Alternative Pilot Study Area Combinations
Possible pilot study areas that were identified and discussed at the last Technical Committee
Workshop are listed in Matrix format in Table 1 along with associated information related to
location, technical factors, cost, and schedule. There are many potential combinations of pilot
areas that could be considered based on the selection matrix. However, we believe it is necessary
to limit consideration to a set of combinations that best meet the expressed needs of the project.
Thus, we have developed a set of six alternatives that we recommend for consideration by the
Committee. Rationale used in developing the alternatives and limiting the number of alternatives
considered is summarized below followed by a brief description and discussion of each
alternative. Finally, we have provided for the Committee’s consideration a preliminary ranking
of the alternatives in order of preference based on consideration of project objectives.
RATIONALE FOR DEVELOPMENT OF ALTERNATIVES
1. Any combination of alternatives should include the Modesto site because this site includes
the most complete set of data and models (WARMF and MODFLOW [regional and local])
available to yield the most accurate accounting of salts and nitrate.
2. Any combination of alternatives should include the Yolo site because this site is largely
included in the WARMF domain and has an extensive countywide database that contains
groundwater quality data organized in a manner that can be queried a variety of ways to
consider the effects of past land use on groundwater quality relative to the salt and nutrient
balance provided from the WARMF model. The WARMF model would be expanded to
include the balance of the proposed study area, which would include urban land use such as
the city of Davis.
3. Any combination of alternatives that considers the Merced Groundwater Subbasin should
also include the area west of the San Joaquin River, because there is evidence to indicate that
there is transfer of salts and nitrates between the east and west sides. Separating the eastern
and western Merced areas would yield incomplete results. The WARMF domain covers both
the eastern and western Merced areas. A groundwater model in progress for this area
(MercedSim) offers significant data and information to relate to the WARMF model results
and also for use of estimated recharge to the WARMF model.
4. The Kings River area was suggested as a potential study area in the southern San Joaquin
Valley Groundwater Basin. There is a groundwater model available for this area; however,
the model domain is very small in comparison with the Tule River model area. It is the
team’s opinion that the Kings River area that could be studied for this project is too small to
yield information that would best meet the objectives of the project (see additional
information in Appendix A). Consequently, the Kings River area was not considered further
as a viable option for this project.
DESCRIPTION OF ALTERNATIVES
The six alternative combinations of pilot study areas recommended for consideration are
designated as Alternatives A through F. The order in which the alternatives are described does
not indicate the final ranking of alternatives. A brief description is provided for each alternative,
including total cost and submittal schedule followed by a brief discussion of the pros and cons of
1
selecting the combination. A more detailed description of the WARMF and groundwater
modeling tools and methodologies that would be used in the various study areas is presented in
Appendix A.
Alternative A: Original 3 Areas (Yolo + Modesto + East Merced)
Cost: $275,000
Schedule:
Work Plan Final – 6/26
Study Final – 10/30
Description:
This alternative is the “no change” alternative. Includes the three pilot study areas and
study methods based on WARMF described in the original proposal. The land use data
for the Modesto and Merced areas would be updated to DWR/NLCD.
Discussion:
Does not address the Tulare Lake Basin or the west side of the San Joaquin Valley
Groundwater Basin. This is the lowest cost option and the does not require a time
extension.
Alternative B: Yolo + Modesto + Combined East and West Merced
Cost: $300,000
Schedule:
Work Plan Final –7/3
Study Final – 10/30
Description:
This alternative expands the Merced area to include the area west of the San Joaquin
River. The area west of the Merced Subbasin (e.g., west of the San Joaquin River) should
also be included because there is evidence to indicate that there is transfer of salts and
nitrates between the east and west sides. Separating the eastern and western Merced areas
would yield incomplete results. A groundwater model in progress for this area offers
significant data and information to relate to the WARMF model results.
Discussion:
Closest to originally recommended areas with expansion of Merced area for slightly
higher cost. Evaluation of the Tule River area would wait for completion of Harter's
research.
Alternative C: Yolo + Modesto + Tule River Basin w/ WARMF
Cost: $386,000
Schedule:
2
Work Plan Final – 7/3
Study Final (Yolo + Modesto) – 10/30
Study Final (Tule River) – 12/30
Description:
This alternative includes the Yolo and Modesto areas as described in the original
proposal as well as the use of the model for the Tule River basin developed by Thomas
Harter and others that couples three submodels, including a surface water model, a landatmosphere interface and unsaturated zone model (also referred to as the unsaturated zone
water budget or UZWB), and a groundwater flow model. There is not yet a water quality
component for the model. Work by Harter is underway to develop a detailed nitrogen
balance; however, this work has been put on hold due to economic factors delaying the
release of the Proposition 50 funds. This alternative involves an approach that
incorporates WARMF model features, including all facets related to salt and nutrient
generation, mobilization, and discharge. The analysis would include evaluation of
nutrient uptake, nitrification and denitrification processes, and also mass balances of the
individual ions that comprise salt. The analysis also accounts for such processes as
cation exchange, adsorption, mineralization, dissolution, and precipitation. Particle
tracking using MODFLOW-MODPATH would support evaluation of salt and nutrient
sources and sinks, including time of travel and locations of discharge (e.g., wells,
boundaries, etc.).
Discussion:
Includes Tule River but excludes the east and west Merced areas. Includes nitrogen
"process" detail and other important chemical processes that affect the movement of the
individual ions that comprise salts.
Alternative D: Yolo + Modesto + Tule River Basin w/o WARMF
Cost: $339,000
Schedule:
Work Plan Final – 7/3
Study Final (Yolo + Modesto) – 10/30
Study Final (Tule River) – 12/30
Description:
This alternative is the similar to Alternative C except that the approach does not
incorporate WARMF model features. The approach instead would involve use of the
inputs and outputs to the Harter Model and couple those with salt and nutrient inputs to
assess movement of these constituents within the modeled system (see Appendix A). The
particle tracking would support evaluation of salt and nutrient sources and sinks,
including time of travel and locations of discharge (e.g., wells, boundaries, etc.).
Discussion:
Includes the Tule River site in the south San Joaquin Valley Groundwater Basin site but
excludes both the east and west Merced areas. Postpones the Tule River "process" detail
until Harter's research is complete. Includes a "non WARMF" approach, which does not
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include such features as nutrient uptake (unless a portion of the nutrients in the water
source is reduced according to land use types to account for an estimated uptake amount),
nor would it account for nitrification and denitrification. The non-WARMF approach
also would not account for such processes as cation exchange, adsorption, mineralization,
dissolution, and precipitation. These processes have been found to be very important for
the nitrate balance in the San Joaquin watershed. Cost is less than for a similar area with
WARMF approach.
Alternative E – Yolo + Modesto + Combined East and West Merced + Tule River
Basin w/ WARMF
Cost: $481,000
Schedule:
Work Plan Final – 7/3
Study Final (Yolo + Modesto + Merced ) – 10/30
Study Final (Tule River) – 12/30
Description:
This alternative combines several areas of high interest to the Committee due to the
broad range of conditions represented and data available. It includes the eastern and
western Merced areas and the Tule River area with the WARMF model features.
Discussion:
Includes all areas of interest with nitrogen "process" detail for Tule River area. Highest
cost. If funding is available, this is the first ranked alternative, because it most completely
meets the objectives of the project.
Alternative F – Yolo + Modesto + Combined East and West Merced + Tule River
Basin w/out WARMF
Cost: $434,000
Schedule:
Work Plan Final – 7/3
Study Final (Yolo + Modesto + Merced) – 10/30
Study Final (Tule River) – 12/30
Description:
This alternative includes several areas of interest, including both the eastern and western
Merced areas and the Tule River area, but without the WARMF model features.
Discussion:
Includes all areas of interest; addresses inclusion of Tule River, but postpones Tule River
nitrogen "process" detail until Harter's research is complete. Includes a "non-WARMF"
approach for comparison to the WARMF model features used in the other areas.
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RANKING OF ALTERNATIVES
A preliminary recommended ranking of the alternatives is presented in Table 2. The order is
based on the team’s assessment of the alternative’s performance relative to the project’s
technical objectives and is provided for the Committee’s consideration.
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Table 1. CV-SALTS Pilot Study Area Selection Matrix
Initial LWA Team Proposed Pilot Areas
Selection Criteria
Yolo
Modesto
Merced (East)
Alternative Pilot Areas
Merced (West)3
Tule River w/o
WARMF
Tule River w/
WARMF
Location
Basin Plan Area
Sac River Basin
SJ River Basin
SJ River Basin
SJ River Basin West
Tulare Lake Basin
Tulare Lake Basin
Mostly
Yes
Yes
Yes
No
No
WARMF
(Mostly existing)
WARMF
(Existing)
WARMF
(Existing)
WARMF
(Existing)
Harter-Lund
Model
WARMF
(New)
Groundwater model –
hydrology
IGSM2/USGS near
future
Yes
BuRec in progress /
USGS near future
BuRec in progress /
USGS near future
Harter / USGS
near future
Harter / USGS
near future
Groundwater model –
quality
No
Yes
No
No
Harter future
Harter future
Groundwater data
available
Yes
Yes
Yes
Yes
Yes
Yes
Groundwater data
organized
Yes
Yes
Partial
Partial
Partial
Partial
In WARMF Domain
Technical Factors
Surface Water / Root Zone
Model
Salinity Tracking
Complete
Complete
Complete
Complete
Conservative
Complete
Nitrate Tracking
Complete (incl.
NH4, reactions,
adsorption, canopy)
Complete (incl.
NH4, reactions,
adsorption,
canopy)
Complete (incl.
NH4, reactions,
adsorption, canopy)
Complete (incl.
NH4, reactions,
adsorption, canopy)
Conservative
Complete (incl.
NH4, reactions,
adsorption,
canopy)
Land use data in WARMF
DWR/NLCD (1997)
USGS GIRAS
(1980)
USGS GIRAS
(1980)
USGS GIRAS
(1980)
DWR
(not in WARMF)
DWR/NLCD
(1999)
Mixed
Mixed
Mixed
Mixed
Mixed
Mixed
Ag/Urban/Rural
Urban/Ag/
Industrial
Ag/Urban/Rural
/Industrial
Ag/ Rural/ Industrial
Ag/ Rural/
Ag/ Rural/
Surface/GW
Surface/GW
Surface/GW
Surface/GW
Groundwater
Groundwater
Yes
Yes
Yes
Yes
Yes
Yes
Water Use
Sources
Sinks
Agency Cooperation
CV-SALTS Pilot Study Area Selection Matrix, continued
Initial LWA Team Proposed Pilot Areas
Alternative Pilot Areas
Tule River w/o
WARMF
Tule River w/
WARMF
Yes
Partially/work
underway by
Harter will improve
Yes
Yes
Partial – not full
nitrogen balance;
comprehensive
work underway by
Harter will address
nitrogen balance
Yes
Yolo
Modesto
Merced (East)
Merced (West)3
Meets Long-term
Objectives
Yes
Yes
Yes
Identify/Quantify Salts &
Nutrients
Yes
Yes
Yes
Selection Criteria
Track Salt & Nutrient Mass
Land
Surface Water
Vadose Zone
Shallow Groundwater
Track Trends
“Deeper” Groundwater
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes/partial
Yes/partial
Yes/partial
Yes/partial
Yes
Yes
Yes
Yes
Empirical/future
with model
Yes with
MODFLOW &
MODPATH
model
Empirical/future
with model
Empirical/future
with model
Empirical/ also
possible with
MODPATH
applied to Harter
model
Empirical/ also
possible with
MODPATH
applied to Harter
model
Costs
Work Plan Cost1
Pilot Study
Cost1
Upgrade to DWR/NLCD Land
Use
Upgrade to Aerial Land Use
$91,000 (original) / $64,000 (revised)3
$184,000 (original) / $208,000
Done
$43,000
MODPATH Analysis
Schedule Affects
(revised)3
$5,000
$28,000
$28,000
$20,000
$106,000
$153,000
Included in
revised
Included in
revised
Included
N/A
Included
$43,000
$43,000
$43,000
Included
--
--
--
Yes
N/A
$43,000
$8K -$10K
$8K -$10K
Yes
Yes
1. For alternative pilot areas, costs shown are for adding a pilot area to the 3 initially proposed.
2. IGSM developed; not a public domain model
3. Cost for original work has been reallocated to move budget from the Work Plan to the Study to provide enough budget to ugrade the land use data to DWR/NLCD.
Table 2. Ranking of Alternative Pilot Study Areas
Rank No.
Alternative
Cost, $
WP Date
Study Date
1
Alternative E:
Yolo + Modesto + E/W
Merced + Tule R w/
WARMF
$481,000
7/3
10/30
12/30
2
Alternative F:
Yolo + Modesto + E/W
Merced + Tule R w/out
WARMF
$434,000
7/3
10/30
12/30
3
Alternative C:
Yolo + Modesto + Tule
R w/ WARMF
$386,000
7/3
10/30
12/30
4
Alternative D:
Yolo + Modesto + Tule
R w/out WARMF
$339,000
7/3
10/30
12/30
5
Alternative B:
Yolo + Modesto + E/W
Merced
$300,000
7/3
10/30
6
Alternative A:
Yolo + Modesto + E
Merced
$275,000
7/3
10/30
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Appendix A: Modeling Tools and Methodologies
MODELS: COMMUNICATION
The MODFLOW groundwater flow model (used for Modesto and the Tule River sites) will be
used to simulate water levels and mass balances for each cell of the model grid and for each of
the stratigraphic layers included. Cell-by-cell values are then summed to evaluate the mass
balance for each layer and the total mass balance in the study area.
Information about recharge rate is shared between the surface water model and the groundwater
model. Where WARMF is employed, the groundwater model will provide this information for
the surface water model, which will use it as input. Where the WARMF model is not employed
and surface inputs are provided in a spreadsheet model, spreadsheet output will serve as the
groundwater model surface recharge input.
The MODPATH particle tracking is a post-processing program that is used in conjunction with
the cell-by-cell flow rates calculated with the MODFLOW flow model and will produce travel
times to wells and source-area delineation. MODPATH can be used to simulate both forward and
backward particle tracking and will be a powerful element in the calibration, validation, and
uncertainty evaluation of the SW/GW coupled models. For example, a map of the distribution of
groundwater originating from different sources can be constructed by tracking a parcel of water
backward from every cell in the model, and then plotting a symbol for the source areas at the cell
centers. Such a simulated map can be compared with the map created by the SW model
(WARMF or spreadsheet) and used to calibrate the model. Calibration will be performed using
the automatic calibration techniques included in UCODE-2005 (Poeter et al., 2005).
The forward-particle tracking option will also be used. The general approach for this option will
be: particles will be started at all inflow locations in the model (inflow locations are provided by
the SW model), including areal recharge, fluxes from boundaries, flow from wells and they will
be tracked to their discharge point. The particles can be distributed on the face of the model cells
associated with the inflow uniformly or not uniformly, and this will be determined by the SW
model. The volume associated with each particle will be computed by dividing the inflow at the
source face by the number of particles started on that face. The subset of particles that
terminated, for example, at a well will be used to define the area contributing recharge to that
well. Particles can be tracked in each layer of the domain and at each possible point of discharge
(e.g., wells, boundaries).
A new package for MODPATH, under development by USGS and expected to be released in
summer 2009, will be able to keep track of the concentration of particles and can be used in this
study. This includes a dispersion factor which is the one produced by heterogeneity or slight
variations in the starting position of a cloud of particles.
TULE RIVER STUDY AREA
As discussed at the June 2, 2009 meeting, the Tule Subbasin (or Tule River area) is of interest as
a possible pilot study area. A WARMF model has not yet been developed for this area. A
comprehensive modeling effort has been conducted in an area covering 541,580 acres (or about
1,500 sq. miles) across the entire Tule Subbasin and also parts of the Tulare Lake and Kaweah
Subbasins (Thomas Harter and others at the University of California at Davis). It includes areas
1
covered by 9,114 land units and 26 water service districts. The model, developed as a
conjunctive use model to better understand the impacts of irrigated agriculture, variable surface
water supplies, and pumping practices on groundwater levels and storage, couples three
submodels, including a surface water model, a land-atmosphere interface and unsaturated zone
model (also referred to as the unsaturated zone water budget or UZWB), and a groundwater flow
model (referred to below as the “Harter Model”). The three submodels address water movement
through the system; there is not yet a water quality component. However, research has been
funded through a Proposition 50 grant to develop a detailed nitrogen balance and other related
work for the Harter Model area. At this time, work has been put on hold due to economic factors
delaying the release of the Proposition 50 funds.
Because of the interest expressed at the June 2 meeting in exploring the Tule River area as a pilot
study area, the LWA team has considered two approaches, including one that would develop the
WARMF model in the Tule Subbasin and adjoining areas and one that would evaluate an
approach that does not incorporate WARMF model features. The latter approach would involve
use of the inputs and outputs to the Harter Model and coupling those with salt and nutrient inputs
to assess movement of these constituents within the modeled system. The UZWB is used to
calculate monthly water storage changes in the soil root zone and deep vadose zone of each land
unit. Inputs to the Harter Model soil root zone water budget include precipitation, and surface
water and groundwater applied to the land surface (largely for irrigation). Each of these inputs
would be assigned constituent concentrations for the different water quality that can be identified
for the different water sources (e.g., attempt to account for varying groundwater quality from
different areas/water districts or varying surface water quality). Fertilization would also be
accounted for with loading rates for each land unit. These input values would be related to the
UZWB, and the calculations would be managed outside the model in spreadsheet format to
produce run to evaluate salt and nutrient balances for the study area. The spreadsheet output
would quantify and spatially identify significant sources and sinks of salts and nutrients.
The approach for the Tule River area would also use particle tracking to evaluate salt and
nutrient sources and sinks, including time of travel and locations of discharge (e.g., wells,
boundaries, etc.).
MERCED (EAST AND WEST) STUDY AREA
The extended East-West Merced area will cover about 900,000 ac. It is highly influenced by
agricultural practices and previous studies (Phillips et al, 1991; Brush at al., 2004; Quinn, N.,
many) showed that groundwater pumpage and recharge from agricultural irrigation are the
dominant hydraulic stresses on the groundwater flow system. Also, groundwater pumpage on the
east side of the San Joaquin River overlying the Corcoran clay and flow from east to west
underneath the San Joaquin River cannot be neglected. This justifies the need to study both the
east and west Merced areas.
Also, in the west Merced area, wetlands are very extensive. Different projects (Quinn et al.,
2002, 2003, 2007) have shown that accurate soil salinity studies are important for evaluating
water needs for wetlands, developing Best Management Practices and documenting trends in
habitat quality.
Groundwater level data have been extensively collected by Nigel Quinn to develop the
MercedSim flow model. MercedSim is an Integrated Water Flow Model (IWFM) application; it
2
includes information on surface water diversions, crop acreage, stream rating tables, aquifer
elevation, and initial conditions from DWR and aquifer properties (top layer), ET, land use,
agricultural/urban water demand from MID/Geomatrix.
Groundwater quality data still need to be collected and included in the WARMF model.
For this first pilot project, the East-West Merced areas can be studied using WARMF and the
available data in an approach similar to the Yolo approach. The main difference will be in the
amount of organized data, which is expected to be less than that developed for the Yolo area.
In future efforts, the MercedSim groundwater model developed by Nigel Quinn could be
integrated with WARMF with a procedure similar to the one described for Modesto and Tule
River areas where the MODFLOW model is available.
KINGS RIVER STUDY AREA
The Kings River area was also discussed as an area of interest at the June 2 meeting. A
comprehensive modeling effort has been conducted for an area covering about 37 square miles
southeast of Fresno and northwest of Sanger and the Kings River (Gary Weissmann and others).
The modeling effort included highly detailed stratigraphic work to understand the influence of
heterogeneity on groundwater ages. The model effort employed application of probability
geostatistics within a sequence stratigraphic framework, 2) simulation with a steady state
groundwater flow model, and 3) estimation of water travel time from the water table to wells
using backward-in-time random walk particle tracking. The study area includes a highly
discretized grid including 950,000 cells within a simulation grid that had the overall dimensions
of 6,300 x 15,000 x 100.5 m. The model data would be coordinated with water quality inputs,
i.e., constituent concentrations would be assigned for the different water quality that can be
identified for the different water sources (e.g., attempt to account for varying groundwater
quality from different areas/water districts or varying surface water quality). Fertilization would
also be accounted for with loading rates for each land unit. These input values would be related
to the model data for the unsaturated zone, and the calculations would be managed outside the
model in spreadsheet format to evaluate salt and nutrient balances for the study area. The
spreadsheet output would quantify and spatially identify significant salt and nutrient sources and
sinks. The approach for the Kings River area would also use particle tracking to evaluate salt
and nutrient sources and sinks, including time of travel and locations of discharge (e.g., wells,
boundaries, etc.).
DIFFERENCES BETWEEN WARMF AND NON-WARMF APPROACH
The WARMF model extracts nutrients from soil according to net plant productivity specified in
the input. The input data also provide a long-term productivity increase per year, a seasonal
pattern of nutrient uptake, a monthly litterfall, a stoichiometric content of plant biomass, and a
root distribution among soil layers from which plants extract nutrients. The data are provided for
each land use so that the WARMF model can calculate the terms for each land use and aggregate
them for the catchment areas. The non-WARMF approach described above would not account
for nutrient uptake unless a portion of the nutrients in the water source is reduced according to
land use types to account for an estimated uptake amount.
3
The WARMF model also accounts for nitrification and denitrification. The non-WARMF
approach would not address these processes. We understand that the Harter research underway
would develop a comprehensive nitrogen balance.
Another main advantage of the WARMF output is that it provides mass balances of the
individual ions that comprise salt, thus providing substantially more information than would be
produced by limiting the mass balance analysis to aggregate salinity parameters such as TDS or
EC. The non-WARMF approach would not account for such processes as cation exchange,
adsorption, mineralization, dissolution, and precipitation.
4