. 

The standard for NO3

-

 in drinking water in the 

United States is 10 mg per L NO3

-

-N (EPA 2004). 

Also, NH3

 is directly toxic to aquatic life with 

susceptibility related to body size, age or sex 

(Mason 2002). 

Nitrogen can also contribute to eutrophication 

(Mason 2002; Zheng et al. 2004). Increased 

algal blooms create low oxygen conditions due 

to decay of organic material and reduce fish and 

plant diversity (Hart et al. 2004). Application of 

N over time can cause microbial sinks to become 

saturated and thus less functional (Hanson et 

al. 1994), releasing large quantities of nitrogen 

oxide (NO) gases to the atmosphere (Burt et al. 

1999; Hefting et al 2003). Although less of an 

issue in the West, a pH of less than 5 will inhibit 

denitrification and cause increased release of 

NO gas (Brady and Weil 2000) causing acid rain 

(Mason 2002). 

How buffers influence N dynamics

Removal through uptake or leaching of NO3

-

 in 

riparian areas has been investigated more than 

any other potential pollutant (Gilliam 1994). Most 

of the research on nitrogen dynamics prior to 

1980 was concerned with surface flow (Correll 

1997). Interest in subsurface processes concerning 

nitrogen began in the early 1980s with studies 

showing reductions in nitrogen concentrations of 

90% through forest buffers on the Atlantic Coastal 

Plain (Gilliam et al. 1997). 

Buffers influence N dynamics through two major 

pathways; plant uptake and denitrification by 

soil microbes in the riparian zone (Gilliam et 

al 1997; Burt et al. 1999; Lamontagne 2001). 

Denitrification is a natural process that occurs 

in the soil where microbes reduce NO3

-

 to dinitrogen (N2

) gas which is then released to the 

atmosphere. Denitrification requires a source of 

N, appropriate microbial population, a soluble 

carbon source for metabolic function of microbes, 

soil moisture, and low oxygen conditions (Hanson 

et al. 1994). Optimum soil temperatures for 

denitrification range between 25 and 35oC (Brady 

and Weil 2000). Although carbon is generally 

plentiful in the upper soil profile, soil microbes 

may only be able to carry out denitrification 

during times of high soil moisture, such as 

spring and early summer (Burt et al. 1999). 

Also, heterogeneous sediments and soils may 

affect subsurface flow paths and residence time; 

therefore, N may bypass the riparian area and 

proceed to the stream channel (Karr et al. 2000). 

The importance of understanding site hydrology 

is critical for this nutrient (Hill 1996; Burt et al. 

1999; NRC 2002).

The role of plant uptake of N in riparian 

systems has not been extensively investigated 

(Hill 1996). In riparian areas with inadequate 

conditions for denitrification, plant uptake may 

play a greater role in removal. Lowrance et al. 

(1984) found that nutrient uptake by trees in a 

riparian zone acted as short to long-term sinks, 

preventing nutrients from entering the stream. 

Periodic removal of vegetation was therefore 

hypothesized to maintain net uptake of nutrients 

in the riparian zone. Peterjohn and Correll (1984) 

found that up to 80% of nitrogen in a deciduous 

forest was returned to the riparian system as 

litter (Peterjohn and Correll 1984), where 

much of this was mineralized by soil microbes. 

Sites with leguminous plants may show no 

vegetation uptake of N because of N fixation and; 

therefore may be more dependent on the role of 

denitrification in the soil (Tate et al. 2000). 

Nitrogen retention through plant removal and 

denitrification depends on many factors. Site 

characteristics, particularly hydrologic features 

such as shallow aquifers with confining layers, 

allow groundwater to flow through the root zone 

and reduce NO3

-

 through denitrification (Wenger 

1999; Lamontagne et al. 2001). Most studies 

found significant decreases of nitrogen with 

increasing buffer width (Matrix E). Most of the 

total NO3

-

 reduction occurred 10 to 35m (32.8 to 

114.8 feet) into the buffer (Peterjohn and Correll 

1984; Jacobs and Gilliam 1985; Lowrance, 

Richard 1992; Haycock and Pinay 1993; Jordan 

et al. 1993; Osbourne and Kovacic 1993; Pinay 

et al.1993; Chaubey et al. 1994; Patty et al. 1997; 

Hubbard et al. 1998; Lim et al 1998; Mendez et 

al. 1999; Lee et al. 2000; Lowrance et al. 2000; 

Spruill, Timothy 2000; Dukes et al 2002; BedardHaughn et al. 2004).

17
Nitrogen in soils are generally not sufficient for 

optimum crop production; therefore it is added 

in fertilizer form. Since N is highly soluble and 

mobile, it is easily leached into groundwater. 

(NRCS 2005). Most N losses into streams 

travel in groundwater though subsurface flow 

and deeper baseflows (NRCS 2005). Although 

up to 50% of N applied as fertilizer is lost to 

groundwater (Mason 2002), NH4

+ in soil organic 

matter adsorbed to clay particles is lost in 

overland flow from erosion. Slope increases flow 

rate; therefore increasing surface roughness can 

play a role in reducing transport (Kleinschmidt 

1999; Johnson and Buffler 2005; NRCS 2005). 

Soil properties such as infiltration rate and timing 

of rainfall or irrigation affects losses of N (Brady 

and Weil 2000). Soils with low infilitration rates 

will have increased rates of N losses through 

overland flow (NRCS 2005). Nitrate moves 

slowly through the unsaturated zone in the soil. 

Because of this, retention in soil can remain for 

long periods of time. 

In general, buffers tended to reduce NO3

-

concentrations with increasing width (Dukes 

et al. 1993; Patty et al. 1997; Hubbard et al. 

1998;Lee et al. 2000; Bedard-Haughn et al. 2004). 

Significant reductions were seen in the first 5 to 

10m of the buffer (Mendez et al. 1999; Lowrance 

2000). Schmitt et al. (2000) found that sediment 

bound N was reduced more effectively in wider 

buffers than dissolved N but others found no 

differences (Vanderholm and Dickey 1978; 

Peterjohn and Correll 1984; Lee et al. 2000).

Both grass, wooded and combination buffers were 

effective in reducing N concentrations. 

(Lowrance et al. 1984; Osbourne and Kovacic 

1993; Castelle et al. 1994; Lee et al. 2000; 

Dukes et al. 2002). Buffers, however, will have 

no effect if NO3

- is bypassing the root zone in 

groundwater (Chaubey ey al. 1995; Karr et al. 2001; 

Wigington et al. 2003). 

Vegetation type and hydrologic and geological 

considerations of the site should be taken into 

consideration in order to appropriately assess 

conditions appropriate for removal of dissolved 

nutrients. 

Dissolved Phosphorus (P)

About 80 to 90% of P in the soil is available very 

slowly. Labile or slowly available forms make 

up about 10 to 20% of the soil P with less than 

1% readily available. Dissolved P is found in 

several forms and include the inorganic mono 

and dicalcium phosphate although in extremely 

alkaline soils, calcium causes P to become 

insoluble. Phosphorus fixation tends to occur 

more readily in clay soils due to their high surface 

area. (Brady and Weil 2000). Organic forms of P 

can be mineralized from decaying plant material 

or manure to provide soluble forms of P for plant 

uptake. Desorption of P from soil and vegetation 

can be transported through rain or snowmelt 

(Uusi-Kamppa 1997). 

Reasons for Concern

Up to 45% of the phosphorus component entering 

riparian areas in runoff is in dissolved form 

(Uusi-Kamppa et al. 1997; Fleming and Cox 

2001). Dissolved P is initiated by desorption from 

soil or plant particles. Adsorption sites on soil 

particles may become saturated causing an excess 

concentration of dissolved P in runoff. Cold soil 

temperatures reduce plant uptake; therefore P 

runoff may be higher in spring (Uusi-Kamppa et 

al. 1997; NRCS 2005). Orthophosphate (PO4

-P) 

is the main source of dissolved inorganic P in 

surface runoff (Uusi-Kamppa et al. 1997). 

How Buffers Influence P Dynamics

Riparian buffers are less effective in reducing 

the amount of dissolved P than sediment bound P 

(Gilliam 1994). Several studies (Matrix C) show 

that a significant amount of PO4

-P was removed 

in 9 to 21m grass buffers (Young et al. 1980; Lim 

et al 1995; Patty et al. 1997; Chaubey et al. 2000) 

although other studies showed that PO4

-P removal 

was less or not effective (Daniels and Gilliam 

1996; Snyder et al. 1998; Schmitt et al. 1999; 

Lee et al 2000) or even increased in the buffer 

(Peterjohn and Correll 1984) (Matrix C). 

Although the EPA (2005) has not set a standard 

for P, the state of Utah recognizes 0.05 mg per L 

as the limit (EPA Utah 2005). As with particulate 

P, BMPs to reduce P before it enters the buffer are 

recommended. Removal of biomass in the buffer 

may also help reduce the amount of P taken up in 

vegetation (Uusi-Kamppa 1997).

18
Buffer Design and Guidelines

The National Resource Conservation Service 

(NRCS 2005) defines conservation buffers as 

“small areas or strips of land in permanent 

vegetation, designed to intercept pollutants and 

manage other environmental concerns. Buffers 

include: riparian buffers, filter strips, grassed 

waterways, shelterbelts, windbreaks, living 

snow fences, contour grass strips, cross-wind 

trap strips, shallow water areas for wildlife, 

field borders, alley cropping, herbaceous wind 

barriers, and vegetative barriers” (NRCS 

2005).

The Intermountain West is unique since most 

streams originate on public lands at higher 

elevations (Fry et al. 1994; Cushing and Allan 

2001). Water quality of higher order valley 

streams is therefore dependent on management 

by federal agencies making placement and design 

of riparian buffers in the watershed critical for 

protecting water quality downstream (Fisher et al. 

2000; Fischer and Fischenich 2000). 

Several buffer designs for watler quality 

developed by federal agencies are currently in 

use. These designs employ various combinations 

of herbaceous plants, grasses, shrubs, and trees. 

The design most widely used is the USDA Forest 

Service’s three zone design (Welsch 1991). These 

guidelines, however, were developed primarily for 

the eastern United States. The Leopold Center for 

Sustainable Agriculture at Iowa State University 

developed the multi-species buffer (MSRBS) 

for small mid-western streams (Schultz et al. 

1994). The MSRBS buffer system is specifically 

designed for use in the Midwest; however, it is 

designed so that the specific width planting zones 

can be varied depending on landowner objectives. 

The MSRBS design also includes constructed 

wetlands for amelioration of agricultural 

chemicals. This design, although slightly more 

flexible, is another variation on the USDA three 

zone design and may not be applicable to the 

Intermountain West. The specified widths for 

these zones are based on “best professional 

judgment” or socio-political concerns (Dillaha 

and Inamdar 1997; Fischer et al. 2000; Fischer 

and Fischenich 2000)

19

Current riparian buffer design guidelines for use 

in the western United States were developed 

primarily by states with substantial forestry 

interests on fish bearing streams (Belt and 

O’Laughlin 1994). Oregon, Washington, and 

California require variable width buffers with 

minimum and maximum width ranges depending 

on variables such as slope, adjacent land use, 

and stream width. This gives consideration to the 

variation in plant density found in these states 

(Belt et al. 1992). These states also require use of 

percent canopy cover and vegetation structure to 

protect stream temperature (Belt and O’Laughlin 

1994). Instead of specific width zones used in the 

east and Midwest, western riparian buffer design 

guidelines tend to be more flexible and use site 

attributes as key determinants of buffer design 

and subsequent success in forested landscapes. 

Oregon has a specific set of guidelines for certain 

circumstances that restrict harvesting to within 10 

to 20 feet (3 to 6m) of the high water mark (Blinn 

and Kilgore 2001) while Idaho has a set minimum 

width of 75 feet (22.9m) for all fish bearing 

streams and a minimum 5 foot (1.5m) buffer 

for non-fish bearing streams. State developed 

guidelines were reviewed by Blinn and Kilgore 

(2001). The most common recommendations 

were a 50 foot (15.2m) fixed width buffer on 

both sides of the stream with 50% to 75% canopy 

crown closure. They found that most guidelines 

include: a minimum width from the high water 

mark of the stream, a minimum amount of 

residual trees following harvest, and other 

guidelines considering land use practices within 

the riparian management zone. Of 16 western 

states, buffer width requirements range from 

40 to 200 feet (12.2 to 60m) for perennial and 

intermittent streams, although none of the western 

states had site specific width requirements (Blinn 

and Kilgore 2001). 

Although fixed width buffers are simple and 

relatively easy to establish and regulate (Fisher 

et al. 2000), variable width buffers allow for 

a variety of options and ecological functions. 

Although more complex, they have the ability 

to provide more effective protection due to 

better response to local site conditions (Belt and 

O’Laughlin 1994; Blinn and Kilgore 2001). For 

instance, proximity to and types of adjacent land 
20

uses should be considered when designing buffers 

(Fischer et al. 2000). 

Guidelines for revegetation of riparian areas in the 

Intermountain West were developed by the Plant 

Materials Center at Aberdeen, Idaho (Carlson et 

al. 1995; Hoag et al. 2001). Although no specific 

width designations are given, the authors provide 

valuable recommendations for planting in the 

appropriate zone depending on the stream type 

and hydrology. These planting zones are based 

on native riparian areas and are used as a guide 

for appropriate planting for restoration. There 

are five basic zones delineated for appropriate 

plant community types: the toe zone, bank 

zone, overbank zone, transitional zone, and the 

upland zone (Hoag et al. 2001). Design criteria 

are based on geomorphology, stream types and 

size, plant community types, velocity, sinuosity, 

bank slope, uniformity, and stratification of 

stream bank materials (Carlson et al. 1995). The 

goal is to establish appropriate, dense, native 

vegetation to stabilize stream banks. These 

restoration recommendations would work well 

within an appropriate set of riparian buffer design 

guidelines.

Recommended buffer widths based on a review of 

the pertinent literature lead to recommendations 

based on a range of widths. Since no studies 

were found comparing buffer widths in the 

Intermountain West, extrapolations from existing 

literature combined with differences between 

riparian areas in the eastern and western U.S. 

were made. The buffer widths recommended in 

Table 6 are based mainly on studies conducted 

in the eastern U.S. with modifications for arid 

landscape conditions.

Contaminant Width* Effect

Nitrogen

mostly 

soluble

20 to >40m 

may be 

narrower 

under 

ideal site 

conditions

Nitrogen trapping 

is dependent 

on vegetative 

uptake and 

transformations 

in the soil, and 

is dependent on 

soil moisture. 

Removal 

increases with 

buffer width 

and is greater in 

woody vegetation. 

Ground and 

surface water 

hydrology plays 

an important role 

in N removal

Sediment

particulate

3 to >10m Sediment trapping 

efficiency declines 

from 3 to 6m into 

buffers, regardless 

of slope. Grass 

buffers are more 

effective than 

forest buffers for 

removal although 

high flows and 

channelization 

will counter any 

beneficial effects

Phosphorus

particulate 

and 

dissolved 

>20m Sediment 

bound P follows 

similar trends 

as sediment, 

however, 

dissolved organic 

and inorganic P 

is more difficult 

to retain. A 

combination of 

grass and forest 

buffers are most 

efficient for 

trapping both 

types of P

Pathogens

associated with 

sediment

 3 to >6m

depending 

on pathogen 

load, 

antecedent 

conditions, 

slope, 

and soil 

conditions

Most pathogens 

can be removed 

from short buffers. 

Increasing slope 

may increase 

surface flow. 

Survivability of 

organisms may 

affect how long a 

buffer needs to be 

to slow movement

Table 6. Summary of buffer width 

recommendations required for removal of selected 

contaminants.
 

Summary

Over 120 documents including scientific 

literature, literature reviews, books, technical 

notes, and reports and proceedings were reviewed 

and summarized. The American Water Resources 

Association 2004 Conference was also a valuable 

source of information. 

Most of the research on riparian buffers was 

conducted in the East or on forested streams in the 

Pacific Northwest or other areas where logging 

activity was the predominant land use. Belt et 

al. (1992) reviewed buffer width requirements 

for Idaho, Washington, California, and Oregon 

and recommended design guidelines for forested 

areas in those states. These guidelines apply to 

low order, high elevation, headwater streams in 

forested landscapes. While protecting headwater 

streams is critical, most streams and rivers found 

in valleys of the Intermountain West (the study 

area) are higher order and run through agricultural 

and rangelands. Typically, these higher order 

streams have narrow or no riparian buffers. 

The literature reviewed strongly suggests 

that buffer width is the most important factor 

influencing removal of contaminants (Davies and 

Nelson 1999; Gilliam 1997; Jones 2001; Hook 

2003). A range of buffer variables including 

attributes related to topography, soils, hydrology, 

and vegetation that affect buffer function and thus 

width was presented in the literature. Criteria used 

to select riparian attributes for determining buffer 

width in this study include:

21

 • strong attribute correlation with buffer 

 function in the Intermountain 

 West

 • readily available data or easily 

 measurable

 • minimal opportunity for subjective 

 interpretation

 • easily replicated

Attributes

Buffer attributes selected based on the criteria 

above include slope, soil infiltration capacity, 

surface roughness, surface water features, 

sand and gravel aquifers, seeps and springs, 

floodplains, wetlands, and stream bank condition. 

Many of these attributes are common to other 

buffer planning methods as noted in Kleinschmidt 

(1999). Slope, soil, and surface roughness have 

the greatest effect on buffer functions for water 

quality (Buffler 2005). 

Primary Attributes 

The literature review of riparian buffer attributes 

in the study area and communications with 

regional resource experts suggests that, in 

general, riparian buffers in the Intermountain 

West should be wider than those recommended 

for other regions of the United States. Reasons 

for increased width based on an assessment of 

regional primary and secondary attributes include 

the following:

• Slope gradient - streambank slopes on 

many high order streams in the study area are 

steeper than those found in other regions often 

a result of channel incisions. Overland flow is 

accelerated and infiltration reduced; thus wider 

buffers are required to attenuate contaminants.

• Soil infiltration - in general, in arid 

landscape soils are shallow, high in clay 

content and often saline. Infiltration rates are 

low and overland flow high necessitating 

wider buffers.

• Surface roughness - in the study area, 

riparian areas are often narrow fringes, plant 

density and percent ground cover are highly 

variable but generally lower than in other 

regions. Uplands adjacent to the buffer, plant 

density and litter are also low. The result 

Pesticides

particulates 

associated

with sediment

 >9m 

depending 

on 

antecedent 

conditions, 

adsorption, 

and 

chemical 

type

Pesticides are 

adsorbed to 

soil particles 

with varying 

effectiveness, 

Other pesticides 

can be infiltrated. 

Trapping 

efficiency 

increases with 

increased 

infiltration. 

Trapping widths 

are variable 

with grass more 

effective in 

removing most 

pesticides

*based on 90% removal rate
is reduced surface roughness and higher 

overland flow in the buffer which suggests that 

wider buffers are required.

Secondary Attributes

• Seeps and springs - springs and seeps, 

often a product of irrigation, are common in 

the study area. Unless buffered, they become 

a conduit for contaminants. Buffers should be 

wider to include seeps and springs. 

• Sand and gravel aquifers - sand and 

gravel aquifers have high infiltration rates 

and can become sub-surface conduits for 

contaminants particularly nitrogen and 

disssolved phosphorus. Buffers need to be 

widened to include these attributes. 

 • Floodplains and wetlands - wide 

floodplains and associated wetlands are 

relatively common on higher order, lower 

elevation streams in the study area (with some 

channelized exceptions). To accomodate these 

features floodplains and associated wetlands are 

considered part of the stream being buffered. 

Buffer widths are calculated from the landward 

edge of these features. 

To conclude this discussion of buffer width, Baker 

et al. (2003) noted that in the Intermountain West, 

sparse vegetation, shallow soils, lower infiltration 

rates and short intense rainfall events may 

necessitate wider buffers. 

Planning Protocol

Several buffer planning protocols were reviewed. 

They varied from protocols based on visual 

estimates to those that were data intense, required 

significant inputs of field collected data and 

utilized computer modeling. Of the protocols 

reviewed, the protocol developed by Klienschmidt 

Associates Method to Determine Optimal Buffer 

Widths for Atlantic Salmon Habitat Protection

(1999) best matched the goals of the RB 

Handbook “develop a protocol for determining 

appropriate riparian buffer widths and guidelines 

on agricultural lands in the Intermountain West. 

“The protocol combines visual estimates, readily 

available resource data, easily measurable 

attributes and requires field verification of all 

mapped information. The protocol incorporated 

the buffer attributes noted above and utilized 

sampling plots (buffer measuring units) that could 

be adapted to western landscape characteristics. 

The protocol emphasized keys and tables 

that expedite data collection, recording and 

calculations, and facilitate replication. Buffer 

attributes keys and tables in the Kleinschmidt 

protocol were easily modified to accomodate 

unique Intermountain West landscape attributes. 

Lastly, the Kleinschmidt protocol adopted by the 

state of Maine to protect spawning habitat for 

the endangered Atlantic salmon was thoroughly 

scrutinized and approved by resource experts and 

regulatory agencies. 

Outcomes from the protocol include a mapped 

variable width riparian buffer for water 

quality and land use zones with management 

specifications. In the Intermountain West 

permitted uses within the buffer and management 

will be key to the long-term effectiveness of 

riparian buffers.

The importance of BMPs in the buffer zone and 

on adjacent lands cannot be overstated. In many 

cases, buffers alone may not be sufficient to 

reduce or eliminate contaminants. Contaminants, 

most importantly NO3

-

, can bypass buffer zones. 

Constructed wetlands such as those used in the 

Leopold Center for Sustainable Agriculture’s 3 

Zone buffer system are specifically designed to 

deal with agricultural chemicals (Schultz et al. 

1994). 

Ecosystems change over time; therefore 

monitoring will become necessary and adaptive 

management a likely possibility. 

 

Bear River, northern Utah. 

Photo credit: Susan Buffler

22
MATRIX A - SEDIMENT

AUTHORS YEAR STATE BUFFER WIDTH AND TYPE SLOPE BENEFIT - TYPE AApplebloom et al. 2002 NC 90cm grass strip NA Compared with no grass strip

 next to a road, reduced sed by an average of 56%.

Barfield et al. 1998 KY 4.6m bluegrass/fescue 9% Conventional and no-till plot

9.1m (well structured soils with 

13.7m No-till plots were more effec

Sediment retention increased  Most of the sediment was  the no-till plots. Trapping 

Barden et al. 2003 KS 12.2m small trees+native grass not Silty clay loam/natural rainfa

12.2m small trees+fallow specified No significant difference in v12.2m fallow (7 yrs) to allow for suspended solids with natu succession 40-75% reduction. Simula

 by 90%. Data highly varia conditions 

Chaubey et al. 1994 AR no buffer 3% Silt loam soils - swine manur

3m grass Effectiveness in reducing tota6m grass extend significantly beyon9m grass15m grass21m grass

Chaubey et al. 1995 AR no buffer 3% Uncultivated areas ammende

3.1m uncultivated Mass transport of total suspen6.1m grass by 35%. Effectiveness in r9.2m grass total suspended solids did 15.2m grass beyond 3m21.4m grass
Daniels and Gilliam 1996 NC 1. fescue strip across lane 4-15% Two locations #1 Sand

y loam 

into groundcover horizons #2. Silt loam / si

or mixed hardwoods 1 and 2 ephemeral and intermand pines Looked at vegetation structur2. narrow fescue to grass natural rainfall

 waterway through Runoff reduced by 50 to 80%

mixed weeds and by 80% small shrubs to larger trees High flows overwhelmed filt

Dosskey et al. 2002 NE 9-35m trees/grass 1-9% Potential sediment removal c

(four farms) due to varying topograph

 concentrated flow reduced 

Fasching and Bauder 2001 MT 12.2m grass / small grains 4% Looked at antecedent soil con

 drained soils with high w

 permeability. (50yr 24hr s sediment concentration in  by 68%. In dry soil concen

Fiener, P. and 2003

German

yvariable 10-59m 3.6-5% Runoff was reduced 90% and 

K. Aueswald mowed grass and no maintenance while sediment delivery w

2 watersheds respectively

Hook 2003 MT 6m 2-20% Looked at buffer structure on 

riparian pasture - sedge wetland, 94-99% sediment retention in 

rush transition, bunchgrass upland vegetation type or slope. V

 combinations. Sediment re stubble height

Jin and Römkens 2001 sim. 6m simulated filter strip 4 and 6% Trapping efficiency increased 

ploypropylene bristles decreased with increasing 

 deposition occurred in the  research plots and bare plo
Lee, Kye-Han et al. 2000 IA no buffer 5% (crop) Cropland = loam; buffer = 

7.1m switchgrass 8% (buffer) Simulated rainfall on bare cro16.3m switchgrass-woody 7.1m switchgrass buffer remo

 sediment and >98% sand, 16.3m switchgrass-woody bu sediment and >98% sand; 

Lim et al. 1998 KY no buffer 3% Silt loam soils / simulated ra

6.1m tall fescue pasture Total suspended solids remov12.2m tall fescue pasture No significant reductions bey18.3m tall fescue pasture

Mendez et al. 1999 VA no buffer ns Sediment deposited in the fir

4.3m grass strip.8.5m grass Sediment concentration was r

 87% (8.5m)

Nerbonne and MN ungrazed grass 32m±16m Looked at upland & riparian Vondracek grazed grass 74±15m structure. Percent fines an

wooded 94±14m with increasing buffer wid

 grassbuffer sites even thou Wooded and grazed buffers  in the streambed, howeve had <50% fines in streamb

Patty et al. 1997 France no buffer 7, 10, 15% 3 sites with silt loam soils ra

6m grass matter. Plots planted with 12m grass cultivated to winter wheat18m grass reduced from 43% to 99.9

 were reduced by 87% to 1

Robinson et al. 1996 IA 18.3m grass 7, 12% Initial 3m of the filter strip re

 sediment. 9.1m of the bu
Schmitt et al. 1999 NE 7.5 and 15m for all treatments 6 to 7% 76-93% reduction of sedimen

25 year grass plots Silt

y cla

y loam to sand

y loa

mixed grass (2 yr) Significant width effect on vo50% grass 50% trees + shrubs (2 yr) all contaminants with mosgrain sorghum (2 yr) 7.5m

Sheridan et al. 1999 GA Zone 1 - 10m hardwoods 3.5% Loam

y sand soils - three for

 Zone 2 - 45-55m managed forest (mature, clearcut and selec

Zone 3 - 8m grass Runoff was reduced 56% to 7

 before it entered the forestNo significant differenced we treatments. 63% of the se the grass filter strip

Syversen et al. 2001 Norway 5m mowed grass and weeds 14% Average particle retention 65

Most of the retention was in t

Tate et al. 2000 CA no buffer rolling Sprinkler and flood irrigated 

10m pasture buffer foothills clovers and 60% grass

Pastures grazed from June to Water use efficiency was low  runoff patterns were obser15% to 69% of the irrigation The authors found more runo produced from pastures wTotal suspended solids (TSS)  sprinkler irrigated pastureTSS concentration was reduc treatments and TSS load w irrigation 
AUTHORS YEAR STATE BUFFER WIDTH AND TYPE SLOPE BENEFIT - TYPE A

REVIEWSstudies showing removal of a substantial portion of sediments in overland flowin Castelle et al. 1994 Broderson 1973 61m Controlled sedimentation eve Ghaffarzadeh et al. 1992 0-18.3m grass 7&12% No slope differences in perfo Horner and Mar 1982 61m grassy swales (85% removal)

Removed 80% suspended sol

 Lynch 1985 30m between logging and wetland/ Removed 75 to 80% of sedim

 streams

 Schellinger 1992 22.9m Removed only 33% of suspen and Clausen  Wong and McCuen 1982 equation determining buffer width If removal needs to increase f

 slope, buffer width needs 

in Wenger, Seth 1999 (% removal of total suspende Clinnick 1985 30m Exhibited similar channel sta Coyne et al. 1995 9m grass as unlogged streams 

99% sediment trapped (poult buffers). Looked at one sim

 Davies and Nelson 1994 30m Logged forests - effects depe

 not on slope, erodability, o

 Desbonnet et al. 1994 25m Most efficient width for sedim (based on a review) 60m Most efficient width for total  Dillaha et al. 1988 4.6m orchardgrass On a simultated feedlot a 81% 

9.1m orchardgrass 91% for 9.1m buffer

 Dillaha et al. 1989 4.6m orchardgrass Below bare fertilized croplan

9.1m orchardgrass reduction. 84% for a 9.1m 

 Gilliam 1994 narrow (width not stated) Trapped 90% of sediment  Maguette et al. 1989 4.6m 3.5% 66% sediment reduction (liqu

9.1m 3.5% 82% sediment reduction (liqu

 Peterjohn 1984 19m 5% 90% removal of TSS and Corell Peterjohn and Correll 1984 50m 5% 94% (agricultural catchment  Rabeni and Smale 1996 Buffer width may not be as im

 characteristics such as she
 Young et al. 1980 21.3m 4% 75-81% removal of TSS

27.4m 4% 93% average removal of TSS

in Fischer 2000and Fischenich Horner and Mar 1982 ≥61m grass filter strip/vegetated 80% of sediment in stormwat

 buffer

 Ghaffarzadeh et al. 1992 ≥9m grass filter strip 7&12% Removed 85% of sediment Lynch et al. 1985 ≥30m Sediment removed 75 to 80% 

 bewteen logging activity a

 Dillaha et al. 1989 ≥9m vegetated filter strip Removed an average of 84% in Fischer 2004 2,5,10,15m grass filter strips Removal of sediment averageand Fischenich 4.6m and 9.1m Sediment reduced by 87% in (White Paper) 4.6m stips Gharabaghi et al. 2000 Mickelson et al. 2003
MATRIX B - PESTICIDES

AUTHORS DATE STATE BUFFER WIDTH AND TYPE SLOPE BENEFIT - TYPE ANArora et al. 1997 IA 20.1m 3% Silty clay loam soils. Natural 

Looked at two drainage to buRetention was dependent on a Atrazine: Retention in buffe Metalochlor: Retention rang Cyanazine: Retention range

Arora et al. 2003 IA 20.1m Looked at two drainage to bu

 rates (15:1 and 30:1)Concentrations of herbicides  than in inflow but greater fAtrizine: 15:1 treatment retain retained 46.8%Metalochlor: 15:1 treatment r treatment retained 48.1%Chlorpyrifos (insecticide): 15 30:1 treatment retained 76No significant differences we treatment Most of the herbicide retentio while insecticide retention 

Barfield et al. 1998 KY 4.6m bluegrass/fescue 9% Conventional and no-till plots 

9.1m (well structured soils with 13.7m Trapping efficiency increa

 infiltrationThe 9.14m buffer trapped an  atrizineEffeciency declined slightly f
Boyd et al. 2003 IA 4.6m grass 3.50% Clay loam; Looked at two dr

9.1m grass (source area) or inflow rates (15:1 and 4

2% filter Infiltration and adsorption pla

 retention. Sediment reduction was highe 45:1 plots for ChlorpyrifosChlorpyrifos was not detectabAtrizine and metalochlor; no  between the 15:1 and 45:1 

Kloppel et al. 1997 Germany10m grass field 8% Field study; titicale with gras

15m grass buffer 5% Looked at channelized flow a20m grass Three flow rates. Three herbi

 isoproturon, and dichlorpr Samples were taken at 10, Runoff was reduced from 46 rates and buffer lengths althou was observed. Higher amo found with increasing flow  applied. Efficiency of herb due to infiltration.

Krutz et al. 2003 TX 3m buffalograss 2% Atrazine and atrazine metabo

saturated clay soil (60 mi

Retention was greater for atra metabolites (19%)

Lowrance et al. 1998 GA 8m grass Loamy sand; natural precipit

40-55m slash pine corn crop. Two treatments 10m hardwoods clear cut and thinned

Alachlor and atrazine reductio buffer. Most of the herbici before June 30. Reduction  of both herbicides at hardwo
Mersie et al. 1999 VA bare 1% 2 water runons were performe

switchgrass herbicide application 

Switchgrass removed dissolve by 52 and 59% of the runo Bare slope removed 41% o metalochlor Grass plots retained most of t cm

Patty et al. 1997 France no buffer 7, 10, 15% 3 sites with silt loam soils ran

6m grass matter. Plots planted with 

12m grass cultivated to winter wheat 18m grass Reduction of herbicides with 

 independent of runoff inteLindane - 72 to 100% Atrazine - 44 to 100%Isoproturon >99%Diflufenican >97% 

Schmitt et al. 1999 NE 7.5 and 15m for all treatments 6 to 7% Silty clay loam soils 

25 year grass plots Permethrin concentrations redmixed grass (2 yr) by 5-43%; alachlor by 10-50% grass 50% trees + shrubs (2 yr) effective for dissolved congrain sorghum (2 yr)

Seybold et al. 2001 OR 3m bare 1% Clay loam soil

3m switchgrass There was no significant diffe

 grass plots in amount of he the leachate was filtered or Switchgrass increased degrad but not atrizine. Overall, 5 herbicide applied was rem
Vellidis et al. 2002 GA 8m grass Loamy sand soil; atrazine an

20m slash pine Restored forest riparian buffe10m hardwoods Most of the surface transport 

 by June 30Concentration reduction was  within the grass buffer striConcentrations were or below  stream

AUTHORS DATE STATE BUFFER WIDTH AND TYPE SLOPE BENEFIT - TYPE ANREVIEWSin Fischer 2004

and Fischenich(White Paper) Mickelson et al. 1998 IA 4.6m grass filter strip Atrazine reduced by 31% and 

9.1m grass filter strip buffers, respectively 

 Rhodes et al. 1980 ns* Trifluralin reduced by 96% an

 filter strips, respectively

 Asmussen et al. 1977 24.4m grassed waterway 2,4-D reduced in runoff by 98

 wet antecedent conditions

*ns=not stated 
MATRIX C - PHOSPHORUS

AUTHORS YEAR STATE BUFFER WIDTH AND TYPE SLOPE BENEFIT - TYPE ANPHOSPHORUSBarden et al 2003 KS 12.2m small trees+ *ns Silty clay loam/natural rainfa

 native grass Total P >50% reduction for a12.2m small trees+fallow12.2m fallow (7yrs) to allowfor succession

Chaubey et al. 1994 AR no buffer 3% Silt loam soils - swine manur

3m grass 3.1m buffer reduced incoming 

6m buffer removed 94%9m 3.1m buffer reduced total P b15m removed 92%21m Mass transport of these substa

Chaubey et al. 1995 AR no buffer 3% Uncultivated areas ammended 

3.1m uncultivated 3.1m buffers reduced mass tra

6.1m by 40 % and 39%, respect9.2m respectively, in the 21.4m 15.2m21.4m

Daniels and Gilliam 1996 NC 1. fescue strip across lane 4-15% Two locations #1 Sandy loam 

into groundcover horizons #2. Silt loam / si

or mixed hardwoods 1 and 2 ephemeral and intermand pines Vegetation structure; cultivate2. narrow fescue to grass Runoff total P was reduced by waterway through soluble PO4 passed throug

mixed weeds and whelmed filters small shrubs to larger trees 
Lee et al 2000 IA no buffer 5% (crop) Switchgrass removed 72 % of 

7.1m swithgrass 8% (buffer) Switchgrass-woody removed 16.3 switchgrass-woody PO4-P, respectively

Lim et al 1998 KY 0m tall fescue pasture 3% Silt loam soils / simulated rai

6.1m tall fesecue pasture Almost all P in runoff was PO

12.2m tall fescue pasture sediment18.3m tall fescue pasture ~75% of total P and PO4 was 

 buffer strip

Lowrance et al. 2000 GA 8m grass Zone 1 2.5% Used USDA three zone system

40m thinned, clear cut, control Movement of PO4 was minimZone 2 patterns15m undisturbed forest Zone 3

Majed et al. 2003 Canada 5m perennial ryegrass 2.3, 5% Silt loam soil - 4% organic m

2,5,10,15m legume + grass P trapping efficiencies ranged 5m bare increasing buffer width5m existing native grasses Authors did not compare all w

Osbourne and Kovacic 1993 IL no buffer-rowcrops to streambank low relief Dense basal till - silty clay lo

39m grass Grass more efficient in reduci16m mature forest During the dormant season bo

 as a total P source

Osbourne and Kovacic IL 10m ryegrass Oats had no significant effect (same article) 20m ryegrass removed in runoff

30m ryegrass 10m buffer had greater total P 20m oats buffer probably due to inu

 sediment deposited
Patty et al. 1997 France no buffer 7, 10, 15% 3 sites with silt loam soils ran

 matter

6m grass Plots planted with ryegrass ne12m grass winter wheat 18m grass Soluble P in runoff was reduc

 increasing buffer width

Schmitt et al 1999 NE 7.5 and15m 25 yr. grasss plots 6 to7% Silty clay loam to sandy loam

7.5 and 15m 2 yr. mixed grass Total P reduced by 55-79%7.5 and 15m 2 yr. 50% grass+ 19-43% reduction of dissolve50% trees / shrubs Most reduction was within fir7.5 and 15m 2 yr. grain sorghum 

Grass did not reduce concentrcompared with sorghumSignificant width effect on vo all contaminants

Snyder et al. 1998 1998 VA 10-40m wetlands 0-6% ag + Soils vary with topography; a

upper woods matter

120m forest buffer 10-20% woods. Corn-soybean rotation w. cov

20%+ small wooded areas. Water table ranged from 10m 1-2% streams No spatial trend; concentratiodraining summer for most sampling wetlands. (9m upper woodland, 2 to 

 wetland)
Tate et al. 2000 CA no buffer rolling Sprinkler and flood irrigated p

10m pasture buffer foothills clovers and 60% grass

Pastures grazed from June to Water use efficiency was low  observed15% to 69% of the irrigation The authors found that more r produced from pastures wiBuffer did not reduce total P c sprinkler or flood irrigatio total P under flood irrigati

AUTHORS YEAR STATE BUFFER WIDTH AND TYPE SLOPE BENEFIT - TYPE AN

REVIEWSin Osbourne and 1993 Efficiency of removal of P - d Kovacic

PERCENT REDUCTION

SUBSURFACE FLOW Peterjohn and Correll 1984 19 m forest 33% Peterjohn and Correll 1984 50 m forest 114% (concentration increaseSURFACE FLOW Cooper and Gilliam 16 m forest 50%

 Peterjohn and Correll 1984 19 m forest 74% Peterjohn and Correll 1984 50 m forest 85% Dillaha et al. 1989 9 m grass 79% Dillaha et al. 1989 5 m grass 61%in Wenger, Seth 1999 Vought et al . 1994 Sweden 8m grass Grassed buffer retained 66% 

 after 16m, 95% retained

 Mander et al. 1997 Estonia 20m and 28m 67 and 81% trapping efficienc

 respectively

 Dillaha et al. 1988 4.6m and 9.1m grass 71.5 and 57.5 respectively tot

 removed less in longer bu
 Dillaha et al. 1989 4.6m and 9.1m grass 61% and 79% total P remove

 Maguette et al. 1987 4.6m and 9.1m 41 and 53% respectively total  Maguette et al. 1989 4.6m and 9.1m 18 and 46% respectively total 

grass, grass/legume/bare/ native grass

 Hubbard 1997 1997 GA 30m No reduction of P in shallow 

PO4-P increased over the dur

 Peterjohn and Corell 1984 MD 50m 84% of total P and 73% of so

 from surface runoff howev increased in shallow groun

 Young et al. 1980 21m corn Total P reduce by 67% and so

96%

 Osbourne and 1993 16m forest No reduction in phosphate fro Kovacic 39m grass cropland)in Fischer 2004

and Fischenich (White Paper) Madison et al. 1989 ME

≥5m grass filter strip Trapped ~90% of PO4

 Shisler et al. 1987 MD

≥19m forest Removed 80% of excess PO4

 Lee et al. 2000 IA no buffer Grass removed 64% total P, 4

7.1m switchgrass Grass/woody buffer removed 16.3m switchgrass-woody

in Uusi-Kamppa et al. 1997 Syversen 1995 Norway 5,10,15m native grass 12-17% Natural rainfall

5m buffer trapped 45-65% of 

10m buffer trapped 56-85%%  PO415m buffer trapped 73% of T
 Uusi-Kamppa and 1996 Finland 10m Natural rainfall

 Ylaranta Buffer trapped 20-36% partic Uusi-Kamppa 1995 Finland 10m Buffer trapped 53-78% partic (unpublished) Schwer and Clausen 1989 VT 26m Dairy waste: 89% retention o

 of PO4. Greatest removal w

 season

 Vought 1994 Sweden 8m 8m buffer removed 66% of P

16m 16m buffer removed 95% of P

*ns - not specified 
MATRIX D - PATHOGENS

AUTHORS DATE STATE BUFFER WIDTH AND TYPE SLOPE BENEFIT - TYPE AAtwill et al. 2002 CA 1m grass (simulation) 5, 10, Looked at three soil textures; 

20% sandy loam

Surface and subsurface measClay soils with lower infiltrat removing oocysts from buPostulated that buffers with h

≤20% slope and ≥3m wide 

 concentrations of Cryptosp

≥99% although greater am

 found in subsurface flow  soils

Chaubey et al. 1994 AR no buffer, 3m grass, 6m grass 3% Silt loam soils - swine manur

9m grass, 15m grass, 21m grass There was a sigificant reduct

 3m but no significant redu

Coyne et al. 1998 KY 4.5m grass sod 9% Silt loam soils

8m grass sod (mean) Poultry waste/fecal coliform 

Mean fecal coli. trapping effi strip; most bacteria trappe 91% in 9m strip Fecal streptococci trapping ef and 74% in 9m strip but c higher than standard

Entry et al. 2000 GA 20m grass / 10m forest 1.5 - 2% Loamy sand (grass); loamy 

10m grass / 20m forest Swine wastewater fecal colifo10m grass / 20m maidencane Wastewater pulse moved fart

 seasons No differences to 2m in wells  treatment
Entry et al. II. 2000 GA 20m grass / 10m forest 1.5 - 2% Loamy sand (grass); loamy 

10m grass / 20m forest Swine wastewater fecal colifo10m grass / 20m maidencane Total and fecal coliforms dec

90 to 120 days amounts simil filter strips

Lim et al. 1998 KY no buffer 3% Silt loam soils / simulated ra

6.1m tall fescue pasture No measurable concentration12.2m tall fescue pasture 6.1m18.3m tall fescue pasture

Tate et al. 2004 CA 1.1m grass (simulation) 5, 12, Sand

y loam soil - 2 hour pre

20% per hour. 5% slope had th

Most of Cryptosporidium par

 in subsurface transportMost of C. parvum oocysts o were found in surface tran

Trask et al. 2004 IL bare ground (simulation) 1.5, 3, Used two rainfall intensities 

bromegrass 4.5% Higher intensity rainfall resul

 C. parvum oocysts in surfOocysts were found in surfac lower rainfall intensity for Vegetated treatment containe bare ground

Young et al. 1980 MN Year 1- corn / orchardgrass / 4% Fecal bacteria - feedlot

sorghum x sudangrass buffer 27.43m Total coliform and fecal colifYear 2 buffer reduced to 21.34m Fecal streptoccoci reduced by  (corn and oats)
MATRIX E - NITROGEN

AUTHORS YEAR STATE BUFFER WIDTH and TYPE SLOPE BENEFIT - TYPE ANBarden et al 2003 KS 12.2m small trees+native grass ns* Silty clay loam/natural rainfa

12.2m small trees+fallow Total N reductions were betw12.2m fallow (7yrs) to allow for depending on buffer type succession

Barfield et al. 1998 KY 4.6m bluegrass/fescue 9% Conventional and no-till plot

9.1m structured soils with high 

13.7m >90% nutrient trapping, 200

 buffer width

Bedard-Haughn et al 2004 CA no buffer (irrigated pasture) 9.5 to 11.9% Rocky loam soils / irrigated p

8m mixed grass Buffers decreased amount of 

16m mixed grass Majority of N attenuation wa

8m buffer decreased NO3 loa16m buffer decreased NO3 loAfter 4 weeks there was a ste runoff

Chaubey et al. 1994 AR no buffer 3% Silt loam soils - swine manur

3m grass Total Kjeldahl N reduced by 6m grass in the 21m buffer9m grass Ammonia reduced by 71% in 15m grass in the 21m buffer21m grass

Chaubey et al. 1995 AR no buffer 3% Uncultivated areas ammende

3.1m uncultivated Mass transport of total Kjelda6.1m grass (3.1m buffer) and 81% (219.2m grass Ammonia was reduced by 4715.2m grass (21.4m buffer)21.4m grass Nitrate from incoming runoff 
Daniels and Gilliam 1996 NC 1. fescue strip across lane 4-15% Two locations #1. Sand

y loa

into groundcover horizons #2. Silt loam / si

or mixed hardwoods 1 and 2 ephemeral and intermand pines Vegetation structure; cultivat2. narrow fescue to grass Filters retained 20-80% of the 

waterway through Kjeldahl N and NO3mixed weeds and High flows overwhelmed filtesmall shrubs to larger trees 

Dukes et al. 2002 NC 8 and 15m cool season grass Wells at three depths

8 and 15m deep rooted grass Effect of vegetation not signi8 and 15m pine/mixed hardwood confounding effects)8 and 15m native vegetation results0m (crops/pasture) Deep wells, reduction of NO3 

 84% (15m buffer) At mid depth wells, reduction  (8m buffer) and 43% (15m 

Haycock and Pinay 1993 GB 16m ryegrass <1% Floodplain with impermeabl

16m Lombardy poplar With increasing NO3 load, NO

Poplar retained 99% of NO3Grass retained 84% of NO3 in 

Vegetative biomass may cont pool even in winter

Hubbard et al. 1998 GA 10m + 20m coastal bermudagrass 1.5-2% NO3 concentrations in runoff 

draining into forest application rate and gener20m + 10m b.grass into forest increasing buffer width10m + 20m b.grass into maidencane Plots with maidencane had th

Jacobs and Gilliam 1985 NC <16m forest with and withought 0-6% Poorly drained to well draine

natural drainage crops with and without wi
Jones, Dryw 2001 CA 5m native forest 5m buffers zones removed 45

3% plant cover No significant difference in s

Measured surface flow

Jordan et al. 1993 MD ~60m forest hillslope / Reduced subsurface flow by 

floodplain drinking water standard)

Most of NO3 change occurred  the edge of the floodplain 

Karr et al. 2001 NC 10 to>100m forest ns Pasture sandy loams / ripari

 sandy Swine waste application to fiNO3 bypassed denitrification 

Lee et al. 2000 IA no buffer 5% (crop) Simulated rainfall - high infil

7.1m switchgrass 8% (buffer) Switchgrass removed 64% to

16.3m switchgrass-woody Switchgrass - woody buffer r

 92% of NO3

 Wider buffer trapped clay 

Lim et al. 1998 KY no buffer pasture (tall fescue) 3% Silt loam soils / simulated rai

6.1m pasture ~75% of total N removed in f12.2m pasture reductions beyond 6.1m18.3m pasture

Lowrance, Richard 1992 GA 50-60ft pine forest 2% Poorly drained loamy sand/

NO3 reduced by a factor or 7 

In the next 40m, N reduced fr per liter. Denitrification po and October
Lowrance et al. 2000 GA 8m grass Zone1 2.5% Used USDA three zone syste

40m thinned, clear cut, control Zone 2 Groundwater NO3 reduced fro

15m undisturbed forest Zone 3 than 2mg per L within 5m 

No Zone 2 forest managemen

 concentrations

Mendez et al. 1999 VA no buffer ns NO3 concentrations reduced b

4.3m grass (8.5m)8.5m grass NH4 concentrations reduced 

 (8.5m)

Osbourne and Kovacic 1993 IL no buffer (row crops) low relief Dense basal till - silty clay lo

39m grass ≥90% reduction in NO3 in bo

16m mature forest No seasonal variation seen fo

Patty et al. 1997 France no buffer 3 sites with silt loam soils ran

6m grass 7, 10, matter - Natural runoff eve12m grass 15% Plots planted with ryegrass ne18m grass winter wheat 

NO3 was reduced from 44 to 

 buffer widthPerpendicular planting impro

Peterjohn and Correll 1984 MD 50m riparian forest ns Deep fine sandy loam with c

Total reductions were 79% fo

 62% for organic NMean annual concentrations d and 98%Most of the reduction occurre

Pinay et al. 1994 France 50m riparian forest 3% Clay and fine silt soils

transect All NO3 removed from first 3
Schmitt et al. 1999 NE 7.5 and15m 25 yr. grasss plots 6 to7% Silt

y cla

y loam to sand

y loa

7.5 and 15m 2 yr. mixed grass Buffers had greater effect on 7.5 and 15m 2 yr. 50% grass+ dissolved nutrients50% trees / shrubs NO3 reduced by 24-48%

7.5 and 15m 2 yr. grain sorghum all 

 contaminants

Schnabel et al. 1996 PA 40m woody gently rolling buffer

18m grass alluvial NO3 levels lowest near stream 

 floodplain Carbon was limiting in the w

Snyder et al. 1998 VA 10-40m wetlands 0-6% ag + Instream NO3 concentrations 

120m forest buffer upper woods field; NH4 no spatial trend 

10-20% woods were higher in summer 20%+ small wooded areas1-2% streamsdraining wetlands

Spruill, Timothy 2000 NC 30m lowland forest Poorl

y drained soils in strea

0m NO3 was 95% less in buffered 

65 to 70% was due to reducti (remaining due to dilution

Tate et al. 2000 CA no buffer rolling Sprinkler and flood irrigated 

10m pasture buffer foothills clovers and 60% grass

Pastures grazed from June to Water use efficiency was low  patterns were observed 15% to 69% of the irrigation No significant reduction in N
Verchot et al. 1997a NC 54.9m pine/hardwood 1 - 4% Surface flow / natural runoff 

67m pine/hardwood 2 - 9% Watershed 1 - fields were san

 sand in forestWatershed 2 - fields were loa sandy loam forestAnnual rotation of winter wh tobacco every 3 yearsBuffer zones ineffective in w

 and organic N loading inc effective in W2. Clay soil

Verchot et al. 1997b NC 54.9m pine/hardwood WS 1 - 4% Subsurface flow / natural run

67m pine/hardwood WS 2 - 9% Watershed 1 - fields were san

 loam

y sand in forest

Watershed 2 - fields were loa

 sand

y loam forest

tobacco  every 3 yearsNO3 loss almost entirely from 

of  N. NO3 concentrations de

 to forest edge at both sites 

Wigington et al. 2003 no buffer (ryegrass seed crop) <3% Poorl

y drained soils 

30-48m noncultivated grass, Buffer significantly reduced N

forbs, sedges and rushes for all sampling dates how

 should be implemented fir from saturated swales in fi the riparian zone
AUTHORS YEAR STATE BUFFER WIDTH and TYPE SLOPE BENEFIT - TYPE AN

REVIEWSin Osbourne 1993and KovacicSUBSURFACE FLOW TYPE and PERCENT REDU Bagley and Gallagher 10m forest 60-98% seasonal variation Dillaha et al. 1989 9 m grass 73% Dillaha et al. 1989 5 m grass 54% Doyle et al. 1977 30 m forest 98% Lowrance et al. 1984 25m forest 68% Pinay and Decamps 1988 30m forest 100% Schnabel 1986 19m forest 40-90m seasonal variation Schnabel 1986 27m grass 10-60% seasonal variationSURFACE FLOW Young et al. 1980 27 m grass 4% grass 84% 

in Castelle et al. 1994 Bingham 1980 1:1 ratio of buffer area to waste area Sufficient to reduce nutrient r

(cumulative surface area of poultry cages) 

 Doyle et al. 1977 3.8m forest Reduced N, P, K and fecal ba

4m grass

 Lynch 1985 30m water 

 standard"10mg/L

 Madison et al. 1992 4.6 vegetated filter strip Filter strip trapped 90% of N 

 9.1m buffers had 96-99.9 no improvement beyond 9

 Overcash et al. 1981 grass 1:1 ratio of buffer area to was

 concentrations of animal w

 Vanderholm 1978 91.5m, 262m 0.5, 4% Removed 80% of the nutrient and Dickey Xu et al. 1992 NC NO3 concentrations reduced f

 0.5mg/kg soil 
in Wenger, Seth 1999

 Fennesey and Cronk 1997 20-30m Can remove 100% of NO3SURFACE RUNOFF Daniels and Gilliam 1996 NC 6m grass Retained 20-80% of NH4 and 

13m grass/forest NO3 (sites had different ch

18m grass/forest

 Dillaha et al. 1988 4.6m, 9.1m Effective for removing total N 

 67% reduction (4.6m buff

 Dillaha et al. 1989 4.6m, 9.1m NO3 reduced by 73% 

9.1m

 Hanson et al. 1994 31m Reduced shallow groundwate

 94% to less than drinking  (downslope from septic)

 Lowrance 1992 50-60m reduction in first 10m

 reduction in first 10m

 Maguette et al. 1987 4.6m, 9.1m 17% and 51%, respectively Maguette et al. 1989 4.6m, 9.1m 0% (for both buffer widths) Mander et al. 1997 20m, 28m 81 and 80% total groundwate

 respectively

 Osborne and Kovacic 1993 IL 16m forest Reduction of shallow ground Peterjohn and Correll 50m Reduced all N in surface runo

 groundwater; other forms 

 Pinay and Descamps 1993 30m Sufficient for N removalSHALLOW SUBSURFACE FLOW Vought 1994 8m Surface reductions of NO3 we

16m buffers. Subsurface flow a

 20m into the buffer 
in Allan R. Hill 1996

 Lowrance et al. 1984 GA forest Shallow lateral flow in a shal

 forest retained 90% of the 

 Schnabel 1986 PA 18m grass Shallow lateral flow with bed

 was >90%

 Pinay and Decamps 1988 France 130m forest Shallow lateral flow with clay 

 reduced 100% 

 Cooper 1990 NZ 9m grass to 1m - 

 1m. Reduced NO3 by >90

 Robertson et al. 1991 Canada 20m grass Groundwater flowing up with 

 the surface - NO3 reduced 

 Simmons et al. 1992 RI 31m forest outwash 

 outwash. NO3 reduced by 

 Brusch and Nilsson 1993 Denmark15-25m fen Overland flow at depth with 2

 Phillips et al. 1993 MD forest Upward flow in 7 to 20m san

 NO3 

 Schipper et al. 1993 NZ pine forest Upward shallow lateral flow 

 clay removed 98% of NO3

(NO3 inputs ranged from

0.6 to 44 mg NO3- /L)*ns=not specified 
50

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