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ASSESSMENT OF WESTERN NAVAJO AND HOPI (WNH)
WATER SUPPLY NEEDS, ALTERNATIVES AND IMPACTS
TECHNICAL MEMORANDUM
WNH THREE CANYONS (WNH3C)
GROUNDWATER FLOW MODEL
This memorandum describes the evaluation and revision of an existing groundwater
flow model for the Three Canyons (Clear Creek, Chevelon Canyon, and Jack’s Canyon)
area between the southwest corner of the Navajo Nation and the Mogollon Rim. The
existing model was developed HydroGeoChem, Inc. (1997) for the Bureau of Indian
Affairs and the reader is referred to that document for supporting information.
HydroGeoChem(1997) used a proprietary model code, called ABEL, to develop the
existing model, now informally called the “Hopi Ranches Model”. The revised model is
called the Western Navajo-Hopi Three Canyons (WNH3C) model and is based on the
freely-available MODFLOW model code. The purpose of the WNH3C model is to
estimate the impacts from pumping on baseflows in Clear Creek and Chevelon Canyon.
This memorandum only addresses the development and calibration of a steady state
simulation using the WNH3C model.
1.0 Initial Model Preparation
The WNH3C model was developed from basic data, rather than conversion of the
input files developed for the ABEL-based Hopi Ranches Model. The first step was to
plot the basic data in the form of GIS files in ArcGIS ArcView version 8.2. The GIS files
are in UTM Zone 12, NAD 1927 coordinates. The WNH3C model uses feet and days as
units. The offset from the origin of UTM Zone 12 to model coordinates is: 1,570,505
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Revision 0 December 24, 2002 HDR Review Draft Western Navajo Hopi Three Canyons Model Technical Memorandum
feet in the X direction, 12,521,635 feet in the y direction, and no tilt from an easterly
orientation. The steady state model was developed from GIS files using Groundwater
Vistas Version 3.3.
The model grid was designed, following the HydroGeoChem (1997) report as a grid
of 211 columns and 183 rows. Each grid cell is a square has the same size: 1320 feet on
a side.
The next step was to plot and contour the available water-level measurements
indicated in HydroGeoChem (1999) and provided as an EXCEL file by John Ward, one
of the authors of the HydroGeoChem (1997) report. The resulting contours were similar
to those presented in HydroGeoChem (1997) and were used to assign prescribed head
boundary conditions around the model periphery.
The top of the C-Aquifer was delineated from surface elevations where the C-Aquifer
is exposed at land surface (determined from the Arizona Geological Survey Geologic
Map of Arizona). Where the Moenkopi and some younger units overlie the C-Aquifer,
modifications were made to the land surface-based estimate for the top of the C-Aquifer.
In the north and northeast areas of the model, where the C-Aquifer is deeply buried,
contours on the base of the overlying Moenkopi Formation were transcribed from Ulrich
& others (1984). The remaining areas covered by Moenkopi Formation were addressed
manually by continuing land surface elevation contours across from opposing sides of
limited areas of Moenkopi Formation occurrence.
The base of the C-Aquifer was derived by subtracting the saturated thickness
presented by HydroGeoChem (1997) from the estimated water-level elevation in the C-
Aquifer for areas of exposed C-Aquifer. For the north-northeast area, a thickness of
approximately 650 feet was subtracted from the elevation of the base of the Moenkopi
Formation.
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Revision 0 December 24, 2002 HDR Review Draft Western Navajo Hopi Three Canyons Model Technical Memorandum
The available hydraulic conductivity estimates were plotted by HydroGeoChem
(1997). The supporting aquifer test data were not obtained or re-analyzed for this effort.
Based on inspection of the plot of the available hydraulic conductivity estimates, a range
of values of 0.1 to 20 feet per day (ft/d) was considered reasonable. No systematic trend
or grouping is apparent for the WNH3C model area from inspection of the
HydroGeoChem (1997) plot. The three-part distribution used by HydroGeoChem (1997)
in their model (one zone each with 1, 6, or 6.5 ft/d) was used as an initial distribution.
The locations of channels potentially interacting with groundwater were identified by
comparing the water-level elevation contours with land surface elevation contours shown
on USGS 7.5 minute quadrangle sheets along Clear Creek and Chevelon Canyon. Three
primary areas were identified as having potential groundwater interaction:
• Clear Creek in the vicinity of Blue Ridge Reservoir,
• Clear Creek near its confluence with the Little Colorado River, and
• Chevelon Canyon near its confluence with the Little Colorado River.
The lower Clear Creek and lower Chevelon Canyon reaches were documented by
HydroGeoChem (1997) as perennial, but no discussion was provided of the perennial
nature of Clear Creek and its tributaries near Blue Ridge Reservoir in the far
southwestern corner of the Hopi Ranches Model. Nevertheless, comparison of water-
level elevations and the land surface confirms the potential for groundwater-surface water
interaction in the vicinity of Blue Ridge Reservoir. The model grid was overlain on the
7.5-minute quadrangle sheets in ArcView 8.2 and parameters for the MODFLOW Stream
Package were estimated fro each cell representing Clear Creek, Chevelon Canyon, and a
few tributaries of Clear Creek near Blue Ridge Reservoir.
Although HydroGeoChem (1997) did not incorporate recharge into their simulation,
review of a recent white paper on recharge developed by HDR (2002) indicated that the
exposed C-Aquifer should receive significant recharge, particularly at the elevations
included in the WNH3C model. Simplified regions of equal recharge based on the
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Revision 0 December 24, 2002 HDR Review Draft Western Navajo Hopi Three Canyons Model Technical Memorandum
elevations, precipitation, and percent of precipitation becoming recharge were adopted as
initial recharge inputs for the WNH3C model for areas of exposed C-Aquifer.
An area in the southeastern portion of the WNH3C model, noted as dry by
HydroGeoChem (1999) was set as inactive in the WNH3C model.
The depths to water across the model were calculated and reviewed. Based on this
review, the potential or evapotranspiration from the groundwater was considered to be
negligible at this time. Future evaluation may provide a basis for adding the simulation
of evapotranspiration in limited areas.
The pre-conditioned conjugate gradient solver package (PCG2 – Hill, 1990) was
selected for the WNH3C model. The solver was set to achieve a head residual of 1 x 10-4
feet and a mass balance residual of 1 cubic foot per day (ft3/d) using 1,000 outer
iterations and 10 inner iterations.
3.0 Water-Level Targets and Calibration
The water-level data provided by John Ward were input to Groundwater Vistas
Version 3.3 as targets for calibration the model was operated with MODFLOW-2000 and
the match of model simulation to measurements was observed. Overall match was
relatively poor so calibration was pursued. Calibration consists of adjusting input
parameters to improve the match of model-simulated water-level elevations to measured
water-level elevations. The hydraulic conductivity and recharge distributions described
above were modified to achieve an acceptable calibration. The required modifications
were well within the range of reasonable values.
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Revision 0 December 24, 2002 HDR Review Draft Western Navajo Hopi Three Canyons Model Technical Memorandum
After acceptable calibration was achieved, a band of cells surrounding the inactive
area in the southeast portion of the model were set to inactive as their bottom elevations
were above the simulated water level elevations.
4.0 Results
The inflow portion of the WNH3C model mass balance for steady conditions consists
of 16,915 acre-feet per year (ac-ft/yr) of inflow from prescribed head boundaries, joined
by 35,450 ac-ft/yr of diffuse recharge, and 2,840 ac-ft/yr of recharge from streams. The
outflow portion of the WNH3C model mass balance for steady conditions consists of
50,330 ac-ft/yr of outflow to prescribed head boundaries and 4,875 ac-ft/yr of baseflow
out to streams. Total inflow or outflow under steady conditions is approximately 53,000
ac-ft/yr.
The base flow gains for Clear Creek and Chevelon Canyon simulated by the WNH3C
model are as follows:
• 4 cubic feet per second (cfs) for Upper Clear Creek in the vicinity of Blue
Ridge Reservoir
• 2.5 cfs for Lower Clear Creek
• 0.4 cfs for Lower Chevelon Canyon
These values are different than those derived from model simulations by
HydroGeoChem (1997), who found:
• No flow for Upper Clear Creek in the vicinity of Blue Ridge Reservoir
• 4 cfs for Lower Clear Creek
• 5.5 cfs for Lower Chevelon Canyon.
A useful assessment of the meaning of the differences between the HydroGeoChem
(1999) and WNH3C models would require detailed analysis of available stream flow
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Revision 0 December 24, 2002 HDR Review Draft Western Navajo Hopi Three Canyons Model Technical Memorandum
records and observations. However, given the acceptable simulation of the water-level
elevations by the WNH3C model, particularly in the areas of the groundwater-surface
water interactions, such an analysis is not considered necessary at this time.
Figure 1 shows the extents of the WNH3C model, modified from the existing
HydroGeoChem model (1997) as discussed in this memorandum. Also shown on Figure
1 are the inactive cells, prescribed head (constant water-level elevations in this case)
cells, stream package cells, the Little Colorado River and lesser surface water channels,
township and range boundaries, and the locations of major roads.
Figures 2 and 3 show the distributions of hydraulic conductivity and recharge in the
calibrated WNH3C model. Figure 4 shows the measured water-level elevations at points,
interpreted contours of the measurements, and the water-level elevations simulated by the
WNH3C model.
Figure 5 shows the cross plot of simulated and measured water level elevations after
calibration. The current standard deviation of the water-level elevation simulation
residuals is 39 feet, which is approximately two percent of the overall range in measured
water-level elevations (1758 feet). Figure 6 shows the distribution of WNH3C
calibration residuals (measured water-level elevation minus simulated water-level
elevation). The WNH3C model is ready for simulations of the response of base flows in
Clear Creek and Chevelon Canyon to future pumping from the C-Aquifer.
4.0 REFERENCES
HDR Engineering, 2002. White Paper – Recharge Assessment of Western Navajo Hopi Water Supply N-Aquifer Model (WNHN), prepared for and presented to the Technical Support Group.
Hill, M. C., 1990, Preconditioned Conjugate-Gradient 2 (PCG2), a Computer Program
for Solving Ground-Water Flow Equations: U.S. Geological Survey Water-Resources Investigations Report 90-4048, 43 pages.
Page 7 of 7
Revision 0 December 24, 2002 HDR Review Draft Western Navajo Hopi Three Canyons Model Technical Memorandum
HydroGeoChem, Inc. 1997. Results of Numerical Simulations of Impacts on Clear and
Chevelon Creeks from Proposed Groundwater Developments on Clear Creek and Aja Ranches (Hopi Ranches), prepared for the U. S. Bureau of Indian Affairs, dated, December 4, 1997, 24 pages plus tables and figures.
Ulrich, G.E., Billingsley, G.H., Hereford, R., Wolfe, E.W., Nealey, L.D., and R.L.
Sutton, 1984. Map Showing Geology, Structure, and Uranium Deposits of the Flagstaff 1 Degree by 2 Degree Quadrangle, Arizona, U.S. Geological Survey, Miscellaneous Investigation Series, Map I-1446.
0 6 12 18 24 303Miles
®
Jacks Canyon
Clear Creek
Chevelon Canyon
Blue Ridge Reservoir
Chevelon Canyon Lake
Little Colorado River
Figure 1 WHN Three Canyons Model Extents, Surface Water Features and Boundary Conditions
ExplanationModel Extents
Roads
Township/Range
Moenkopi Extents
Unique Model Cell Type
CH
Noflow
Stream
ExplanationModel Extents
Roads
Township & Range
Kx0.6
7
12
0 10 20 30 402.5 5 7.5Miles
Figure 2 Distribution of Calibrated Hydraulic Conductivity WNH Three Canyons Model
Kx = horizontal hydraulic conductivity in feet per day
Area where C-Aquiferis assumed to be dry.
ExplanationModel Extents
Roads
Township & Range
Recharge R
0
0.00009
0.0001
0.00015
0.0003
Recharge Rate is a flux density in feet per day
Figure 3 Distribution of Recharge Applied to WNH Three Canyons Model
®
0 6 12 18 24 302 4Miles
Area where C-Aquiferis assumed to be dry.
5600
5100
5000
5700
5200
4900
5800
5500
4800
5300
5400
5900
6000
61006200
6300
4700
6400
65006600
6700
68006900
5000
5700
4900
5800
5100
4800
5600 5200
5500
5300
5400
5900
6000
6100
6200
4700
6300
6400
6500
660067006800
5100
5200
5600
5500
4707 46774925
469646794750465649045005 4719
47844810 4725 47354710482848314724
5008 4770 4723 47124744
47844819 4754 4789 47754884
482648804922 4803 48335007 4930 484448434848
485648505090
48754878 4908
4871 496949004883 49864969
48994899 4951 50124987
49865109 5003499049144940 5000
501349405109
4997500549665135 50065140
501251335131
5017 5060
5193 50985058
50875272 5048 50555235 5036
53265077 5084
5300 515560705812 5200
56675654 527651805825
58936340
6375 634964026258 5405
637355236372 5463
6414
57615525
552555836280
58225618559359206020 56576726
5833 559755946907
®
0 10 20 30 402.5 5 7.5Miles
Figure 4 Water-Level Elevations WNH Three Canyons Model Area
Interpreted Contour of Equal MeasuredWater-Level Elevation(thick solid blue line)
Contour of Equal Simulated Water-Level Elevation(thinner - dashed blue line)
Area where C-Aquiferis assumed to be dry.
Measured Water-Level Elevation
Road
Township-Range Boundary
4500 4750 5000 5250 5500 5750 6000 6250 6500Measured Water-Level Elevation (feet above mean sea level)
4500
4750
5000
5250
5500
5750
6000
6250
6500Si
mul
ated
Wat
er-L
evel
Ele
vatio
n (fe
et a
bove
mea
n se
a le
vel)
Water-level ElevationsC-Aquifer Water Levels1:1 (exact correspondence)+/- 1 SD (38.9 feet)
Figure 5 Cross Plot and Residuals Plots for Measured and Simulated Water-Levels, WNH Three Canyons Model
4500 4750 5000 5250 5500 5750 6000 6250 6500
-150
-100
-50
0
50
100
150
Resid
ual (
mea
sure
d - s
imul
ated
)
$+$+ $+ $+ $+$+
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$+$+$+ $+$+$+ $+
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65
47
-4
-9
27
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5.50.2
-336.8
1.3
6.33.1
3.79.6
1.32.8
3.4 0.21.3
-32
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76.7-0.7-0.532.7
39.619.734.1 12.6
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-13.8
-98.9-20.1
-22.3-95.9
0 6 12 18 24 303Miles
®
Figure 6 WHN Three Canyons Model Calibration Residuals
Explanation$+ Residual (feet)
Model Extents
Roads
Township/Range
Unique Model Cell Type
CH
Noflow
Stream