integrated groundwater/surface water modelling to assess irrigation demand and drought response in a...

Integrated Groundwater/Surface Water Modelling

to Assess Irrigation Demand and Drought Response

in a Southwestern Ontario Watershed

Dirk Kassenaar, E.J. Wexler Peter J. Thompson, Michael Takeda

CWRA Montreal May 25, 2016

Presentation Outline

1. Introduction: Understanding Irrigation Demand

2. Integrated SW/GW Modelling

3. Pilot Watershed: Whitemans Creek Tier 3/ Low Water Response Project

4. GSFLOW Code modifications and conceptual testing

5. Simulation of farm operations in Whitemans Creek

6. Conclusions

Integrated Simulation of Irrigation Demand - Introduction 2

Agricultural Water Use

Agricultural irrigation is growing in response to:

▪ An increase in climate variability

▪ Contract farming: “supply chain” management and production certainty

▪ Advances in precision agriculture • “Irrigation is next frontier in precision agriculture” (Farm Press, Oct, 2014)

Irrigation operations are frequently driven by dynamic soil moisture

▪ Highly adaptive water use

We need a method to simulate “soil moisture-based irrigation water use”, including: ▪ Losses of irrigation water to ET or runoff to streams

▪ Return flows – irrigation water that re-infiltrates

▪ Effect of precipitation events on recently irrigated crop land

Integrated Simulation of Irrigation Demand - Modelling Approach 3

Integrated SW/GW Modelling: Advantages

Better estimate of groundwater recharge and feedback (rejected recharge)

Better representation streamflow and head-dependent leakage

Better representation of SW/GW storage.

Better representation of cumulative effects of takings.

Better calibration: input total precipitation, calibrate to total flows (no baseflow separation)

It’s just better...


California Department of Water Resources

USGS GSFLOW

USGS integrated GW/SW model ▪ Based on MODFLOW-NWT and PRMS

(Precipitation-Runoff Modelling System)

▪ Fully-distributed: Cell-based representation

▪ Excellent balance of hydrology, hydraulics and GW

▪ Open-source, proven and very well documented

5 - Modelling Approach

Irrigation Module for GSFLOW

Earthfx Inc. has developed a new irrigation module for GSFLOW

The general technical approach is based on work by the USGS for the simulation of water use in California’s Central Valley

▪ The MODFLOW-OWHM code includes the “Farm Process” module

▪ OWHM, however, is only a groundwater model, and therefore does not represent the soil zone, runoff processes and total streamflow routing

▪ GSFLOW is a complete and integrated representation of the hydrologic processes that drive irrigation demand

The implementation of this new soil-moisture irrigation demand module is currently being tested in the Whitemans Creek Watershed with funding support from the Ontario MNR, MOECC and Grand River Conservation Authority


PILOT WATERSHED - WHITEMANS CREEK

Integrated Simulation of Irrigation Demand – Watershed Overview 7

Study Area

Whitemans Creek watershed is located southwest of Cambridge, Ontario


Numerous groundwater-fed wetlands.

Streams are deeply incised in southeast.

Fluctuations in shallow water table affects recharge, runoff, ET, and groundwater discharge to streams.

Main branch of Whitemans Creek is a cold-water stream supporting Brown, Brook, and Rainbow trout.

Uplands of watershed generally classed as warm-water reaches.

Main valley serves as a continuous habitat corridor from GR Valley into Oxford County.

Wetlands and streams in the Whitemans Creek subwatershed

Natural Features

Integrated Simulation of Irrigation Demand - Watershed Overview 9

Current Land Use

10 Integrated Simulation of Irrigation Demand - Watershed Overview

(SOLRIS v2, 2015)

Agricultural Usage

11

Corn, sod farms, tobacco, mixed..

Water usage can vary considerably by crop type (sod vs. hay/pasture).

Includes significant irrigated water use in Norfolk Sand Plain

Integrated Simulation of Irrigation Demand - Watershed Overview

Integrated Simulation of Irrigation Demand - Geologic & Hydrostratigraphic Model 12

Conceptual Hydrostratigraphic Model

Wisconsinan glaciation (85,000 to 11,000 years ago)

Regional Till Sheets (minor tills in report) ▪ Canning Till – very stiff clay till; overlies discontinuous “pre-

Canning” tills and “pre-Canning” sands.

▪ Catfish Creek Till - stony, over-consolidated, sandy silt to silty sand till; outcrops at Bright.

▪ Tavistock Till – major unit; outcrops in north and to west of Whitemans; clayey silt till.

▪ Port Stanley Till - major unit; outcrops in middle of study area; stiff clayey silt to silt till; sandier to north.

▪ Wentworth Till – Outcrops to east near Bethel Rd; silty sand till; overrides outwash and Lake Whittlesey deposits.

Erie Phase Deposits

▪ Waterloo Moraine-age deposits; overlie Catfish Creek and Maryhill Tills.

Grand River Outwash

▪ Ice recession during Mackinaw phase.

▪ Difficult to distinguish from overlying Lake Whittlesey sands.

Lacustrine Deposits

▪ Associated with Glacial Lake Whittlesey

▪ Source of the fine sands of Norfolk sand plain

Integrated Simulation of Irrigation Demand - Geologic & Hydrostratigraphic Model 13

Quaternary Geology

Simulated Streams

Integrated Simulation of Irrigation Demand - GW Model Construction/Calibration 14

1,767 km of simulated stream channels. ▪ 15,729 Reaches (GW Cell Interactions)

Properties assigned by Strahler Class ▪ Manning’s Roughness, 8-Point Cross Section, Bed

Conductances

▪ Class 1 represents 842 of 1767 km

Simulation Results: Long Term Average ET (WY1976-WY2010)

Integrated Simulation of Irrigation Demand – PRMS (Hydrologic Submodel) 15

Potential Actual

Simulated Runoff


Long Term Average Recharge Comparison


PRMS

(248 mm/year)

GAWSER

(243 mm/year)

18

Actual ET

Integrated Simulation of Irrigation Demand – Preliminary GSFLOW Model Calibration

Animation shows daily Actual ET from the PRMS submodel for WY2007, a relatively dry year

AET response is sinusoidal but varies spatially depending on available soil moisture

AET is reduced in the dry years because of basin-wide limitations in available soil moisture

Animation Link

https://youtu.be/IaVaFkUCdP0?t=1m25s



19

Water Levels


Animation shows transient water levels from the MODFLOW submodel in Layer 3 for WY2007

Groundwater response appears muted because of contour interval places but change is in range of 1-2 metres

Animation Link





20

Streamflow


Animation shows transient streamflow for WY2007

Results show:

▪ Streamflow response to dry year

▪ Where streamflow is intermittent

▪ Location of reaches which might be more sensitive to drought

Simulated flows at locations of active and historic gauges can be compared to observed.

Animation Link




21

Streamflow


Animation shows transient streamflow for WY2007

Results highlight an area of the watershed with relatively low permeability surface materials.

Animation Link





WATER USE Whitemans Creek Tier 3

Integrated Simulation of Irrigation Demand - Water Use 22

Significant agricultural water takings: ▪ Over 95% of reported takings

▪ Takings vary by crop, season, and antecedent rainfall/ET

Need historic consumptive use for model calibration.

Need to predict future usage for drought analysis.


Water Use - Overview

Permits to take Water: ▪ Permit ID can be assigned to multiple sources (e.g., 2 different wells).

▪ Sources have generic names (e.g., “Well 1”, “Pond”).

▪ Locations linked to Permit ID, no link to WWIS Well ID.

▪ Sometimes source locations plot close enough to existing wells to assign.

▪ Maximum Permitted Taking often well in excess of actual.

Water Taking Reporting System ▪ Self reporting compliance poor in 2009; improves in subsequent years.

▪ WTRS data linked to Permit ID/Source; no locations or names.

▪ Queries to match PTTW to WTRS partly successful; varies by year.

• 65% matched in study area; 62% in Whitemans in 2012

• Does (38%) non-reporting equal no usage ?

▪ Taking not always separated by source; is taking amalgamated?

WTRS Sources matching PTTW Sources


Reconciling Provincial Data

Simulated SW Use

Integrated Simulation of Irrigation Demand - GW Model Construction/Calibration 25

A total of 70 surface water permits with 92 sources simulated in the model

Surface water permits processed to assign location of source streams: ▪ Represented using MODFLOW-SFR package

▪ Script used to assign takings (diversions) to closest simulated stream segment

▪ All ponds assumed to be online with no mitigative storage effects

Groundwater Permits – by Primary Purpose

Agricultural Groundwater Permits – by Sub-Purpose


Annual Takings for Groundwater Permits – 2012

Annual Takings for Agricultural GW Permits – 2012


Analysis of WTRS data

provides Insights

Daily Takings

for Agriculture by Crop Type

(2012)


Variation in Water Use by Crop

Daily Takings for Wet vs. Dry Year

(2011-2012) at a Sod Farm


Variation in Water Use by Year

Daily Takings for Agriculture

Sod Farm 1 vs. Sod Farm 2

(2012)


Variation in Water Use by Location

Model calibration runs for GSFLOW Model based on daily taking data from PTTW/WTRS.

470 GW takings

Well locations and aquifers determined by matching PTTW to WWIS data.


Use of PTTW/WTRS Data

Water Use - Conclusions

Data compiled from multiple sources.

WTRS data provides good snapshot of recent takings.

Daily data used in model calibration phase.

WTRS provides targets for development/calibration of irrigation submodel.


SOIL MOISTURE DEMAND-BASED IRRIGATION MODULE

Earthfx GSFLOW Code Extension

Integrated Simulation of Irrigation Demand - Streamflow Data 33

Irrigation Demand Submodel - Methodology

Need to predict water use under drought or future development conditions

▪ Simply using maximum permitted rate does not help us understand real crop needs under future drought conditions.

Proposed method to estimate water use requires daily takings:

▪ GSFLOW/PRMS daily estimate of soil moisture used to “trigger” irrigation.

▪ Irrigation starts when available soil moisture falls below trigger

▪ Trigger can be defined based on soil and crop type

▪ Irrigation water can be lost to ET, runoff or returned to the GW system

Predictive irrigation submodel can be calibrated with actual WTRS data.

▪ PTTW/WTRS data used estimating historic use for model calibration.


Irrigation Demand Submodel – Code Features

Each farm represented by multiple PRMS cells (fully distributed)

▪ Each farm can have multiple crop types and unique moisture content triggers

▪ Each well is linked to a Farm ID with max pumping rate

▪ Farm SW diversions can take a defined percentage of current daily streamflow

Soil moisture calculated on a daily basis in PRMS and used to trigger GW pumping or SW diversion

Total GW well pumping or SW diversion per farm passed back to PRMS

▪ PRMS adds pumped volume to precipitation (for spray irrigation) or to net precipitation after interception (for drip irrigation) over farm cells.

▪ PRMS calculates runoff and infiltration in usual manner


Integration of Irrigation Module

Low moisture levels in soil zone reservoir can trigger spray irrigation from either GW pumping wells or SW diversions.

With drip irrigation, water is added to the recharge zone

Integrated Simulation of Irrigation Demand - Climate Data 36

Groundwater Model MODFLOW NWT

PRMS

GW

Pum

pin

g

SW

Pum

pin

g

Simple problem with streams lakes and multiple irrigated and non-irrigated farms

Farm wells and SW diversion used for irrigation

Different triggers used for each well

Different irrigation types (drip/spray)

Animation shows soil moisture in farm vicinity, farm well pumping, and streamflow

Animation Link

Simple Submodel Testing




Sub-model Testing

Example shows one Water Year (Oct 1-Sept 30) ▪ Soil moisture on irrigated farm fields

▪ Groundwater levels as blue contours

▪ Pumping wells shown as small circles

Fall-winter: Water levels stable – no pumping ▪ Irrigation starts in late May

Soil moisture represented as color – pumping adjusted to maintain moisture levels

GW drawdown cones grow over the summer and recover in the fall after irrigation stops

Animation Link




Whitemans Test Simulation

Testing of GSFLOW Farm Process module in the Whitemans Creek model


Whitemans Simulation

Farm wells linked to classified crop areas.


Soil Moisture Animation link

Example shows




Whitemans Simulation: Soil Moisture vs Pumping

Example compares soil moisture in an irrigated field vs a field outside of the farm.

Pump comes on when moisture levels drop – Irrigated field never dries out


43

Conclusions

Integrated Simulation of Irrigation Demand - Conclusions & Next Steps

Predicting and simulating cumulative water use under future drought conditions requires an understanding of farm irrigation processes and triggers

The new GSFLOW irrigation module developed by Earthfx integrates farm water management practices into a comprehensive and fully integrated SW/GW model

Historic climate and WTRS data can be used to develop farm-specific water use practices and triggers.

▪ Alternatively, standard or best management practices could be represented in the model to simulate and evaluate improved water use and informed permit renewal

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