itrc‐metric and net groundwater use/rechargecalirrigation.com/events_80_1797495549.pdfnet...

© ITRC 2018

ITRC‐METRIC and Net Groundwater Use/Recharge

Dan Howes, Ph.D., P.E.

9/5/2018

Irrigation Training and Research Center (ITRC)California Polytechnic State University (Cal Poly)

San Luis Obispo, CA 93407‐[email protected]

www.itrc.org

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• Topics:

1. Net To/From Groundwater as an alternative to metering (into the future)

2. ITRC‐METRIC Actual Evapotranspiration3. Pilot Project Results

Introduction

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Alternative to Well Metering

• For On‐Farm Irrigation Management–Well flow and volume metering are important

• Irrigation scheduling and well efficiency trending

• For GW Basin Sustainability Monitoring–Well flow and volume metering are misleading–Meters provide the GROSS amount pumped– They do not report how much groundwater was used

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Issues with existing groundwater policies

• Just having a policy does not mean it’s a good one.

• New Mexico and Arizona limit gross GW pumping– Farmers improve efficiency…. and expand area or switch crops….. increasing consumption

– Increased overdraft instead of solving the problem

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Water Rights and Groundwater

• Poor understanding of groundwater consumption…..as opposed to gross pumping

Consumption vs. Availability of water

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• Consumptive Right = Surface Right + Net Sustainable Yield

• Ignore Irrigation Efficiency

NEW Concept Consumptive Rights

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Alternative to Metering GW Pumping

• Remote Sensing of actual consumption• Net to and from groundwater

– Surface deliveries, seepage, etc.– Precipitation– Compare to existing groundwater levels

• Use this as the basis for evaluating the potential future scenarios

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Net To and From Groundwater

• Local evaluation of NET groundwater consumption

• Can be evaluated on a parcel level• Tool for water managers and groundwater modelers

• Tool for farm level regulation•Monthly results• No GW pump flows needed

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NET to/from Groundwater (NTFGW)

Change in SMD

ACTUAL

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Remote Sensing of Actual ETc

• Modified METRICTM algorithm with LandSAT images• IS NOT NDVI based ET estimation!!

• Basic Principle – Evaporative cooling

• Cooler fields have higher ET

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Instantaneous ETc images

February July

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Other Inputs

• Applied surface water:– Irrigation District delivery records by account– Converted to deliveries by parcel/group of fields

• Precipitation:– Interpolated by PRISM program out of Oregon State

• Runoff leaving farm boundaries:– Estimated if it occurs. Not common in SJV

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• ET is 6”• Surface deliveries = 5”• Runoff = 0”, Precip = 0”

• Net GW Pumping = 6”‐ 5”‐ 0”‐ 0” = 1”

• Grower may have pumped 5”, but 4” would be lost to deep percolation (either surface or GW) back to aquifer. The net GW used is 1”

• It is a bit more complicated because we incorporate soil moisture change from the beginning of the month as well but this is the basic premise.

Simplified Monthly Example

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Results• Blue = Net TO GW• Yellow and Red = Net FROM GW

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Average‐Dry Year

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2011 2014

‐250,000‐200,000‐150,000‐100,000‐50,000

050,000

100,000150,000200,000250,000

2007

2008

2009

2010

2011

2013

2014

2015

2016

AVER

AGEDistrictw

ide An

nual NTFGW (A

F)

Total NTFGW LTRID Total NTFGW PID

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Pilot Project

• 19 Farms• Measured GW pumping volumes

• Measured SW delivery volumes

• Compared ITRC‐METRIC to Applied Water

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FARM CODE ACRES

20141 2015 2016

APPLIED FROM GW

NTFGW RESULT

APPLIED FROM GW

NTFGW RESULT

APPLIED FROM GW

NTFGW RESULT

1 717.1 48.3 ‐30.6 51.0 ‐25.72 484.1 27.8 ‐9.1 36.8 ‐2.83 935.4 45.2 ‐27.9 41.2 ‐29.1 40.5 ‐20.54 115.1 36.8 ‐42.2 35.5 ‐34.1 50.2 ‐39.65 717.3 47.8 ‐28.3 39.8 ‐29.7 31.0 ‐21.76 156.4 37.5 ‐36.8 26.6 ‐26.1 33.6 ‐21.77 78.8 37.3 ‐29.7 34.7 ‐22.78 77.9 36.0 ‐29.4 42.1 ‐37.09 157.0 42.5 ‐38.1 39.6 ‐32.9 39.1 ‐32.710 77.6 43.0 ‐42.4 34.8 ‐32.2 29.5 ‐22.911 153.2 37.4 ‐36.4 34.6 ‐27.3 38.9 ‐34.712 157.8 19.6 ‐15.9 25.4 ‐11.813 469.9 51.4 ‐26.5 57.7 ‐12.5142 312.2 32.1 ‐30.0 36.7 ‐26.9 35.0 ‐35.015 616.5 53.1 ‐22.5 44.6 ‐21.7 47.7 ‐15.316 38.3 37.9 ‐41.5 36.6 ‐40.9 32.9 ‐29.917 102.7 6.7 1.1 12.6 3.018 118.0 36.5 ‐28.6 40.2 ‐35.819 206.3 36.4 ‐23.1 36.5 ‐27.5WEIGHTED AVERAGE 44.5 ‐25.4 39.2 ‐23.4 40.9 ‐17.6

Gross Pumping vs. Net GW Use

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Why you need NET GW numbers ?

• What is your Sustainability Number?• GW sustainability has little/nothing to do with gross groundwater pumping

• GW use can be independently tracked and verified

• Historical evaluations of existing conditions• Includes seepage and recharge (banking) at the GSA and Farm Level

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• Extraction of GW within one GSA for use in a different GSA

• In this case GROSS = NET because all of the water is moved out of the basin

Where is metering required

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• There will be an initial cost to get setup and provide ~9 or more years of historical NTFGW. – ~$100,000 – 140,000 per GSA

• Ongoing cost $30,000‐40,000 per GSA per year (or ~$0.30‐$0.50/acre per year)

• Monthly ITRC‐METRIC and NTFGW by the 15thof the following month

Cost

itrc‐metric and net groundwater use/rechargecalirrigation.com/events_80_1797495549.pdfnet...

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