WESTERN PLACER COUNTY GROUNDWATER

MANAGEMENT PLAN MODELModel Development and Site Conceptual

Model

Model Domain

Bear River

Feather River

Sacramento River

Sierra Nevada

Mokelumne River

Area Acres % Model Domain

North American Sub Basin 340,170 39.2%

South American Sub Basin 247,745 28.5%

Cosumnes Sub Basin 280,490 32.3%

Total Model Domain Acreage: 868,405 100.0%

AREAS

Model Layering and Outcrops

Riverbank Formation

View Facing North View Facing South

General Features:

Middle to Late Pleistocene deposits (formerly the Victor Formation)

Consists of sands, silts, and clays from floodplain and alluvial deposits

Superjacent ancestral stream channels cut across this formation creating

lateral channels of gravels and unconsolidated sediments

Hardpan deposits are prevalent in this formation that inhibit vertical

infiltration of recharge from applied water and precipitation

Model Layer 1

Turlock Lake Laguna Formation

View Facing North View Facing South

General Features:

Early Pleistocene to late Pliocene deposits (formerly the Fair Oaks Formation)

Predominantly consists of sands, silts, and clays

Superjacent ancestral stream channels cut across this formation, creating

lateral channels of gravels and unconsolidated sediments

Characteristic feature: white to grey tuff and tuffaceous silts “white clay”

Model Layers 2 and 3

Mehrten Formation

View Facing North View Facing South

General Features:

Pliocene deposits formed during an erosional sequence following chain of

volcanic eruptions

Composed of two dominant units: Black andesitic sands “salt and pepper sand” and

blue and brown clays Hard gray and black tuff-breccias “lava”

Localized confining units , degree of confinement increases to the west

Significant water bearing unit

Model Layers 4 and 5

Valley Springs Formation

View Facing North View Facing South

General Features:

Middle Miocene deposits formed during sequence of volcanic eruptions

Consists of rhyolite ash, quartz sand , and ashy clay

Characteristic features: olive green – greenish gray tone of clays, silts

Typically low permeable deposits

Near Lincoln area, productive zone with upward groundwater gradients

Model Layer 6

Ione Formation

View Facing North View Facing South

General Features:

Consists primarily of sandstone and clays deposited during the Eocene epoch,

a time when the ancient sea became fresh to brackish.

The Ione Formation outcrops to the east, where freshwater remains at

shallow depths

Generally low in permeability, although secondary fracturing near the

outcrops is believed to provide a source of water to unit

Model Layer 7

GeoSections

Hydrogeology

Ancestral Streams

Rivers

Rivers

Begin with a simplified approach

River stage data used as model input

Flow data used for calibration (net flux)

Locations along the Sacramento River have been

adjusted for tidal influences

Flow at river confluences estimated using upstream

gages

Assumption that a portion of the flow discharges

from the Sacramento River to the Deep Water Channel and Steamboat Slough

Streams package is available if warranted

Recharge

Estimating Recharge in the WPCGMP Model:

Gridded Surface Subsurface Hydrologic Analysis

Simulation Modeling (GSSHA):• 2D Grid Based Hydrologic Model• Overland Flow, Stream Flow,

Infiltration• Soil Data (Soil Data Mart)• Land Use Data (Farm Data)• Precipitation Gages• Meteorological Data• Water Year Classifications• Custom codes for output and

data processing

GSSHA Simulations run for representative water

years to develop recharge factors for specific water year classifications

19 Soil Type Land Use Combinations (STLUs)

Recharge factors for each of the 19 STLUs were

developed, accounting for change in land use and water year type, and used to develop subsurface infiltration from precipitation and applied irrigation water and inflow from ungaged watersheds

1

2

3

45

67

Ungaged Watersh

eds

Recharge Work Flow

ESRI Model Builder Applications

Estimating Recharge in the WPCGMP Model :

Parameter-elevation Regressions on Independent Slope Model (PRISM)

monthly gridded precipitation data published by the PRISM Climate Group (monthly)

• Correlation with local rainfall gages

Applied water from irrigation (monthly) – output from Water Demand

Model

Recharge factors from GSSHA simulation modeling

GMS Zone Codes

GMS Zone Codes

• Assignment of

Demand Factors

• Budget Summary

• Supply Data

• Surface Water

Supply

• Additional Groundwater Pumping

Land Use Patterns

Master Land Use File

Farm Data

Change from Non-urban to Urban

Supply and Delivery Data

Groundwater Supply Data

Surface Water Delivery Data

SGA Data Management System

City of Lincoln Summary Data

City of Roseville Supply Data

City of Lincoln Supply Data

SGA Data Management System

Western Placer Groundwater Storage Study

Surface Water Entitlements PCWA City of Roseville City of Lincoln Natomas Central Mutual Water

Co. Pleasant-Grove Verona Mutual

Water Co. South-Sutter Water DistrictCity of Lincoln Groundwater

Management Plan City of Lincoln Supply and Private

Contracts 15% of private supply comes

from GW Nevada Irrigation District – all

SWFlorin-Vineyard Gap Community Plan

Summary of Sacramento County General Plan

Master Water Study for the Florin-Vineyard

Community Plan Zone 41 Urban Water Management

Plan California American Water Supply

Assessment

Wrime Technical Report: Model Refinement North

Area Surface Water Delivery

Summary for: City of Sacramento Rio Linda/Elverta

Community WD Natomas Central Mutual

Water Co. City of Folsom Aerojet Area

Water Unit Demand Factors

Agricultural Demand Factors (DWR)

Urban Demand Factors

Water Year Index

2002 ITRC Crop Evapotranspiration

Rates for Eto Zone 14 ITRC Report 02-001,

funded by CALFED and Agricultural Research Initiative of California State Univ.

Model Output for Representative Water Years

Normalization Factor based on Water Year Index

Monthly Conversion

Factors

Water Demand Model

Workflow

Determine Change in Land Use (every two years)

Assign WUD factors (monthly) Regional Urban Demand Factors for “New Growth”

developed for each WP

Calculate Acreage

Calculate Total Demand (monthly)

Tabulate Total Surface Water Supply (monthly)

Tabulate Total Groundwater Pumping (monthly)

Tabulate Surface Water Entitlements (annual)

Assign Deficit in Budget to Existing Wells for each GMS Zone Code (monthly)

Comparison with Existing Models

SACIGSM v3

Aerojet Model

Modeling Platform: Public Code (MODFLOW) Public Code (MODFLOW)Proprietary Code (IGSM w updates)

Model Processes: Finite Difference Finite DifferenceFinite Element

Pre-Post Processors: GMS & Arc Hydro Groundwater GWVISTAS v 4.21IGSM

Domain: Regional (3 subbasins) Local Scale (Aerojet)Regional (multiple models)

Projection: NAD 83, State Plane, CA 2 (ft) NAD27, State Plane, CA2 (ft) UTM Zone 10, NAD27 (m)

Model Layers: 7 Layers 6 Layers5 Layers (2 fresh-water aq.)

Layering Approach: Wedge (outcrops) Flat – StackedFlat – Stacked

Base of Model: Modified Continental Deposits Bedrock/Cont. DepositsContinental Deposits (DWR)

Input Assignments: Materials Approach Grid AssignmentInterpolated Nodes

Conceptual Model: Stored in Model External to ModelExternal to Model

Grid Refinement: Automated, map over inputs Manual w/o CMManual

North Boundary: Bear River (gage data) General Heads Links to NARIGSM models

(post 1995 values held constant) South Boundary: Mokelumne River (gage data) No flow

Links to STNIGSM models

(post 1993 values held constant) West Boundary: Sacramento & Feather Rivers General Heads

Links to CVIIGSM models

(post 1995 values held constant) East Boundary: Ungaged Watersheds No flow

Ungaged Watersheds Primary Inflow: Streamflow Recharge

Deep Percolation Primary Outflow: Pumping Pumping

Pumping Calibration Period: 1998-2008 (Phase 1) 1956-2006

1969-2004

WPCGMP