An Analysis of the Potential for Glen Canyon Dam 

Releases to Inundate Archaeological Sites in the 

Grand Canyon, Arizona

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2014–1193
Cover: View of the Colorado River and its left bank at river mile 72.7, looking north 

from Unkar Delta. Photograph taken by A. East, U.S. Geological Survey, May 3, 2013.
An Analysis of the Potential for Glen Canyon Dam 

Releases to Inundate Archaeological Sites in the 

Grand Canyon, Arizona

By Hoda A. Sondossi and Helen C. Fairley

Open-File Report 2014–1193

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014 

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Suggested citation: 

Sondossi, H.A., and Fairley, H.C., 2014, An analysis of the potential for Glen Canyon Dam releases to inundate 

archaeological sites in the Grand Canyon, Arizona: U.S. Geological Survey Open-File Report 2014-1193, 26 p., 

http://dx.doi.org/10.3133/ofr20141193. 

ISSN 2331-1258 (online)

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endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Abstract ......................................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 1

Study Area..................................................................................................................................................................... 3

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

Source Data............................................................................................................................................................... 4

Cultural Site Data ................................................................................................................................................... 5

Modeled Water-Surface Elevation Data ................................................................................................................. 6

Topography ............................................................................................................................................................ 6

Virtual Shorelines ................................................................................................................................................... 6

Analysis ........................................................................................................................................................................10

Results..........................................................................................................................................................................11

Differences between Restricted Raster and Canyon-Wide Vector Analyses ............................................................15

Discussion ....................................................................................................................................................................16

References Cited..........................................................................................................................................................17

Appendix A. Site-Specific Inundation Data and Summary of Area Inundated by Site Groupings and 

Stage Elevation ............................................................................................................................................................19

Figures

Figure 1. Map showing project area, located in the Colorado River corridor between Lees Ferry and 

Diamond Creek, Grand Canyon National Park, Arizona ................................................................................................ 3

Figure 2. Diagram showing longitudinal profile and cross sections similar to those used to generate 

virtual shorelines............................................................................................................................................................ 7

Figure 3. Diagram showing a water-surface raster created from linking cross section water-surface elevations......... 8

Figure 4. Diagram showing how the “subtract” command is used to generate areas of inundation by a 

given modeled discharge............................................................................................................................................... 8

Figure 5. Diagram showing how a small range of error in predicting water-stage results in large 

uncertainty in extent of inundation in areas of low slope.............................................................................................. 10

Figure 6. Diagram showing how a cultural site polygon may interact with virtual shoreline polygons ........................ 11

Figure 7. Graph showing number of cultural sites in Groups A and B that likely would be inundated by six 

modeled discharges, Colorado River corridor between Lees Ferry and Diamond Creek, Grand Canyon 

National Park, Arizona................................................................................................................................................. 13

Figure 8. Graph showing percentage of cultural sites, by count, in Groups A and B that likely would be 

inundated by six modeled discharges, Colorado River corridor between Lees Ferry and Diamond Creek, 

Grand Canyon National Park, Arizona......................................................................................................................... 13

Figure 9. Graph showing total area within cultural sites in Groups A and B that likely would be inundated 

by six modeled discharges, Colorado River corridor between Lees Ferry and Diamond Creek, Grand Canyon 

National Park, Arizona................................................................................................................................................. 14

Figure 10. Graph showing percentage of total area within cultural sites in Groups A and B that likely would be 

inundated by six modeled discharges, Colorado River corridor between Lees Ferry and Diamond Creek, Grand 

Canyon National Park, Arizona.................................................................................................................................... 14

Figure 11. Diagram showing why a higher number of cultural sites are shown to interact with virtual shoreline 

polygons in the vector analysis compared to the restricted raster analysis. ................................................................ 15
iv

Tables

Table 1. Summary statistics for the two cultural site datasets (Groups A and B), Colorado River corridor 

between Lees Ferry and Diamond Creek, Grand Canyon National Park, Arizona......................................................... 5

Table 2. Number of cultural sites that likely would be partially inundated by each discharge, Colorado River 

corridor between Lees Ferry and Diamond Creek, Grand Canyon National Park, Arizona ......................................... 12

Conversion Factors and Datums

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

mile (mi) 1.609 kilometer (km)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

SI to Inch/Pound

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square meter (m2) 0.0002471 acre 

square meter (m2) 10.76 square foot (ft2) 

Flow rate

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88)

Horizontal coordinate information is referenced North American Datum of 1983 (NAD 83)

Elevation, as used in this report, refers to distance above the vertical datum.
1 

An Analysis of the Potential for Glen Canyon Dam 

Releases to Inundate Archaeological Sites in the 

Grand Canyon, Arizona

By Hoda A. Sondossi1 and Helen C. Fairley2

Abstract

The development of a one-dimensional flow-routing model for the Colorado River between Lees 

Ferry and Diamond Creek, Arizona in 2008 provided a potentially useful tool for assessing the degree to 

which varying discharges from Glen Canyon Dam may inundate terrestrial environments and potentially 

affect resources located within the zone of inundation. Using outputs from the model, a geographic 

information system analysis was completed to evaluate the degree to which flows from Glen Canyon 

Dam might inundate archaeological sites located along the Colorado River in the Grand Canyon. The 

analysis indicates that between 4 and 19 sites could be partially inundated by flows released from Glen 

Canyon Dam under current (2014) operating guidelines, and as many as 82 archaeological sites may 

have been inundated to varying degrees by uncontrolled high flows released in June 1983. Additionally, 

the analysis indicates that more of the sites currently (2014) proposed for active management by the 

National Park Service are located at low elevations and, therefore, tend to be more susceptible to 

potential inundation effects than sites not currently (2014) targeted for management actions, although 

the potential for inundation occurs in both groups of sites. Because of several potential sources of error 

and uncertainty associated with the model and with limitations of the archaeological data used in this 

analysis, the results are not unequivocal. These caveats, along with the fact that dam-related impacts can 

involve more than surface-inundation effects, suggest that the results of this analysis should be used 

with caution to infer potential effects of Glen Canyon Dam on archaeological sites in the Grand Canyon. 

Introduction

For more than two decades, research has been done by various Federal agencies and cooperating 

scientists to improve the understanding of how varying releases from Glen Canyon Dam interact with 

and affect downstream aquatic and shoreline resources (Gloss and others, 2005). One category of 

shoreline resources is the numerous archaeological sites situated on and in alluvial deposits derived 

from the Colorado River (Fairley and others, 1994; Fairley, 2003). These archaeological sites range in 

age from more than 8,000 years before present to the mid-20th century, and include masonry structures, 

inscriptions, scatters of artifacts, roasting pits, and various other physical remains representing the past 

8,000 years of human use and occupation along the banks of the Colorado River. 

____________________________________ 

1

U.S. Fish and Wildlife Service (previously with the U.S. Geological Survey). 2

U.S. Geological Survey.
2 

National Park Service (NPS) managers and archaeologists have known for some time that some 

archaeological sites are located within areas inundated by past floods and pre-dam-controlled releases, 

and that some sites have been partially preserved through burial by prehistorical and historical flood 

deposits (Hereford and others, 1993, 1996; Draut and other, 2005); however, the precise number of 

archaeological sites occurring within areas previously inundated by past floods or located within the 

area of potential inundation from dam-controlled flows was previously unknown. 

Prior to 2008, a significant limitation to resolving the controversy about the relation between 

archaeological sites and potential for inundation by river flows was the lack of a system-wide stagedischarge model capable of accurately predicting the elevation of streamflow reached by historical

floods and the flow regime typically released through Glen Canyon Dam. In 2008, a one-dimensional 

flow-routing model was developed and published by Magirl and others (2008). The original intent for 

developing this model was to analyze how tributary debris flows and main stem floods have interacted 

over the past several centuries, resulting in channel incision and (or) aggradation at particular places in 

the Colorado River corridor of the Grand Canyon (C.S. Magirl, U.S. Geological Survey, oral commun., 

2009). Managers and stakeholders involved in the Glen Canyon Dam Adaptive Management Program 

(GCDAMP) quickly recognized the potential applicability of this model for a wide variety of other 

research purposes, such as analyzing potential inundation of terrestrial habitats under varying flow 

regimes. Soon after the model was published, GCDAMP stakeholders requested that the U.S. 

Geological Survey (USGS) undertake an analysis to identify archaeological sites with the highest 

potential to be directly affected by dam operations through inundation. 

In response to this request, the Grand Canyon Monitoring and Research Center (GCMRC) staff 

conducted a geographic information system (GIS) analysis to determine how various releases from Glen 

Canyon Dam, as well as historical (or future) uncontrolled flood events, might inundate, and thereby 

affect, downstream archaeological sites in the Grand Canyon. One objective of this analysis was to 

develop flow-based criteria for prioritizing archaeological sites for future treatment, monitoring and 

other management purposes. A second objective was to clarify the extent to which past flood events 

may have affected these archaeological resources. This analysis involved a comparison of predicted 

water-surface elevations (stages) associated with six discrete discharges (708 m3

/s [25,000 ft3/s]; 1,274 

m3

/s [45,000 ft3/s]; 2,747 m3/s [97,000 ft3/s]; 3,540 m3/s [125,000 ft3/s]; 4,814 m3/s [170,000 ft3/s]; and 

5,947 m3/s [210,000 ft3/s]) to ground-surface elevations within cultural sites located along the Colorado 

River, in order to determine the likelihood and possible extent of inundation. The six discharges reflect 

the maximum stage of the three highest pre-dam floods (Topping and others, 2003), plus three important 

discharge levels of the post-dam era (U.S. Department of the Interior, 1995, 1996; Melis, 2011). Three 

different GIS analyses were conducted to evaluate the potential for inundation under these six 

discharges. In this report, we briefly describe each of these analyses and explain the usefulness and 

limitations of each set of results; however, this report focuses primarily on the results of the third 

analysis, which incorporates estimated ranges of uncertainty associated with each of the modeled stage 

elevation projections. 
3 

Study Area

The focus of this analysis is on the Colorado River corridor between Lees Ferry, near the mouth 

of the Paria River, and the confluence of Diamond Creek (fig. 1), a distance of approximately 364 km 

(226 mi). Glen Canyon Dam is about 25 km (15.5 mi) upstream of Lees Ferry. The one-dimensional 

flow-routing model developed by Magirl and others (2008) does not include the section of the river 

corridor upstream of Lees Ferry, nor does it extend downstream of Diamond Creek (Magirl and others, 

2008). 

The study area includes most, but not all, of the archaeological sites located in the area 

potentially affected by past and current river flows between Lees Ferry and Diamond Creek, as 

documented by Fairley and others (1994) during the 1990–91 inventory of the 410-km (255-mi) long 

Colorado River corridor between Glen Canyon Dam and Separation Canyon, near the head of Lake 

Mead. A total of 283 archaeological sites were recorded in this inventory in the presumed area of 

potential effects from dam operations downstream of Lees Ferry. Location information for 242 of these 

283 sites was provided by the NPS for this analysis in the form of either GIS polygons or Universal 

Transverse Mercator (UTM) coordinates. In keeping with U.S. Department of the Interior policy, 

precise archaeological site locations are not disclosed in this report, but are on record with the NPS, 

Grand Canyon National Park, Division of Science and Resource Management, at Grand Canyon, 

Arizona. 

Figure 1. Map showing project area, located in the Colorado River corridor between Lees Ferry and Diamond 

Creek, Grand Canyon National Park, Arizona. 
4 

Methods

Using the six “virtual shorelines” developed by Magirl and others (2008), an initial GIS analysis 

was conducted as a basic assessment of the potential of the Colorado River to inundate cultural sites in 

the Grand Canyon at the six discharges listed in the introduction. (Metric values of these six discharges 

are rounded throughout the remainder of this report, as follows: 700 m3

/s [25,000 ft3/s]; 1,270 m3/s 

[45,000 ft3

/s]; 2,750 m3/s [97,000 ft3/s]; 3,500 m3/s [125,000 ft3/s]; 4,800 m3/s [170,000 ft3/s]; 5,900 

m3/s [210,000 ft3/s]). This initial analysis did not account for the uncertainty (as discussed by Magirl 

and others, 2008) associated with the predicted stages. A subsequent GIS analysis was limited to only 

the area within the boundaries of the cultural sites. This second analysis is referred to hereinafter as the 

“restricted raster analysis.” In the third analysis, the steps Magirl and others (2008) took to generate 

“virtual shorelines” were repeated to generate additional water-surface polygons representing the upper 

and lower bounds of error for each of the six modeled discharges, as previously defined by Magirl and 

others (2008). The resulting GIS water-surface polygons then were used to analyze the likelihood of 

inundation at the 242 archaeological sites in relation to the full range of possible error associated with 

each of the modeled discharges. In this report, we present the results of the final canyon-wide analysis 

and explain the differences between the results of this analysis and the restricted raster analysis. 

Source Data

The following spatial datasets were used in this analysis: 

1. Unpublished cultural site boundary data (vector: polygons). Source: NPS, Grand Canyon 

National Park, Division of Science and Resource Management, supplemented with unpublished 

spatial point data provided by G. O’Brien and J. Pederson, Department of Geology, Utah State 

University. 

2. Water-surface elevation (raster: grids). Source: USGS, GCMRC. Unpublished data developed by 

M. Breedlove and H. Sondossi, GCMRC. 

3. Topography (raster: grids). Source: USGS, GCMRC. Unpublished digital surface-elevation data 

developed by ISTAR America, Inc., under contract to GCMRC. 

4. Virtual shorelines (vector: polygons), representing the intersection of water-surface elevations

with canyon topography between Lees Ferry and Diamond Creek. Published data developed by 

Magirl and others (2008) and unpublished data developed by H.A. Sondossi. Source: USGS, 

GCMRC. 

The same source data were used for all analyses involving virtual shorelines and cultural sites. In 

the following sections, each of these data sources is described in more detail
5 

Cultural Site Data

Spatial data, in vector (polygon) format, from 242 archaeological sites were used for this 

analysis. These 242 sites included 161 sites that have been identified by the Bureau of Reclamation and 

the NPS as potential candidates for future excavation or other forms of management “treatment” such as 

erosion control (Damp and others, 2007), along with an additional 81 sites not currently slated for 

treatment but considered sensitive to potential adverse effects from present and future dam operations 

(O’Brien and Pederson, 2009). 

Digital polygon data delineating the areas occupied by 232 of the cultural sites used in this 

analysis were generated and provided to the GCMRC by the NPS. No polygon data existed for 10 of the 

cultural sites. However, point data (in UTM coordinates) for these 10 sites had been created prior to this 

study for the purposes of completing a geomorphic assessment of the stability at these sites (O’Brien 

and Pederson, 2009). These coordinates were used as centroids to generate circular buffer polygons 

(using the “buffer” command in the Environmental Systems Research Institute, Inc. [ESRI] ArcMapTM

program) with a 4-m diameter. The exact extent of at least two of these cultural sites is known to be 

larger than the artificial circles generated by this method. 

The 242 sites were partitioned and analyzed as two separate groups—Groups A and B: 

1. Group A consisted of 151 sites that had been identified as candidates for future treatment (Damp 

and others, 2007) plus 10 sites identified for excavation by the Museum of Northern Arizona 

(total of 161 sites). 

2. Group B included other sites potentially affected by dam operations (81 sites). 

Three sites in Group A and two sites in Group B subsequently were determined to be 

downstream of Diamond Creek, beyond the geographical extent of the flow-routing model; therefore, 

these five sites were not included in the final analysis. 

Basic summary statistics pertaining to the size distribution of the two sets of cultural sites are 

shown in table 1. The two groups of cultural sites differ in overall range of size distribution, as well as 

in the arithmetic mean and median. These differences have a bearing on the likelihood of inundation. 

Table 1. Summary statistics for the two cultural site datasets (Groups A and B), Colorado River corridor between 

Lees Ferry and Diamond Creek, Grand Canyon National Park, Arizona.

[m2

, square meter]

Cultural site area and site count Group A Group B

Total area of all sites (m2) 386,400 87,717

Site count 158 79

Mean site area (m2) 2,440.9 1,110.3

Median site area (m2) 808.5 313

Maximum site area (m2) 42,170 13,346

Minimum site area (m2) 6 5
6 

Modeled Water-Surface Elevation Data

Water-surface elevations associated with the six different discharges initially were modeled for 

the 364 km (about 226 mi) between Lees Ferry and Diamond Creek (fig. 1) as part of the Magirl and 

others (2008) study. The lowest discharge (700 m3/s [25,000 ft3/s]) represents the maximum release 

level from Glen Canyon Dam currently permitted under normal operating criteria of the Modified Low 

Fluctuating Flow regime (U.S Department of the Interior, 1996). The second-lowest discharge (1,270 

m3/s [45,000 ft3/s]) represents the maximum level possible for experimental flood releases, when all 

turbines in Glen Canyon Dam are fully operational and the jet tubes are operating simultaneously at full 

capacity (Melis, 2011). The third-lowest discharge (2,750 m3/s [97,000 ft3/s]) represents the maximum

post-dam discharge that occurred in June 1983, as a result of an uncontrolled release of excess water 

from Lake Powell. The three highest discharges (3,500 m3

/s [125,000 ft3/s], 4,800 m3/s [170,000 ft3/s], 

and 5,900 m3/s [210,000 ft3/s]) are the maximum flows of pre-dam spring floods in 1957, 1921, and 

1884, respectively, as calculated by Topping and others (2003). For the final analysis, additional watersurface polygons representing the upper and lower bounds of each of the six discharges were created 

following the same GIS methods used to create the original six water-surface polygons described in 

Magirl and others (2008). 

Topography

Terrestrial surface topography was derived from aerial imagery collected by ISTARTM America, 

Inc., under contract to the GCMRC during a May 2002 overflight of the same above-mentioned extent 

of the Grand Canyon. Automated digital photogrammetry, with an accuracy of ±0.3 m (Davis, 2004), 

was used to create a 1-m digital surface model (DSM) for the entire river corridor. 

Virtual Shorelines

Virtual shorelines are shoreline projections created by intersecting modeled surface-water 

elevations with three-dimensional terrain models representing the topography of the river corridor. 

Magirl and others (2008) generated the original set of virtual shorelines using topographic data and

modeled water-surface elevations developed specifically for the Colorado River in the Grand Canyon. 

As noted in the “Topography” section above, the primary source of topographic data was a 1-m 

resolution DSM derived from ISTARTM-automated digital photogrammetry collected in 2002, with an 

accuracy of ±0.3 m (Davis, 2004). Magirl and others (2008) used these DSMs to generate 2,680 cross 

sections along the length of the Colorado River between Lees Ferry and Diamond Creek (fig. 1). These 

cross sections relied on the topography derived from the 2002 DSM to define channel geometry above 

the 227 m3

/s discharge level; below this level, channel geometry was created synthetically, based on 

assumptions about typical cross-sectional form in varying geomorphic contexts (Magirl and others, 

2008), unless more detailed and accurate data existed from local surveys (for example, Hazel and others, 

2006). The cross sections were used to model water-surface elevations using the one-dimensional 

modeling system originally developed by Magirl (2006), which is based on the Hydrologic Engineering 

Center River Analysis System (HEC-RAS) software application (Version 3.1), designed by the U.S. 

Army Corps of Engineers (Brunner, 2002). HEC-RAS is a “standard step” model used in this case to 

predict water-surface elevation (stage) associated with various discharges using parameters such as 

cross-section geometry, flow velocity, and local slope (fig. 2). 
7 

Figure 2. Diagram showing longitudinal profile and cross sections similar to those used to generate virtual 

shorelines.

Magirl and others (2008) used the 2,680 cross sections to generate water-surface elevation grids 

for each modeled discharge. To create these cross sections, a line (vector) layer of the Colorado River 

channel centerline first was generated, and from this centerline, perpendicular lines were extended in 

either direction at the designated locations of the 2,680 cross sections (fig. 3). Cross-section locations 

were selected by Magirl and others (2008) based on recommendations in the hydraulic literature 

(Benson and Dalrymple, 1967; Davidian, 1984; Randle and Pemberton, 1987) to capture the fall of the 

water surface at rapids and outside of eddies. For each modeled discharge, these cross-section lines were 

attributed with elevations in real-world coordinates for water-surface elevations at that discharge. 

Elevation values between each pair of cross sections were interpolated by essentially connecting them 

with a straight line in three-dimensional space (figs. 2 and 3). The three-dimensional data were used to 

generate canyon-wide 1-m resolution grids (raster layers) of water-surface elevation for the modeled 

discharges.

In order to generate the virtual shorelines, Magirl and others (2008) compared the generated 

water-surface elevation layers to the topography layer in raster format using the “subtract” command in 

ArcGridTM, the raster analysis module within ARC/InfoTM. This generated a third raster layer with areas 

of positive and negative “difference” values (fig. 4). Next, the “Gridpoly” command was used in 

Arc/InfoTM to generate polygons separating areas of positive value from areas of negative value. These 

polygons are the virtual shoreline polygon layers. The various steps described above can be 

accomplished by a variety of means using ArcGISTM (ESRI) software, but the above description provides 

the conceptual underpinnings of the process. 
8 

Figure 3. Diagram showing a water-surface raster created from linking cross section water-surface elevations.

Figure 4. Diagram showing how the “subtract” command is used to generate areas of inundation by a given 

modeled discharge.
9 

Magirl and others (2008) identified several factors affecting the accuracy of their modeled 

water-surface elevation layers and the associated virtual shorelines. These included prediction errors 

inherent in the model itself, as well as errors built into the DSM used in constructing the cross sections 

and longitudinal channel geometry. 

A potentially significant source of error is the synthetic bathymetric cross sections. Most of the 

cross-sectional geometry below the water surface is constructed based on assumptions about typical 

channel geometries in various geomorphic contexts (straight channel sections, channel form near 

tributaries, etc.). Reliance on synthetic bathymetry was necessary because at the time the model was 

being constructed (2005–06), few subaqueous channel sections of the Colorado River had been 

accurately mapped. 

Another source of potential error derives from the challenges associated with accurately 

characterizing channel-bed roughness. This is an important characteristic for modeling flow, especially 

near constriction points and rapids. Magirl and other (2008) addressed this issue at some length in their 

report. They recognized that the accuracy of water-surface elevation predictions could be improved with 

new bathymetric data based on actual channel measurements and with considerable additional labor to 

refine the roughness coefficients used in their model; however, no attempt was made to refine the model 

for the current GIS analysis. 

Magirl and others (2008) tested the predictive accuracy of their hydraulic model by comparing 

its results to stage-discharge relations established at USGS streamgages at Lees Ferry and in the Grand 

Canyon near Phantom Ranch, stage data collected by Konieczki and others (1997) during a 1996 

experimental high-flow release from Glen Canyon Dam, discharge rating curves at select sandbar study 

sites monitored by Northern Arizona University (Hazel and others, 2006), and high water marks 

indicated by driftwood strandlines left by historical floods (Draut and others, 2005). Magirl and others 

(2008) qualitatively evaluated the accuracy of model predictions by examining historical photographs 

taken on known dates with known discharges, as well as driftwood lines of historical floods of known 

magnitude surveyed in the field. Using all these information sources, Magirl and others (2008) 

determined that the modeled water-surface elevations were accurate within the following ranges:

1. ±0.4 m for discharges less than 1,300 m3/s, 

2. ±1.0 m for discharges between 1,300 and 2,500 m3

/s, and 

3. ±1.5 m for discharges between 2,500 and 5,900 m3

/s. 

These uncertainty bounds were subsequently incorporated into the GIS analysis. 
10

Analysis

The canyon-wide analysis began with the generation of a new set of “difference” raster layers, as 

described in the “Methods” section. However, in order to account for the full range of possible errors, 

an additional step was added—two new columns were appended to the attribute tables of each layer, and 

simple arithmetic operations of addition and subtraction were performed by querying the attribute table 

to determine the upper and lower range of error associated with each discharge. For example, for the 

3,500 m3/s discharge, 1.5 m was added and subtracted from the “value” column to populate the “lower” 

and “upper” columns of the table, respectively. We were conservative in assigning error bounds to 

discharges that approached the upper discharge level in each uncertainty range. For example, for the 

1,270 m3

/s discharge, 1.0 m was added and subtracted from the “value” column, rather than 0.4 m.

The next step was to generate sets of polygons for the upper and lower ranges of possible error 

associated with each of the six modeled discharges. The fundamental reason for consideration of the 

upper and lower limits of error in map view is that in low-slope (that is, nearly flat) areas, a small rise in 

water stage can result in inundation of large areas (fig. 5). Thus, accounting for the full range of possible 

error in predicting stage improves the usefulness of the virtual shoreline data. 

Figure 5. Diagram showing how a small range of error in predicting water-stage results in large uncertainty in 

extent of inundation in areas of low slope.
11

Finally, the “Union” command in ArcGISTM was used to overlay the cultural sites layer onto the 

virtual shoreline layers and to identify areas in common between cultural sites and all three parts of each 

virtual shoreline polygon set associated with each modeled discharge (fig. 6). The attribute tables of the 

resultant layer then were exported as text files, and then tabulated, summarized, and analyzed in 

Microsoft Excel®. 

Figure 6. Diagram showing how a cultural site polygon may interact with virtual shoreline polygons.

Results

The resulting data from the GIS analysis were applied to the two designated groups of cultural 

sites—Groups A and B. The canyon-wide vector analysis allowed us to determine which sites in each 

group likely would be at least partially inundated at the various discharges. The number and 

distribution of cultural sites in Groups A and B that likely would be at least partially inundated by the 

upper (maximum) and lower (minimum) range of six modeled discharges are summarized in table 2.

The central tendency value associated with each of the six virtual shorelines is shown in figure 7, with 

error bars representing the upper and lower range of each modeled discharge. The same data are shown 

in figure 8 as percentages of the total number of sites within each dataset.
12

Table 2. Number of cultural sites that likely would be partially inundated by each discharge, Colorado River 

corridor between Lees Ferry and Diamond Creek, Grand Canyon National Park, Arizona.

[m3

/s, cubic meter per second]

Group A Group B

Discharge ( m3/s) Maximum Minimum Maximum Minimum

700 4 4 1 0

1,270 17 4 2 1

2,750 66 15 16 2

3,500 94 38 21 6

4,800 123 67 36 17

5,900 140 84 51 29

Although the criteria used by NPS managers for assigning sites to Groups A or B were not 

defined explicitly, elevation above the river (and, therefore, likelihood of inundation) may have been

one consideration. As shown in figures 7 and 8, a larger percentage of sites in Group A occur at low 

elevations; therefore, more sites in Group A likely would be inundated than sites in Group B. For 

example, nearly 80 percent of sites in Group A likely would be at least partially inundated by a 

discharge of 5,900 m3/s, whereas the same discharge would partially inundate less than 50 percent of 

sites in Group B. 

Another result of this analysis is the ability to account for how much of each cultural site is 

inundated by each of the discharges, including the upper and lower limits of potential error. As shown in 

figure 9, the total area that likely would be inundated by a given flow is much smaller in Group B than 

in Group A. However, there are fewer sites in Group B, and the mean size of sites in Group B is much 

smaller than in Group A (table 1). To evaluate whether the apparent difference persists when 

measurements are normalized relative to the total site area of each group, the percentage of the total 

inundated area was calculated for all cultural sites in each group (fig. 10). This analysis confirms that

proportionally, a much smaller area of Group B sites is likely to be inundated by any given flow. 

The percentage of area in Group B that likely would be inundated by a discharge less than 2,750 

m3/s is nearly zero; thus, only a very small percentage of Group B sites likely would be inundated by 

discharges less than this magnitude. 

Additional details concerning the results of the analyses, including the site-specific and groupspecific calculations of archeological site area potentially inundated under varying discharges, are 

presented in appendix A. 
13

Figure 7. Graph showing number of cultural sites in Groups A and B that likely would be inundated by six modeled 

discharges, Colorado River corridor between Lees Ferry and Diamond Creek, Grand Canyon National Park, 

Arizona. Columns represent "central" value resulting from interaction of original virtual shorelines with cultural sites. 

Error bars represent upper and lower ranges of inundation by each discharge.

Figure 8. Graph showing percentage of cultural sites, by count, in Groups A and B that likely would be inundated 

by six modeled discharges, Colorado River corridor between Lees Ferry and Diamond Creek, Grand Canyon 

National Park, Arizona. Columns represent "central" value resulting from interaction of original virtual shorelines 

with cultural sites. Error bars represent upper and lower ranges of inundation by each discharge.
14

Figure 9. Graph showing total area within cultural sites in Groups A and B that likely would be inundated by six 

modeled discharges, Colorado River corridor between Lees Ferry and Diamond Creek, Grand Canyon National 

Park, Arizona. Columns represent "central" value resulting from interaction of original virtual shorelines with cultural 

sites. Error bars represent upper and lower ranges of inundation by each discharge.

Figure 10. Graph showing percentage of total area within cultural sites in Groups A and B that likely would be 

inundated by six modeled discharges, Colorado River corridor between Lees Ferry and Diamond Creek, Grand 

Canyon National Park, Arizona. Columns represent "central" value resulting from interaction of original virtual 

shorelines with cultural sites. Error bars represent upper and lower ranges of inundation by each discharge.
15

Differences between Restricted Raster and Canyon-Wide Vector Analyses 

To determine whether using different GIS data types and methods resulted in different analytical 

outcomes, we conducted an experiment to compare outcomes using a restricted raster method to 

outcomes using vector-based analytical methods. The basic results are similar, but they are not exactly 

the same (appendix A, table A1). Compared to the results of the raster analysis, results of the canyonwide vector analysis indicate a higher number of cultural sites being at least partially inundated at all six 

discharge levels in both Groups A and B. The reason for this difference is that in the raster analysis, for 

a given pixel to be included within a given boundary, its centroid must be within that boundary. In 

converting from raster to vector format, the polygon boundaries were redrawn around “squares” 

representing pixels of same value. This makes it possible for two polygons to overlap even if the 

original rasters that were used to produce them did not interact. A graphical representation of this 

concept is shown in figure 11. The value of the canyon-wide vector analysis is that it identifies cultural 

sites that may be adversely affected because they are near the edge of the waterline, even though they 

may not be inundated by a given discharge. 

Figure 11. Diagram showing why a higher number of cultural sites interact with virtual shoreline polygons in the 

vector analysis compared to the restricted raster analysis. In the raster analysis, a pixel is assumed to interact with 

a cultural site only when its centroid is within the site, even though visually each pixel is represented by a square. 

When the same raster data were converted to vector polygons, any area of the square pixel around which the 

polygon was constructed could overlie part of the cultural site polygon. The black dots represent the centroids of a 

raster dataset, and the green area represents the vector layer generated from the same raster dataset. In the case 

of this site, the raster analysis detected no interaction, whereas the vector analysis resulted in interaction between 

upper limit of 708 cubic meters per second (m3/s) virtual shoreline and this site.
16

Discussion

The basic analysis presented in this report indicates the potential use of virtual shoreline data for 

assessing the likelihood of archaeological sites or other terrestrial resources to be inundated by various 

dam releases; however, the limitations of these data need to be underscored as well. An awareness of the 

range of uncertainty associated with each modeled discharge is important. It is also necessary to be 

cognizant of the wide band of terrain that can be inundated in areas of low slope. In such low-slope 

areas, even a small difference in stage elevation can significantly change the amount of area subject to 

inundation. Thus, if inundation is considered to be a potentially adverse effect, such as in the case of 

cultural sites, then the upper end of the error bound should be of particular importance in analyses. 

A fundamental assumption (and important consideration) of the model used to construct the 

virtual shorelines is lack of supercritical flow (Magirl and others, 2008). In reality, supercritical flow is 

a common phenomenon in many rapids in the Grand Canyon; consequently, the model does not claim to 

accurately predict stage at rapids. In contrast, flow in pools, where most of the cross sections used to 

construct the dataset are located, is subcritical. Because less than 10 percent of the length of the 

Colorado River is in rapids (Leopold, 1969) at most discharge levels, the modeled stages likely are

fairly accurate for most of the river corridor. Nonetheless, it is important to recognize that many 

archaeological sites are preferentially located near the mouths of tributary canyons (Fairley and others, 

1994), and because most rapids in the Grand Canyon are formed by debris flows emanating from 

tributaries (Webb and others, 2000), a disproportionate number of archaeological sites are concentrated 

in areas where the model is least accurate.

A second important consideration in using the virtual shoreline data is that they are based on 

channel geometry and stage-discharge relations present in 2002. Tributary and main stem floods, as well 

as tributary debris flows, can alter local geometries and change stage-discharge relations locally or 

potentially for long reaches. For this reason, using these virtual shoreline data to assess levels of 

inundation by prehistorical floods (for example, Anderson and Neff, 2011) or the range of discharge 

associated with pre-dam era deposits is potentially problematic. 

A third important consideration in using the virtual shoreline data is to be aware that the cross 

sections used to construct the water-surface elevations relied on synthetic bathymetry rather than actual 

channel geometry below the 227 m3

/s discharge level [8,000 ft3/s]. The GCMRC currently (2014) is in 

the process of collecting bathymetric data below the 227 m3

/s discharge level within pools for 30-mi 

long reaches in the Grand Canyon (Paul Grams, oral commun., 2013). The objective of this channelmapping effort is to document existing fine-sediment storage conditions as a baseline for long-term 

sediment flux monitoring. These data may potentially replace the artificial, idealized cross sections used 

by Magirl and others (2008). However, replacing the synthetic bathymetry with actual channel 

measurements is not likely to change the virtual shoreline polygons significantly, if at all. This is 

because the original stage-elevation water surface polygons produced by Magirl and others (2008) were 

generated to predict the likelihood of inundation by discharge levels higher than 227 m3/s and were 

calibrated with actual stage-discharge curves at key locations. 

It also is important to understand that the results produced by this GIS analysis are based on site 

locations that are mapped onto surface topography on the basis of archaeological evidence that is 

expressed on the ground surface. Thus, the results of the analysis assume that archaeological sites are 

strictly surface phenomena, an assumption that is clearly untrue in the Grand Canyon where 

archaeological sites often extend several meters below the ground surface (Fairley, 2003). Thus, some 
17

sites potentially could be affected by low-elevation flows either because the flows undermine terrace cut 

banks adjacent to the sites or they saturate sedimentary deposits below the ground surface. Stated 

another way, some archaeological sites potentially could be affected by future dam operations without 

actually being inundated at the ground surface. Such scenarios are not represented in the results of the 

present analysis. 

Finally, inundation by dam-released flows is only one way that dam operations may affect 

cultural sites in the Grand Canyon. Potential indirect effects to archaeological sites also result from loss 

of sandbars that serve as sources of wind-blown sand and from progressive incision of gullies that no 

longer are being backfilled by flood sands above the 1,270 m3

/s discharge level. Thus, even if an 

archaeological site is not directly inundated, it may be subject to other types of effects stemming from 

dam operations. This caveat, along with the others mentioned earlier in this section, points to the 

importance of not relying exclusively on the results of this analysis to make judgments or decisions 

about which sites may need future monitoring and treatment because of the operations of Glen Canyon 

Dam.

Given these caveats, the results of the GIS analysis nonetheless indicate that numerous 

archaeological sites along the Colorado River between Lees Ferry and Diamond Creek are potentially 

affected directly by dam operations, with at least four sites partially inundated by flows of 700 m3/s

(25,000 ft3/s), and up to 19 sites potentially affected by experimental high flows at the 1,270 m3/s 

[45,000 ft3

/s] discharge level. Furthermore, the analysis indicates that some level of inundation from 

uncontrolled dam releases in June 1983 possibly affected as many as 82 sites, and pre-dam floods within 

the past 130 years could have inundated all or some portion of as many as 191 archaeological sites. 

References Cited

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during A.D. 1050–1170 along the Colorado River in the Grand Canyon, Arizona, USA, Catena v. 85, p. 

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Canyon: Tucson, Arizona, Statistical Research, Inc., Technical Series 79, 179 p. 
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Fairley, H.C., Bungart, P.W., Coder, C.M., Huffman, J., Samples, T.L., and Balsom, J.R., 1994, The Grand 

Canyon River Corridor Survey Project—Archaeological survey along the Colorado River between Glen 

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the Glen Canyon Environmental Studies Program, Cooperative Agreement No. 9AA-40-07920, December 

1994, 276 p. 

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Canyon: U.S. Geological Survey Circular 1282, 220 p. 

Hazel, J.E., Kaplinski, M., Parnell, R., Kohl, K., and Topping, D.J., 2006, Stage-discharge relations for the 

Colorado River in Glen, Marble, and Grand Canyons, Arizona, 1990–2005: U.S. Geological Survey OpenFile Report 2006-1243, 7 p.

Hereford, R., Fairley, H.C., Thompson, K.S., and Balsom, J.R., 1993, Surficial geology, geomorphology, 

and erosion of archeologic sites along the Colorado River, eastern Grand Canyon, Grand Canyon National 

Park, Arizona: U.S. Geological Survey Open-File Report 93-517, 45 p., 4 pl. 

Hereford, R., Thompson, K.S., Burke, K.J., and Fairley, H.C., 1996, Tributary debris fans and Late 

Holocene alluvial chronology of the Colorado River, eastern Grand Canyon, Arizona: Geological Society 

of America Bulletin, v. 108, no. 1, p. 3–19. 

Konieczki, A.D., Graf, J.B., and Carpenter, M.C., 1997, Streamflow and sediment data collected to 

determine the effects of a controlled flood in March and April 1996 on the Colorado River between Lees 

Ferry and Diamond Creek, Arizona: U.S. Geological Survey Open-File Report 97-224, 55 p. 

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Powell—A collection of papers honoring Powell on the 100th anniversary of his exploration of the 

Colorado River, 1869–1969: U.S. Geological Survey Professional Paper 669, p. 131–145. 

Magirl, C.S., 2006, Bedrock-controlled fluvial geomorphology and the hydraulics of rapids on the Colorado 

River: Tucson, University of Arizona, Ph.D. dissertation. 

Magirl, C.S., Breedlove, M.J., Webb, R.H., and Griffiths, P.G., 2008, Modeling water-surface elevations and 

virtual shorelines for the Colorado River in Grand Canyon, Arizona: U.S. Geological Survey Scientific 

Investigations Report 2008-5075, 32 p. 

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from Glen Canyon Dam, Arizona: U.S. Geological Survey Circular 1366, 147 p. 

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Grand Canyon National Park, Arizona, final report: Submitted by Department of Geology, Utah State 

University, Logan, to U.S. Geological Survey, Grand Canyon Monitoring and Research Center, Flagstaff, 

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River in Grand Canyon: Flagstaff, Arizona, Glen Canyon Environmental Studies, NTIS Report PB88-

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Topping, D.J., Schmidt, J.C., and Vierra, L.E., Jr., 2003, Computation and analysis of the instantaneousdischarge record for the Colorado River at Lees Ferry, Arizona—May 8, 1921, through September 30, 

2000: U.S. Geological Survey Professional Paper 1677, 118 p. 

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statement, Colorado River Storage Project, Coconino County, Arizona: Salt Lake City, Utah, Bureau of 

Reclamation, Upper Colorado Regional Office, Utah, 337 p. 

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D.C., Office of the Secretary of Interior, 13 p. 

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of the Colorado River in Grand Canyon, Arizona: U.S. Geological Survey Water-Resources Investigations 

Report 00-4055, 67 p. 
19

Appendix A. Site-Specific Inundation Data and Summary of Area Inundated by Site Groupings and Stage 

Elevation

Table A1. Results of geographic information system analysis, showing sites potentially inundated by flows of 700 cubic meters per second (m3/s) (25,000 cubic 

feet per second [ft3/s]), 1,270 m3/s (45,000 ft3/s), and 2,750 m3/s (97,000 ft3/s), including upper (+) and lower (-) error bounds of each of these flows, Colorado 

River corridor between Lees Ferry and Diamond Creek, Grand Canyon National Park, Arizona.

[A zero (0) value indicates that the entire site was above the level of inundation, whereas a value greater than zero indicates the amount of area inundated in square meters. 

Sites highlighted in gray were shown to be inundated by the vector analysis but not by the raster analysis. Site key: All site numbers are prefaced with the initials AZ] 

Site key 700- 700.0 700+ 1,270- 1,270.0 1,270+ 2,750- 2,750 2,750+ 3,500- 3,500 3,500+ 4,800- 4,800 4,800+ 5,900- 5,900 5,900+ 

m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s

Group A (MNA)

B:15:138 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 67.9 0.1 66.2 216.8 155.4 252.0 300.0 262.6 307.2 343.4

C:02:096 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 13.3 1.8 11.5 17.9 14.3 16.3 49.5 19.4 45.1 53.4

C:13:010 0.0 0.0 0.0 0.0 125.1 1,099.3 687.3 2,525.0 3,960.3 1,936.4 3,517.2 4,731.5 3,197.0 4,560.7 5,551.5 3,377.1 5,224.4 5,694.6

C:13:070 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.8 125.7 0.6 117.8 366.0 140.1 443.7 707.0 152.7 709.0 745.1

C:13:099 0.0 0.0 0.0 0.0 0.0 0.0 0.0 39.6 1,601.9 0.0 921.3 4,244.8 942.9 4,244.7 4,244.7 942.9 4,244.7 4,244.7

C:13:100 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 51.6 0.0 3.9 601.7 3.9 590.2 1,346.5 3.9 1,346.5 1,346.5

C:13:291 1.5 5.6 36.6 36.8 83.7 190.7 144.0 677.2 1,137.8 515.1 988.6 1,388.5 926.6 1,242.1 1,700.6 1,058.1 1,471.4 1,863.7

C:13:347 0.0 0.0 0.0 0.0 0.0 3.2 0.0 55.4 108.9 37.5 87.5 149.0 88.7 135.3 230.0 104.6 202.9 241.8

C:13:371 0.0 0.0 0.0 0.0 56.8 256.1 358.6 755.2 1,204.6 682.7 1,183.8 1,493.7 1,215.2 1,574.0 1,901.4 1,420.1 1,890.6 2,074.9

G:03:020 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13.1 257.4 183.3 397.2 584.6 444.0 689.2 1,140.5

Group A

A:15:001 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.7 0.0 3.5 49.1

A:15:003 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 51.4 0.0 15.3 959.4 115.4 1,858.4 7,731.1 2,544.8 7,858.3 8,323.1

A:15:004 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 34.2 0.0 5.4 412.6

A:15:005 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 14.1 0.0 20.0 94.4 23.9 81.9 340.8

A:15:018 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 65.7 0.5 92.2 203.3 109.3 191.3 237.0

A:15:020 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 530.1 0.0 373.0 1,356.1 674.0 1,524.8 2,367.5 1,492.7 2,394.2 3,900.3

A:15:021 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.3 0.0 19.7 80.8

A:15:022 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 198.1 0.0 162.9 905.6

A:15:025 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:15:026 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 49.7 0.0 14.7 803.4

A:15:027 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20.3 0.0 36.9 196.8 47.8 198.0 726.4

A:15:028 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3

A:15:029 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:15:031 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.5 0.0 10.6 109.2

A:15:032 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.9 0.0 6.7 34.9 8.5 31.8 100.1

A:15:033 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 48.6

A:15:038 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:15:039 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.3 0.0 8.5 27.7 4.8 25.5 116.6

A:15:047 4.2 8.3 27.4 34.3 115.2 258.8 283.1 444.3 499.2 428.8 491.2 514.1 498.1 513.5 521.8 513.7 520.1 528.1

A:15:048 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 53.7 0.0 2.7 292.0 76.8 331.0 397.2 323.6 404.6 477.3

A:16:004 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 401.8 0.0 279.5 977.2
20

Site key 700-

m3/s

700.0 

m3/s

700+ 

m3/s

1,270-

m3/s

1,270.0 

m3/s

1,270+ 

m3/s

2,750-

m3/s

2,750 

m3/s

2,750+ 

m3/s

3,500-

m3/s

3,500 

m3/s

3,500+ 

m3/s

4,800-

m3/s

4,800 

m3/s

4,800+ 

m3/s

5,900-

m3/s

5,900 

m3/s

5,900+ 

m3/s

Group A —Continued

A:16:148 0.0 0.0 0.0 0.0 0.0 0.0 0.0 105.2 621.8 3.4 618.6 623.0 622.5 622.7 622.7 623.0 623.0 664.2

A:16:151 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.03 22.4 0.3 17.9 148.1 45.9 254.4 481.9 295.5 474.8 733.5

A:16:158 0.0 0.0 0.0 0.0 0.0 2.9 4.2 7.9 8.2 7.3 8.5 9.2 7.5 10.0 10.0 9.1 10.0 10.8

A:16:159 0.0 0.0 0.0 0.0 4.0 22.7 15.8 64.3 103.2 42.5 105.9 116.3 101.5 118.8 125.7 113.6 127.2 130.7

A:16:160 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 59.2 0.0 75.2 216.3

A:16:167 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.4 250.9 6.2 252.8 822.6

A:16:171 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 105.4

A:16:174 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.7 60.3 2.3 61.8 185.2 113.8 243.2 392.2 245.3 397.3 663.3

A:16:175 0.0 0.0 0.0 0.0 0.0 0.0 0.0 58.8 155.6 23.6 156.1 274.7 149.9 323.9 1,019.4 298.6 1,046.9 2,295.8

A:16:180 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.2 0.0 1.2 45.0 6.4 67.5 135.0 70.1 133.3 174.6

A:16:185 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.4 0.0 10.8 97.0

B:09:316 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 18.7 1.8 19.1 38.4 29.6 42.9 52.4 45.6 52.9 56.3

B:09:317 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.0 0.3 1.3 0.8 1.7 50.2

B:10:111 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

B:10:224 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 1.2 5.9 3.3 25.4 32.3

B:10:237 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 26.2 0.0 18.9 179.2

B:11:272 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 21.9 0.0 46.1 117.0

B:11:275 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

B:11:277 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.4 41.6 282.4 519.6 519.6 879.5 1,375.1

B:11:281 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17.2

B:11:284 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

B:14:093 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.3 0.0 0.1 102.8 8.3 153.5 357.4 138.6 350.3 500.9

B:14:095 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 106.6 0.0 97.9 405.5

B:14:105 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 22.8 0.0 32.4 84.9 26.8 82.2 220.0

B:14:107 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.0 2.7 113.4 2.6 91.3 283.6

B:15:096 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.3

B:15:118 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 21.7 0.4 37.6 96.9

B:15:123 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.1

B:15:124 1.6 12.6 23.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5

B:15:127 0.0 0.0 0.0 0.0 0.0 0.0 9.0 38.0 44.9 35.9 44.5 44.5 44.5 44.5 44.5 44.5 44.5 44.5

B:15:139 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.6 0.0 7.2 40.5

B:16:170 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.2 0.0 11.0 12.4 11.1 12.5 12.5

B:16:259 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.4

C:02:092 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.4 21.4 1.3 17.5 35.4 27.4 35.8 49.8 42.0 46.7 55.1

C:02:094 0.0 0.0 0.0 0.0 0.0 0.6 3.5 41.9 74.1 48.8 68.0 77.0 75.8 76.7 83.0 78.9 80.8 92.0

C:02:098 0.0 0.0 0.0 0.0 4.9 19.7 38.2 110.9 204.8 104.2 211.5 248.5 237.5 250.2 250.2 250.2 250.3 250.3

C:05:004 0.0 0.0 0.0 0.0 0.0 6.5 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8

C:05:031 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.4

C:05:037 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.1

C:05:039 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:06:005 0.0 0.0 0.0 0.0 0.0 12.2 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5

C:06:008 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.6 12.3 9.8 13.9 16.9 15.3 26.5 49.0 37.0 70.0 70.0

C:09:030 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 37.2

C:09:034 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.5 35.1 8.2 37.1 51.1 35.1 50.8 51.0 51.0 51.1 51.1

C:09:050 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:09:051 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 70.0 0.0 44.7 327.4

C:09:052 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:09:062 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 49.4 0.0 26.6 478.4 0.0 366.9 696.1

C:09:065 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 2.9 1.9 2.8 7.4 6.1 6.4 10.2

C:09:068 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.5 356.8 0.0 320.2 771.0
21

Site key 700-

m3/s

700.0 

m3/s

700+ 

m3/s

1,270-

m3/s

1,270.0 

m3/s

1,270+ 

m3/s

2,750-

m3/s

2,750 

m3/s

2,750+ 

m3/s

3,500-

m3/s

3,500 

m3/s

3,500+ 

m3/s

4,800-

m3/s

4,800 

m3/s

4,800+ 

m3/s

5,900-

m3/s

5,900 

m3/s

5,900+ 

m3/s

Group A —Continued

C:09:072 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 19.2

C:09:082 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 407.8

C:09:084 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17.8 0.0 9.7 53.2 14.2 59.5 60.9 53.1 60.8 60.8

C:09:088 5,359.6 6,358.0 7,629.0 9,297.3 12,386.1 15,331.5 16,899.5 20,364.3 23,382.7 20,126.4 23,145.5 26,023.8 23,623.8 26,455.0 29,054.6 26,430.6 29,075.1 31,409.4

C:13:005 0.0 0.0 0.0 0.0 0.0 14.3 0.0 47.1 241.5 20.2 119.7 416.9 79.1 350.9 615.9 230.0 529.0 780.6

C:13:006 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.3 0.0 16.9 104.1 16.5 106.0 226.4

C:13:007 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.6 0.0 0.0 14.2 0.0 4.3 61.9 0.0 22.8 177.6

C:13:009 0.0 0.0 0.0 0.0 0.0 1.4 0.0 229.1 1,491.1 17.0 625.7 2,409.7 518.7 2,015.9 4,322.0 1,067.9 3,299.0 5,913.0

C:13:069 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 0.0 0.0 110.8 0.0 61.5 349.4 0.0 242.2 349.4

C:13:092 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 26.6 0.0 17.9 67.3 11.7 71.1 158.8 20.1 131.6 219.9

C:13:098 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 456.8 0.0 452.2 836.4 0.0 836.3 836.3

C:13:101 0.0 0.0 0.0 0.0 0.0 0.0 0.0 130.9 2,286.9 0.0 1,316.9 4,257.0 1,362.6 4,253.7 4,683.8 1,462.2 4,683.7 4,683.7

C:13:272 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 236.5 0.0 110.9 934.6 122.6 895.1 1,387.1 122.6 1,387.0 1,387.0

C:13:273 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.8 0.0 0.0 128.6 0.0 41.3 702.6 0.0 303.8 1,016.3

C:13:321 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 121.1 0.0 60.6 319.0 48.0 301.0 713.3 73.7 598.8 773.9

C:13:322 0.0 0.0 0.0 0.0 0.0 0.3 0.0 1.4 2.9 0.6 1.4 1.4 0.6 1.4 2.7 0.6 1.8 2.9

C:13:323 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:327 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:329 0.0 0.0 0.0 0.0 0.0 0.0 5.6 362.7 548.9 252.0 518.5 696.5 539.9 758.6 972.3 717.7 979.5 1,136.5

C:13:333 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 125.5 0.0 45.9 498.0 0.0 225.0 6,76.6

C:13:334 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1,591.6 0.0 1,490.5 1,896.5 0.0 1,896.4 1,896.4

C:13:336 0.0 0.0 0.0 0.0 0.0 0.0 0.0 35.9 555.2 0.0 397.5 892.1 413.6 891.8 891.8 413.6 891.8 891.8

C:13:337 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:338 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 30.5 0.0 15.6 50.4 10.8 47.1 91.2 31.6 77.4 145.3

C:13:339 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 225.1 0.0 128.2 328.5 63.9 274.5 483.4 81.4 385.9 494.2

C:13:340 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:342 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 45.9 0.0 2.2 46.4

C:13:343 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 25.4 0.0 19.9 87.7 0.0 66.1 113.0

C:13:346 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 363.8 0.0 266.6 815.0 0.0 708.2 895.7

C:13:348 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 88.1 0.0 43.6 119.4

C:13:349 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 116.3 0.0 66.4 219.4 47.8 215.8 336.0 106.3 305.9 369.3

C:13:352 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 133.5 0.0 57.0 215.4

C:13:353 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 249.6 0.0 157.0 677.9 257.4 766.9 924.2 732.3 925.4 953.1

C:13:355 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.8 0.0 0.0 82.8 0.0 9.5 526.5 0.0 216.4 1,127.0

C:13:359 0.0 0.0 0.0 0.0 0.0 0.0 0.0 19.9 104.4 0.8 67.7 231.9 41.6 199.1 389.6 79.2 322.7 514.9

C:13:364 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.1 0.0 1.6 21.7 0.0 17.1 21.8

C:13:368 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.1 0.0 3.4 3.4 2.2 3.4 3.8 2.2 4.6 4.6

C:13:373 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:377 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.4 0.0 2.0 70.9 0.0 47.4 102.4

C:13:379 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 164.0 0.0 133.6 273.0 170.5 285.1 401.9 181.5 387.4 406.7

C:13:381 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 0.0 1.2 16.0 0.0 10.9 16.0

C:13:385 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:386 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:387 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 58.0 0.0 38.5 52.1

C:13:389 0.0 0.0 0.0 0.0 0.0 0.0 0.0 23.2 169.3 14.4 118.8 212.8 163.0 213.1 213.1 213.1 213.1 213.1

C:13:393 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:02:009 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:02:100 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:02:103 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:02:108 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
22

Site key 700-

m3/s

700.0 

m3/s

700+ 

m3/s

1,270-

m3/s

1,270.0 

m3/s

1,270+ 

m3/s

2,750-

m3/s

2,750 

m3/s

2,750+ 

m3/s

3,500-

m3/s

3,500 

m3/s

3,500+ 

m3/s

4,800-

m3/s

4,800 

m3/s

4,800+ 

m3/s

5,900-

m3/s

5,900 

m3/s

5,900+ 

m3/s

Group A —Continued

G:03:002 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 85.3 0.0 84.7 808.1

G:03:003 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 65.7 3.0 139.5 635.8 206.9 695.5 1,836.1

G:03:024 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 22.6 0.0 53.4 427.9 73.8 431.6 1,542.8

G:03:025 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 96.9 0.0 123.8 1,166.0

G:03:026 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 18.3 0.0 372.1 4,048.3 905.4 4,598.0 9,867.9

G:03:028 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 60.2 0.0 82.9 910.7

G:03:029 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 27.5 0.0 46.4 95.2

G:03:030 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.3 350.6 15.5 508.2 1,594.7 1,314.6 2,361.3 3,309.8 2,659.2 3,516.4 4,054.0

G:03:032 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.4 0.0 13.0 86.3

G:03:034 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 171.3 23.3 209.1 381.3

G:03:037 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 16.3

G:03:038 0.0 0.0 0.0 0.0 0.0 0.4 2.6 108.9 193.3 83.4 183.6 265.3 185.9 304.0 720.0 270.1 665.9 1,140.2

G:03:040 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 35.4

G:03:041 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 40.8 0.0 37.4 230.9 84.9 256.7 487.9 230.9 388.0 1,030.1

G:03:043 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.0 540.1 0.0 365.1 1,058.4 680.3 1,282.7 4,405.9 1,415.0 4,519.1 4,586.4

G:03:044 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.6 0.5 28.1 112.7 37.8 134.4 225.1

G:03:048 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:052 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.8 0.0 11.4 30.9

G:03:055 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 56.4 14.9 147.6 527.8 187.7 627.2 868.9

G:03:056 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.5

G:03:057 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 17.4

G:03:058 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:060 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 442.8 0.0 438.5 1,297.7 535.4 1,861.8 6,257.4 1,402.7 5,425.9 10,747.1

G:03:064 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 102.4 0.0 103.8 511.9 142.4 669.6 2,356.6 511.8 1,693.3 6,580.7

G:03:067 0.0 0.0 0.0 0.0 0.0 0.0 0.0 69.4 725.5 6.0 460.3 1,924.0 718.5 2,379.8 4,543.8 2,799.4 4,901.1 6,036.2

G:03:071 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 13.8 0.0 16.8 22.5 13.7 22.5 22.5

G:03:072 0.0 0.0 0.0 0.0 0.0 0.0 0.0 47.5 183.1 46.8 184.7 349.8 226.7 429.2 896.7 433.9 1,016.7 2,063.6

G:03:076 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:077 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.0 10.2 12.5 12.5 12.5 12.5

G:03:080 0.0 0.0 0.0 0.0 0.0 0.0 0.0 42.1 508.0 39.2 446.2 1,113.0 697.7 1,330.2 2,229.5 1,452.9 2,275.1 3,116.6

G:03:083 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13.6 15.4 14.0 15.3 15.3 15.4 15.4 15.4 15.4 15.4 15.4

Group B

A:15:035 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17.8 0.0 5.4 77.7 26.8 94.0 135.6 99.5 134.7 135.5

A:15:036 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:15:037 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.3 498.3 6.3 409.9 649.8 503.0 710.7 1,343.9 693.2 1,267.4 1,817.4

A:15:040 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 70.4 0.0 58.9 84.5 72.5 83.1 95.6 86.5 93.3 105.4

A:15:042 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 271.9 0.0 201.7 670.8 250.9 731.2 1,060.4 670.7 998.1 1,314.0

A:15:043 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 29.4

A:15:044 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 28.8 0.0 33.8 128.5 52.7 139.9 193.3 140.7 188.7 2,11.6

A:15:051 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 29.6

A:16:149 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 87.6 0.4 117.8 377.0

A:16:150 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:16:153 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 44.7 0.0 61.3 171.1

A:16:154 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.9 13.5 3.9 15.5 16.7 14.3 19.3 21.0 16.4 22.7 25.0

A:16:155 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:16:157 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:16:161 0.0 0.0 0.0 0.0 0.0 7.6 34.8 171.7 370.0 162.3 349.2 642.5 437.9 740.1 842.7 759.3 840.8 849.7

A:16:162 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:16:163 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

A:16:173 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.5 0.0 16.0 55.2 15.6 55.6 105.6
23

Site key 700-

m3/s

700.0 

m3/s

700+ 

m3/s

1,270-

m3/s

1,270.0 

m3/s

1,270+ 

m3/s

2,750-

m3/s

2,750 

m3/s

2,750+ 

m3/s

3,500-

m3/s

3,500 

m3/s

3,500+ 

m3/s

4,800-

m3/s

4,800 

m3/s

4,800+ 

m3/s

5,900-

m3/s

5,900 

m3/s

5,900+ 

m3/s

Group B—Continued

A:16:176 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.0 3.5 4.8 2.0 5.7 6.2

A:16:184 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

B:10:225 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.3 64.4 42.4 101.7 157.9

B:10:249 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 14.0 0.0 9.1 56.0 23.5 111.9 269.8 170.6 286.4 318.1

B:10:261 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 106.2 0.0 107.2 411.0 87.6 398.8 803.9

B:11:271 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 23.8 69.4 68.3 120.2 182.5

B:11:278 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.5 3.3 0.9 3.0 4.4 2.2 5.0 8.2 4.1 7.3 21.4

B:11:279 0.0 0.0 0.2 0.6 1.1 6.8 9.2 18.8 34.1 16.8 28.1 44.7 30.9 40.9 72.2 42.5 61.6 156.7

B:11:280 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

B:11:282 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.5 0.0 18.2 63.4 22.9 72.9 140.9

B:11:283 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.7 2.5 35.5 89.9 95.3 117.2 145.1 144.6 168.6 201.3

B:13:001 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 33.3 5.9 53.5 276.1 55.9 309.5 884.1

B:13:002 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17.2 0.0 28.0 129.2

B:15:097 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

B:15:119 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.0 5.6 26.0

B:15:134 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1

B:16:003 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0

B:16:257 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 102.4

B:16:258 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

B:16:261 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:02:097 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 51.9 0.0 65.7 121.9 93.6 141.2 147.3 131.6 151.7 156.0

C:02:101 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 17.7 0.1 28.4 59.3 27.9 61.7 84.9

C:05:009 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.03

C:06:003 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 253.9 42.1 407.5 1,105.1

C:06:010 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.4

C:09:005 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.3 0.6 10.1 37.2 13.2 30.3 107.5

C:09:032 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:09:053 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 109.3 0.0 21.8 347.9

C:09:054 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 78.5

C:09:056 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:09:059 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:09:061 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:09:067 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:09:069 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 145.6 0.0 6.3 1,382.1

C:09:071 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 24.2

C:09:073 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 201.0

C:09:083 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 109.3 0.0 110.8 476.2 134.4 494.1 747.3 476.1 732.2 1,067.3

C:13:008 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:033 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:325 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 199.1 0.0 71.0 229.6

C:13:335 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:354 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 23.7 0.0 19.5 46.0 22.1 45.8 61.8 22.1 58.2 63.4

C:13:360 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:362 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.1

C:13:363 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:370 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:372 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:374 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 84.3

C:13:392 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

C:13:486 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
24

Site key 700-

m3/s

700.0 

m3/s

700+ 

m3/s

1,270-

m3/s

1,270.0 

m3/s

1,270+ 

m3/s

2,750-

m3/s

2,750 

m3/s

2,750+ 

m3/s

3,500-

m3/s

3,500 

m3/s

3,500+ 

m3/s

4,800-

m3/s

4,800 

m3/s

4,800+ 

m3/s

5,900-

m3/s

5,900 

m3/s

5,900+ 

m3/s

Group B—Continued

G:03:006 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 118.1 26.8 278.2 831.7

G:03:023 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:049 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 211.7 0.7 245.3 312.5

G:03:053 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7

G:03:059 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:061 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 8.7

G:03:062 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 64.3 0.4 71.5 104.2

G:03:065 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:066 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 321.7 32.7 344.2 372.1

G:03:073 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:082 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

G:03:085 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.9 0.0 8.3 150.9
25

Table A2. Summary data concerning numbers of sites and amount of site area potentially affected by flows of 700 cubic meters per second (m3/s) (25,000 

cubic feet per second [ft3/s]), 1,270 m3/s (45,000 ft3/s), and 2,750 m3/s (97,000 ft3/s), including upper (+) and lower (-) error bounds of each of these flows, 

Colorado River corridor between Lees Ferry and Diamond Creek, Grand Canyon National Park, Arizona. 

Category Site 

key

700-

m3/s

700

m3/s

700+

m3/s

1,270-

m3/s

1,270

m3/s

1,270+

m3/s

2,750-

m3/s

2,750 

m3/s

2,750+

m3/s

3,500-

m3/s

3,500 

m3/s

3,500+

m3/s

4,800-

m3/s

4,800 

m3/s

4,800+

m3/s

5,900-

m3/s

5,900 

m3/s

5,900+

m3/s

All sites

Sum of site 

area 473,372 5,366.9 6,384.5 7,716.8 9,381.5 12,789.3 17,247.3 45,448.9 26,703.7 18,529.1 24,755.6 40,313.2 71,654.9 43,709.2 76,450.3 126,054.3 64,393.1 122,948.8 178,637.3

Number of 

sites

242 4 4 5 5 9 19 82 48 17 44 76 115 84 123 159 113 160 191

Percentage 

of site area

1.1 1.3 1.6 2.0 2.7 3.6 9.6 5.6 3.9 5.2 8.5 15.1 9.2 16.2 26.6 13.6 26.0 37.7

Percentage 

of sites

1.6 1.6 2.1 2.1 3.7 7.9 33.9 19.8 7.0 18.2 31.4 47.5 34.7 50.8 65.7

Group A only

Sum of site 

area 386,400 5,366.9 6,384.5 7,716.6 9,381.0 12,788.2 17,233.0 18,485.1 26,497.9 43,925.0 24,562.9 38,966.9 68,371.1 41,942.5 72,706.5 118,293.7 60,496.3 115,113.7 163,617.9

Number of 

sites

158 4 4 4 4 8 17 15 41 66 38 62 94 67 97 123 84 123 140

Percentage 

of site area

1.4 1.7 2.0 2.4 3.3 4.5 4.8 6.9 11.4 6.4 10.1 17.7 10.9 18.8 30.6 15.7 29.8 42.3

Percentage 

of sites

2.5 2.5 2.5 2.5 5.1 10.8 9.5 25.9 41.8 24.1 39.2 59.5 42.4 61.4 77.8 53.2 77.8 88.6

Group B only

Sum of site 

area

87,717 0.0 0.0 0.2 0.6 1.1 14.4 44.0 205.7 1,523.9 192.7 1,346.3 3,283.7 1,766.6 3,743.8 7,760.6 3,896.8 7,835.1 15,019.4

Number of 

sites

79 0 0 1 1 1 2 2 7 16 6 14 21 17 26 36 29 37 51

Percentage 

of site area

0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.2 1.7 0.2 1.5 3.7 2.0 4.3 8.8 4.4 8.9 17.1

Percentage 

of sites

0.0 0.0 1.3 1.3 1.3 2.5 2.5 8.9 20.3 7.6 17.7 26.6 21.5 32.9 45.6 36.7 46.8 64.6
26

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For more information concerning the research in this report, contact the

 SBSC staff, Southwest Biological Science Center

U.S. Geological Survey

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http://sbsc.wr.usgs.gov/
Sondossi and Fairley—An Analysis of the Potential for Glen Canyon Dam Releases to Inundate Archaeological Sites in the Grand Canyon, Arizona—Open-File Report 2014–1193

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141193