Salt and Nutrient Management Plan

TAC Meeting, MWA Headquarters, Apple Valley, CA April 4, 2013

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Mojave Salt and Nutrient Management Plan (SNMP) Introduction Planning Area Components

Technical Approach to Mojave SNMP Development Examples Refinements and Improvements

Overlap with OWTS Policy Next Steps and Schedule

Presentation Outline

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SNMP Introduction

2007 MWA evaluated TDS More formal SNMP guidance

2009 Recycled Water Policy Plans adopted by RWQCB

(Water Boards) Basin Plan water

quality objectives

Recycled Water Policy - SWRCB

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Colorado River Basin (Region 7)

Lahontan (Region 6V)

MWA Service Area

MWA Service Area Groundwater Basins

Two Water Boards

Planning Area

SNMP Key Technical Components

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SNMP

Stakeholder Process

Goals and Objectives

Conceptual Model

Water Quality and Assimilative

Capacity Salt and Nutrient Balances

Future Water Quality

Anti-Degradation

Analysis

Monitoring Program

Implement. Measures

Salt and Nutrient Loading? Follow the Water

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Technical Process

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Water quality data compilation and analysis for initial conditions

S/N loading estimates for sources and sinks to develop baseline conditions

STELLA Modeling Route S/N with water through

groundwater recharge and discharge

Stella Model: Salt Loading and Mixing

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STELLA: software package to simulate systems Structural Thinking Experimental Learning Laboratory with

Animation Salt loading and mixing model Sources and sinks of salt in each of 22 sub-regions Simulates a 70-year period Limitations: instantaneous mixing; average over large areas;

no absolute concentrations computed at a given location Advantages: fast simulations over large areas, compatible

with relative analysis at planning level; good screening tool for decision making

Incorporates flows from USGS regional calibrated groundwater flow model

Stella Model Sub-regions

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MWA Service Area 22 Sub-regions Smaller sub-regions

in areas of changing water quality

Flows between basin sub-regions

• Initial Concentrations • Salt Sources: Flows;

Concentrations

Water Development Scenarios: • Water Imports • Storage Projects • Recycle/Reuse • New Well Fields • New sources • Remove sources • ……

Water Quality Database

+ Salt Sources

Inventory

Stella Salt Mixing Model Conceptual Flowchart

Simplifying flow correlations

Example Methodology: Existing Groundwater Quality

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• Wells assigned to sub-region/depth • Advantages of median (vs. average) values

Does not assume normal distribution of data Minimizes outlier effects; no data removed Can be reliably calculated for datasets with mix

of censored (e.g., NDs) and non-censored data o Kaplan-Meier Statistical Method

Well Medians

Use GIS Spatial Analyst

volume-weighted

average conc.

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• Important to manually contour before interpolating surface to provide control in areas with limited data

Methodology: Existing Groundwater Quality

Well Medians

Contour Maps

Use GIS Spatial Analyst

volume-weighted

average conc.

Methodology: Existing Groundwater Quality

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Well Medians

Contour Maps

GIS Spatial Analyst

volume-weighted

average conc.

Central Basin TDS (mg/L)

Lyr1 538

Lyr2 610

Lyr3 533

Lyr4 480

Lyrs 1-4 530

Ammonia Volatilization

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Plant Residue

Applied Ammonium-N Applied Nitrate-N

Plant Uptake

Dent

rifica

tion

Leaching

N2 & N2O gasses

NITROGEN CYCLE

Applied Organic N

Nitrate-N

Atmospheric N

Soil Organic Matter

Ammonification

Nitrification

Ammonium-N Immobilization

Atmospheric Nitrate-N

GROUNDWATER

Loading Calculations: It’s COMPLICATED!

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Lyr3

Example Methodology:Regional Trend Analysis to “Calibrate Loading”

Mann‐Kendall analysis of concentration trends by well Tally results to identify regional concentration trends

LA            Forebay

Montebello Forebay

Whittier Area

Central Presssure

Central Basin

West Coast Basin

TOTALIncreasing Trend 8 14 1 35 58 30

No Trend 4 60 4 81 149 48Decreasing Trend 1 21 0 21 43 16

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Montebello Forebay

Whittier Area

Central Presssure

Central Basin

West Coast Basin

TOTALIncreasing Trend 8 14 1 35 58 30

No Trend 4 60 4 81 149 48Decreasing Trend 1 21 0 21 43 16

Baseline Loading - Calibration

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Adjust key loading factors with highest uncertainty Apply any adjustments consistently for each subarea

LA Forebay

Montebello Forebay

Whittier Area

Central Presssure

Central Basin

West Coast Basin

TOTALIncreasing Trend 8 14 1 35 58 30

No Trend 4 60 4 81 149 48Decreasing Trend 1 21 0 21 43 16

Simulated Concentrations during Baseline Period

Flat / slightly decreasing Flat / slightly increasing

Existing Average Groundwater Quality = 700 mg/L

Basin Plan Objective = 500 mg/L

Existing Average Groundwater Quality = 300 mg/L

No Assimilative Capacity

Available AC = 200 mg/L

Assimilative Capacity - TDS

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0

200

400

600

800

1,000

1,200

1,400

1,600

LosAngelesForebay

MontebelloForebay

WhittierArea

CentralPressure(w/ coast)

CentralPressure

(no coast)

CentralBasin

(w/ coast)

CentralBasin

(no coast)

WestCoastBasin

(w/ coast)

WestCoastBasin

(no coast)

WestCoastBasin

(no coast/no plume)

Ave

rage

TD

S C

once

ntra

tion

(m

g/L)

Available Assimilative Capacity (AC)

Water Quality Objective

Some areas have available AC Some areas have no AC

Future Water

Balance

Future S/N Loading

Estimates

Spreadsheet Mixing Model

Future WQ and

Assimilative Capacity

Estimate Use of AC by RW

Projects

Example: Future Water Quality Simulation

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10% Assimilative Capacity

Basin Plan Objective

Future Planning Horizon of 15 Years (2011-2025)

Mojave Sub-regions: Example Centro Regional

1- Oeste Regional 2- Alto Left Regional 3- Este Regional 4- Transition Zone Regional 5- Centro Regional 6- Harper Lake Regional 7- Baja Regional 8- Afton Canyon 9- Baja North Regional 10- Alto Floodplain 11- Transition Zone Floodplain 12- Centro Floodplain 13- Baja Floodplain 14- Alto Right Regional 15- Narrows Floodplain 16- Alto Mid Regional 17- Helendale Floodplain 18- Lucerne Basin 19- Johnson valley 20- Copper Mtn Valley 21- Mean Ames 22- Warren Valley

Water Quality Database Concentrations Averaged per Sub-Region

Various consumptive rates were used (industrial, golf, etc.)

Detailed set of calculations using Stella subroutines

Free Production Allowances (FPA) included

Detailed Consumptive Use Calculations

Summary Mass Fluxes Regional Centro Sub-region

Centro Regional Sub-region Flux to Baja

Cons

umpt

ive

use

(Ag,

G

olf,

..etc

)

Flux to Harper Flux from Alto Transition Zone

Dairies

Flux from Centro Floodplain

Salt Sources Salt Sinks

Municipal Return Flows

(Septic)

Alternatives Evaluation Process

Subtract

Subtract

Subtract

Subtract

Base Case

Alternative 1

Alternative 4

Alternative 3

Alternative 2

Refinements and Improvements to 2007 Analysis Take advantage of the work that has been

accomplished since 2007 Additional monitoring data Improved understanding of conceptual model Improved temporal and spatial interpretations

Well medians and contouring for appropriate initial conditions in groundwater

Vertical depth to bedrock Add nitrogen data and loading

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Overlap with OWTS Policy

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SNMP Support: Density and loading

from current septic systems for SNMP

“Calibrated” loading impacts

Support for future Lamps

Onsite Wastewater Treatment Systems (OWTS) Adopted by SWRCB 2012 Tiered approach to regulating density and discharge for OWTS Allows development of Local Area Management Plans

(LAMPS)

Current Work and Next Steps Groundwater Quality Data compilation MWA, USGS, CDPH, Geotracker, Dairies, Permitted

Facilities, VVWRA, other QA/QC, trend analysis Identification of sources and sinks and loading

Run Stella Model for Baseline Characterization Develop S/N characterization Develop Monitoring Program Identify Implementation Measures Identify future projects for analysis

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Plan Preparation Schedule

Questions?

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