M ODELING P LAN PEIR FOR G ROUNDWATER O RDINANCE I MPLEMENTATION - - PowerPoint PPT Presentation

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MODELING PLAN

PEIR FOR GROUNDWATER ORDINANCE IMPLEMENTATION

June 16, 2016 Presented to: Turlock Groundwater Basin Association Facilitated by: Mike Tietze, PG, CEG, CHG Robert Abrams, PhD, PG, CHG

Overview

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Objectives: Discussion and solicitation of feedback regarding modeling objectives and approach Expected Outcome: Input for preparation of a Draft Modeling Plan Topics

• 1. Work Plan Revisions and Modeling Approach

Refinements

• 2. Review of Available Models and Codes
• 3. Review and Discussion of Options

Work Plan Revisions and Modeling Approach Refinements

Revised Task Structure

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Rearranged tasks to emphasize dual purpose of GSP Support and Local Groundwater Ordinance Support: Task 1 Grant Administration Task 2 GSP Development Support

Task 2.1 Hydrologic Modeling Task 2.2 GSA Support

Task 3 Local Groundwater Ordinance Support

Task 3.1 PEIR Preparation and Processing

Revised Modeling Scenarios

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Forecast Component Scenarios 1 2 3 4

Current and Forecasted Groundwater Demand     Ordinance Implementation   Alternative Management Strategies  Mitigation Concepts  Climate Change    

Removed speculative modeling of unimpaired flow and GSP implementation. Added modeling of “Alternative Management Strategies”:

Work Plan Clarifications

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Clarified language around impact assessment:

• Explicitly recognized that Ordinance impacts will
• ccur primarily prior to GSP implementation
• Clarified that impacts will be evaluated under CEQA
• References to undesirable results are tied to the

definition under the Ordinance, and evaluated under CEQA criteria, not GSP standards

• References to unsustainable extraction are tied to

the definition under the Ordinance

Model Domain and Boundaries

 52 x 52 miles  2,704 mi2  NE and SW No-Flow

boundaries

 NW and SE General

Head boundaries based on larger model results

 Includes entire

Modesto and Turlock Subbasins

Temporal Boundaries

2000

• 2005
• 2010
• 2015
• 2020
• 2025
• 2030
• 2035
• 2040
• 2042

Existing Model Data Model Update SCHM Calibration Period Primary Effects from Ordinance Primary Effects from GSP Implementation Model Forecast Scenarios

Review of Available Models and Codes

MODFLOW-OWHM vs. IWFM

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MODFLOW-OWHM (USGS)

• Source code for CVHM and MERSTAN
• Farm Process: Land use-based water budgets
• Vision for future updates includes cloud-based data

updates and compatibility with remote sensing data IWFM (DWR)

• Source code for C2V-Sim, Merced County model

and San Joaquin County model

• Used by DWR for Water Plan updates
• Will be used by DWR to assess GSP performance

Model Adaptability and Support

Model Feature C2VSim (Fine Grid) CVHM MERSTAN

Expected Updates 2017 Late 2016 or 2017 None Planned Beta Data Availability DWR will make beta data available Generally not available Not Applicable Expected Assistance Availability Assistance offered Some assistance may be available Some assistance may be available Compatibility with IDC Good Fair Fair Compatibility with CalLite Good Fair Fair Ease of Update with MERSTAN lithology Fair Good Not Applicable

Key Model Code Features

Model Code Feature C2VSim (IWFM) CVHM (MODFLOW-OHM)

Riparian ET Only simulates downward flux; does not simulate root-zone anoxia. Simulates upward flux from water table and root zone anoxia. Irrigation Demand User specified or dynamically calculated soil moisture deficit irrigation, similar to actual practice User specified or dynamically calculated as unmet water demand Root Zone Moisture Dynamically adjusts root zone moisture storage Root zone moisture storage is modeled as steady state Actual ET Linear interpolation when soil moisture < 50% Field Capacity Hydrus 2D model – about 75% of IWFM results Runoff from Precipitation SCS curve number method; runoff subtracted from water available for infiltration and ET User specified and routing of infiltration in excess of Ksat; fraction of excess left over after ET

Model Resolution and Accuracy

Model Feature C2VSim (Fine Grid) CVHM MERSTAN

Cell Size 0.6 mi2 cell size 1 mi2 cell size 0.25 mi2 cell size Calibration Wells 40-50 wells 10-15 wells 109 wells Lithology Data Set Based on cross sections from earlier model versions (?) ~8,500 wells in 20,000 mi2 ~4,500 wells in 1,000 mi2 Simulation of Stanislaus and Tuolumne Rivers Fair to good match to stream data Fair to good match to stream data Good match to stream data Simulation of East Turlock Subbasin Poor resolution Poor resolution Reasonable dimensions, but location wrong

Model Water Balance C2VSim vs. CVHM

Model Feature C2VSim CVHM

Total Water Demand 737,000 AFY 491,000 AFY Return Fraction of Applied Water 16 % 24 % Recharge from Applied Water 62,000 AFY 13,000 AFY Net Groundwater Demand 185,000 AFY 59,000 AFY Change in Groundwater Storage

• 22,000 AFY

10,000 AFY

Modesto Subbasin water budget averages for 1980 to 1993 from Chou, et al, 2013

• Negative storage change consistent with developing

cone of depression in Modesto area during this time

Reported Water Demand and Calculated Net Groundwater Extraction

1. Calculated using a return fraction of applied irrigation water of 16%. 2. Calculated using a return fraction of applied irrigation water of 24%. 3. Taken from the Integrated Regional Groundwater Management Plan for the Modesto Subbasin, Bookman Edmonston, 2005 (Based on Burrow, 2004)

Water Year Total Water Demand Total Groundwater Pumpage Applied Irrigation Water Net Groundwater Extraction – High 1 Net Groundwater Extraction – Low 2

2000 3 590,000 AF 206,500 AF 534,000 AF 121,000 AF 78,000 AF

Review and Discussion

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Options

Model Options Considered

• 1. CVHM with embedded MERSTAN model

Retains features and details of MERSTAN model Geographic limitation and boundary condition issues of

MERSTAN addressed by incorporating within CVHM

Some work focused on combining models Requires additional effort to develop model interface Advantages and limitations of Farm Process Advantages of future CVHM upgrades and ability to

incorporate remote sensing data

Model Options Considered

• 2. C2VSim with imported MERSTAN lithology

Incorporates lithologic and permeability details of

MERSTAN

Advantage of DWR support and availability of beta data Easier interface with CalLite Advantages and limitations of Irrigation Demand

Calculator

Compatibility with source codes for models to the north

and south

Model Options Considered

• 3. Optional Addition of Remote Sensing Data to

Support Model Update

Use of remote sensing data to calibrate crop coefficients

in IDC or Farm Process during model update period

Possibility to use data for direct update of model with

direct measurement of ET data

Improves reliability of groundwater extraction

calculations and model results in either CVHM or C2VSim

Calibrates a key unknown variable

SEBS Eta Measurement

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SEBS Eta Measurement

Conversion from Rangeland to Orchard