Design 

of the 

National Trends Network 

for Monitoring the Chemistry of 

Atmospheric Precipitation 

U. S. Geological Survey Circular 964 
ABOUT THE COVER: Average annual sulfate deposition in the United States, mg/m2 , July 1978-September 1980. 
National Acid Precipitation 

Assessment Program 

Design 

of the 

National Trends Network 

for Monitoring the Chemistry of 

Atmospheric Precipitation 

By J. K. Robertson and J. W. Wilson 

U. S. Military Academy at 

West Point, New York 

Prepared for the 

Deposition Monitoring Task Group 

Sponsored by the U. S. Geological Survey 

under Contract No. 4000-2868-81 

U.S. Geological Survey Circular 964 

1985 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1984 

Free on application to: 

Branch of Distribution 

U. S. Geological Survey 

604 S. Pickett Street 

Alexandria, VA 22304 
Preface: 

This is a report of the Interagency Task Force on Acid Precipitation. The Task Force was created 

under the Acid Precipitation Act of 1980 (Title VII of P. L. 96-294) to conduct a comprehensive 

research program on the causes and effect of acid precipitation, and on means by which any adverse 

effects might be reduced. 

The research program is managed through a series of task groups, each of which is responsiblE: for 

planning and conducting a segment of the program. A lead agency has been assigned for each of the 

task groups as follows: 

Task Group 

A. Natural Sources 

B. Man-made Sources 

C. Atmospheric Processes 

D. Deposition Monitoring 

E. Aquatic Efferts 

F. Terrestrial Effects 

G. Effects on Materials & Cultural Resources 

H. Control Technologies 

I. Assessments 

J. International Activities 

Lead Agency 

Nat'l Oceanic & Atmospheric Administration 

Department of Energy 

Nat'l Oceanic & Atmospheric Administration 

Department of the Interior 

Environmental Protection Agency 

Department of Agriculture 

Department of the Interior 

Environmental Protection Agency 

Environmental Protection Agency 

Department of State 

TheN ational Acid Precipitation Assessment Program is intended to focus federally-funded research 

on the timely development of a firmer scientific basis for policy decisions related to acid precipitation. 

Reports are released both as Task Force reports on multi-agency efforts and as individual agency 

reports on single-agency projects. 

This report is a product of the Deposition Monitoring Task Group. The members of the task group are 

as follows: 

Members: 

Lead agency: U.S. Geological Survey 

U.S. Environmental Protection Agency 

U.S. Department of Energy 

Nat'l Oceanic & Atmospheric Administration 

Cooperative State Research Service 

U.S. Forest Service 

National Park Service 

U.S. Bureau of Land Management 

Tennessee Valley Authc:dty 

Pacific Northwest National Laboratory 

Brookhaven Nat'l Laboratory 

National Bureau of Standards 

U.S. Bureau of Reclamation 

U.S. Fish and Wildlife Service 

U.S. Ofc. of Surface Mining & Reclamation 

CONTENTS 

Page 

ABSTRACT 1 

INTRODUCTION 2 

Acknowledgements ........................................................................................................ 2 

MODELS FOR DISTRIBUTION OF NETWORK SITES . ..... ......... ..... ..... .. ... .. ..... .. ... .. ..... .. .. 3 

Pre-Bear Mountain Models .. . . . . . . . ... .. .. ... ....... ...... ....... .. . . .. . .. ... .. . . . . . . ....... .. .. . .. . . . . . . . . . .. . . . . . . .. 3 

Uniform or Random Distribution 3 

A Regional Approach 3 

From Model to National Trends Network Recommendations 10 

Weighting Factors for Site Distribution ... .......... ....... ..... ..... .. ... .. ... ....... ... .. .. ..... ....... ... .. 10 

Mean Annual Precipitation .................. .................................................................. 10 

Precipitation Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Ambient Concentrations of Air Pollutants .. .. ... .. . . . . . .. .... ... .. .. .. . .. . . . . . . . . .. . . . . .. .. . .. . .. . . . . . . 11 

Air Pollutant Emissions .................................................................... ...................... 11 

Topography 12 

Existing Wet Deposition Chemistry Data ......................... ..................... .... .............. 12 

Potential Sensitivity to Acid Deposition . ...... ... . ... .. . . . . . ... . . . . ... . . . .. ............ ... .. .. . .. .. . . . .. 15 

Combination of Weighting Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Discussion at Bear Mountain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Framework for the Discussion ......... ................................................................. ............ 18 

Flexibility of the Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Weighting Factors for Site Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Precipitation Variability 18 

Air Pollutant Emissions . . . . . . . . .. . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Existing Wet Deposition Chemistry Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 9 

Potential Sensitivity to Acid Deposition _ ................................................................ _ 1 9 

v 
CONTENTS 

Page 

Post Bear Mountain Model 19 

POPULATING THE MODEL 20 

Existing Sites to be Considered 20 

Multistate Atmospheric Power Production Pollution Study . . . . . . . . . . . . .. . . .. . . .. ... . . . . . .. . . . . . . .. .. 20 

National Atmospheric Deposition Program ................................................................. _ 20 

Tennessee Valley Authority Trend Stations . . . . . . .. .. . ..... ........ .. . . . . . . . . . . ... .. . . . . . .. ... .. .. . ...... ... 20 

Utility Acid Precipitation Study Program ...... ....... ............... ..... ...................... ............ 20 

NOAA Reference Climatological Station Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

Co located Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

Available Site Data ......................................................................................................... 22 

Site Description Information ................................................. ..... .................................. 22 

Air Pollutant Emissions Data .. . .. .. . . . ... . . . .. . . .. . . . . . . . . ... .. .. ... ..... ........ .. . . . .. . . . . . . . . . . . .. .. . .. . . . .. . . . 22 

Wet Deposition Chemistry Data ................................................................................. _ 24 

Procedure for Evaluating Existing Sites ..................................................................... - 24 

Procedure for Evaluating Areas Where No Station Exists (New Sites) ...................... 24 

Example of Site Selection on Equal-Area Basis by Ecoregion 25 

Site Selection Based on Gradient Definition 25 

Site Selection to Ensure Coverage of Sensitive Areas 25 

Allowances for Other Considerations ......................................................................... _ 25 

The Proposed National Trends Network 30 

REFERENCES 32 

Appendix A Guidelines for Design of a National Trends Network (NTN) ....................... - 34 

Appendix B Ecoregion Hierarchy................................................................................... 38 

Appendix C Site Codes and Abbreviations Used in the Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 

VI 
Figure 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

ILLUSTRATIONS 

Page 

Map ofEcoregions of the Conterminous United States...................................................... 6 

Map of Randomly Selected, Equal-Area Weighted Ecoregion 

Distribution for a 100-Site Network ................................................................................. 10 

Map of Precipitation Variability in the Conterminous United States .............................. _ 11 

Map of Randomly Selected, Precipitation Variability Weighted 

Network of 100 Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Diagram of Average Annual Sulfate Deposition (mg/m2) over North America .................. 13 

Diagram of Deposition Isopleths for Sulfate (mg/m2) Redrawn with Missing 

Isopleths Interpolated .. . . . . . . . . . .. .. . . . . . .. . . . . . . . .. . . . . . .. . .. . .. .. . . . . . . . .. . .. . . . . . . . . . . . .. . . .. . . .. . .. .. . . . .. . . . . . . . . .. .. 14 

Map of Quadrangles with High Deposition Gradients for Calcium, Sulfate, 

or Hydrogen Ions ............................................................................................................ 15 

Map of Quadrangles with Weighting Due to High Precipitation Variability, 

Low Emissions or High Deposition Gradients ................................................................. _ 15 

Map of Existing Precipitation Monitoring and Climate Monitoring Sites .......................... 21 

Diagram of a Sample Plot of Emission Sources Within 20 km of a 

Proposed Site at Finley Farm, NC ................................................................................. _ 22 

11. Form for Site Suitability Analysis ................................................................................. - 23 

12. Diagram of an Emission Plot for the Raleigh Quadrangle ................................................ 24 

13. Map of Possible Monitoring Sites in Province 2510 Considered for 

Inclusion in the NTN ....................................................................................................... 26 

14. Map of Ninety-Six Sites Proposed for Incorporation into NTN Based on the 

Equal-Area Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 

15. Map of Twenty-Seven Sites Proposed for Incorporation into NTN Based on 

Semonin's Gradient Maps ................................................................................................ 28 

16. Map of Fifteen Sites Proposed for Incorporation into NTN Based on 

Sensitive Area Coverage ................................................................................................. 29 

17. Map of Thirteen Sites Proposed for Incorporation into NTN Based on 

Other Considerations ...................................................................................................... 29 

18. Map of the Proposed National Trends Network Sites ........................................................ 31 

vii 
TABLES 

Page 

Table 1. General Environmental Characteristics of Domains and Divisions................................... 5 

2. Ecoregion Distribution of Sites Based on Equal-Area Weighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

3. Ecoregion Distribution of Sites Based on High Precipitation Variability, 

Low Emissions, and High Deposition Gradient Weighting Factors ................................... 16 

4. Final Ecoregion Distribution of Sites Based on Equal Area (97 Sites) ................................ 27 

viii 
Design of the National Trends Network for Monitoring 

the Chemistry of Atmospheric Precipitation 

By J. K. Robertson and J. W. Wilson 

ABSTRACT 

Long-term monitoring (10 years minimum) of the 

chemistry of wet deposition will be conducted at 

National Trends Network (NTN) sites across the 

United States. Precipitation samples will be collected 

at sites that represent broad regional characteristics. 

Design of the NTN considered four basic elements 

during construction of a model to distribute 50, 75, 

100, 125 or 150 sites. The modeling oriented design 

was supplemented with guidance developed during 

the course of the site selection process. Ultimately, a 

network of 151 sites was proposed. 

The basic elements of the design are: 

(1) Assurance that all areas of the country are represented in the network on the basis of regional 

ecological properties (96 sites); 

(2) Placement of additional sites east of the Rocky 

Mountains to better define high deposition 

gradients (27 sites); 

1 

(3) Placement of sites to assure that potentially 

sensitive regions are represented (15 sites); 

(4) Placement of sites to allow for other 

considerations, such as urban area effects (5 

sites), intercomparison with Canada (3 sites), and 

apparent disparities in regional coverage (5 

sites). 

Site selection stressed areas away from urban 

centers, large point sources, or ocean influences. 

Local factors, such as stable land ownership, nearby 

small emission sources (about 10km), and close-by 

roads and fireplaces (about 0.5km) were also 

considered. All proposed sites will be visited as part of 

the second phase of the study. 
INTRODUCTION 

The Deposition Monitoring Task Group of the 

Interagency Task Force on Acid Precipitation is 

charged in the National Acid Precipitation 

Assessment Plan (Interagency Task Force on Acid 

Precipitation, 1982) with developing three types of 

precipitation monitoring networks: a Global Trends 

Network, a National Trends Network (NTN), and 

research support networks as needed. 

This paper deals with the development of the NTN. 

The task group viewed the design of the network and 

selection of sites as comprising five distinct steps: 

(1) Establishment of siting and operating criteria 

against which candidate sites would be judged for 

their acceptability for incorporation into the 

network. 

(2) Development of a distribution model which would 

provide a basis for distributing sites across the 

conterminous United States. 

(3) Evaluation of existing precipitation monitoring 

sites for acceptability in meeting the siting 

criteria and to see how well they satisfy the 

distribution established by the model. 

(4) Identification of tentative new sites needed to fill 

voids in the distribution model. 

(5) On-site evaluation of the suitability of each site. 

The task group's concept of the NTN and its siting 

criteria used in this project (step 1) can be found in 

Appendix A. Steps 2, 3, and 4 are addressed in this 

paper. 

2 

On-site evaluation of site suitability will be 

performed at a later date and will be reported 

separately. 

ACKNOWLEDGEMENTS 

Site operators and supervisors in each of the 

networks provided much of the site information 

which made this analysis possible. We would 

particularly like to thank Mr. Richard Cram, 

National Oceanic and Atmospheric Administration; 

Dr. Leo Topol and Mr. George Kilby of Rockwell 

International; Dr. William Parkhurst of the 

Tennessee Valley Authority; and Dr. Paul Michael of 

Brookhaven National Laboratory for providing 

information or assisting in getting their networks' 

cooperation in providing information. 

Many maps were needed to support this analysis. Mr. 

Richard Ipri, the U.S. Military Academy map 

librarian provided numerous U.S. Geolo~ical Survey 

guadrangle maps and base maps that were needed for 

the drawing. Dr. Frederick Lanery of the Fish and 

Wilqlife Service, St. Petersburg, Florida .. provided a 

complete set of the Ecoregion and Land-Surface Form 

maps for the United States. Without thP.ir help the 

analysis could not have been completed. Other 

valuable adminstrative support was provided by Miss 

Sue Romapo, Mrs. Shirley Bonsell, and Mrs. Judi 

Dubaldi. 
MODELS FOR DISTRIBUTION OF NETWORK SITES 

The design of the NTN proceeded in several stages 

and involved the interaction of the authors with a 

panel of reviewers that met at Bear Mountain, New 

York, in March 1982, and interaction with the task 

group on numerous occasions. The resulting design is 

a product of the authors enhanced by input and 

direction from these groups. Two important phases of 

model development exist: pre-Bear Mountain and 

post-Bear Mountain. The pre-Bear Mountain 

material presented on the pages that follow represent 

several attempts at incorporating knowledge of 

atmospheric deposition chemistry and factors which 

control this chemistry into a relevant distribution 

approach. At the Bear Mountain workshop, the 

review panel and the task group discussed the 

various approaches. Some approaches were retained, 

some discarded, and others modified. The post-Bear 

Mountain model incorporates these changes and 

serves as a basis against which potential sites were 

evaluated. The model establishes the number of sites 

per region and does not deal in specific site locations. 

Evaluation of existing sites and selection of sites to 

fill voids in the design are discussed later under the 

section on Populating the Model. 

PRE-BEAR 1\IOUNTAIN MODELS 

Wet deposition samples are collected in buckets 

having openings of approximately 678 cm2 but the 

data are then extrapolated over areas of hundreds 

and thousands of km2. The dilemma then becomes 

one of siting 50 to 150 samplers in regions of the 

country so that measurements from each are 

representative of large areas of the United States. 

Uniform or Random Distribution 

If nothing were known about emissions, ambient air 

data, precipitation chemistry, or sensitive 

ecosystems, one of two methods for designating sites 

would probably be tried. [n the first method, a grid 

with the appropriate number of intersections would 

be laid over a map of the United States. At each 

intersection, or as close to each intersection as 

possible, a sampling site meeting the established 

criteria would be located. The product of this exercise 

would be a network of uniform distribution. 

The second method is similar to the first in that the 

country be over-lain by a grid. With a grid of 150 

boxes, one site would be placed within each of the 150 

boxes. If a finer grid was used, such as a 470 grid 

resulting from use of the t:250,000-scale series of 

topographic maps (L.S. Geological Survey, 1980) 

then a technique would be necessary to choose only 

3 

150 boxes. Each box could be assigned a nonrepeating random number between 1 and 470. Many 

150-site networks could be generated by this method. 

These networks could then be examined to search for 

one network where the sites best meet the 

established siting criteria. 

The above techniques yield sampling locations 

unbiased by subjective criteria. But they suffer by not 

using information about emissions, p0tentially 

susceptible ecosystems, and existing wet deposition 

data. 

A Regional Approach 

The next level of complexity that one might like to 

incorporate into a site distribution model is some 

method of assuring that all areas of the country 

differing from each other by some property or 

properties are represented by a sampling site. A 

number of maps of the United States have been 

produced which divide the United States into regions 

based on different properties. Some of the more 

familiar are road atlases showing State 2nd county 

boundaries. Most of these utilize political or other 

boundaries to divide the country and are not at all 

suited for this kind of analysis. [n this study 

environmental properties of representation were 

sought because of their relevance to the potential 

effects of acid rain. 

Many maps of the United States do exist which divide 

the country into regions based on physical, biological 

or other environmental relationships. Atwood's 

(1940) "Physiographic Provinces of North America" 

is one such division of the country using landforms as 

the basis of its division. Another is the soils map of 

the United States (U.S. Geological Survey, 1966), 

which displays the pattern of soil orders and 

suborders. Kuchler (1964) produced a map based on 

potential vegetation types. Hammond (1964) divided 

the country into classes of land-surface form. 

Thornthwaite (1931) produced a climatic map of 

North America. Garrison and others ( 1971) define 34 

ecosystems into which all the land of the 

conterminous United States was classified. Bailey 

(1976, 1978, and 1980) described ecoregions of the 

United States based on climatic and vegetative 

factors. 

Bailey's Ecoregions of the United States ,~,as chosen 

as the ideal regional discriminator for this network 

design. It combines biotic and abiotic factors into one 

classification system, and generalizes pro{:'erties over 

broad areas (Bailey, l978 and l980, and Bailey and 

Cushwa 1981), thus producing a reasonable number 
of regions with which to work. Bailey's scheme is 

hierarchical with many levels of generalization. This 

allows aggregating of data at different levels as 

needed. 

Bailey's scheme uses a four-digit code, sometimes 

preceded by an alphabetic character, to represent the 

ecoregion hierarchy. The first digit in the scheme 

represents the domain. Three are recognized in the 

conterminous United States--humid temperate 

domain (2000), dry domain (3000), and humid 

tropical domain (4000). A fourth domain, polar 

domain (1000), is found in Alaska and Canada. 

Domains are located on the basis of annual rainfall 

and mean temperature of the warmest month. 

The second digit in the scheme represents a 

subdivision of the domains into divisions. The humid 

temperate domain (2000) is divided into six divisions 

-warm continental {2100); hot continental (2200); 

subtropical (2300)~ marine (2400)~ prairie (2500); and 

mediterranean (2600). The dry domain (3000) has 

steppe (3100) and desert (3200) divisions. The humid 

tropical domain (4000) has savanna (4100) and rain 

forest (4200) divisions, but only the savanna is 

exhibited in the conterminous United States. General 

environmental characteristics of the domains and 

divisions are shown in Table l. 

Divisions are then subdivided into provinces, the 

third digit in the scheme, based on uniform regional 

climate and the type or types of zonal soils. 

Sections represent the fourth digit of the scheme. 

These indicate, where present, local climatic 

variations and areas which have a single vegetative 

climax type. Figure 1 summarizes Bailey's ecoregion 

breakdown. 

Usually a single vegetative climax association is 

characterized by the province, but two or more 

climaxes may need to be represented, for example, on 

highlands. This often happens on mountains where 

each altitudinal zone may have a different climax. So, 

at the province level, highland provinces are 

distinguished by the use of an alphabetic modifier 

preceding the four-digit. code. The three types of 

highland are: mountain (M), plateau (P), and 

altiplano (A). (Instead of further differentiating each 

of the altitudinal variations on each highland thus 

creating a multitude of small areas, these are 

categorized by the climatic regime of the lowlands in 

which they occur). A list of the area of each province 

and their composite sections are provided in 

Appendix B. 

4 

Not all of Bailey's provinces are subdivided into 

sections. For this reason the province level has been 

chosen as a benchmark for the analysis. To initially 

allocate network sites based on provinces, the ratio of 

the area of each province relative to the total area of 

the United States was calculated. This fraction was 

then multiplied by the desired number of sites (50, 

75, 100, 125, or 150) in the network to yield the 

number of sites, by province, in the provisional 

network. Fractions greater than 0.5 were rounded up. 

Any province which did not receive a fite based on 

area was given a site to ensure complete ecoregion 

representation in the network. 

PROVINCES GIVEN ONE SITE TO ENSURE 

REPRESENTATION 

~TWORKSIZE 50 75 100 125 150 

Provinces 2410 2410 2410 4110 4110 

2610 3120 3120 

3120 3140 4110 

3140 4110 

4110 

When provinces were subdivided and rnore than one 

site was allocated to the province, the fractional area 

relative to province area was used to distribute sites 

within the province. All sections were not allocated 

sites under this procedure, because design criteria 

ensured ecoregion representation at the province 

level, not the section level. For example, province 

2110 has four sections. Based on a 50-site network, 

four sites should be in province 2110. The options 

were to place one site in each section, thereby 

allocating by section, or to allocate sitef on an area 

basis, which is the method of choice, whereby section 

2111 would get one site, section 2114 would get one 

site, section 2113 would get two sites, and section 

2112 would get none. The area basis for section 

distribution was used throughout. 

Table 2 shows results of provisional network 

selections based solely on equal area-weighting of 

ecoregions for five different network sizes. Also 

shown are existing monitoring sites l'y network 

within each ecoregion. (A description of each network 

is included in the section on Populating tre Model.) 
TABLE 1 

General Environmental Characteristics of Domains and Divisions 

(after Bailey 1976) 

DOMAIN DIVISION TEMPERATURE RAINFALL VEGETATION SOIL* 

2000 Humid 2100Warm Coldest month below Adequate Seasonal forests, Gray-Brown Podzolic 

Temperate Continental 0°C warmest month throughout mixed (Spodosols, llfisols) 

(22°C the year coniferous 

2200 Hot Coldest month below Summer Deciduous Gray-Brown Podzolic 

Continental ooc warmest month maximum forests (Alfisols) 

)22°C 

2300 Coldest month Adequate Coniferous Red and Yell ow 

Subtropical between 18°C and throughout and mixed Podzolic (Ult.isols) 

-3°C, warmest month the year coniferous - )22°C deciduous forest 

2400 Marine Coldest month Maximum in Coniferous Brown Forert and 

between l8°C and winter forest Gray-Brown Podzolic 

-3°C, warmest (22°C (Alfisols) 

2500 Prairie Variable Adequate Tall grass, Prairie soils, 

all year, park lands Chernozems 

excepting (Mollisols) 

dry years, 

maximum 

in summer 

2600 Coldest month Dry Evergreen Mostly immature 

Mediterra- between 18°C and - summer, woodlands and soils 

nean 3°C, warmest month rainy shrubs 

)22°C winters 

3000 Dry 3100 Steppe Variable, winters Rain {50 Short grass, Chestnut, Brown 

cold em/yr. shrubs soils and Sterozems 

(Mollisols, Aridisols) 

3200 Desert High summer Very dry in Shrubs or sparse Desert ( Ariclisols) 

temperature, mild all seasons grasses 

winters 

4000 Humid 4100 Coldest month )l8°C, Dry season Open grassland, Latosols (Qyisols) 

Tropical Savanna annual variation with {6 scattered trees 

( l2°C em/yr. 

* Names in parentheses are soil taxonomy orders 

5 
(j'\ 

Figure 1.- Ecoregions of the Conterminous United States (after Bailey, 1976). 
TABLE2 

Ecoregion Distribution of Sites Based on Equal-Area Weighting 

DIVISION ECO- 50 75 ioo 125 150 NADP SITES IN ECOREGION OTHER SITES IN 

REGION ASOFMAY 1982 ECOREGION 

2100Warm 2111 1 1 1 1 2 MI25, MN16, MN18, WI37 

Continental 

2112 0 0 1 1 1 MI22, WI36 R6 

2113 2 3 3 4 5 MI09, MI53, NY08, NYlO, M2, RIO, U5, U15, 

NY12, NY52, NY65, CAN2, CArr3 

P A 29, WI28, WI36 

2114 1 2 2 3 3 MAQ8, MEOO, ME02, Ml, R16, U1, U2, 

ME09, ME99, NH02, U3, Ul4 

NY20, V'TOl 

M2111 0.5 0.5 1 1 1 

M2112 0.5 0.5 1 1 1 ID04, MTO;> 

2200 Hot 2211 1 1 1 2 2 OH49 U4,U6 

Continental 

2212 1 2 2 2 3 MI26, OH17, OH71 M8, R21, U18 

2213 l 1 2 2 2 R1 

2214 2 3 4 5 6 MA01, MA13, NC25, N.J99, M3, M6, M9, R4, 

NY51, PA42, TNOO, TN11, R15, T3, Ul6 

VA13, VA28, WV18 

2215 2 3 4 6 7 AR27, IL35, IL63, M003, R13, T1, T2, U7, 

M005 U17 

2300 2311 2 3 4 5 6 FLOO, FL03 R17, U8 

Subtropical 

2312 1 1 1 2 2 

2320 5 7 9 12 14 AR02, GA41, MD13, MS14, M4, M7, RE, R19, 

NC03, NC1i, NC33, NC34, U9, UlO, U11, Ul9 

NC35, NC41, SC18, TX21, 

TX38 

2400 Marine 2410 1 1 1 1 1 OR99 

M2411 0 0 1 1 WA14 

M2412 0 0 0 0 

M2413 1 1 1 1 1 OR02 

M2414 d 0 0 0 CA45 

M2415 1 1 l 1 OR08, OR10 

7 
TABLE2 

(Continued) 

Ecoregion Distribution of Sites Based on Equal-Area Weighting 

DIVISION ECO- 50 75 iOO 125 150 NAD P SITES IN ECO REGION OTHER SITES IN 

REGION ASOFMAY 1982 ECOREGION 

2500 Prairie 2511 2 4 4 5 7 IL11, IL18, IL19, IL47, M5, U12 

IN34 

2512 2 2 3 4 4 TX52, TX53 

2521 1 1 1 2 2 

2522 0 0 1 1 1 

2523 1 1 1 1 2 R2 

2531 2 3 4 5 6 MN27, NE15 R8, U13 

2532 1 1 2 2 3 SDOO 

2533 1 2 2 3 3 

2600 Medi- 2610 1 1 1 1 1 CA88 R9 

terrane an 

M2610 1 1 1 1 2 CA75, CA99 

M2620 1 1 1 2 2 CA42, CA85 

3100 Steppe 3111 2 2 3 4 4 

3112 2 3 4 4 6 ND07, WY99 R7, CAN1 

3113 2 4 5 6 7 C022 Rll 

M3111 1 1 1 1 2 ID15 R20 

M3112 1 2 4 4 5 WY08 R3,R14 

M3113 1 2 2 3 3 COOO, C019, C021, NM07 

3120 1 1 1 1 1 OR17 

M3120 1 1 1 2 2 AZ03 R12 

3131 2 3 3 4 5 ID03, ORII 

3132 1 1 1 1 2 CA34 

3133 1 1 2 2 2 

3134 0 1 1 1 1 

3135 0 0 0 1 1 

8 
DIVISION 

3100 Steppe 

(Cont'd) 

3200 Desert 

4100 

Savanna 

TOTAL 

TABLE2 

(Continued) 

Ecoregion Distribution of Sites Based on Equal-Area Weighting 

ECO- 50 75 100 125 150 NADP SITESINECOREGION OTHER SITES IN 

REGION ASOFMAY 1982 ECORE~ION 

P3131 1 1 1 2 2 UT02 

P3132 1 2 2 2 3 C099, NM09 

3140 1 1 1 1 1 AZ01, AZ99 

A3141 0.5 0.5 1 1 1 

A3142 0.5 0.5 1 1 1 C015, WY06 

3211 0.5 1 1 1 1 R18 

3212 0.5 1 1 2 2 TX04 

3221 0.5 1 1 2 2 

3222 0.5 1 2 2 2 AZ06 

4110 1 1 1 1 1 FL11 

57 80 100 127 149 

9 
Knowing how many sites were to be recommended in 

each ecoregion, the next step chosen was to overlay 

the index map for the 1:250,000-scale map series 

(U.S. Geological Survey, 1980) with Bailey's 

ecoregion map (see Figure 2). Each grid box of the 

index map then had associated with it the two most 

predominant ecoregion provinces present (or one, if 

only one was present). Boxes so designed were 

randomly sorted by computer until a solution for the 

ecoregion quota was met. One product from this 

sorting, satisfying the 100-site provisional network 

from Table 2, is shown in Figure 2. (Figure 2 is not a 

unique solution to the 100-site provisional network of 

Table 2.) When a grid box was selected for a 

particular ecoregion, only that area of the ecoregion 

in that grid box is filled in. Locations for sampling 

sites would then be restricted to the filled in portion 

of the grid boxes shown in Figure 2. 

Figure 2 - Randomly Selected, Equal-Area Weighted 

Ecoregion Distribution for a 100 Site Network. 

From Model to National Trends Network 

Recommendations 

The model developed above was not the final 

distribution model. Based on guidance from the task 

group, additional factors were considered as 

explained later. However, the development of Figure 

2 gives the opportunity to explain how the procedure 

for model building led to the final recommendation 

fortheNTN. 

Two lists were ultimately provided to the task group: 

(a) Those existing precipitation monitoring sites 

that met the siting criteria and are in ecoregions 

designated by the distribution model. 

10 

(b) Ecoregions where the model calls fer sites, but 

where current monitoring sites rr.eeting the 

siting criteria do not exist. 

The first list is easily derived. If, for example, the 

model designates a grid box in ecoregion 2111 then 

all the existing precipitation monitoring sites that 

fall in ecoregion 2111, and that meet the siting 

criteria, will be listed. For ecoregions with more 

existing monitoring sites meeting the siting criteria 

than sites called for in the final distribution model, 

recommendation for selection would be made on the 

basis of which sites would provide the broadest 

distribution within the ecoregion, and ~'hich would 

meet the greatest number of nice-to-have features in 

their siting criteria, for example, a colocated calibrated watershed, a colocated acid rain effects 

research study site, or a long-term ob~ervational 

record. The second list consists of recommended site 

locations for ecoregions with fewer existing 

monitoring sites meeting the siting criteria than 

called for in the distribution model. 

Weighting Factors for Site Distribution 

A number of factors which affect the distribution of 

acid deposition or in turn are affected by acid 

deposition were considered for use in wf.ighting the 

initial distribution of recommended sites for the 

NTN. To clarify, it was agreed that all ecoregion 

provinces must be represented in the final network 

design. In addition, other factors than equal areaweighting alone were to be used. This section details 

the various weighting factors considered by the task1 

group, most of which were later rejected as irrelevant/ 

or unworkable. But, their consideration provided 

valuable insights for the final design of the network. 

Mean Annual Precipitation 

Wilson and others (1982) have shown that, at least in 

the northeastern United States, wet dE: position is 

roughly proportional to the amount of precipitation. 

This being the case, then some measure of rainfall is 

a natural candidate for a weighting factor. However, 

in Bailey's classification, the amount of p"'ecipitation 

is considered in the delineation of ecoregions at the 

domain level and at the division level. For this reason 

annual precipitation was not considered as a 

weighting factor, for to do so would have given double 

weighting to precipitation. 

The possibility of using some level of annual 

precipitation as a cutoff he low which a site would not 

he recommend was considered. This war discarded 

because it was likely that in some areas of low 
precipitation, much of the precipitation that did 

occcur, occurred in several large events, the 

chemistry of which could have important ecological 

effects on the ecoregion receiving it. 

Precipitation Variability 

Several measures of precipitation variability were 

examined: precipitation efficiency, thunderstorm and 

snowstorm frequency, and the coefficient of variation 

of annual precipitation (variability). 

Precipitation efficiency, the percent of available 

moisture in the atmosphere which actually falls, has 

a small variability (2.5 to 12.5 percent) across the 

conterminous United States and was not used for this 

reason. 

Thunderstorm and snowstorm frequency each depict 

a single part of precipitation variability. Although 

the two together provide a good approximation of 

precipitation variability, the coefficient of variation 

or variability (Hershfield , 1962) of annual 

precipitation, as estimated on 1:250,000-scale 

quadrangle sheets, was considered a better measure. 

Figure 3 shows those quadrangles with high 

precipitation variability and those with low 

precipitation variability, i.e ., where variability 

exceeds 25 percent ofthe mean annual precipitation. 

Figure 3 - Precipitation Variability in the Conterminous 

United States. Cross Hatch = low variability; 

Dot Pattern = high variability 

The quadrangles identified in Figure 3 with high 

precipitation variability were doubly weighted in an 

ecoregion-coupled selection process to produce the 

provisional 100-site network shown in Figure 4. The 

effect of double-weighting can be see n by comparing 

Figure 4 with Figure 2. Ecoregions in the south and 

11 

west in Figure 4 are more densely sited, while 

conversely, other ecoregions without doubleweighting show fewer sites. 

Figure 4 - Randomly Selected, Precipitation Variability 

Weighted Network of 100 Sites. 

Ambient Concentrations of Air Pollutants 

In locating sampling sites, the intention was to 

generally place sites away from point source 

pollutant concentrations to avoid skewing the data, 

i.e., hot spots were to be avoided. 

Data from the National Air Monitoring Stations 

(NAMS) network which contains particulate data 

from 80, mostly urban, sites across the United States 

and data from the Storage and Retrieval of 

Aerometric Data (SAROAD) data base were 

examined for possible use in siting. Except for 

particulate data, there are not enough data available 

across the country to reasonably indicate background 

concentrations of pollutants. 

Air Pollutant Emissions 

Several data bases exist which contain data on 

pollutant emissions from point sources of pollution. 

The Multistate Atmospheric Power Production 

Pollution Study (MAP3S) Emissions Inventory 

(Benkovitz, 1980) was used in the analysis to 

compare one area against another. The MAP3S data 

base contains emissions data for particulates, sulfur 

dioxide, nitrogen oxides, carbon monoxide, and 

hydrocarbons as well as information on stack height, 

plant operating characteristics, etc. The data base 

has a file of emissions by county. It also contains 

information on more than 50,000 stationary sources. 

The data were summarized on 1:250,000-scale 

quadrangle maps. Only the data for sulfur dioxide, 

nitrogen oxides, and particulates were used as these 
have the most potential for influencing precipitation 

chemistry. 

Based on an arbitrary division of the country into 

three regions (Northeast-north of latitude 38°N, 

east of longitude 94oW; Southeast-south of latitude 

38oN, east of longitude 94oW; and West--west of 

longitude 94oW) regional means for each pollutant 

were calculated, as well as values one and two 

standard deviations from the mean. Values greater 

than two standard deviations above the mean were 

used to find grid boxes that had excessively high 

emissions. The intent was to exclude quadrangles 

with extremely high emissions, as opposed to hot 

spots, from the NTN. This' approach was abandoned 

however, because this might seriously underestimate 

the background acid deposition across the United 

States. The approach was changed to favor the 

selection of grid boxes with the lowest 10 percent of 

emissions in each of the 3 regions defined above. This 

approach would underestimate deposition to some 

extent but this seemed more desirable than skewing 

the data because of high emission. The grid boxes 

representing the 10 percent of each region with 

lowest sulfur dioxide, nitrogen oxides and particulate 

emissions were identified. Any grid box which had 

low emissions in one or more species was double 

weighted. A quadrangle low in two or three emission 

types was not weighted more heavily than one that 

was low in only one emission type. This approach still 

allowed some regions to be chosen with moderately 

high background emissions, but the probability of 

being chosen was reduced. 

As with the precipitation variability weighting 

process, Table 2 was then modified to reflect double 

weighting due to low emissions. This revised table 

was then used as the basis for another random 

computer selection of grid boxes. (Emissions 

weighting was later dropped from consideration in 

the post-Bear Mountain models, however, sites 

downwind of large point sources, within 

approximately 50km, were avoided in the final list of 

recommended sites.) 

Topography 

To ensure representativeness of the data accumulated by the NTN, it is important not to favor one 

climatic or meteorological regime over another. 

Bailey's ecoregions ensures that all regions of the 

country, both windward and leeward, are represented. It also identifies the high altitude regimes. 

12 

Although no attempt was made early on to ensure 

representativeness of altitudinal variation, this was 

later attempted in the site selection process described 

in the section on Populating the Model. 

Existing Wet Deposition Chemistry Data 

Wet deposition data already collected from operational networks allows an opportunity to use these 

data for shaping site selection. Following a review of 

the summary isopleth maps available (Gibson, 1982; 

Semonin, 1981 and Work Group 1, 1983), Semonin's 

deposition-based maps were selected for use because 

they represent total and seasonal loading over 

several years, while the others confined their presentations to concentrations over single years. The 

main use of these maps was to place sites so as to 

better define areas with steep gradients of pollutant 

concentrations. 

Because the goals of NTN are long-term trend 

delineation over years, rather than over seasons, 

Semonin's summary maps were used rather than his 

seasonal maps. His isopleth maps for calcium, 

magnesium, chloride, sulfate, nitrate, sodium, 

potassium and hydrogen ions were examined. For 

simplicity, only three of these maps were used to 

shape site selection. They were chosen to reflect an 

indication of a neutralizing constituent, calcium; the 

major acidifying constituent for most areas, sulfate; 

and hydrogen ion; which summarizes net acidic 

input. 

Semonin's isopleth maps, a sample of which is given 

in Figure 5, used unequal intervals between isopleths 

for better resolution in the western United States. 

Therefore, to visually determine gradients on the 

same relative scale, the isopleth maps were replotted 

onto the 1:250,000-scale index map and isopleths for 

the missing increments were then interpolated by 

observation. An example of one of these maps is 

shown in Figure 6. (The pattern also suggests the 

sulfate maxima over the northeastern United States.) 

With equally separated isopleths now in place, it was 

a simple matter to estimate the gradient of each 

constituent in any 1:250,000-scale grid box. The 

number of isopleths passing through the grid box 

were counted. The steeper the gradient, the more 

isopleths that passed through the box. The quadrangles with a high number of calcium, sulfate or 

hydrogen ion isopleths passing through the box are 

shown in Figure 7. 
Figure 5.- Average Annual Sulfate Deposition (mg/m2 ) over North American, july 1978-September 1980. (Semonin, 1981.) 

13 
--a 

~ 

Figure 6.- Deposition lsopleths for Sulfate (mg/m2 ) Redrawn with Missing lsopleths Interpolated. (Modified from Semon in, 1981.) 
Figure 7 - Quadrangles with High Deposition Gradients 

for Calcium, Sulfate, or Hydrogen Ions. 

Potential Sensitivity to Acid Deposition 

Several maps of potential sensitivity of a region to 

the effects of acid deposition have been published. 

The map by McFee (1980) for the Eastern United 

States is based on soil types. The map by Hendrey 

and others (1980) is based on bedrock geology. A third 

map, by Omernik and Powers (1982), uses alkalinity 

as a measure of relative sensitivity to acidic 

deposition. Any of these might be used as a measure 

of potential susceptibility. Initially, the task group 

did not see a need for site selection based on potential 

susceptibility of a region. So, it was not used in the 

pre-Bear Mountain phase in determining recommended site locations. 

Combination of Weighting Factors 

In this section it is shown how the four 

parameters-ecoregion equal area distribution, high 

precipitation variability, low emissions, and high 

deposition gradients--are combined onto one 

15 

weighting scheme. To derive Table 3, the random 

selection process by ecoregion was repeated with each 

1:250,000 grid box favored by either high 

precipitation variability, low emissions or high 

deposition gradient given twice the opportunity for 

selection, and any grid box favored by more than one 

of these weighting factors given three times the 

chance of being selected. Figure 8 shows the 

1:250,000-scale quadrangles favored by one or more 

of the weighting factors. Table 3 yields several 

possiblenetworks for the NTN. Each ensures that all 

ecoregion provinces of the United States are 

represented. Each favors placement of sites in: (1) 

areas of low pollutant emissions, (2) areas with 

highly variable precipitation and, (3) areas that 

present data indicate are transitional between areas 

of highly polluted precipitation and areas of 

relatively clean precipitation. 

Figure 8 - Quadrangles with Weighting Due to High 

Precipitation Variability, Low Emissions, or 

High Deposition Gradients. 

Dotted Pattern = one weighting factor; 

Cross Hatch -two weighti ng factors; 

Solid = three weighting factors 
TABLE3 

Ecoregion Distribution of Sites Based on High Precipitation Variability, Low 

Emissions, and High Deposition Gradient Weighting Factors 

DIVISION ECOREGION 50 75 100 125 150 

2100 Warm Continental 2111 1 1 1 1 2 

2112 1 1 1 1 1 

2113 2 3 4 5 7 

2114 1 3 3 4 2 

M2111 0.5 0.5 1 1 1 

M2112 0.5 0.5 1 1 1 

2200 Hot Continental 2211 1 1 1 2 2 

2212 1 2 2 2 3 

2213 1 1 2 2 2 

2214 2 3 4 5 6 

2215 2 3 4 6 7 

2300 Subtropical 2311 1 3 5 6 7 

2312 1 1 1 3 3 

2320 6 9 12 15 18 

2400 Marine 2410 1 1 1 1 1 

M2411 0 0 0 1 1 

M2412 0 0 0 0 1 

M2413 1 1 1 1 1 

M2414 0 0 0 1 1 

M2415 1 1 1 1 1 

2500 Prairie 2511 2 3 4 4 6 

2512 2 2 4 5 5 

2521 1 1 1 2 2 

2522 0 1 1 1 1 

2523 1 1 1 1 1 

2531 1 2 3 4 4 

2532 1 1 2 2 2 

2533 1 1 1 2 2 

16 
TABLE3 

(Continued) 

Ecoregion Distribution of Sites Based on High Precipitation Variability, Low 

Emissions, and High Deposition Gradient Weighting Factors 

DIVISION ECOREGION 50 75 100 125 150 

2600 Mediterranean 2610 1 1 1 1 1 

M2610 1 1 1 1 2 

M2620 1 1 1 1 1 

3100 Steppe 3111 2 2 4 4 6 

3112 2 2 4 4 6 

: 3113 1 2 4 4 5 

M3111 1 1 1 1 2 

M3112 1 1 3 3 4 

M3113 1 2 2 2 2 

3120 1 1 1 1 1 

M3120 1 1 1 1 1 

3131 2 2 2 4 4 

3132 1 1 1 1 3 

3133 1 1 2 2 2 

3134 1 1 1 1 1 

3135 0 0 1 1 1 

P3131 1 1 1 2 2 

P3132 1 2 2 2 2 

3140 1 1 1 1 1 

A3141 0.5 1 1 1 1 

A3142 0.5 1 1 1 1 

3200 Desert 3211 0.5 1 1 1 1 

3212 0.5 1 1 1 1 

3221 1 2 2 3 3 

3222 1 1 2 2 2 

4110 Savanna 4110 1 1 1 1 1 

TOTAL 59 79 105 128 148 

17 
DISCUSSION AT BEAR MOUNTAIN 

A draft document consisting of the material reviewed 

above, plus some additional tables, similar to Table 2, 

detailing the effect of each weighting factor were 

distributed to a panel of nine reviewers 

knowledgeable in the workings of the task group. 

Each provided written comments which were 

summarized and then used at the Bear Mountain 

workshop for joint discussion with the reviewers and 

the task group. 

The discussion covered two basic areas; (1) the 

framework of the design; and, (2) the use or abuse of 

weighting factors. 

Framework for the Discussion 

There was a discussion of the relationship of network 

goals to network size. Information from a paper by 

Haszpra ( 1980) showed that in a uniformly 

distributed network of 150 stations each station 

would represent a square 220 kilometers on a side. 

The relative error of which, for annual sulfate 

deposition, would be approximately 8 percent, while 

the seasonal error could be in excess of 30 percent. 

(Eight years of data from the European Atmospheric 

Chemistry Network were used in the statistical 

analysis.) Haszpra (1980) also showed that if a nonuniform or random grid is used, or if the deposition 

field has "hot spots," then an even denser network 

would be needed to keep the relative error the same 

as the uniformly distributed case. While agreeing in 

principle that more sites are desirable, the task group 

felt that they could not justify funding for sites in 

excess of 150. 

Several additional considerations were suggested 

which might have given the siting model another 

dimension, for example; (1) energy development, such 

as, mine mouth powerplants, oil shale retorting, or 

coal gasification; (2) agricultural/forestry activities, 

such as stripping and clearing for grazeland; (3) 

changing demographic patterns; and (4) water 

utilization. There was general agreement that it 

would be impossible to know with certainty all these 

kinds of possible changes. 

Flexibility of the Network 

Several reviewers were concerned that the network 

design was not flexible enough. Items brought up for 

consideration included: 

• Samplers should be colocated with samplers 

from other networks. (Because of the networks 

being considered in the second phase of this 

18 

project, there was reason to b£:lieve this 

concern would be satisfied.) 

• Some fraction of the network siter should be 

mobile stations to address changing network 

needs such as ••hot spots" or unrepresentativeness of one or more chemicals. (The task 

group agreed that the network should be 

reevaluated periodically to optimize siting 

based on current knowledge.) 

• That sites placed to better define tho. gradients 

be reevaluated periodically to see if they are 

needed or should be repositioned. (In response, 

the task group confirmed its comnitment to 

periodic reevaluation of these sites.) 

• That the design of the NTN '"aS being 

separated from the National Acid Precipitation Assessment Program's study sites for 

streams and lakes and from long-term 

research on plants and soils. (In formulating 

the NTN, as many sites as possil'le will be 

established with these studies in mind.) 

Weighting Factors for Site Distribution 

Everyone accepted the ecoregion basis for 

distributing sites. There were some reservations. One 

reviewer was concerned that the inherent ecoregion 

weighting might lead to separating the collectors too 

far apart to provide statistically adequate coverage 

for ascertaining temporal trends. There was concern 

that by using other weighting factors the statistical 

objectivity of the study might be lost. The orginial 

design concept held that by using several factors, the 

weighting bias, if any, would eventually even out, 

and that in essence there would be a return to equal 

area distribution. As Figure 8 illustrater-, this was 

not the case. A detailed discussion of each weighting 

factor follows: 

Precipitation Variability 

It was pointed out that Hershfield's map (1962) was 

too coarse for use in mountainous regions. It was 

thought to favor the West, South, and Midwest too 

much, and emphasize the arid parts of the country too 

much. After considerable discussion, precipitation 

variability was dropped as a weighting factor. 

Air Pollutant Emissions 

Comments in this area can be summarized best by 

quoting one of the reviewers: "Use of emissions 

weighting is questionable because by focudng on low 

emissions the NTN would monitor only background 
areas. The network should be designed to depict the 

real picture, not just where the sheep graze." 

Emissions as a weighting factor was subsequently 

discarded. 

Existing Wet Deposition Chemistry Data 

All participants favored incorporating these data 

somehow. Opinions on how to do it differed. One 

reviewer preferred using seasonal as opposed to 

annual gradients. Another preferred the use of 

precipitation concentration instead of deposition 

loading to avoid the effect of precipitation amount. 

Use of Semonin's maps was later decided as the best 

way to deal with these considerations. 

Potential Sensitivity to Acid Deposition 

Almost all reviewers wanted some measure of ecological sensitivity included in the weighting scheme. 

Typical comments ranged from: "Current concern 

with acid deposition has focused on sensitive areas; 

changes in these areas cannot be overlooked": to 

ttEcological sensitivity is a factor but not one which 

should dominate site selection." The group recommended incorporating potential sensitivity as a basic 

consideration in siting. 

POST-BEAR MOUNTAIN MODEL 

Following the workshop the task group met while 

still at Bear Mountain to decide which parts of the 

19 

pre-Bear Mountain model to retain, and which to 

discard. The following guidance evolved: 

• Place between 75 and 100 sites on the basis of 

equal area weighting by ecoregion. 

• Place between 25 and 50 sites east of the Rocky 

Mountains on the basis of the known deposition gradients for hydrogen ion, nitrate, 

sulfate and ammonium. 

• Place 15 sites in areas potentially susceptible 

to the effects of acid deposition, but not represented by either of the above placements. 

• Place up to 10 sites allowing for c ther considerations, such as urban area effects, 

intercomparision with Canada and apparent 

disparities in regional coverage. 

This guidance was based on the task group's view 

that weighting by formula was not particularly 

appropriate, and that the ecoregion concept took into 

account most of the climatic and meteorological 

characteristics proposed as weighting factors. Special 

attention to regions showing high susceptibility to 

acidification and abrupt increases in deposition 

loadings with distance could be provided by 

insightful addition of extra sites. 
POPULATING THE MODEL 

Two very different analytical tasks were involved in 

the final evaluation of potential sites for 

incorporation into the NTN: the first was that of 

looking at existing operating sites; the second was 

that of evaluating areas without existing stations. 

For the first, a wealth of information was available; 

maps, sketches, photographs, and precipitationchemistry data. For these sites, data bases are often 

available which provide information on emissions 

and meteorological data in and around the sites. For 

the second task of siting in new locations, special 

maps, emissions data, and meteorological data, etc. 

are often unavailable. 

Existing sites can be screened to distinguish between 

good sites and bad sites. This screening can be used 

with the information available from maps and from 

data on emissions and meteorology to project the 

suitability of potential sites for the NTN. In this 

section, the kinds of data available and the potential 

uses of this information in site analysis are 

examined. 

EXISTING SITES TO BE CONSIDERED 

From the outset it was agreed to limit consideration 

of candidate sites for the NTN to those operated by 

the Multistate Atmospheric Power Production 

Pollution Study (MAP3S), National Atmospheric 

Deposition Program (N ADP), Tennessee Valley 

Authority (TVA), and the Utility Acid Precipitation 

Study Program (UAPSP). Meteorological stations of 

the NOAA Reference Climatological Station (RCS) 

Program were also considered. 

Multistate Atmospheric Power Production 

Pollution Study 

The MAP3S network consists of the nine stations 

tabulated in Appendix C and shown in Figure 9. Four 

of the stations (Whiteface, Ithaca, Penn State, and 

Virginia) began operation in 1976. A second group of 

four sites (Illinois, Brookhaven, Lewes, and Oxford) 

began operation in 1978. Oak Ridge was added in 

early 1981. Samples are wet-only collected on a 

modified-event basis defined by the opera tor. 

Analysis is done at Battelle's Pacific Northwest 

Laboratories. The network is funded by the U.S. 

Department of the Energy and the U.S. 

Environmental Protection Agency. 

National Atmospheric Deposition Program 

The NADP network, at the time of model 

preparation, consisted of the 101 sites operating on 

May 30, 1982, and an additional 7 sites that had been 

located, but had not yet collected any samples. These 

sites are listed in Appendix C and plotted in Figure 9. 

The network utilizes an Aerochem-Metrics !I weUdry 

precipitation collector. Wet-only samples are 

collected weekly. A dry-deposition sample is collected 

every 8 weeks. Both are analyzed at the Central 

Analytical Laboratory at the Illinois State Water 

Survey. Each site in the network is funded by a 

sponsoring agency, either Federal, State, 

educational, or private sector. Coordination funds are 

provided by the U.S. Department of Agri~ulture and 

the U.S. Geological Survey. The U.S. Geological 

Survey and other agencies have contributed quality 

control/assurance services, and the time of their 

personnel for leadership roles. 

Tennessee Valley Authority Trends Stations 

The TV A network consists of the three sites listed in 

Appendix C and plotted in Figure 9. The~~~ sites are 

the remnants of a small network started in 1971 

which grew to 11 stations by 1979 but rev~rted to its 

present size in 1982. The network us~s wet/dry 

collectors of the Health arid Safety Laboratory design 

(Volchok and Graveson, 1975). Sampling is biweekly 

on the wet-only side and bimonthly on the dry. 

Samples are analyzed in the Chattanooga 

Laboratory. Funding is by TVA and the Electric 

Power Research Institute (EPRD. 

Utility Acid Precipitation Study Program 

The UAPSP network consists of the 19 sites listed in 

Appendix C and plotted in Figure 9. Tl'e network 

started operation in October 1981, but six of the sites 

had prior history as part of the E PPJ Eastern 

Regional Chemistry Network (EPRI, 1979). The 

network utilizes an Aerochem-Metrics sampler to 

collect a wet-only sample on a daily basis. Analyses 

are performed by Rockwell International. The 

network is funded by 34 electric utilities in the 

Eastern United States and receives technical 

guidance from EPRI. 

NOAA Reference Climatological Station 

Program 

The RCS network consists of 21 mete()rological 

stations listed in Appendix C and plotted in Figure 9. 

The network is run by contractors, mostly State 

Agricultural Experiment Stations, under the supervision of the National Weather Service ir Asheville, 

North Carolina. No wet deposition data were being 

collected at the time of model preparation. 

!I Use of trade name does not denote endorsement by the U.S. Goverment. 

20 
1\.J 

...... 

EXISTING 

• 

• 

..... • •: • 

• . : 

• • 

• 

• • 

;.e .. • .. •• 

• 

SITES 

• Iii: 

. ... · ... 

__ ·, __ 

Iii'· 

• 

• 

.. 

Iii'···. 

• 

• 

CONSIDERED 

• Iii 

•• ..... .,.· Iii 

• Iii 

• ~: •. 141 • 

• :.~ .. ' ...... . Iii. • • · .. . :' • Iii Iii 

Iii •· • 

'-······· 

Figure 9 · Existing Precipitation Monitoring and Climate Monitoring Sites. 

: .. .. .• 

.... 

• 

e- NADP 

•- RCS 

A.- MAP3S 

+-TVA 

~- UAPSP 
Because of their geographic spread and the level of 

training of their operators, these sites were thought 

to have potential for new sites. 

Colocated Sites 

Sites from several of the above networks are 

co located. These sites are listed below: 

M5 - Illinois (MAP3S) colocated with IL11-

Bondville (N ADP) 

M9 - Oak Ridge (MAP3S) colocated with TNOOWalker Branch (NADP) 

R9 - Davis (RCS) colocated with CA88-Davis 

(NADP) 

R21 - Wooster (RCS) colocated with OH71-

W ooster (N AD P) 

U19- Raleigh (UAPSP) colocated with NC41-

Finley Farm (NADP) 

AVAILABLE SITE DATA 

Site Description Information 

The Site Criteria and Standards Subcommittee of the 

NADP requires each N ADP site to supply the 

following information. Comparable data was sought 

for each candidate NTN site: 

• site location; 

• site logistics information (accessibility, 

power, security, etc.); 

• equipment on hand (raingage, wind instruments, pH and conductivity meters); 

• information on period of operation of the site; 

• topography, soil type, tall objects around the 

site; 

• civilization around the site (roads, airfield, 

powerplants, industry, etc.); 

• a listing of all meteorological instruments 

co located; 

• aerosol and gas samplers at the site; 

• description of any nearby associated acid rain 

effects research; 

• description of any nearby calibrated 

watershed; 

• a sketch map of the site showing all objects 

over 4 feet in height within 100 feet of the 

site; 

• a set of eight photographs in the principal 

compass directions with sampler in the 

foreground; 

• a soils map and associated soil description for 

the area surrounding the site; 

• maps: 1:250,000-scale and either the 7.5 or 15 

minute topographic quadrangle. 

22 

Air Pollutant Emissions Data 

As noted earlier, the MAP3S Emission Inventory was 

used as the data base for locating both point and area 

sources. This inventory was compile-:{ from the 

National Emissions Data System, from information 

supplied by the Federal Power Com1nission, as 

updated during the MAP3S regional experiment 

studies (Benkovitz, 1980). In the inventory point 

sources are tabulated for all 48 conterminous States 

as well as Canada. 

Area sources were available for the conterminous 

United States only. Emissions of particulates, sulfur 

oxides, nitrogen oxides, hydrocarbons, and carbon 

monoxide were also extracted from the ~ifAP3S data 

base. Area sources for each county are listed in the 

MAP3S data base by the latitude and lon~itude of the 

county centroid. 

To make the emissions data easy to use a computer 

graphics program was written. The output produces 

two plots; the first displays the area surr~unding the 

site out to 20-km (Figure 10) and places a character 

where each emission source is located. The Standard 

Industry Code was used as a guide to display 

potentially heavy industrial sources as an alphabetic 

character, while all potentially lo'v emitters 

(apartment houses, light industry, government 

complexes, etc.) were displayed as plus Eigns ( + ). A 

second plot with the same information for a 50-km 

radius was also generated. 

FINLEY FARM 20 KM SCAN . A 

A A 

20 

A 

+ + 

20 

Figure 10- Sample Plot of Emission Sources Within 20 km of 

a Proposed Site at Finley Farm, Nort, Carolina. 
NATIONAL TRENDS NETWORK 

SITE SUITABILITY ANALYSIS 

DATE: SITE CODE: 

SITE NAME: NETWORK AFFILIATION: 

DATA AVAILABLE 

0 1:250,000 map 

0 site questionnaire 

0 site photos 

0 other(specify) 

SITE OWNERSHIP: 

0 federal 

SITE MANAGER/INSTITUTION: 

LOCAL CONDITIONS; 

LONG RANGE CONDITIONS: 

0 1 :62,500 map 

0 supplemental questionnaire 

0 Emissions plot 

0 state 0 other(specify) 

ANNUAL PRECIPITATION 

AMOUNT: 

PRECIPITATION CHEMISTRY: 

EQUIPMENT STATUS: (within 50 meters of sampler) 

0 Automatrc Wet Precrp Collector. 

0 Rcdg Rain Gage 

0 Type ________ _ 

0 Conductivrty meter 

0 pH meter 0 other instruments on srte 

ASSOCIATED RESEARCH/CALIBRATED WATERSHED 

Figure 11- Form for Site Suitability Analysis 

23 

0 1:24,000 map 

0 sketch map 

0 wmd rose 

0 LrdRcd ________ _ 

0 Balance 
The point source emission tabulation and the two 

emission plots for each potential NTN site were 

produced and added to the site description file for 

each site. 

Wet Deposition Chemistry Data 

At the time the site review was taking place 

(March-July 1982), wet-deposition data was not 

always available for a site being considered. To solve 

the problem of how to evaluate a site which had no 

data, it was decided not to consider any site-specific 

data thereby treating all sites equally. 

PROCEDURE FOR EVALUATING EXISTING 

SITES 

For comparison of sites, the form shown in Figure 11 

was designed to answer the following questions: 

(1) Who owns the land on which the site is situated? 

(2) Who is managing/operating the site? 

(3) What are local conditions (1-2-km radius) around 

the site? 

(4) What are regional conditions like within a 50-km 

radius? 

(5) What is the annual precipitation at the site? 

(6) What equipment is on hand at the site? 

(7) Is any acid rain effects research being performed 

at the site and/or does a calibrated watershed 

exist nearby? 

Each site was given a subjective rating of good, 

marginal, or bad. The good sites were useable as they 

were, the marginal sites required some upgrading, 

and the bad sites were not considered useable even 

with upgrading. Insofar as possible the one-page form 

for site suitability analysis was filled out for each 

site. All ratings are based on an analysis of the form 

and the other information available for the site. 

Some bias in how sites were pre-selected to fill out the 

recommended network was unavoidable. NADP sites 

would generally be given preference over sites of 

equal stature from other networks because the NADP 

sites followed the same operational protocal adopted 

for NTN and required no out-of-pocket expense to 

comply with the NTN protocol. (In no case was a 

lesser quality N ADP site given preference over 

another site of better quality). U APSP sites were at a 

disadvantage because they are almost exclusively on 

private land and could violate the long-term land 

use/ownership stability guideline. Other network 

sites, including RCS sites, were considered essenti24 

ally equal because they all would requir'} About the 

same expense in new equipment to join NTN. 

PROCEDURE FOR EVALUATING AREAS 

WHERE NO STATION EXISTS (NEW SITES) 

The main requirements in the selection process for 

new sites were: 1) to identify a location unaffected by 

local sources; 2) stable land ownership; and 3) ease of 

servicing. 

Figure 9 shows that the majority of existing sites 

were located in the eastern half of the United States 

requiring new selections in the West, South, and 

Central sections of the country. Some existing sites 

did not meet the general siting criteria necessitating 

selection of replacement sites. 

The MAP3S Emission Inventory (Benkovitz, 1980) 

was utilized to produce 470 plots of stationary 

emission sources for the conterminous United States, 

each equalivant to a 1:250,000 scale map sheet 

(USGS, 1980), (Figure 12). These plots were used to 

identify large areas that might be suitable for sites. 

Powerplants and large stationary emitters were 

identified on the plots so areas could be selected to 

minimize these influences. 

Next the selected areas were closely exarrined, using 

the 1:250,000 scale map sheets equali,·ant to the 

emission plot to identify locations stal,le in land 

ownership and having personnel available for 

servicing the site. State and Federally controlled 

areas were prime candidates in this respect. National 

parks, national forests, national wildlife refuges, 

state parks, and agricultural experiment stations 

were selected most often. If a site was a candidate to 

..... 

Q 

::> 

1-

i= 

< 

... 

RALEIGH NO. OF PTS - 252 

36 :1-

. 

. 

30' 

. 

+ X 

. 

·,. + 

.. 

. , 

lol •• 

.. 

• + 

. . • + p • 

,. 

. . .. ~ X 

x~x• •t • .. N 35~~--+-~--~--~~--+-~--~~~~~ 

80 30' 79 30' 78 

LONGITUDE 

Figure 12 - Emission Plot for the Raleigh Quacrangle. 
represent a specific ecoregion, then the 1:250,000-

scale ecoregion and land-surface form map 

equivalent to the map sheet was checked to ensure 

that the candidate site was indeed in that ecoregion. 

In some cases, the N ADP Coordinator knew of 

interest in establishing a monitoring site in an area 

of need, or knew of other special study sites. Lists of 

watershed studies were furnished by the U.S. 

Geological Survey and the TV A. 

More than 300 candidate sites were identified in this 

manner before the final 42 new sites were selected. 

(See Appendix C for a list of new sites). All 300 sites 

were closely analyzed for proximity to local 

influences and practically of operation. Emission 

plots were used to provide detailed data on stationary 

and area sources near each candidate site. The best 

site in an area that provided adequate spatial 

resolution with adjacent stations was chosen. An 

example of how this sorting was done for one 

ecoregion follows in the next section. 

EXAMPLE OF SITE SELECTION ON 

EQUAL-AREA BASIS BY ECOREGION 

The Prairie Parkland Province, 2510, is a large 

irregular area extending from the Gulf of Mexico to 

the Great Lakes (Figure 13). Seven sites are planned 

for the province according to the distribution model of 

100 sites adopted for ecoregion representation (Table 

3). These are distributed with four in section 2511 

and three in section 2512. 

In section 2511, two if the existing sites are in the 

Chicago urban area, Argonne, IL19, and Indiana 

Dunes, IN34, and were dropped from further consideration as equal-area sites. Bondville/Champaign, 

IL11/M5, was chosen to represent the northeastern 

part of the ecoregion and Salem, IL4 7, was chosen to 

represent the southeastern part of the ecoregion. 

Lancaster, U12, was selected in the West. A new site, 

McNay Research Center, N30, is proposed for the 

northwestern corner. The existing site at Shabbona, 

IL18, and the new site at Roseville, N42, were added 

later based on the high gradient definition. 

In section 2512, (Figure 13), the existing site at 

Victoria, TX53, and the planned site at McKinney 

Falls, TX52, had less than desirable site characteristics. Three new sites, N15, Attwater Prairie 

Chicken National Wildlife Refuge; N17, USDA Black 

Creek Headquarters (now part of the LBJ National 

Grassland); and Nl9, the National Severe Storms 

Laboratory were selected for the ecoregion. 

25 

Figure 14 shows the 96 sites recommended on the 

basis of representing each of the ecoregion~ in proportion to its area, i.e., 97 sites (Table 4), 2 desert sites 

not retained, plus 1 site added in A3140. (A 

distribution of 96 sites fitted the spatial cistribution 

better in parts of the East and West than the model of 

100 sites depicted in Table 2.) The 96 sites are the 

core of the NTN, the minimum monitoring~ effort over 

the long-term. 

SITE SELECTION BASED ON GRADIENT 

DEFINITION 

Semonin's (1981) isopleths for hydrogen ion, sulfate, 

nitrate, and ammonium (see Figure 5) were used to 

identify areas east of the Rocky Mountains where 

more sites were needed to better define the nature 

and extent of the gradients. Figure 14 (96-site map) 

was overlain by Semonin's gradient 1naps. The steep 

gradient areas were highlighted. Existing sites with 

acceptable siting criteria were also highlighted, 

again with an eye toward spatial distribution. If no 

existing sites were in an area of steep gradient or if 

the existing sites were not acceptable, new sites were 

nominated using the method outlined earlier. Figure 

15 shows the gradient sites chosen. 

SITE SELECTION TO ENSURE COVERAGE 

OF SENSITIVE AREAS 

The task group required that sensitive areas be 

monitored by an NTN site whenever possible. A 

preliminary copy of the map of alkalinity of surface 

waters by Omernik and Powers ( 1982) was used as a 

surrogate for sensitivity. This map was checked 

against the list of new and candidate sites. Sensitive 

area sites had to meet all the siting criteria outlined 

above. In some cases a region of high sensitivity was 

not picked because of the lack of stable land ownership, proximity to large emission sources, or because 

a suitable existing monitoring site was close by in a 

slightly less sensitive area. The sites selected are 

shown in Figure 16. 

ALLOWANCES FOR OTHER 

CONSIDERATIONS 

As the network developed and the preliminary 

working maps were shown to associates, the authors 

came under criticism for developing a positive 

network; a network whose sites were loc2ted in such 

a manner that the deposition recorded nationwide 

would understate the actual deposition. 'fl1e problem 
• NADP 

• RCS 

• MAP3S 

• TVA 

11 UAPSP 

o NEW SITES 

2510 

PRAIRIE PARKLAND PROVINCE 

N30 

0 

• • •• ... • 

~N42 

•• 0 

• 

····················-: 

MS • 

IL11e 

• 

2511\ 

•• •• • 

·.-·. --- . 

I L 11 - Bondville, I L 

IL 18- Shabbona, IL 

IL19- Argonne, IL 

IL47- WSO-Salem, IL 

IN34- Indiana Dunes, IN 

MS- Champaign, IL 

TX52 - McKinney Falls, TX 

TX53 - WSO-Victoria, TX 

U12 - Lancaster, KS 

N15 - Attwater Prairie Chicken N\'VR, TX 

N17 - USDA Black Creek HDQS, TX 

N19 - NSSL-Norman, OK 

N30 - McNay Res Ctr- Chariton, lA 

N42- Roseville, IL 

Figure 13- Possible Monitoring Sites in Province 2510 Considered for Inclusion in the NTN. 

26 
TABLE4 

Final Ecoregion Distribution of Sites Based on Equal Area (97 Sites) 

Humid Domain (2000) Dry Domain (3000) Tropical Domain (4000) 

Ecoregion Required Ecoregion Required Ecoregion Required 

2111 1 3111 3 4110 1 

2112 1 3112 4 

2113 3 3113 4 

2114 2 M3111 1 

M2111 1 M31112 3 

M2112 1 M3113 2 

2211 1 3120 1 

2212 2 M3120 1 

2213 2 3131 3 

2214 4 3132 l 

2215 4 3133 2 

2311 4 3134 1 

2312 1 3135 0 

2320 9 P3131 1 

2410 1 P3132 2 

M2411 0 3140 1 

M2412 0 A3140 1 

M2413 1 3211 1 

M2414 0 3212 1 

M2415 1 3221 l 

2511 4 3222 2 

2512 3 

2521 1 

2522 1 

2523 1 

2531 4 

2532 2 

2533 2 

3610 1 

M2610 1 

M2620 1 

Total 2000 60 Total 3000 36 Total 4000 l 

27 
ECOSYSTEM EQUAL-AREA SITES 

~D03 

o"7 . ..• .. 

0 

.. ur.rz 0 

AZ03 Nil 

0 

AZOS 

. e NADP 

• RCS 

• MAP3S 

+ TVA 

Ill UAPSP 

. 

AZ99 . 

o NEW SITES 

WY06 

. 

~01!5 

.. 

0 i:OIIt 

. 

NM09 

. 

ND07 

. 

WY99 Rl . . 

NH 

0 

.. ~ 

... ~ . ci'' 

NIO 

tl 

.•. 

0 

... 0 

TX04 . 

... 0 

.RII 

... 

0 

... 

0 

0 .... . 

... 0 

011120 

... 

0 

H17 

0 

R2 

. 

N~p OH.7 wv: ILII 

. .. .jl2 U6 . IL4J '" 1100> . ... IL83- 0 . .. . eAR27 

..... ... 0 

GA41 

A\0~ . U9 

~oo '" 

Rl7 • 

Note: See appendix C for site abbreviations code. 

Figure 14- Ninety-six Sites Proposed for Incorporation into NTN Based on the 

Equal Area Distribution. 

• NADP 

• RCS 

• MAP3S 

+TVA 

tJ UAPSP 

o NEW SITES 

DEPOSITION GRADIENT SITES 

0 

... 0 

... 

M005 

. 

0 

... 

TO • 

OH49 

. 

Note: See appendix C for site abbreviations code. 

Figure 15- Twenty-seven Sites Proposed for Incorporation into NTN Based 

on Semonin's Gradient Maps. 

28 
CA7!5 . 

• NADP 

• RCS 

"" MAP3S 

+ TVA 

t1 UAPSP 

o NEW SITES 

. 

W'I'08 

SENSITIVITY SITES 

TN II 

. 

Note: See appendix C for site abbreviations code. 

Figure 16- Fifteen Sites Proposed for Incorporation into NTN Based on 

Sensitive Area Coverage. 

• NADP 

• RCS 

"" MAP3S 

+TVA 

r;;~ UAPSP 

o NEW SITES 

SUPPLEMENTARY SITES 

N40 

D 

.... 

Note: See appendix C for site abbreviations code 

CAN3 

. 

Figure 17 -Thirteen Sites Proposed for Incorporation into NTN Based on Other 

Considerations. 

29 
at hand was how to walk the fine line between a 

regionally representative site and one not overly 

affected by local influences. In response to the 

objections, five sites were added to the network even 

though they did not generally meet the NTN siting 

criteria because of their locati<>n near large urban 

complexes (Figure 17). These sites are located near 

Los Angeles, Philadelphia, and New York, and in the 

urban complexes of Chicago and Boston. These sites 

should show up as hot spots in the data. 

Other sites were selected to continue the intercomparison of U.S. and Canadian data. N ADP and 

CANSAP have had 6 colocated collectors operating (3 

in the U.S. and 3 in Canada) for the past several 

years. To ensure continuation of this effort the three 

U.S. sites in Canada were selected for the NTN. The 

remaining five sites chosen were selected to fill gaps 

(areas with low site density) in the network. 

THE PROPOSED NATIONAL TRENDS 

NETWORK 

Figure 18 represents the complete design of 151 NTN 

sites recommended to the Task Group on Deposition 

Monitoring. It embodies the best of the model 

30 

development and the advice and guidance of the Bear 

Mountain reviewers as it evolved over the course of 

the study (attachment A). There are four elements 

built into the design: (1) assurance that all areas of 

the country are represented in the netFork on the 

basis of regional ecological properties; (~) placement 

of additional sites east of the Rocky Mountains to 

better define high deposition gradients; (3) assurance 

that potentially sensitive regions are reryresentated; 

and (4) allowance for other considerations, such as 

urban area effects, intercomparison with Canada, 

and apparent disparities in regional coverage. 

On July 8, 1982, the task group met in '¥ ashington, 

D.C., to review the design and program plan. The 

plan was adopted, and follow-up site visitations were 

funded to confirm the suitability of the sites. 
• 

31 
REFERENCES 

Atwood, W. W., 1940, The Physiographic Provinces 

of North America: Boston, Massachusetts, Ginn 

and Co. 

Bailey, R. G., 1976, Ecoregions of the United States: 

Ogden, Utah, U.S. Forest Service Intermountain 

Region, scale 1:77 500,000. 

Bailey, R. G., 1978, Description of the Ecoregioins of 

the United States: Ogden, Utah U.S. Forest 

Service Intermountain Region. 

Bailey, R. G., 1980, Description of the Ecoregions of 

the United States; U.S. Department of 

Agriculture, Miscellaneous Publication no. 1391. 

Bailey, R. G., and Cushwa, C. T. 1981, Ecoregions 

ofNorth America after the Classification of J. M. 

Crowley: Kearneysville, West Virginia, U.S. Fish 

and Wildlife Service, Eastern Energy and Land 

Use Team, scale 1:12,000,000. 

Baldwin, J. L., 1973, Climates of the United States: 

Washington, D.C., National Oceanic and 

Atmospheric Administration Environmental 

Data Service. 

Benkovitz, C. M., 1980, Emission Inventory 

Progress Report: Brookhaven, National 

Laboratories Progress Report BNL-51378. 

Electric Power Research Institute, 1981, EPRI 

Sulfate Regional Experiment: Results and 

Implications: Palo Alto, California, EPRI 

EA-2165-SY -LD. 

Garrison, G.A., Bjugstad, A. J., Duncan, D. A., 

Lewis, M. E., and Smith, D. R., 1977, Vegetation 

and Environmental Features of Forest and-Range 

Ecosystems: U.S. Forest Service Agricultural 

Handbook 475. 

Hammond, E. H., 1964, Classes of Land-Surface 

Form in the Forty-eight States, Association of 

American Geographers Annals 54. Map 

Supplement no. 4, scale 1:5,000,000. 

Haszpra, L., 1980, On the Planning of Precipitation 

Chemistry Network, L Sulfate Data; Case of 

Uniformly Distributed Stations: Idojaras, v. 84, 

p.121-129. 

Hendrey, G. R., Galloway, J. N., Norton, S. A., 

Schofield, C. L., Shaffer, P. W., and Burns, D. A., 

1980, Geological and Hydrochemical Sensitivity 

of the Eastern United States to Acid 

Precipitation: Corvallis, Oregon, Environmental 

Protection Agency, EP A-600/3-80-024. 

32 

Hershfield, D. M., 1962, A Note on the Variability of 

Annual Precipitation: Journal of Applied 

Meteorology, v. 1 p. 575-578. 

Interagency Task Force on Acid Predpitation, 

1982, National Acid Precipitation Assessment 

Plan. 

Karol and Myatch, 1972, Data from European 

Atmospheric Chemistry Network. 

Kuchler, A. W., 1964, Potential Natural Vegetation 

ofthe Conterminous United States: American 

Geographical Society Special Publication 36, 

scale 1:3,168,000. 

Landsberg, H. E., 1975, Drought, A Rec-lrrent 

Element of Climate in Drought, Special 

Environmental Report No.5: Geneva, 

Switzerland, World Meteorological 0-ganization, 

WMO-No. 403. 

MacCracken, M. C., 1979, The Multistate 

Atmospheric Power Production Pollution StudyMAP3S; Project Report FY 1977 and FY 1978, 

U.S. Department of Energy, DOE/EV-0400. 

McFee, W. W., 1980, Sensitivity of Soil Regions to 

Acid Precipitation: Corvallis, Oregon. 

Environmental Protection Agency, 

EP A-600/3-80-0 13. 

Omernik, J. M., and Powers, C. F., 1982, Total 

Alkalinity of Surface Waters-AN ational Map: 

Corvallis, Oregon, Environmental Pr1tection 

Agency, EPA-600/D-82-333. 

Semonin, R. G., 1981, Seasonal Precipitation 

Concentrations and Depositions for North 

America from the CANSAP/NADP Network, ch. 

8, in Nineteenth Progress Report to tl'~ U.S. 

DOE: U.S. Department of Energy Pollutant 

Characterization and Safety Researcl' Division, 

Contract DE-AC02-76EV01199. 

U.S. Soil Conservation Service, Soil Survey Staff, 

1970, Soil Taxonomy of the National Cooperative 

Soil Survey: Washington, D.C. 

Thornthwaite, C. W., 1931, The Climates of North 

America According to aNew Classification: 

Geographical Review v. 21, p. 633-655. 

U.S. Fish and Wildlife Service, 1975, The 

Ecoregions and Land-Surface Form 1\'faps: scale 

1:250,000. 
REFERENCES 

U.S. Geological Survey, 1966, Distribution of 

principal kinds of soils; orders, suborders, and 

great groups; National Atlas, scale 1:7,500,000. 

1980, Index to National Topographic Maps, 

1:250,000-scale series, revised February 1980. 

U.S. Environmental Protection Agency, 1979, Air 

Quality Data -1978. Annual statistics including 

summaries with reference to standards: Research 

Triangle Park, North Carolina, Office of Air, 

Noise, and Radiation, Office of Air Quality 

Planning and Standards, EPA-450/4-79-037 .. 

1980, Air Quality Data- 1979. Annual statistics 

including summaries with reference to 

standards: Research Triangle Park,N orth 

Carolina, Office of Air, Noise, and Radiation, 

33 

Office of Air Quality Planning and Stan~ards, 

EPA-450/4-80-014 

Volchok, H., and Graveson, R.T., 1975, Wet/dry 

fallout collection: Proceedings of the 2nd Federal 

Conference on the Great Lakes: Washington, 

D.C., ICMSE-Federal Council for Scien~e and 

Technology 

Wilson, J. W., Mohnen, V. A., and Kadle~~ek, J., 

1982, Wet Deposition as Observed by MAP3S; 

Atmospheric Environment, v. 16, p. 16~7-1676. 

Work Group 1, Impact Assessment, Final 

Report, February 1983, United States-Canada 

Memorandum of Intent on Trans boundary Air 

Pollution. 
APPENDIX A 

GUIDELINES FOR DESIGN OF A NATIONAL TRENDS NETWORK (fTTN) 

Purpose 

To determine the spatial and temporal variations in 

the quality of atmospheric deposition within the 

United States for a period measured in decades. 

Objective 

To establish a record that will allow the detection of 

temporal and spatial trends in the chemical 

composition of atmospheric deposition in an effort to 

provide information needed to gain a better 

understanding of the sources, movement, and 

transformation of materials contributing to or 

associated with acidic atmospheric deposition in the 

United States. 

To determine the chemical composition of 

atmospheric deposition on a broad regional and 

national scale, validate transport models, estimate 

the exposure of large areas to acidic deposition, 

develop a sound technical basis for decisions on land 

and water management practices, and monitor the 

effectiveness of emission control strategies. 

Approach 

Long-term monitoring of the chemistry of 

atmospheric deposition will be conducted in a 

National Trends Network (NTN) consisting of 100-

150 sites nationwide. Sites will be placed so as to 

collect precipitation samples whose chemical 

composition is representative of precipitation falling 

over a broad region. 

34 

This requires that the sites be located outside the 

influence of local atmospheric emission sources. 

The foundation for development of the NTN will be 

existing public agency networks such as the NADP, 

WMO/NOAA/EPA, TVA, DOE and MAP3S 

networks, and appropriate private-sector networks 

such as U APSP and NCA. 

Justification 

Recent evidence indicates that acid-forming 

materials in atmospheric deposition have caused 

acidification of a number of lakes and streams in the 

United States and Canada. Other chemical 

constituents may also be causing problems of which 

we as yet are unaware. In order to maintain a 

continuing assessment of the chemical composition of 

atmospheric deposition, a national network of 

deposition monitoring sites operated on a consistent 

basis is needed. 

In order to observe and understand geographic 

differences in the chemical composition of 

atmospheric deposition, it will be necessary to 

monitor such deposition in areas known, or 

anticipated, to be receiving acidic deposition as well 

as those areas expected to have alkaline deposition 

but which serve as sources for downwin':l deposition 

in acidic-deposition areas. Emphasis, however, will 

be on areas receiving acidic deposition. 
LOCATION AND OPERATIONAL CRITERIA 

It is envisioned that within any particular region 

there will exist a range in chemical compostion of 

atmospheric deposition depending upon the 

proximity and direction of local atmospheric emission 

sources. However, there will be areas within a region 

that are outside the noticeable influence of any one 

emission source and represent an average of 

atmospheric deposition derived from sources outside 

the region plus contributions, after dispersion and 

mixing, from sources within the region. Sites will be 

located in such areas and the data obtained should be 

suitable for the objectives of the network as stated 

above. 

A site is considered representative of the region in 

which it is located when measurements taken at that 

site are within a prescribed variation, range, or limit 

of other measurements taken elsewhere in the 

region. The allowable variation or range may differ 

from region to region depending upon various factors 

such as soil sensitivity, proxmity to emission sources, 

and other factors. 

Chemical and physical measurements will be made 

in the field and laboratory of those properties and 

chemical constituents of atmospheric deposition 

which pose the greatest real or potential threat to 

terrestrial and ayuatic ecosystems. Each site should 

also operate equipment needed to obtain data to 

support efforts to understand the influence or 

meteorological conditions on the chemical 

composition of the atmospheric deposition samples. 

Site Location Criteria 

In the placement of sites, it is not possible to be 

quantitative with regard to distance downwind of 

major point or line emission sources, local 

topographic influences, proximity to structure and 

the like since local conditions may influence 

beneficially or adversely the regional representativeness of the atmospheric deposition samples collected. 

Good judgment in the design of the network must 

prevail. Future assessments of site suitability will be 

based on an analysis of data obtained. The following 

guidelines are offered. 

(1) Sites are to be located in areas where the 

prevailing land use is unlikely to change for a 

period of decades. It is desirable that the 

surrounding land be Federally owned but State 

or other public ownership is acceptable. 

(2) Grass cover or equivalent should surround the 

site for a distance equal to or greater than twice 

35 

the height of the nearest object taller than the 

deposition sample collector. 

(3) Sites should be located in rural areas sufficiently 

far away from urban centers, major industrial 

areas, and large fossil-fueled powerplants to 

prevent the chemical composition of t~~ samples 

collected from being dominated by emissions 

from one source. In selecting the site, prevailing 

wind direction, storm tracks, and nearby 

emission sources should be considered. In the 

case of very large industrial areas, cities or 

powerplants, sites may have to be 50 kilometers 

or more downwind to avoid domination by 

emissions frone one source area. 

(4) Sites should be located so as to minimize 

influence from local controlled burning. In most 

rural areas, a few kilometers distarce should 

suffice. Forest and brush fires cannot be avoided 

but the site operator should be aware of their 

occurrence and note the fact on U'e sample 

documentation. 

(5) Sites should be located to minimize influence 

from major line sources of emission such as 

heavily-traveled interstate highways, major 

airports, and railroad complexes. Sites may have 

to be as much as 15 km from such emission 

sources. Sites should be located near enough to 

secondary roads to provide convenient access but 

far enough to avoid influence from e,-haust and 

dust from vehicles using those roads. In most 

cases in rural areas, 1 km distance should be 

adequate. Where possible, the access road to the 

site should be paved. If not, the site should be 

upwind of the access road and several hundred 

meters away from it to avoid dust. 

(6) Influences from local topographic features such 

as rain shadows, valleys where fog and dew may 

accumulate, and oceans or salt-water bodies 

which may contribute significant salt spray 

should be a voided. 

(7) Because they have research potential, areas with 

soils sensitive to acid deposition and areas where 

related studies are ongoing or planned should be 

given priority consideration as site locations. 

Preferred locations of opportunity are: 

- Calibrated watersheds where material 

budgets are being studied. 

- Basins where the streams and lakes are being 

monitored for effects of acid deposition. 
LOCATION AND OPERATIONAL CRITERIA 

- Areas with sensitive soils regardless of 

whether or not effects of acid deposition have 

been observed. 

- Areas where related research on effects of 

acid deposition on soils, forests, aquatic 

systems, or materials is ongoing and expected 

to continue for decades. 

- Areas where extensive meteorological, airquality, or precipitation chemistry data are 

available. 

(8) Logistics have moderate priority when cost of 

sampling gear, analyses, interpretation, and 

impact of possible regulatory action are 

considered; costs of getting power and personne I 

to sampling sites should not be of prime 

importance except where costs are unusually 

high. 

Operational Criteria 

The objective of the program can be accomplished 

only by long-term station operation. Each station 

should be operated for decades in a manner consistent 

with the operations at all stations in the program. 

Changes in operational criteria during the life of the 

program will be made as the technology advances but 

each change will be fully investigated and 

documented as to the bias it introduces in or removes 

from the data. 

Deposition monitoring stations will be operated along 

the following guidelines: 

(1) An appropriate weUdry deposition collector will 

be used at each station. Modifications to the 

collector will be made as the technology advances 

to provide for improved sample integrity between 

collections. 

(2) To provide supporting data, each station will 

have a suitably placed precipitation gage to 

provide a continuous record of rainfall. Whenever 

feasible, stations should include instruments to 

measure and record wind speed and direction, 

relative humidity, and temperature. 

(3) The wet deposition sample will be collected or 

analyzed until a better understanding is gained 

through research of the processes involved in the 

deposition of the other-than-wet material and a 

logical basis for the interpretation of data on the 

chemical composition of dry deposition is 

established. 

36 

(4) The following measurements and analyses will 

be performed on the wet deposition sample: 

Field Measurements: pH, specific conductance, 

and quantity of sample collected using 

appropriate portable instruments. When 

convenient and accurate instrumentation 

becomes available at reasonable cost, acidity 

by Gran's titration method and alkalinity by 

an incremental titration method will be added 

to the field protocol. 

Laboratory Analyses: Samples v'ill be sent to 

an approved laboratory for analysis. Samples 

will be filtered in the laboratory as necessary 

for proper performance of analytical 

instrumentation. The samples will be analyzed 

for the following: 

pH 

Specific conductance 

Calcium 

Magnesium 

Sodium 

Potassium 

Chloride 

Sulfate 

Nitrite plus nitrate 

Ammonium 

Orthophosphate 

Analyses for selected trace metals and manmade 

organic compounds will be invertigated and 

incorporated into the laboratory ana lysis protocol 

as appropriate. 

(5) Because the field operations require great skill 

and attention to detail in order to ob~ain suitable 

field measurements and a void sample 

contamination, scientifically trained personnel 

should be used whenever possible. Where an 

untrained observer must be employed, every 

effort should be made to provic1e adequate 

training and careful supervision. 

Quality Assurance 

A quality assurance program including training for 

site operators will be established for the NTN 

consistent with the procedure and limits 

recommended in the "Quality Assurance Handbook 

for Precipitation Chemistry Measurements Systems" 

USEPA, EMSL/RTP, 1981, and "Quality Assurance 

Practices for the Chemical and Biological Analyses of 

Water and Fluvial Sediments," USGS Open-File 

Report 81-650, 1981. The plan will encompass site 

and laboratory operations and anlayses, and data 

transfer, storage, and retrieval practices. 
LOCATION AND OPERATIONAL CRITERIA 

Data Base Management 

1. Data should go by the most expeditious route to 

the Acid Deposition System (ADS) established by the 

Environmental Protection Agency at the Pacific 

Northwest National Laboratory. 

37 

2. The ADS data base should be upgradecl to meet 

the needs of all agencies that supply data to it. 
2000 Humid Temperate Domain 

APPENDIXB 

ECOREGION HIERARCHY 

2100 Warm Continental Division 

2110 Laurentian Mixed Forest Province 

2111 Spruce-Fir Forest Section 

2112 Northern Hardwoods-Fir Forest Section 

2113 Northern Hardwoods Forest Section 

2114 Northern Hardwoods-Spruce Forest Section 

Total2110 

M2110 Columbia Forest Province 

M2111 Douglas-Fir Forest Section 

M2112 Cedar-Hemlock-Douglas-fir Forest Section 

Total M2110 

2200 Hot Continental Division 

2210 Eastern Deciduous Forest Province 

2211 Mixed Mesophytic Forest Section 

2212 Beech-Maple Forest Section 

2213 Maple-Basswood Forest + Oak Savanna Section 

2214 Appalachian Oak Forest Section 

2215 Oak-Hickory Forest Section 

Total2210 

2300 Subtropical Division 

2310 Outer Coastal Plain Forest Province 

2311 Beech-Sweetgum-Magnolia-Pine-Oak Forest Section 

2312 Southern Floodplain Forest Section 

Total2310 

2320 Southeastern Mixed Forest Province 

2400 Marine Division 

2410 Willamette-Puget Forest Province 

M2410 Pacific Forest Province 

M2411 Sitka Spruce-Cedar-Hemlock Forest Section 

M2412 Redwood Forest Section 

M2413 Cedar-Hemlock-Douglas-fir Forest Section 

M2414 California Mixed Evergreen Forest Section 

M2415 Silver-Fir-Douglas-fir Forest Section 

Total M2410 

38 

Section 

Area 

Sq. Miles 

35,900 

18,000 

91,600 

59,200 

11,400 

33,900 

38,400 

58,300 

44,300 

103,400 

123,400 

107,500 

42,600 

6,300 

5,100 

22,000 

4,300 

25,300 

Province 

Area 

Sq. Miles 

204,700 

45,300 

367,800 

150,100 

257,900 

13,000 

63,000 
Section Province 

Area Area 

Sq. Miles Sq. Miles 

2000 Humid Temperate Domain Continued 

2500 Prairie Division 

2510 Prairie Parkland Province 

2511 Oak-Hickory-Bluestem Parkland Section 124,200 

2512 Oak+ Bluestem Parkland Section 80,400 

Total2510 204,600 

2520 Prairie Brushland Province 

2521 Mesquite-Buffalo Grass Section 32,200 

2522 Juniper-Oak-Mesquite Section 24,100 

2523 Mesquite-Acacia Section 27,300 

Total2520 83,600 

2530 Tall-Grass Prairie Province 

2531 Bluestem Prairie Section 111,600 

2532 Wheatgrass-Bl uestem-N eedlegrass Section 49,400 

2533 Bluestem-Grama Prairie Section 62,000 

Total2530 223,000 

2600 Mediterranean Division 

2610 California Grassland Province 201200 

M2610 Sierran Forest Province 32,600 

M2620 California Chaparral Province 35,500 

3000 Dry Domain 

3100 Steppe Division 

3110 Great Plains-Shortgrass Prairie Province 

3111 Grama-N eedlegrass-Wheatgrass Section 83,800 

3112 Wheatgrass-N eedlegrass Section 102,800 

3113 Grama-Buffalo Grass Section 131,000 

Total311Q 317,600 

M3110 Rocky Mountain Forest Province 

M3111 Grand Fir-Douglas-fir Forest Section 32,600 

M3112 Douglas-fir Forest Section 94,500 

M3113 Pondersoa Pine-Douglas-fir Section 60,200 

Total M3110 187,300 

39 
Section Province 

Area Area 

Sg. Miles Sq. Miles 

3000 Dry Domain Continued 

3120 Palouse Grassland Province 12,400 

M3120 Upper Gila Mountains Forest Province 36,100 

3130 Intermountain Sagebrush Province 

3131 Sagebrush-Wheatgrass Section 89,800 

3132 Lahontan Saltbush-Greasewood Section 33,300 

3133 Great Basin Sagebrush Section 46,900 

3134 Bonneville Saltbush-Greasewood Section 22,200 

3135 Ponderosa Shrub Forest Section 11,200 

Tota13130 203,400 

P3130 Colorado Plateau Province 

P3131 Juniper-Pinyon Woodland + 39,600 

Sagebrush Saltbush Mosaic Section 

P3132 Grama-Galleta Steppe+ 55,100 

Juniper-Pinyon Woodland Mosaic Section 

Total P3130 94,700 

3140 Mexican Highland Shrub Steppe Province 17,500 

A3140 Wyoming Basin Province 

A3141 Wheatgrass-N eedlegrass-Sagebrush Section 13,100 

A3142 Sagebrush-Wheatgrass Section 29,200 

Total A3140 42,300 

3200 Desert Division 

3210 Chihuahuan Desert Province 

3211 Grama-Tobosa Section 18,200 

3212 Tarbush-Creosote Bush Section 45,900 

Total3210 77,500 

3220 American Desert Province 

3221 Creosote Bush Section 36,700 

3222 Creosote Bush-Bur Sage Section 40,800 

Tota13220 64,100 

4000 Humid Tropical Domain 

4100 Savanna Division 7,800 

4110 Everglades Province 

40 
APPENDIXC 

SITE CODES AND ABBREVIATIONS USED IN THE REPORT 

Multistate Power Production Pollution Study (MAP3S) + 

Code Site State Latitude Longitude Ecoregion 

M1 Whiteface NY 44o24' 73o52' 2114 

M2 Ithaca NY 42o23' 76°43' 2113 

M3 Penn State PA 40o47' 77o57' 2214 

M4 Virginia VA 38o03' 78o33' 2320 

M5 Illinois IL 40o03'12" 88o22'19" 2511 

M6 Brookhaven NY 40o52' 72o53' 2214 

M7 Lewes DE 38o46' 75oOO' 2320 

M8 Oxford OH 39o32' 84o44' 2212 

M9 Oak Ridge TN 35o57'41" 84o17'14" 2214 

Reference Climatological Stations (RCS) + + 

R1 Arlington WI 43o18' 89o21' 2213 

R2 Beeville TX 28o27' 97o42' 2523 

R3 Bozeman MT 45o40' 111o09' M3112 

R4 Blue Hill MA 42o13' 71o07' 2214 

R5 Calhoun LA 32o31' 92o20' 2320 

R6 Chatham MI 46o21' 86o56' 2112 

R7 Cottonwood SD 43o58' 10lo52' 3112 

R8 Crete NE 40o37' 96o57' 2f31 

R9 Davis CA 38o32' 121o46' 2f.10 

R10 Geneva NY 42o53' 77o02' 2113 

R11 Goodwell OK 36o36' 101o37' 3113 

R12 Grand Canyon AZ 36003' 112o09' M3120 

R13 Jackson TN 35o37' 88o50' 2Z15 

R14 Logan UT 41o40' 111 o54' M3J 12 

R15 Norfolk CT 41o58' 73ol3' 2214 

R16 Presque Isle ME 46o39' 68oOO' 2114 

Rl7 Quincy FL 30o36' 84o33' 2311 

Rl8 NM State Univ NM 32o17' l06o45' 3211 

R19 Sterling VA 38o59' 77o28' 2320 

R20 Union OR 45o13' 117o53' M3111 

R21 Wooster OH 40o47' 81o55' 2212 

Tennessee Valley Authority Trends Stations (TV A)+ + + 

T1 Land Between KY 36o47'27" 88o04'01" 2215 

the Lakes 

T2 Giles County TN 35ol7'05" 86o54'11" 2215 

T3 Loves ~ill VA 36o44'12" 81o4l't:r· 2214 

41 
Utility Acid Precipitation Study Program (U APSP)* 

Code Site State Latitude Longitude Ecoregion 

U1 Winterport ME 44o37'05" 68o58'30" 2114 

U2 Underhill VT 44o31'42" 72o52'08" 2114 

U3 Big Moose NY 43o49'03" 74o54'08" 2114 

U4 McArthur OH 39o14'06" 82°28'41" 2211 

U5 Gaylord MI 44o56'58" 84o38'30" 2113 

U6 Clearfield KY 38o08'10" 83o27'17" 2211 

U7 Alamo TN 35o47'06" 89o07'06" 2215 

us Uvalda GA 32o03'18" 82o28'25" 2311 

U9 Selma AL 32o28'25" 8T05'03" 2320 

U10 Clinton MS 32o21'06" 90o17'15" 2320 

U11 Marshall TX 32o39'58" 94o25'06" 2320 

U12 Lancaster KS 39o34'10" 95o18'17" 2511 

U13 Brookings SD 44o19'54" 96o49;45" 2531 

U14 Turners Falls MA 42o35'50" 72o32'55" 2114 

U15 Tunkhannock PA 41o34'30" 75o59'40" 2113 

U16 Zanesville OH 39o59'02" 82o01'05" 2214 

Ul7 ~ockport IN 37o53'40" 87o07'15" 2215 

Ul8 FortWanye IN 41o02'08" 85o19'30" 2212 

U19 Raleigh NC 35o43'43" 78°40'48" 2320 

National Atmospheric Deposition Program (NADP) *-(as of30 May 1982) 

AK03 Mt McKinley AK 63o43'27" 148o57'55" 

AR02 Warren AR 33o36'15" 92o06'02" 2320 

AR27 Fayetteville AR 36o06'02" 94ol0'24" 2215 

AS01 Samoa-GMCC AS -14o15'08" 170o33' 48" 

AZ03 Grand Canyon AZ 36o04'18" 112o09'11" M3120 

Natl Park 

AZ06 Organ Pipe AZ 31o57'02" 112o48'00" 3222 

AZ99 Oliver Knoll AZ 33o04'17" 109051'53" 3140 

CA34 WSO-Bishop CA 37o22'15" 118o21'59" 3132 

CA42 Tanbark Flat CA 34o12'17" 117o45'39" M2620 

CA45 Hopland CA 39o00'17" 123005'05" M2414 

CA75 Sequoia Nat Pk CA 36o34'09" 118o46'40" M2610 

CA88 Davis CA 38o32'07" 121 o46'30" 2610 

CA99 Yosemite Na'l. CA 37o47'49" 119o51 '30" M2610 

Park 

CAN1 Lethbridge CAN 49o38'13" l12o47'16" 3110 

CAN2 Mt Forest CAN 43o59'29" 80o44'46" 2110 

CAN3 Kejimkujik CAN 44o25'58" 65ol2'20" 2110 

cooo WSO-Almosa co 37o26'36" 105o51'55" M3113 

C015 Sand Spring co 40o30'27" l07o42'07" A3142 

C019 Rocky Mountain co 40o21'52" 105o33'37" M3113 

Nat. Pk 

C021 Manitou co 39o06'04" l05o05'31" M3113 

C022 Pawnee co 40o48'23" l04o45'15" :n 1~3 

C099 Mesa Verde co 37ot1'56" 1 Q8D29'26" P3132 

Nat'l. Pk 

42 
FL03 Bradford FL 29o58'29" 82011'53" 2311 

Code Site State Latitude Longitude Ecoregion 

FLll Everglades FL 25o23'40" 80o41'45'' 4110 

GA41 Georgia Stn GA 33o10'40" 84o24'22" 2320 

HIOO Mauna Loa HI 19o32'22" 155o34'45" M4210 

1003 Craters of the ID 43o27'48" 113o33'31" 3131 

Moon 

IL11 Bondville IL 40o03'12" 88o22'19" 2511 

IL18 Shabbona IL 4to50'29" 88o51'04" 2511 

IL19 Argonne IL 41o42'04" 87o59'43" 2511 

IL35 SIU IL 37o42'36" 89o16'08" 2215 

IL47 WMOSalem IL 38o38'36" 88o58'01" 2511 

IL63 Dixon Springs IL 37o26'08" 88o40'19" 2215 

IN34 Indiana Dunes IN 41o37'57" 87o05'16'' 2511 

MA01 Atlantic Coastal MA 41o58'23" 70oQ1'12" 2214 

Laboratory 

MA08 Cadwell Creek MA 42o21'40" 72o23'27" 2114 

MA13 East MA 42o23'02" 71o12'53" 2214 

MEOO WSOCaribou ME 46o52'08" 68o00'55" 2214 

ME02 Bridgton ME 44o06'27'' 70o43'44'' 2114 

ME09 Greenville Stn ME 45o29'23" 69o39'52" 2114 

ME99 Acadia Nat Park ME 44o22'27" 68o15'39" 2214 

MI09 UM Biological MI 45o33'40" 84o40'42" 2113 

Stn 

Ml22 Houghton MI 47o13'33" 88o37'50" 2112 

MI25 Isle Royale N atl MI 47o54'43" 89o09'10" 2111 

Park 

MI26 Kellogg Bio Stn MI 42o24'37" 85o23'34" 2212 

MI53 Wellston MI 44ot3'28" 85o49'07" 2113 

MN16 Marcell Exp MN 47o31'52" 93o28'07" 2111 

Forest 

MN18 Fernberg Stn MN.... 47o56'45" 91o29'43" 2111 

MN27 Lamberton MN 44o14'14" 95o18'02" 25~1 

M003 Ashland Wildlife MO 38o45'13" 92o11'55" 2215 

Area 

M005 University ForestMO 36o54'39" 90o19'06" 2215 

MS14 WSO-Meridian MS 32o20'04" 88o44'42" 23ZO 

MT05 Glacier Fire MT 48o30'37" 113o59'44" M2112 

Weather 

NC03 Lewiston NC 36o07'40" 77o10'30" 23ZO 

NC11 RTI NC 35o54'09" 78o52'12" 23ZO 

NC25 Coweeta NC 35o03'38" 83o25'50" 2214 

NC33 EPA-RTP NC 35o53'47" 78o51'38" 2320 

NC34 Piedmont NC 35o41'48" 80o37'22" 2320 

Research Stn 

NC35 Clinton Crops NC 35o01'26" 78o16'45" 2320 

Rsch Stn 

NC41 Finley Farm NC 35o43'43" 78o40'52' 2320 

ND07 Teddy Roosevelt ND 47o36'09" 103ol5'54" 3112 

NE15 Mead NE 41o09'11" 96o29'34" 2531 

43 
Code Site State Latitude Longitude Ecoregion 

NH02 Hubbard Brook NH 43o56'35" 71o42'12" 2114 

NJ99 Washington NJ 4Qo18'54" 74o51'17" 2214 

Crossing 

NM09 Cuba NM 36o02'27" 106o58'17" P3132 

NYOS Aurora NY 42o44'02" 76o39'35" 2113 

NYlO Chautaugua NY 42ol7'58" 79o23'47" 2113 

NY12 Knobit NY 42o22'41" 73o3Q'10" 2113 

NY20 Huntington NY 43o58'19" 74o13'25" 2114 

NY 51 WestPoint NY 41o2t'OO" 74o02'22" 2214 

NY 52 Bennett Bridge NY 43o31'34" 75o56'50" 2113 

NY65 Jasper NY 42006'22" 77032'08" 2113 

OH17 Delaware OH 4Qo21'19" 83o03'58" 2212 

OH49 Caldwell OH 39o47'34" 81o31'52" 2211 

OH71 Wooster OH 4Qo46'48" 81o55'31" 2212 

OR02 Alsea Guard Stn OR 44023'13" 123037'22" M2413 

OROS Lost Creek Dam OR 42o40'04" 122o40'59" M2415 

ORlO Andrews Exp OR 44013'23" 122o14'32" M2415 

Forest 

ORll Vines Hill OR 43o53'57" 117o25'37" 3131 

OR17 WSO-Pendleton OR 45041'23" 118o5Q'16" 3120 

OR99 Schmidt Farm OR 44o37'35" 123o12'50" 2410 

PA29 Kane Exp Forest PA 41035'52" 78o46'04" 2113 

PA42 Leading Ridge PA 40o39'32" 77o56'10" 2214 

SC18 Clemson sc 34o40'28" 82o50'09" 2320 

SDOO WSO-Huron SD 44o23'02" 98o13'14" 2532 

TNOO Walker Branch TN 35o57'41" 84o 17'14" 2214 

TNll Elkmont TN 35o39'52" 83o35'25" 2214 

TX04 K-Bar TX 29018'07" 103010'38" 3212 

TX38 Forest Seed Ctr TX 31o33'38" 94o51'39" 2320 

TX53 WSO-Victoria TX 28o50'43" 96o55'12" 2512 

UT02 Cedar Mountain UT 39o10'15" 110o37'05" F3131 

VA13 Horton's Stn VA 37o20'06" 80o33'28" 2214 

VA28 Shenandoah N tl VA 38030'51" 78o25'45" 2214 

Park 

VTOl Bennington VT 42o52'34" 73o09'48" 2114 

WA14 Olympic N atl Pk WA 47o51'36" 123o55'57" M2411 

Wl36 Trout Lake WI 46o03'09" 89o39'11" 2112 

Wl37 Spooner WI 45o49'21" 9lo52'30" 2111 

WV18 Parsons wv 39o05'23" 79o39'44" 2214 

WY06 Pinedale WY 42o55'44" I09o47'12" A3142 

WYOS Tower-Yellow- WY 44o55'02" 110o25'13" M3112 

stone 

WY99 Newcastle WY 43o52'24" 104o11'32" 3112 

NADP Inactive Sites (as of30 May 1982) 

AZOl Tombstone AZ 3to42'30" 11 Oo03'24" 3140 

CA85 Channel Islands CA 34oQQ'57" 119o21 '43" M2620 

FLOO Austin Cary FL 29o45'37" 820l1'56" 2311 

NJ29 GFLD Princeton N.J 2214 

44 
NADP Sites Planned But Not in operation (as of 30 May 1982) 

Code Site State Latitude Longitude Ecoregion 

1004 Headquarters ID 46o37'40" 115o49'10" M2112 

1015 Smith's Ferry ID 44ot7'56" lt6o04'36" M3111 

MD13 Wye MD 38o54'47" 76o09'09" 2320 

NM07 Bandelier Natl NM 35o46'54" 106ot6'03" M3113 

Monument 

TX21 Longview TX 32o22'53" 94o42'49" 2320 

TX52 McKinney Falls TX 30ot0'44" 97o43'14" 2512 

WI28 Lake Dubay WI 44o39'53" 89o39'08" 2113 

45 
New Stations 

Code Site State Latitude Longitude Ecoregion 

N01 Chuchupate Ranger Station CA 34o48' 22" 119o00'38" M2620 

N02 Havre Experiment Station MT 48o29' 52" 109047' 44" 3111 

N03 Custer National Battlefield MT 45o34' 02" 107o26'21" 3111 

N04 Alder Ranger Station co 37o43' 106o43' M3113 

N05 Dry land Experimental Station WA 47oOO' 118o35' 3120 

N06 Silver Lake Ranger Station OR 43o07' 22" 121o03'28" 3131 

N07 Winnemucca NV 40o58' 117o44 3132 

NOS Meadows Canyon Ranger Station NV 38o43' 116055' 3133 

N09 Desert Range Experimental Farm UT 38o35' 44" 113o45' 12" 3134 

N10 Guadalupe Mountains Nat. Pk. TX 31o54'30" 104o48'10" 3212 

N11 Davis Dam NV 35o13' 114o35' 3221 

N12 Shasta National Forest-Castle Lake CA 41o13'51" 122o22'32" M2610 

Nl3 Sauk Guard Station WA 48o29' 121038' M2415 

N14 Texas A&M Spur TX 33o30' 100o50' 2521 

N15 Attwater Prairie Chicken NWR TX 29o41' 20" 96o16'29" 2512 

N16 San Angelo TX 31o20' 100o30' 2521 

N17 LBJ National Grassland TX 33o23' 30" 97o38'23" 2512 

N18 NM State AG Farm Clovis NM 34o36' 00" 103012'55" 3113 

N19 Severe Storms Laboratory OK 34o58' 48" 97o31'16" 2512 

N20 Oklahoma State Fish Hatchery OK 36o45' 98010' 2533 

N21 Los Animas State Fish Hatchery co 38o07' 04" 103018'57" 3113 

N22 Kanapolis State Park KS 34o40' 98oOO' 2531 

N23 Fort Hartsuff State Hist. Park NE 41o45' 99oOO' 2532 

N24 Icelandic State Park ND 48o46' 57" 97o45' 15" 2531 

N25 Camp Ripley MN 46o14'58" 94o29'50" 2213 

N26 Perryville Battlefield State Park KY 37o40' 39" 84o57' 25" 2215 

N27 Janice MS 31o01' 51" 88o59'09" 2311 

N28 Santee State Park sc 33o30' 80°30' 2320 

N29 Coffeyville Pines MS 34oOO' 06" 89o47' 40" 2215 

N30 McNay Memorial Research Ctr. lA 40o57' 51" 93o23'29" 2511 

N31 Sand Lake NWR SD 45o45' 98o15' 2532 

N32 Colby Agricultural Station KS 39o20' 10lo03' 2533 

N33 Mead Ranger Station MT 47o10' 111 oOO' 3111 

N34 Canfield Lake ND 47o12' 24" 100024'06" 3112 

N35 Nashua Agricultural Station lA 42o54' 92032' 2531 

N36 Sand Mtn. Agricultural Center AL 34o17' 30" 85o57' 32" 2211 

N37 Babcock State Park wv 37o58' 47" 80o56'59" 2214 

N38 Iberia Livestock Experimental Station LA 29o55' 47" 91o42'54" 2312 

N39 Myakka River State Park FL 27o15' 82o15' 2311 

N40 Bedford Agricultural Station IN 38o46' 86o30' 2212 

N41 Caddo River AR 34ol0'46" 93o05'55" 2320 

N42 Roseville IL 4Qo50' 90°30' 2511 

Legend 

Locations were obtained from sources below. 

+Source: MacCracken, 1979. 

++Source: RichardS. Cram, National Climatic Center, Asheville, N.C. 

+++Source: William Parkhurst, Tennessee Valley Authority. 

*Source: Measured from maps marked by each site operator. 

46