ITRC METRIC and Net Groundwater Use/Recharge

Transcription

1 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

2 Introduction Topics: 1. Net To/From Groundwater as an alternative to metering (into the future) 2. ITRC METRIC Actual Evapotranspiration 3. Pilot Project Results

3 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

4 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

5 Water Rights and Groundwater Poor understanding of groundwater consumption..as opposed to gross pumping Consumption vs. Availability of water

6 NEW Concept Consumptive Rights Consumptive Right = Surface Right + Net Sustainable Yield Ignore Irrigation Efficiency

7 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

8 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

9 NET to/from Groundwater (NTFGW) ACTUAL Change in SMD

10 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

11 Instantaneous ETc images February July

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13 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

14 Simplified Monthly Example ET is 6 Surface deliveries = 5 Runoff = 0, Precip = 0 Net GW Pumping = = 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.

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

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17 Average Dry Year

18 Total NTFGW PID AVERAGE Total NTFGW LTRID , , , ,000 50, , , , , , Districtwide Annual NTFGW (AF) 2011

19 Tracking NTFGW on a Farm Basis ITRC METRIC ETc NTFGW

20 Pilot Project 19 Farms Measured GW pumping volumes Measured SW delivery volumes Compared ITRC METRIC to Applied Water

21 Gross Pumping vs. Net GW Use FARM CODE ACRES APPLIED FROM GW APPLIED APPLIED NTFGW NTFGW FROM FROM RESULT RESULT GW GW NTFGW RESULT WEIGHTED AVERAGE

22 Pilot Project Issues with Meters Issue with METRIC Overall very good results in the comparison

23 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

24 Where is metering required 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

25 Cost There will be an initial cost to get setup and provide ~9 or more years of historical NTFGW. ~$100, ,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 15 th of the following month

26 Thank You Questions