United States Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-B-16-0 01
2017 National Lakes Assessment
Site Evaluation
Guidelines
Version 1.0, 16 May 2016
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NOTICE
The intention of the 2017 National Lakes Assessment (NLA 2017) project is to provide a comprehensive
"State of the Lakes" assessment for lakes, ponds, and reservoirs across the United States. The complete
documentation of overall project management, design, methods, and standards and Quality
Assurance/Quality Control measures is contained in this document and companion documents,
including:
2017 National Lakes Assessment: Field Operations Manual (EPA 841-B-16-002)
2017 National Lakes Assessment: Laboratory Operations Manual (EPA 841-B-16-004)
2017 National Lakes Assessment: Quality Assurance Project Plan (EPA 841-B-16-003)
These documents together comprise the integrated set of QAPP documents. This document (Site
Evaluation Guidelines) describes the process to compile the final list of candidate lakes for sampling. The
process includes locating a candidate lake, evaluating the lake to determine if it meets the criteria for
inclusion in the target population and is accessible for sampling, and, if not, replacing it with an
alternate candidate lake. These guidelines are revised from those developed for the 2012 NLA (USEPA
2011), and are intended for specific use in the 2017 NLA. Mention of trade names or commercial
products in this document does not constitute endorsement or recommendation for use
The suggested citation for this document is:
USEPA. 2016. 2017 National Lakes Assessment. Site Evaluation Guidelines. EPA 841-B-16-001.
U.S. Environmental Protection Agency, Washington, DC.
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TABLE OF CONTENTS
TITLE PAGE I
NOTICE Ill
TABLE OF CONTENTS V
LIST OF FIGURES V
LIST OF TABLES VI
1 INTRODUCTION 1
1.1 Selection of the Master List of Candidate Lakes 2
2 LAKE EVALUATION PROCESS 3
2.1 Lake Replacement 3
2.2 Procedure for Selecting Replacement Lakes from the Oversample List 5
2.3 GIS-based Evaluation (Q1-Q3) 9
2.4 Desktop Evaluation (Q2, Q4-6) 13
2.5 Field Evaluation (Q2, Q4-6) 15
3 DETERMINING IF A LAKE IS PHYSICALLY ACCESSIBLE (Q6) 17
3.1 Target, Inaccessible-Barrier/Safety 17
3.2 Target, > 1 Day Needed 17
3.3 Target, Extreme Effort Required, Inaccessible-Effort 17
4 OBTAINING PERMISSION TO ACCESS CANDIDATE LAKES (Q7) 18
4.1 Identify Landowner 18
4.2 Request Permission to Access Lake 18
4.3 Denials 19
4.4 Frequently Asked Questions 19
5 LITERATURE CITED 20
APPENDIX A: EXAMPLE LETTER REQUESTING PERMISSION TO ACCESS A LAKE 21
APPENDIX B: EXAMPLE LANDOWNER PERMISSION SLIP 23
APPENDIX C: NATIONAL LAKES ASSESSMENT 2017 SURVEY DESIGN 25
APPENDIX D: NATIONAL LAKES ASSESSMENT 2017 FACT SHEET 32
APPENDIX E: CONTACTS 35
APPENDIX F: FREQUENTLY ASKED QUESTIONS 38
LIST OF FIGURES
Figure 1. Evaluating a lake 7
l/l
Figure 2. Process Flow of the Lake Evaluation Spreadsheet 8 h
Figure 3. GIS-based evaluation 12 llj
Figure 4. Desktop evaluation 15 z
Figure 5. Field evaluation 16 u
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LIST OF TABLES
Table 1.1 Exceptions to NLA 2017 Target Population
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1 Introduction
The objectives of the 2017 National Lakes Assessment (NLA) include:
1) Using a statistically valid approach, determine the percent of the nation's lakes that are least
disturbed, moderately disturbed, and most disturbed for key indicators of ecological health,
trophic state, and recreation;
2) Determine the relative importance of key stressors as they relate to the condition of lakes across
the United States;
3) Evaluate changes and trends in the condition of lakes in the United States since the 2012 NLA and
2007 NLA;
4) Expand the capacity of State and Tribal programs to monitor and assess the condition of lakes.
The word lake in the remainder of this document includes lakes, reservoirs, and ponds. This document
describes the steps involved to evaluate candidate lakes for the NLA, and arrive at a final list of lakes to
visit and sample. Evaluation of candidate lakes serves several purposes. Lakes that do not meet the
criteria for inclusion in the NLA target population are identified and replaced. The target population is
that component of the resource (i.e., lakes, ponds, and reservoirs) that could be sampled to assess
condition. Table 1.1 lists the exceptions for inclusion in the target population of lakes, ponds, and
reservoirs.
Table 1.1 Exceptions to NLA 2017 Target Population
Exceptions to the NLA 2017 Target Population
Ephemeral waterbodies (i.e., highly likely to be dry between May and September of the sampling
year)
Lakes or ponds along the coast or near an estuary (below the head of salt) that are tidally-influenced
(i.e., maintained solely by surface inflow of brackish water or seawater)
Run-of-the-river reservoir with retention time < 1 week
Used exclusively for aquaculture
Ponds or reservoirs with no recreational or aquatic life uses
Sewage lagoons
Disposal ponds (e.g., mine tailings)
Evaporation ponds
Storm water retention basins
Constructed solely for storage of drinking water (e.g., up-ground reservoirs, p.8)
Active quarries
Borrow pits
Stock or farm ponds that were constructed where there previously was no waterbody (with no other
uses)
Surface area less than 1 hectare
Total area of open water (does not have to be continuous) < 1000 m2 (at time of sampling).
Maximum depth less than 1 m (at time of sampling)
Lakes that meet the criteria, but that cannot be sampled, are also identified and replaced. Information
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obtained about important characteristics of candidate lakes (e.g., lake origin) is used to classify lakes for
analysis and reporting. All of these activities improve the sample frame and allow the population of
lakes assessed for ecological condition to be described more precisely. In addition, the number of field
visits to lakes that should not or cannot be sampled is reduced.
The evaluation process for the NLA differs from many other monitoring and assessment studies in that
the accounting of candidate lakes that end up not being sampled is almost as important as identifying
the lakes that will ultimately be sampled. Accounting for the status of all candidate lakes, sampled or
not, provides the means to improve the survey design and site selection process, refine the sampling
frame to reduce the number of non-target sites, and acknowledge any potential caveats to interpreting
the results of the assessment in terms of sites that were identified as target but could not be sampled. In
the 2012 NLA, the final set of sampled lakes represented only 70% of the target population—the other
30% represented a portion of the intended target population that could not be assessed because of lack
of permission or physical inaccessibility (USEPA in prep). This unassessed portion of the target
population is likely biased towards certain types of lakes and/or geographic regions. This constrains the
ultimate objective of reporting the condition of all target lakes in the conterminous US. Any activity that
reduces the proportion of unassessed lakes results in a more robust and representative assessment.
Given the scale and time constraints of NLA, and the desire to utilize local knowledge about lakes, the
evaluation process involves many different persons. It is critical to apply the evaluation process
consistently across all lakes and evaluators. To help make the process consistent and efficient, an
electronic spreadsheet with drop-down menus and pick lists is used for the NLA 2017. For those lakes
ultimately identified for sampling, it is also important to apply a reasonable (and consistent) level of
effort to obtain permission when required, and to visit and sample lakes that are difficult to access
because of physical barriers to access (e.g., distance, terrain).
1.1 Selection of the Master List of Candidate Lakes
Lakes were chosen from a sample frame of lake polygons represented in the National Hydrography
Dataset (NHD), following a Generalized Random Tessellation Stratified (GRTS) survey design for a finite
resource (Stevens and Olsen 2004). Appendix C: National Lakes Assessment 2017 Survey Design
provides additional details regarding the survey design. The final sample frame for 2017 incorporates
sampled lakes from both NLA 2007 and NLA 2012 for use in estimating change between and trends
among lakes surveys.
The "master" list of sites selected for the NLA 2017 using the survey design contains approximately
8,500 candidate lakes. A sufficient number of lakes from this list must be evaluated in order to produce
a final list of approximately 1,000 lakes that will be visited and sampled. The evaluation process is
conducted separately for each State to arrive at the required number of sampling sites for the entire
NLA. Additional lakes from the list may need to be evaluated if a State will be implementing a more
intensive sampling regime in order to produce a State-level assessment of lakes. Approximately 220 of
these 1,000 lakes are lakes that were previously sampled as part of the 2012 NLA and approximately 225
lakes were previously sampled as part of the 2007 NLA. These lakes may not require a detailed
evaluation for 2017 (other than to confirm each is still target and accessible).
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2 Lake Evaluation Process
For 2017, the NLA lake evaluation process consists of four phases:
1) A Geographic Information System (GlS)-based evaluation on candidate lakes to assign an
initial status to as many as possible;
2) A Desktop Evaluation to assign a final status to as many of the remaining candidate lakes as
possible;
3) A Field Evaluation to assign a final status to any remaining candidate lakes;
4) A final refinement of the candidate lake list based on the ability to obtain Permission to
sample, and whether the lake meets open water and depth criteria when visited.
The master list of candidate lakes (1.1) can be apportioned into lists of candidate sites for each State.
Each phase assigns a final status to as many candidate lakes on a State list as possible, with the next
phase working primarily on the remaining lakes. By the end of the third phase, all candidate lakes
evaluated should have a final status assignment. The fourth phase of the process refines the list of
candidate lakes to identify those that will be visited and sampled in the NLA.
The general process for conducting the evaluation within any given phase is presented in Figure 1. The
process consists of answering a series of Yes/No questions, as shown in Figure 2. A Yes answer moves
the site to the next question, while a No answer generally involves assigning a final site status and
selecting a replacement site for evaluation. When a question cannot be answered definitively, the status
is classified as Uncertain, and the site is moved to the next phase of the evaluation.
For the NLA 2017, the GIS-based evaluation phase will be conducted by the states. Two shape files will
be provided for the purposes of GIS-based evaluation: a shape file of points representing the design
coordinates for each lake selected to be part of the survey design, and a shape file of lake polygons
associated with each sampling point. After the GIS phase, the list of candidate sites will undergo
desktop and field evaluations (when required). The GIS-based, desktop, and field evaluation phases are
used to determine if a candidate lake is part of the target population, if it is safe to access, and if
permission is needed (in the case of no public access). Then, if needed, permission is requested as the
fourth phase of the process.
During any given phase, candidate lakes that are determined to be nontarget, or are determined to be
part of the target population but cannot be sampled, are replaced with alternate candidate lakes
selected from a list of oversample lakes. It is important that alternate lakes are selected properly (i.e.,
from the correct group without skipping over any) to maintain the random nature of the final list of
sampled lakes. The procedure for selecting a replacement lake is described in the following section.
Final status determinations should be recorded on each state's site evaluation spreadsheet, which
includes the list of candidate sites as well as oversamples for each state. The spreadsheets shall be
updated regularly throughout the index period and posted to the NLA SharePoint site. The NLA field
logistics contractor will be checking the site evaluation spreadsheets throughout the field season to
ensure proper replacement lake selections.
2.1 Lake Replacement
Lakes on the master site list are evaluated separately by State. A sufficient number of lakes on the list
for each State must be evaluated in order to arrive at the required number of target and accessible lakes
assigned to that State. There are five "base panels" included in the NLA 2017 survey design:
1) NLA 2007 resample lakes (NLA17_07RVT): These are lakes that were initially sampled in NLA
2007 and again in NLA 2012. Lakes with the RVT code will be sampled once in 2017.
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2) NLA 2007 resample and revisit lakes (NLA17_07RVT2): These are lakes that were initially
sampled in NLA 2007 and again in NLA 2012. Lakes with the RVT2 code will be "revisit" lakes
and sampled two times in 2017.
3) NLA 2012 resample lakes (NLA17_12RVT): These are lakes that were initially sampled in NLA in
NLA 2012. Lakes with the RVT code will be sampled once in 2017.
4) NLA 2012 resample and revisit lakes (NLA17_12RVT2): These are lakes that were initially
sampled in NLA 2012. Lakes with the RVT2 code will be "revisit" lakes and sampled two times in
2017.
5) NLA 2017 lakes (NLA17_17): These are new lakes selected from the 2017 sample frame and will
be visited once in 2017.
Note the subtle but important distinction between resample and revisit lakes: Resample lakes are
visited and sampled in different years). Revisit lakes are visited and sampled twice within a single year.
None of the "new" NLA 2017 lakes will be revisited in 2017.
There are also four different "oversample" panels that serve as the source for replacement lakes:
1) NLA 2007 resample lake oversample (NLA17_07RVT_OverSamp): This list is used to replace
either NLA 2007 resample or resample and revisit lakes that are either non-target or that cannot
be sampled in 2017.
2) NLA 2012 resample lake oversample (NLA17_12RVT_OverSamp): This list is used to replace
either NLA 2012 resample lakes that are either non-target or that cannot be sampled in 2017.
3) NLA 2012 resample and revisit lake oversample (NLA17_12RVT2_OverSamp): This list is used
to replace NLA 2012 resample and revisit lakes that are either non-target or that cannot be
sampled in 2017. NOTE: This panel is not present in all states. If a state does not have this
panel, replace NLA17_12RVT2 lakes using the NLA17_RVT Oversample list.
4) NLA 2017 lakes oversample (NLA17_17_OverSamp): This list is used to replace NLA 2017 lakes
that are either non-target or that cannot be sampled in 2017.
Within each state(column name=STATE) and base panel group (column name=PANEL17), lakes
evaluated for potential sampling must have all site IDs (column name SITEID_17) from the lowest to the
largest number evaluated. For example, Alabama has eight lakes that need to be sampled (two
NLA17_07RVT, one NLA17_07RVT2, one NLA17_12RVT, one NLA17_12RVT2, and three NLA_17_17
lakes). A sufficient number of base and oversample sites from each panel needs to be evaluated to end
up with the required number of sampled lakes. It is important to select oversample lakes from each
panel in numerical order of site ID (i.e. do not skip over any).
If you determine a lake to be non-target, or target but not accessible, during any phase of the evaluation
process, select the next available replacement lake from the appropriate oversample list. Section 2.2
presents the procedure for selecting replacement lakes. The replacement process differs slightly based
on whether the lake being replaced is part of the national NLA 2017 design versus a state-level design
(intensified sampling to allow a State to perform its own assessment). Candidate lakes identified as part
of the national design must all be evaluated and sampled if they are determined to be target and
accessible. For a state-level design, all candidate lakes identified as part of the national design and all
candidate lakes identified as part of the state-level design must be evaluated and sampled if they are
determined to be target and accessible.
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2.2 Procedure for Selecting Replacement Lakes from the Oversample List
At the end of the evaluation process, you should have a list of lakes for your state that includes the list
of "base" sites (Section 2.2.1), plus a sequential list of replacement Site ID numbers needed to have the
required number of target and accessible lakes. If your State is planning to do a separate State-scale
assessment, the "base" list of sites is expanded to include additional sites (Section 2.2.2) that must also
be evaluated (and replaced if necessary).
2.2.1 National Design
1. The initial list of candidate "base panel" lakes within a state that are required for the national
assessment are identified by the following values for the column name= PANEL17:
a. NLA17_07RVT: NLA 2007 resample lakes that will be sampled once in 2017.
b. NLA17_07RVT2: NLA 2007 resample and revisit lakes that will be sampled two times in
2017.
c. NLA17_12RVT: NLA 2012 resample lakes that will be sampled once in 2017.
d. NLA17_12RVT2: NLA 2012 resample and revisit lakes that will be sampled two times in
2017.
e. NLA17_17: NLA 2017 lakes that will be sampled once in 2017
2. You must evaluate all of these base panel lakes within your State to meet the sample size
requirements for the national assessment. If the evaluation for a lake results in it being assigned
a final status of nontarget or target but not accessible, select the first available lake (i.e., with
the lowest Site ID number) from the appropriate oversample list and evaluate it.
a. If you need to replace a 2007 resample and revisit site (NLA17_07RVT2), attempt to
replace this revisit from the NLA 2007 resample lake oversample list
(N LA17_07RVT_OverSamp).
b. If you need to replace a 2012 resample and revisit site, attempt to replace this revisit
from the NLA 2012 resample and revisit lake oversample list
(NLA17_12RVT2_OverSamp). This will become your new 2012 revisit site. This may not
always be possible. If not, replace it as you typically would and make the replacement
lake a revisit site.
c. If all replacement lakes with PANEL17 = NLA17_17 have been evaluated, and additional
replacement lakes are needed, begin using lakes with PANEL17 = NLA17_17_OverSamp
2.2.2 State Level Design (Intensification)
1. As of fall 2016, nine intensifications and two State-specific survey designs have been identified
for inclusion in the 2017 NLA. This is subject to change before the 2017 NLA is actually
implemented.
2. For a State-level (intensified) design, the "base" list of candidate lakes includes all lakes
identified as part of the national design (see 2.2.1 above), plus those with PANEL17=NLA17ST.
3. You must evaluate all of these lakes within your State to meet the sample size requirements for
both the national and your State-specific assessments. If the evaluation for a lake results in it
being assigned a final status of nontarget or target but not accessible, select the first available
lake (i.e., with the lowest Site ID number) with PANEL17= NLA17_17_OverSamp and evaluate it.
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d.
e.
NOTE: If your State elects not to include lakes with surface area less than 4 ha (which
are part of the national design), or have some other deviation from the national target
lake criteria, you must still evaluate (and sample if target and accessible) all lakes
(regardless of surface area) identified as part of the national design, including any
replacement lakes needed for these.
For the additional State-level lakes (PANEL=NLA17ST), you can exclude those that do not
meet your State-specific target criteria (e.g., with surface areas < 4 ha), and skip over
any replacement lakes (PANEL17= NLA17_17_OverSamp) that do not meet your State-
specific target criteria). Assign a final evaluation status of Nontarget_State to these
excluded lakes.
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List of candidate lakes from survey design
BASE PANEL LISTS OVERSAMPLE LISTS
^ GIS-based EVALUATION (by State)
Evaluate all base panel lakes per State
(NLA17_07RVT2, NLA17_07RVT.
NLA1712RVT2, NLA1712RVT, NLA1717)
Candidate
Target lakes
i
1
Uncertain
Nontarget
lakes
lakes
DESKTOP EVALUATION
1
Target
Target
but not
and
sampleable
physically accessible
Target
Uncertain
but not
sampleable
Select next available
oversample lake for
evaluation
Nontarget
Select next available
oversample lake for
evaluation
Determine
Lake Origin
Type
FIELD EVALUATION
Target
and physically
accessible
Uncertain
Target
but not
sampleable
List of
candidate
lakes
to be visited
for sampling
Permission
Granted?
Nontarget
Select next available oversample lake for evaluation
OBTAIN ACCESS PERMISSION
Target
but not
sampleable
Select next
available
oversample
lake for
evaluation
Figure 1. Evaluating a lake.
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1 m?
Q3
GIS evaluation status
Q4
> 1000 m2 of open water?
Q2
Does the lake meet any nontarget criteria?
Figure 2. Process Flow of the Lake Evaluation Spreadsheet.
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2.3 GIS-based Evaluation (Q1-Q3)
Figure 3 presents an overview of the GIS-based phase of lake evaluation. At this phase, evaluate all base
lakes on each State list (i.e., those with PANEL17= NLA17)07RVT2, NLA17_07RVT, NLA17_12RVT2,
NLA17_12RVT, and NLA17_17). In addition to the two shape files provided by EPA (NLA 2017 site points
and lake polygons), the GIS-based phase makes use of two ESRI map service layers loaded in ArcMap®: a
background United States Geologic Survey (USGS) topographic map service and a map service of world
imagery from ESRI loaded as layer files in ArcMap®. Examine each lake point (and polygon)) in ArcMap®
using background topographic maps and imagery. Use the procedure presented in Section 2.3.1 to
attempt to answer the questions in the evaluation spreadsheet file (see Figure 2) based on just these
layers in ArcMap®. The GIS-based phase is designed primarily to address questions Q1 and Q2 of the
evaluation questionnaire (Figure 2). All lakes evaluated during the GIS phase are assigned a GIS status
(Q3 of the questionnaire).
The intent of the GIS phase is to reduce the number of candidate lakes that must be reviewed in more
detail during the Desktop and Field phases of the evaluation. Ideally, decisions will be made quickly for
the vast majority of lakes based on background topographic maps and imagery alone. For any lake in the
initial list of base lakes to which you cannot definitively assign a GIS status of Candidate target or Non-
target, assign a GIS status of Uncertain. Lakes with GIS status of Candidate target and Uncertain are
moved to the Desktop phase of the evaluation process. For lakes that have been sampled previously (in
2007 and/or 2012) and for large, named lakes, the GIS review should be very fast. For "new" lakes being
sampled for the first time in 2017, and for smaller lakes and unnamed lakes, responding to the
evaluation questionnaire will likely take more time and there may be more lakes assigned to a GIS status
of Uncertain.
The GIS phase also identifies instances where the lake polygon as rendered in the NLA lake polygon
shape file does not match up with the lake shape depicted on either the image and/or the topographic
map. Examples include:
1) where part of a lake (an arm or other embayment) is not represented within the lake polygon;
2) where part of a lake is not represented by a polygon because of a bridge or causeway; or
3) a single polygon encompasses more than one lake.
These inconsistencies may be due to mapping or delineation errors in NHDPIus that have not been
corrected in the NLA sampling frame, or to more recent changes in basin morphology as a result of
precipitation patterns. In the case of the latter, it may not become evident until the desktop evaluation
(Section 2.4) or even later (i.e., when you visit the lake to sample it). If you encounter one of these
errors during the GIS evaluation (Qlb of the evaluation questionnaire), notify Marc Weber of the NLA
design staff at WED-Corvallis so the error can be corrected in the sample/analysis frame, and then
proceed with evaluating the lake. These errors affect the sampling frame in two ways: they result in an
incorrect delineation of the catchment, and, in the case of a single polygon representing more than one
lake, they might impact the weighting factor.
Ephemeral lakes that are expected to be dry during the index period (May through September) of the
sampling year are not part of the target population. Coastal lakes, or lakes near an estuary that are
under tidal influence, are not part of the target population. A tidally-influenced lake is operationally
defined as being maintained solely by the surface inflow of brackish or salt water due to water level
changes during tidal cycles. Permanent lakes near the coast, or near an estuary below the head of salt,
with no surface connection to the ocean at high tide are considered part of the target population (even
if saline). Dune lakes (primarily located along the Gulf Coast), are part of the target population. These
lakes are permanent and almost always isolated from the ocean, but periodically will flood or "blow
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out," forming a connection with the ocean or estuary and incur an influx of brackish or salt water.
Waterbodies along the coast that are considered to be estuarine or part of a larger coastal wetland area
are not part of the target population. Inland lakes that are saline or have high conductivity (> 1000
piS/cm @ 25 °C) are part of the target population (the Great Salt Lake has already been excluded as part
of the survey design). Oxbows are considered target lakes if they are completely separated from a river
(no surface connection). However, oxbows that have either flowing water or a wetland connection to a
river are not lakes, and should be assigned a GIS evaluation status (Q3) of Nontarget. Side-channel
reservoirs and drinking water reservoirs (where water is pumped from nearby rivers, termed upground
reservoirs in some parts of the US) that do not have recreation or aquatic life uses are not considered
part of the target population. Abandoned mine lakes used for recreation or other beneficial uses (e.g.,
wildlife) are considered to be part of the target population.
The GIS-based phase (Section 2.4) will likely not provide definitive information to address whether a
candidate lake is ephemeral, has sufficient open water, or a maximum depth of at least 1 m, especially
for smaller lakes. You can attempt to use the surrounding topography to make these determinations - if
there is not much relief, chances are it will not be very deep. Do not answer the open water or lake
depth questions (Q4 and Q5), or conclude the lake is ephemeral, unless you are sure that a Yes or No
response applies based on the available imagery for the lake. Lakes that are assigned a status of
Uncertain during the GIS evaluation phase are further evaluated as part of the Desktop evaluation phase
of the evaluation process.
2.3.1 Lake Evaluation using GIS Layers and Imagery
This procedure describes the GIS phase of the evaluation process that will be conducted by the states. If
questions come up, contact Marc Weber (541-754-4469) or Dave Peck (541-754-4426).
From the NLA 2017 SharePoint Maps folder, download 'NLA_GIS_files_2017.zip' to the folder of your
choice. Right-click the zip file and click 'WinZip' 'Extract to Here'. You'll then see three folders and one
map package (.mpk).
If you are familiar with working in ArcGIS, double-click the 'NLA_Design_Sites_for_Evaluation.mpk'. This
will open an ArcMap project that includes all NLA sites and design polys, as individual state layers.
Expand the 'Base', 'Oversample' and 'Design Polys' group layers, by clicking the plus sign next to the
names. Then scroll down until you see the appropriate state. Click the plus sign next to the chosen state.
You'll then see the symbol used for the layer. Click the check box next to the layer to make it visible.
To zoom to your state, right-click the desired state layer and choose 'Zoom to Layer'.
To utilize Google Earth in reviewing the NLA GIS files, use the .kmz files in the three folders: 'Base_KMZ',
'Oversample_KMZ' and 'Design_Polys_KMZ'. Double-clicking on any of the state files within these
folders will launch Google Earth (if you already have the software installed). Once Google Earth is open,
additional .kmz files can be dragged into the interface from Windows Explorer. Locate the 'Places' pane
on the left side of Google Earth and expand the .kmz layer you're viewing by clicking on the triangle next
to the layer. Next, click on the triangle next to the layer below the .kmz layer. This will list the features
within the layer by 'NLA17JD'. Clicking on any of these links in the 'Places' pane will bring up a pop up
of the layer's attributes. Double-clicking on any of these links in the 'Places' pane will pan and zoom to
that specific feature.
Then
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1. Open the NLA 2017 Lake Evaluation Spreadsheet available on the NARS SharePoint
(NLA_2017_LAKE_EVAL_FORM_20160517.xlsx, or the corresponding State workbook if not
being done centrally).
a. The worksheet has key variables from the shape file, sorted in the same order
b. The evaluation questionnaire begins with the column labeled Ql. Is Waterbody a Lake?
2. For each State, evaluate all lakes in each base panel using just the imagery provided in ArcMap®
Evaluate lakes in order, looking at lakes in ArcMap® and filling in columns in the spreadsheet. All
of the evaluation questionnaire columns have drop down lists for entries.
3. The GIS evaluation involves answering the first 2 questions of the lake evaluation questionnaire
and assigning a status of Nontarget, Candidate Target, or Uncertain as Q3 of the evaluation.
a. If the polygon for the lake from the NLA lake polygon shape file does not match up with
the lake outline as shown on either the imagery or the topographic map, notify Marc
Weber so corrections can be made to the shape file and sampling frame.
4. If you can determine a final status of Nontarget (e.g., a nontarget evaporation pond), assign the
appropriate responses to Q3, Q9 and Q10 of the evaluation questionnaire and proceed to
evaluate the next site on the list.
5. If the responses to questions Ql and Q2 indicate that the lake is a candidate target lake, or you
cannot determine its status, assign a GIS status (Q3) of Candidate Target or Uncertain,
respectively. Proceed to the next lake on the list. Lakes categorized as Candidate Target or
Uncertain will be evaluated further during the Desktop phase.
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List of candidate sites
(base and replacement) from survey design
Is waterbody a
lake?
YES
NO
Does NLA polygon
match lake shape?
YES
NO
Does lake name
match NHD name?
YES
CANNOT
DETERMINE
NO
Target
Lake?
YES
Determine and
assign lake origin
(if possible)
Assign final
status of
Nontarget
Desktop Evaluation
Select next
lake
Add name to
spreadsheet
GIS Status=
Nontarget
GIS Status=
Uncertain
GIS Status3
Candidate Target
Notify NLA
Design Team
(ORD-Corvallis)
NOTE: State sample size and lake list includes Tribal lakes.
y which may require separate evaluation and sampling J
Base panel list of candidate lakes for a State
{~50 lakes per State)
Figure 3. GIS-based evaluation.
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2.4 Desktop Evaluation (Q2, Q4-6)
Continue the second phase of the evaluation process to complete the evaluation questionnaire for any
remaining lakes assigned an interim status of Uncertain during the GIS-based phase, and to continue to
complete the evaluation for candidate lakes during the GIS phase. For the desktop evaluation, the
master evaluation file will be split into separate files for each state. The general process for conducting
the desktop phase is presented in Figure 4. Use a variety of available information sources to proceed
through the evaluation questionnaire (Figure 2). Google Earth® and other ancillary layers (e.g.,
Wikipedia®, Panoramio® photos, geographic features, etc.) may provide sufficient information to answer
all of the questions in the evaluation questionnaire successfully. A Google Earth® kmz (or kml) file of all
lake polygons will be made available.
In addition to Google Earth®, conduct Web searches for each remaining lake based on the lake name or
location information to try to answer the questions in the evaluation questionnaire and assign a final
status category for each lake. Some lakes may require an investigation of maps, reports, or
conversations with local experts who are familiar with the current conditions of the lake being
evaluated. Obtaining information from local experts will help to minimize the number of lakes that will
require a field visit. If possible, determine the lake origin using these resources. For a run-of the river
reservoir, it is important to determine if the estimated residence time is greater than 1 week; if less, it is
considered to be nontarget and requires replacement.
For the NLA, the status of a lake is that existing in the year (and ultimately on the day) of sampling.
There will be lakes (more likely smaller ones) that will meet the target criteria one year but not meet
them in another year due to precipitation (or lack of) or other natural causes. Temporary changes to a
lake's status due to deliberate management/restoration activities (e.g., weed control, rotenone
application, dredging, etc.) do not render a lake as nontarget for that year. Criteria pertaining to open
water area and maximum depth may not be able to be determined until you actually visit the lake to
sample. Note that the open water criterion is based on a total area of 1000 m2; and does not have to be
continuous.
In some areas, there is the possibility that neighboring lake basins may become joined during periods of
heavy precipitation, and this will be evident from the available images. In these cases, treat the
combined lakes as a single waterbody and sample it if it meets the target criteria. Do not just consider
the part of the lake represented by the NLA polygon. Note the presence of the combined waterbodies
and the reason (e.g., is it temporary or does it appear to be a permanent change). Notify the NLA design
staff in Corvallis so that the sample/analysis frame can be adjusted if necessary.
There is also the possibility that a single lake may become divided into two or more neighboring basins
because of drought conditions. You must look at the NLA polygon coverage and determine which basin
has the NHDPIus labeling point associated with it and treat this basin as the "official" lake for the
purposes of evaluating and sampling in 2017. If the basin meets the target criteria, sample it (but not
any of the neighboring basins). If the basin does not meet the target criteria, assign it as non-target and
select a replacement lake. In either case, note the presence of the separated waterbodies and the
reason (e.g., is it temporary or does it appear to be a permanent change). Notify the NLA design staff in
Corvallis so that the sample/analysis frame can be adjusted if necessary. Lakes on Tribal lands require
some additional considerations. Tribal lakes are included as parts of individual state lists (and are part of
the total sample size assigned to the state). Tribal lakes need to be evaluated by someone (the Tribal
nation, EPA Region, State, or a third party), and a final status assigned. For lakes identified as target,
distinguish between those lakes where no permission to sample was ever sought (Tribal-Other), from
lakes where permission was requested from a Tribal nation, but was not granted (Target-Access denied).
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At this phase of the evaluation, you should begirt to compile a dossier of access-related information for
each lake that has been definitively identified as target and accessible. This information includes any
issues associated with accessing the lake such as steep terrain; livestock; thick, nuisance vegetation-
locked gates and the presence and type of boat ramps available at a lake. You can obtain some of this
information from a local expert during the Desktop phase, from the Field evaluation (if needed), or
when you attempt to obtain permission to sample a lake (Section 4.0). Lakes that are still assigned a
status of Uncertain after the Desktop evaluation phase are moved to the Field evaluation phase of the
evaluation process.
0)
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o
L_
Q_
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o
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LU
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Base panel list of remaining
candidate lakes for a State or Tribe
(GIS Status assigned)
NOTE: State sample size and lake list includes Tribal lakes,
which may require separate evaluation and sampling
List of oversample lakes
for a State or Tribe
(GIS Status not assigned)
i
Desktop Evaluation (EPA Regions/States/Tribes)
Select next
available
oversample lake
GIS Status
Not assigned
GIS Status=
Candidate Target
GIS Status
Uncertain
Target
Lake?
Status=
Nontarget
yes / Physically
Accessible?
CANNOT
DETERMINE
Final status3
Target-
Inaccessible
CANNOT
DETERMINE
Status=
Uncertain
Respond to
questions
in GIS
evaluation
Field
Evaluation
Determine and
assign lake origin
(if possible)
Status=
Target
If mismatches between
images and NLA
polygon are discovered
Notify NLA Design
Team (ORD-Corvallis)
Obtain
Access
Permission
Assign final
status of
Nontarget
14
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Figure 4. Desktop evaluation.
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2.5 Field Evaluation (Q2, Q4-6)
Continue the third phase of the evaluation process to complete the evaluation questionnaire for any
remaining lakes assigned an interim status of Uncertain during the Desktop phase. The general process
for conducting the Field phase is presented in Figure 5. The field evaluation phase differs from previous
phases in that lakes whose status is still uncertain after a field visit are considered candidate target
lakes. The final status of these lakes may not be determined until a field crew actually visits the lake with
the intent to sample it.
Get as close as you can to the lake during a field visit. For remote lakes, this may require hiking to, or
possibly flying over, the lake. For other lakes, you may be able to drive near the lake and use binoculars
to conduct the evaluation. Determine the lake origin during the field visit if it has not been determined
in a previous phase. While at the lake, remember to gather information that will be useful to a field crew
when they come to sample it (e.g., launch facilities, surrounding terrain, best access routes, etc...).
After completing the field evaluation phase, you will have a list of candidate lakes that are physically
accessible. The last phase of the process involves obtaining access permission for those lakes that
require it.
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List of candidate lakes for a State or Tribe
Status after GIS and Desktop phases=
Uncertain
List of oversample lakes
for a State or Tribe
(Status not assigned)
NOTE: State sample size and lake list includes Tribal lakes,
which may require separate evaluation and sampling
Field Evaluation EPA Regions/States/Tribes
Select next
available
oversample lake
Status=
Not assigned
Status=
Uncertain
Target
Lake?
Respond to
questions
in GIS
evaluation
Status=
Nontarget
YES OR
CANNOT
DETERMINE
Final
status=
Target
Inaccessible
Physically \N9
Accessible?
Desktop
Evaluation
YES OR
CANNOT
DETERMINE
Determine lake origin
(if possible)
Status=
Candidate Target
Request
Access
Permission
Assign final
status of
Nontarget
Figure 5. Field evaluation.
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3 Determining if a Lake is Physically Accessible (Q6)
Lakes for the National Lakes Assessment were selected from the population of lakes across the U.S.
through a probabilistic survey design. In order to achieve the most robust results possible with the
probabilistic sampling design, a concerted effort is required to sample the base lakes on your list.
It is very important not to reject a lake that meets the criteria for the target population based on
inconveniences in access. At some lakes, a field crew can drive its truck to a boat ramp and launch.
Other lakes may require a lengthy hike or portage with a small boat. Some lakes in extremely remote
areas are impossible to safely access (e.g., trail conditions, temperature extremes). A lake is considered
permanently inaccessible if it is unlikely to be sampled by anyone due to physical barriers that prevent
access (e.g., cliffs). Safety concerns that may prohibit access include the presence of dangerous wildlife
or potentially threatening groups of people.
Physically inaccessible lakes may be target lakes.
3.1 Target, Inaccessible-Barrier/Safety
Occasionally, a lake is determined to be target, but cannot be sampled due to physical barriers or safety
concerns. Assign these lakes a response of NO to Q6, Target to Q9, and Inaccessible-Barrier/Safety to
Q10 (Figure 2). Describe why the lake is inaccessible in the COMMENTS column of the evaluation
spreadsheet. You will then need to select and evaluate a replacement lake.
3.2 Target, > 1 Day Needed
Very large lakes may require either more than one day to sample completely (including travel time), or
require more than one field crew to complete the sampling in a single day (including shoreline stations.
Assign these lakes a response of YES, BUT> 1 DAY/CREW NEEDED to Q6 (Figure 2). If you determine that
these lakes cannot be sampled, assign a response of Target to Q9 and a final status of Target Other for
Q10. Remember that on large lakes (>10,000 ha), shoreline stations are not established, so these lakes
should be sampled at the index site if at all possible.
3.3 Target, Extreme Effort Required, Inaccessible-Effort
Some remote lakes may be physically accessible, but the effort required to reach them to sample is
prohibitive in terms of the time and or cost required, or because an extreme effort (in terms of time
and/or cost), as opposed to inconvenience, is required to obtain access. Assign these lakes a response
of YES, BUT EXTREME EFFORT IS REQUIRED to Q6, Target to Q9, and Inaccessible-Effort to Q10 (Figure
2). Describe the extreme effort constraint (i.e., the time or cost that would be needed) in the
COMMENTS column of the evaluation spreadsheet. You will then need to select and evaluate a
replacement lake.
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4 Obtaining Permission to Access Candidate Lakes (Q7)
Many of the lakes will be publicly accessible with either boat ramps or convenient small boat access. In
these cases, explicit permission to access the lake is not needed and little prior work needs to be done
outside of determining the best access routes for the sampling crew. However, for those lakes on
privately owned land, landowner permission is required to obtain access and sample these lakes.
Obtaining permission well in advance of the sampling day is important to minimize loss of time on the
part of the field team. Many states have an existing protocol for securing landowner permission; if this is
the case for your state, use the existing protocol for this study.
4.1 Identify Landowner
The initial lake list file contains an initial assignment of ownership as federal (and which agency has
jurisdiction), non-Federal, or possibly Tribal. For non-Federal ownership, determine whether the lake is
publicly accessible or located on private property. If the lake is on private property, you will need to
obtain the name and address of the landowner. Some states or EPA Regions may provide you with
additional identification of public versus private lakes and some landowner information. If no landowner
information was obtained for a lake, contact the county office. The county office can direct you to the
agency that is responsible in your state/county for holding landowner records, and you can work with
the appropriate agency to obtain the information.
Be aware that this process can be time consuming, as you may need to work with several different
agencies and numerous people. Be prepared to submit maps via fax machine, as some counties do not
have landowner information in a GIS database and are unable to use coordinates to obtain the
information. In addition, if your state or county uses the township/range/section system for identifying
parcels of land, you will need to know this information for your lake also, and this may require
contacting yet another agency. You may need to visit the records office to obtain this information. Each
county will be different in terms of the organization of its records and its ability (and willingness) to
assist you.
4.2 Request Permission to Access Lake
Once you identify the landowner and confirm that a lake is part of the target population and is physically
accessible, you can begin to request permission to access and sample the lake following whatever
protocol is in effect for your organization. If no protocol exists, use the most personal contact
practicable. Obtaining permission (or denial) early does provide you with more time to select and
evaluate any replacement lakes before sampling begins.
4.2.1 Contact Landowner through In-Person Visit (when possible)
The initial contact with the landowner is best done through an "in-person" visit. You can ask a local
representative (e.g., state or county official, NRCS county agent, district fish and game biologist, etc.) to
make the initial contact. These people are usually more familiar with landowners in their jurisdictions,
and are usually more effective at getting access permission than a federal agent or a contractor. You can
also make the initial contact as part of the field evaluation for those lakes that require one. This visit
provides an opportunity to explain the purpose of the study, answer any questions or concerns a
landowner may have, and obtain written permission to access the lake during the sampling season,
which could be a part of the field evaluation. Landowners are much more likely to grant permission if
they actually meet and speak with a study representative instead of receiving a phone call or letter.
Note: With advanced planning, it may be possible to schedule landowner visits during other
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fieldwork in the area that is occurring before the NLA sampling begins. This would maximize
efficiency and ensure the best possible responses from the landowners.
4.2.2 Contact Landowner through Other Means
If you cannot visit the landowner to obtain permission, attempt to contact him or her by telephone. A
local representative may be more effective in securing permission, so it is important to request
assistance at this level if you are not local to the area. If you cannot reach the landowner by telephone,
prepare and mail out a cover letter (Appendix A: Example Letter requesting Permission to Access a
Lake) with an updated fact sheet (
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Appendix D: National Lakes Assessment 2017 Fact Sheet) and a permission slip (Appendix B: Example
Landowner Permission Slip) for the landowner to return.
4.2.3 Signed Permission Slip
A signed permission slip is important for the field crew to use as documentation on the day of sampling
if questions arise about the field crew's presence on a lake.
4.3 Denials
If one landowner denies access, check to see if there are other landowners that may allow access to the
lake via their property. If no other landowner options exist, or all other landowners deny access, select
NO as the response to Q7, Target as the response to Q9, and Access Denied as the response to Q10 in
the evaluation spreadsheet (Figure 2). Select the next available replacement lake to evaluate. For
landowners contacted by phone or mail, no response is considered denial.
4.4 Frequently Asked Questions
Some frequently asked questions pertaining to the overall evaluation process are presented in Appendix
F: Frequently Asked Questions. Use this as the first resource to try to answer any questions that may
come up as you attempt to evaluate a lake. If you cannot find an answer there, contact the EPA NLA
Regional Coordinator (Appendix E: Contacts). He or she will either answer your question or pass it along
to someone who can answer it.
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5 Literature Cited
Stevens, D. L., Jr. and A. R. Olsen. 2004. Spatially balanced sampling of natural resources. Journal of the
American Statistical Association 99:262-278.
USEPA (United States Environmental Protection Agency). 2012. Survey of the Nation's lakes: lake
evaluation guidelines. EPA 841-B-11-003, U.S. Environmental Protection Agency, Office of Water
and Office of Environmental Information, Washington, DC.
USEPA (United States Environmental Protection Agency), in prep. National Lakes Assessment: a
collaborative survey of lakes in the United States. EPA 841-R-16-004, U.S. Environmental
Protection Agency, Office of Water and Office of Research and Development, Washington, DC.
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Appendix A: Example Letter requesting Permission to Access a Lake
(Date)
Dear Landowner,
The US Environmental Protection Agency, in cooperation with State Agencies, is conducting an
environmental assessment of lakes across the United States. A computer was used to randomly select
these lakes. A total of 910 sampling lakes were selected for sampling in 2017. Water quality, chemistry,
aquatic life, recreation use and habitat will be evaluated at each lake. The findings of the study will be
used to give a broad scale picture of the health of our nation's lakes and are not intended for
enforcement or regulatory purposes.
We are contacting you to request your permission to access a lake from your property. The sampling of
your lake will be used to help guide the protection of waters across the United States. We will respect
your landowner rights at all times, ensure that you know in advance when the sampling will occur, and
recognize that access to your property is a privilege granted by you..
Enclosed with this letter is a map of the sampling location and an Access Permission Form. Please return
the completed Form in the enclosed, postage paid envelope by (DATE). If you have any questions
concerning this request, please feel free to contact me at (phone / e-mail). I look forward to your reply
and appreciate your help in this important survey.
Sincerely,
(Name)
Regional Monitoring Coordinator
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Appendix B: Example Landowner Permission Slip
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I grant permission to the biological field crew from (state agency or contractor) to access the lake
sampling lake located on my property as part of the EPA's National Lakes Assessment project.
Do grant permission
Do grant permission but with the following restrictions:
Do not grant permission
Landowner Name (Please print):
Landowner Signature:
Date:
Phone Number:
Address:
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Appendix C: National Lakes Assessment 2017 Survey Design
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National Lakes Assessment 2017 Survey Design
Target Population
All lakes, reservoirs, and ponds within the 48 contiguous United States greater than 1 hectare in surface
area that are permanent waterbodies. The word "lake" in the remainder of this document includes
lakes, reservoirs and ponds. Lakes used for aquaculture, disposal-tailings, sewage treatment,
evaporation, or other unspecified disposal use are excluded.
Survey Design
A Generalized Random Tessellation Stratified (GRTS) survey design for a finite resource was used with
stratification and unequal probability of selection defined below.
Stratification
The survey design is stratified by state.
Panels
The survey design has five base panels:
• NLA17_07RVT2 - Panel of lakes originally sampled twice in NLA 2007, were also sampled in NLA
2012 and will be sampled twice in NLA 2017. Note that these lakes will be sampled twice again
in NLA 2022.
• NLA17_07RVT - Panel of lakes originally sampled once in NLA 2007, were also sampled in NLA
2012 and will be sampled once in NLA 2017. Note that these lakes will be sampled again in NLA
2022.
• NLA17_12RVT2 - Panel of lakes originally sampled twice in NLA 2012 and will be sampled twice
in NLA 2017. Note that these lakes will be sampled twice again in NLA 2022 and in NLA 2027.
• NLA17_12RVT - Panel of lakes originally sampled once in NLA 2012 and will be sampled once in
NLA 2017. Note that these lakes will be sampled again in NLA 2022 and in NLA 2027.
• NLA17_17 - Panel of new lakes to be sampled once in NLA 2017. Note that these lakes will be
sampled again in NLA 2022 and in NLA 2027.
The survey design has four Over Sample panels:
• NLA17_07RVT_OverSamp - Over sample lakes to be used as replacements for NLA17_07RVT
lakes when they cannot be sampled for any reason.
• NLA17_12RVT2_OverSamp - Over sample lakes to be used as replacements for NLA17_07RVT2
lakes when they cannot be sampled for any reason.
• NLA17_12RVT_OverSamp - Over sample lakes to be used as replacements for NLA17_12RVT
lakes when they cannot be sampled for any reason.
• NLA17_17_OverSamp - Over sample lakes to be used as replacements for NLA17_17 lakes
when they cannot be sampled for any reason.
• Note that no lakes where available for NLA17_07RVT2 over sample lakes.
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Unequal Probability Categories
Unequal probability categories were used in the NLA 2007 and NLA 2012 survey designs. The
documentation for those survey designs should be consulted for their definition. For the NLA17_17 new
lake design, unequal probability categories were defined based on lake area: 1 to 4 ha, 4 to 10 ha, 10 to
20 ha, 20 to 50 ha and greater than 50 ha.
Expected Sample Size
In NLA 2017 904 lakes will be sampled; and 96 of the lakes will be sampled twice for a total of 1000 lake
visits. The 904 lakes consist of three sets of lakes. The first set are 226 lakes that were originally
sampled in NLA 2007, resampled in NLA 2012 and will be resampled again in NLA 2017. Of these 43
lakes will be sampled twice in NLA 2017. The second set are 218 lakes originally sampled in NLA 2012
and will be resampled again in NLA 2017. Of these 53 lakes will be sampled twice in NLA 2017. The
third set are 460 new lakes that will be sampled for the first time in NLA 2017. The intent is to have four
main NLA panels with 226 lakes each for a total of 904 lakes: NLA07_TS4, NLA12_TS4, NLA17_TS4 and
NLA22_TS4. Each panel name designates the year the panel is first sampled, that it consists of lakes that
were sampled and that the lakes will be sampled for 4 NLA cycles. That is, NLA07_TS4 will be lakes
sampled in 2007, 2012, 2017 and 2022 and NLA12_TS4 will be lakes sampled in 2012, 2017, 2022, and
2027.
For the NLA17_17 new lake design, the expected number of lakes in each of the five lake area categories
was approximately 90 lakes. Based on NLA experience with lake evaluations in 2007 and 2012, an
adjustment was made to achieve approximately 90 target and sampled lakes in each category. The
number of lakes expected in the five categories were multiplied by 8, 4, 3, 2 and 2. That is, 720, 360,
270, 180 and 180 lakes for 1 to 4ha, 4 to 10 ha, 10 to 20 ha, 20 to 50 ha and >50 ha categories. The first
90 of these were then designated to be "base" and the remaining designated at "Over Sample".
Additional over sample lakes were selected to provide sufficient lakes for states who implement a state-
level design and for new lake panel in the NLA 2022 design.
State Level Assessments
Minnesota and New Hampshire will do state level assessments. Both states provided their state sample
frame. Minnesota sample frame is NHD High Resolution sample frame. It was combined with NLA 2017
sample frame where SOURCE variable identifies whether lake in sample frame is in NLA 2017 sample
frame or in additional lakes in Minnesota sample frame. New Hampshire sample frame is state specific
to meet their state law requirements. It was combined with NLA 2017 sample frame where SOURCE
variable identifies whether lake in sample frame is in NLA 2017 sample frame in additional lakes in New
Hampshire sample frame. Note that this results in some lakes less than 1 ha in area.
Minnesota will sample 50 lakes for state level assessment using NLA 2017 field protocols as well as
Minnesota field protocols if protocol differs. An additional 100 lakes will be sampled using Minnesota
field protocols. New Hampshire will sample required 11 lakes using NLA 2017 field protocols and an
additional 39 lakes using New Hampshire field protocols.
Lake Use and Replacement
Each lake selected to be sampled is given unique site identification (NLA17JD, formerly named sitelD).
Site numbers consist of NLA17_ST-nnnnn where ST is two letter state code and nnnnn is a number
between 10001 and 99999. It is critical this lake ID be used in its entirety to make sure that the lakes are
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correctly identified. Lakes evaluated for potential sampling must have all NLA17JD s from the largest to
the lowest number evaluated within a state and within an NLA17_PNL level (see figure as well):
• Within a state, lakes in panel NLA17_07RVT2 must all be evaluated and sampled if possible.
There is no NLA17_07RVT2_OverSamp panel. If a lake in the panel cannot be sampled, then the
lowest NLA17JD available within the state from NLA17_07RVT_OverSamp must be evaluated.
If all lakes in NLA17_07RVT_OverSamp have been used, then the lowest NLA17JD available
within the state from NLA17_12RVT2_OverSamp must be evaluated.
• Within a state, lakes in panel NLA17_07RVT must all be evaluated and sampled if possible. If a
lake in the panel cannot be sampled, then the lowest NLA17JD available within the state from
NLA17_07RVT_OverSamp must be evaluated.
• Within a state, lakes in panel NLA17_12RVT2 must all be evaluated and sampled if possible. If a
lake in the panel cannot be sampled, then the lowest NLA17JD available within the state from
NLA17_12RVT2_OverSamp must be evaluated. If none are available within
NLA17_12RVT2_OverSamp, then lakes in panel NLA17_12RVT_OverSamp must be evaluated.
• Within a state, lakes in panel NLA17_12RVT must all be evaluated and sampled if possible. If a
lake in the panel cannot be sampled, then the lowest NLA17JD available within the state from
NLA17_12RVT_OverSamp must be evaluated. If a lake in the panel cannot be sampled, then the
lowest NLA17JD available within the state from NLA17_17_OverSamp must be evaluated.
• Within a state, lakes in panel NLA17_17 must all be evaluated and sampled if possible. If a lake
in the panel cannot be sampled, then the lowest NLA17JD available within the state from
NLA17_17_OverSamp must be evaluated.
Since the lakes in NLA17_07 and NLA17_12 panels have been sampled previously, the expectation is that
most of them will be available to be sampled again in 2017. Lakes in the new NLA17_17 panel have not
previously been evaluated so the expectation is that many of them will not be able to be sampled;
hence increasing the number lakes that must be evaluated to meet the sample size requirements.
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NLA17 07RVT
NLA17 17
NLA17 12RVT
NLA17 12RVT2
NLA17 07RVT2
N LA17_17_OverSam p
N LA17_12RVT_OverSam p
N LA 17_12 RVT2_OverSam p
N LA17_07 RVT_Ove rSam p
Secondaryoversamplelist(useif primarylistof
oversample lakes have all been evaluated
For Minnesota and New Hampshire, the lake replacement will follow the above process. In additional
lakes in NLA17_12RVT_MN lakes will be replaced with NLA17_12RVT_MN_OverSamp lakes.
Sample Frame
The sample frame was derived from the National Hydrography Dataset (NHD). Sample frames for NLA
2007 and 2012 designs were based on NHDPIus and are documented as part of those designs. Note that
updates to the sample frame were made based on lake evaluations from those surveys. That updated
sample frame was combined with NHD High Resolution lakes with lake areas from 1 to 5 ha. This was
done to rectify the known deficiency in NHDPIus for small lakes due to the 1:100,000 scale mapping.
Lakes that were in NHD High Res that were also in NHDPIus were eliminated. The NLA 2017 sample
frame preserves the lake polygons from prior surveys while improving the coverage for small lakes.
Once the initial shape file that included all lake objects in NHD was prepared additional attributes were
created to identify lakes included in the sample frame and other properties used to construct the survey
design. First, lakes that were less than or equal to 1 hectare were excluded.
Lakes included were DES FTYPEs:
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Lake/Pond
Lake/Pond: Hydrographic Category = Perennial
Lake/Pond: Hydrographic Category = Perennial; Stage = Average Water Elevation
Lake/Pond: Hydrographic Category = Perennial; Stage = Date of Photography
Lake/Pond: Hydrographic Category = Perennial; Stage = Normal Pool
Lake/Pond: Hydrographic Category = Perennial; Stage = Spillway Elevation
Lakes excluded were:
Estuary
Playa
Swamp/Marsh
Lake/Pond: Hydrographic Category = Intermittent
Lake/Pond: Hydrographic Category = Intermittent; Stage = Date of Photography
Lake/Pond: Hydrographic Category = Intermittent; Stage = High Water Elevation
Reservoir
Reservoir: Construction Material = Earthen
Reservoir: Construction Material = Nonearthen
Reservoir: Reservoir Type = Aquaculture
Reservoir: Reservoir Type = Cooling Pond
Reservoir: Reservoir Type = Disposal
Reservoir: Reservoir Type = Disposal; Construction Material = Earthen
Reservoir: Reservoir Type = Evaporator
Reservoir: Reservoir Type = Evaporator; Construction Material = Earthen
Reservoir: Reservoir Type = Tailings Pond
Reservoir: Reservoir Type = Tailings Pond; Construction Material = Earthen
Reservoir: Reservoir Type = Water Storage
Reservoir: Reservoir Type = Water Storage; Construction Material = Earthen; Hyd*
Reservoir: Reservoir Type = Water Storage; Construction Material = Nonearthen
Reservoir: Reservoir Type = Water Storage; Hydrographic Category = Perennial
Reservoir; Reservoir Type = Treatment"
Next lakes were excluded that were evaluated during the NLA 2007 and were identified as lakes that did
not meet definition of a lake for NLA 2017. These were lakes with evaluation codes of Lake_Saline,
Lake_Shallow, Lake_Special_Purpose, Lake_Vegetated, Non_Target, or Not_Lake".
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Lake Selection and Sample Frame Summary
See accompanying spreadsheet NLA2017 Design Summary 20160215.xlsx
Evaluation Process
The survey design weights that are given in the design file assume that the survey design is implemented
as designed. Typically, users prefer to replace sites that cannot be sampled with other sites to achieve
the sample size planned. The site replacement process is described above. When sites are replaced, the
survey design weights are no longer correct and must be adjusted. The weight adjustment requires
knowing what happened to each site in the base design and the over sample sites. EvalStatus is initially
set to "NotEval" to indicate that the site has yet to be evaluated for sampling. When a site is evaluated
for sampling, then the EvalStatus for the site must be changed. Recommended codes are:
EvalStatus Code
Name
Meaning
TS
Target Sampled
Site is a member of the target population and was sampled
LD
Landowner Denial
Landowner denied access to the site
PB
Physical Barrier
Physical barrier prevented access to the site
NT
Non-Target
Site is not a member of the target population
NN
Not Needed
Site is a member of the over sample and was not evaluated for
sampling
Other codes
Many times it is useful to have other codes. For example, rather than
use NT, may use specific codes indicating why the site was non-target.
Statistical Analysis
Any statistical analysis of data must incorporate information about the monitoring survey design. In
particular, when estimates of characteristics for the entire target population are computed, the
statistical analysis must account for any stratification or unequal probability selection in the design.
Procedures for doing this are available from the Aquatic Resource Monitoring Web page
http://www.epa.gov/nheerl/arm. A statistical analysis library of functions is available from the Web
page to do common population estimates in the statistical software environment R.
For further information, contact:
Anthony (Tony) R. Olsen
USEPA NHEERL
Western Ecology Division
200 S.W. 35th Street
Corvallis, OR 97333
Voice: (541) 754-4790
Fax: (541) 754-4716
Email: Olsen.Tony@epa.gov
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Appendix D: National Lakes Assessment 2017 Fact Sheet
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In development
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Appendix E: Contacts
Title
Name
Contact Information
EPA HQ Project Lead
Amina Pollard, OW
oollard.amina(® eoa.gov
202-566-2360
EPA Wetlands, Oceans, and
Watersheds
1200 Pennsylvania Ave NW (4503T)
Washington, DC 20460
EPA HQ NARS QA Lead
Sarah Lehmann, OW
lehmann.sarah(® eoa.gov
202-566-1379
EPA Wetlands, Oceans, and
Watersheds
1200 Pennsylvania Ave NW (4503T)
Washington, DC 20460
EPA HQ Logistics Lead
Colleen Mason, OW
mason. colleen(® eoa.gov
202-343-9641
EPA Wetlands, Oceans, and
Watersheds
1200 Pennsylvania Ave NW (4503T)
Washington, DC 20460
EPA ORD Site Evaluation
Coordinator
Dave Peck, ORD
peck.david@epa.gov
541-754-4426
Marc Weber, ORD
weber.marc@epa.gov
541-754-4469
Contract Field Logistics
TBD
Coordinator
NARS Information Management
Marlys Cappaert, SRA
caooaert.marlvs(® eoa.gov
Coordinator
International Inc.
541-754-4467
541-754-4799 (fax)
EPA Regional NLA Coordinators
Hilary Snook, Region 1
snook. hilarv(® eoa.gov
617-918-8670
EPA Region 1
11 Technology Drive
North Chelmsford, MA 01863
Jim Kurtenbach, Region 2
kurtenbach.iames(® eoa.gov
732-321-6695
EPA Region 2
2890 Woodbridge Avenue
Edison, NJ 08837
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Title Name Contact Information
Frank Borsuk, Region 3
borsuk.frank(® eoa.gov
304-234-0241
EPA Region 3
1060 Chapline Street, Suite 303
Wheeling, WV 26003
William Richardson, Region 3
Richardson, william eoa.gov
215-814-5675
EPA Region 3
1650 Arch Street
Philadelphia, PA 19103
David Melgaard, Region 4
melgaard. david(® eoa.gov
404-562-9265
EPA Region 4
61 Forsythe Street SW
Atlanta, GA 30303
Mari Nord, Region 5
nord.mari(®eoa.gov
312-886-3017
EPA Region 5
77 West Jackson Blvd
Chicago, IL 60604
Robert Cook, Region 6
cook, robert (Seoa.gov
214-665-7141
EPA Region 6
1445 Ross Avenue, Suite 1200
Dallas, TX 75202
Gary Welker, Region 7
welker.garv(® eoa.gov
913-551-7177
EPA Region 7
901 N. Fifth Street
Kansas City, KS 66101
Kris Jensen, Region 8
iensen.kris(® eoa.gov
303-312-6237
EPA Region 8
1595 Wynkoop Street
Denver, CO 80202
Jeff McPherson, Region 8
mcoherson.ieffrev(® eoa.gov
303-312-7752
EPA Region 8
16194 West 45th Drive
Golden, CO 80403
Janet Hashimoto, Region 9
hashimoto.ianet(® eoa.gov
415-972-3452
EPA Region 9
75 Hawthorne Street
San Francisco, CA 94105
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Title Name Contact Information
Lil Herger, Region 10
herger.lillian(® epa.gov
206-553-1074
EPA Region 10
1200 Sixth Avenue, Suite 900
Seattle, WA 98101
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Appendix F: Frequently Asked Questions
Frequently asked questions
Q ~ If questions arise concerning lake status, who should I contact?
A ~ Please e-mail a detailed description of your concerns about the lake to your EPA Regional NLA
Coordinator and the project lead, Amina Pollard (Pollard.Aminaffiepa.gov). They will work with the
EPA ORD lab to help you determine the final status of the lake.
Q ~ Some reservoirs may be < 1 m deep or < 1 ha in area late in the irrigation season - should
these lakes be sampled?
A ~ Reservoirs that are expected to be more than 1 m deep and more than 1 ha during the index
period (generally May through September) ARE part of the target population and should be
scheduled for sampling. However, on the day of the sampling visit, if the depth at the deepest point
is less than 1 m (or the lake area is < 1 ha), then the lake is assigned a status of Nontarget and is not
sampled. Select the next available replacement lake, evaluate it, and schedule it to be sampled.
Q ~ What criteria should be used to determine if a lake should be dropped from the sample
population due to salinity?
A ~ Inland lakes that are saline or have high conductivity (>1000 piS/cm) ARE part of the target
population, with the exception of the Great Salt Lake.
In the case of a coastal lake or lake adjacent to an estuary, tidally-influenced lakes are not part of
the target population. A tidally-influenced lake is operationally defined as being maintained solely
by the surface inflow of brackish or salt water due to water level changes during tidal cycles.
Permanent lakes near the coast or near an estuary below the head of salt, with no surface
connection to the ocean at high tide are considered part of the target population (even if saline).
Dune lakes (primarily located along the Gulf Coast), are part of the target population. These lakes
are permanent and almost always isolated from the ocean, but periodically will flood or "blow out"
forming a connection with the ocean or estuary and incur an influx of brackish or salt water.
Waterbodies along the coast that are considered to be estuarine or part of a larger coastal wetland
area are not part of the target population. These represent waterbodies that should be included in
the sampling frames for the National Coastal Condition Assessment or the National Wetland
Condition Assessment.
Q ~ Should oxbows, backwaters, and side-channel reservoirs be sampled?
A ~ Oxbows ARE lakes if they are separated from a river and ARE part of the target population and
should be scheduled for sampling. However, oxbows that have either flowing water or a wetland
connection to a river are NOT lakes and should be assigned a status of Nontarget and not sampled.
Side-channel reservoirs and drinking water reservoirs where water is pumped from a nearby river
that does not have recreation or aquatic life uses ARE NOT part of the target population and should
be assigned a status of Nontarget and not sampled.
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Q ~ Should ephemeral lakes be sampled?
A ~ Ephemeral lakes are operationally defined as being highly likely to be dry during the index
period of the sampling year, but you may not be able to make this decision until you actually visit
the lake to sample it. Lakes that do not meet the inclusion criteria on the date of a sampling visit
ARE NOT part of the target population.
Q ~ Should mining pits be sampled?
A ~ Actively used quarry pits, mine tailing disposal lakes, borrow pits, and storm water treatment
ponds ARE NOT in the target population. Abandoned mine lakes that are used for recreation or
other beneficial uses (e.g., wildlife) ARE part of the target frame. The lake evaluation spreadsheet
includes a place (Q8) to note lake origin to assist in data interpretation.
Q ~ What constitutes difficulty of access in sampling a lake?
A ~ The objective of the National Lake Assessment is to sample lakes that are representative of the
full range of conditions found across the country. Therefore, field crews should make a concerted
attempt to sample remote lakes that are identified as being part of the target population. Lakes that
pose safety risks because of their remoteness or where the cost and effort required are prohibitive
in terms of completing the rest of the NLA sampling, are considered to be target but not accessible
and are replaced with a lake from the oversample list.
It is recognized that sampling remote lakes may result in samples being shipped and/or received
past the target holding times (esp. for water chemistry). As long as you can keep the samples cold
and in darkness (or as close to frozen as possible if the sample requires it), there is a high probability
that the samples will maintain their integrity past the target holding times.
Q ~ What if extreme weather hits, the lake is in flood stage, or there are other unsafe conditions ?
A ~ If it is unsafe to sample the lake and the lake cannot be re-scheduled within the index period,
then it is considered to be target but not accessible and should be replaced with a lake from the
oversample list.
Q ~ What if boats are not allowed on a publicly-accessible lake?
A ~ Try to gain permission to sample by boat or other means such as rafts. If permission cannot be
obtained, then assign the lake a final status of Target Other and select a replacement lake from the
oversample list.
Q ~ If a lake drops from my list, can I replace it with the next oversample site, or do I need to wait
until the replacement is assigned by my Regional Lake Coordinator?
A ~ If a lake is dropped, replace it with the first available site on your state's oversample list and
conduct a GIS (if necessary), desktop and/or field evaluation; DO NOT skip lakes on your oversample
list. Please record the dropped lake on your Site Evaluation Spreadsheet.
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