Irrigation and Nutrient Management Plan (INMP) FAQ 

What information is required in the INMP report?

The INMP report consists of the TNA report (nitrogen applied) PLUS nitrogen removed and specific irrigation information.  

  • Measurement of irrigation water applied using a flow meter.  
  • Precise nitrogen concentration from ALL sources of irrigation water, not just the primary irrigation source.  
  • Evapotranspiration for each crop. Acceptable methods include, but are not limited to, using reference evapotranspiration data from a local weather station (e.g., California Irrigation Management Information System (CIMIS)8 or an on-farm station) with a crop coefficient conversion value, and direct measurement. 
Can I use my electricity bill to estimate water applied for INMP?

No, electricity bills are considered an estimation versus a measurement of volume of irrigation water applied. Flow meters will need to be used to measure the amount of irrigation water applied.  

When do I need to start reporting INMP?

This depends on your Groundwater Phase area which can be found in the top right corner of your Geotracker account.  

  • Groundwater Phase 1 Area: First INMP report is due by March 1, 2024, so monitoring will begin in 2023. 
  • Groundwater Phase 2 Area: First INMP report is due by March 1, 2026, so monitoring will begin in 2025.  
  • Groundwater Phase 3 Area: First INMP report is due by March 1, 2028, so monitoring will begin in 2027. 
For 2023, what are the well sampling requirements for the INMP report?

Growers with ranches in Groundwater Phase 1 areas are required to sample all irrigation wells on their GW Phase 1 ranches this year (2023) for INMP reporting next year. Growers are required to begin conducting monitoring and recordkeeping as of January 1, 2023, to submit Irrigation and Nutrient Management Monitoring and Reporting Requirements (INMP) summary reports by March 1, 2024. At a minimum, growers must obtain and report precise nitrogen concentrations from all sources of irrigation water used for their ranch during the reporting period (i.e., all irrigation wells, rather than only the primary irrigation well for Total Nitrogen Applied [TNA] reporting) (General Waste Discharge Requirements for Discharges from Irrigated Lands, Order No. R3-2021-0040 [MRP(https://www.waterboards.ca.gov/centralcoast/water_issues/programs/ilp/docs/ag_order4/2021/ao4_att_b.pdf) ], INMP Summary Report Requirements, 15.a).    

What are the requirements for non-primary [irrigation] wells?

For non-primary irrigation well sampling, it is acceptable for a grower to use either laboratory analysis OR a portable measuring device (does not require a specific sampling company) to obtain precise measurements of nitrogen in irrigations wells for INMP summary reporting purposes (MRP, and page 5 of Domestic and Irrigation Well Monitoring and Reporting Guidance: https://www.waterboards.ca.gov/centralcoast/water_issues/programs/ilp/docs/gw-mon-guide-eng.pdf).  Sampling of non-primary irrigation well(s) for INMP reporting can be conducted throughout 2023 (monitoring period = calendar year [Jan. 1 – Dec. 31]) (MRP, Table 2, page 34) and is not required to be completed within the 2023 March 1 – June 30th groundwater sampling period. 

What if a crop I grow is not listed in the table?

For crops that do not yet have approved crop conversion coefficients, growers must either select a crop conversion coefficient from Table MRP-4 for a crop that is similar to their crop or develop their own crop conversion coefficient. Growers who elect to develop their own crop conversion coefficient must do so by obtaining a laboratory result from samples collected from their own crop and fields, following the standard protocols described in Irrigated Lands Program Crop Nitrogen Removal Conversion Coefficient Standard Protocols.  (https://www.waterboards.ca.gov/centralcoast/water_issues/programs/ilp/docs/tna/n_rmvl_cffcnt_prtcls.pdf) Growers must maintain any data collected and rationale used in determining their individual crop conversion coefficient in the Farm Plan. 

What are the removal terms?

From pg 8 of Attachment B- MRP (https://www.waterboards.ca.gov/centralcoast/water_issues/programs/ilp/docs/ag_order4/2021/ao4_att_b.pdf) : Dischargers must monitor and report the total amount of nitrogen removed from the field through harvest (RHARV), sequestration (RSEQ), scavenging (RSCAVENGE), treatment (RTREAT), or other removal methods (ROTHER).   

R = RHARV + RSEQ + RSCAVENGE + RTREAT + ROTHER 

Contact Info

  • PO Box 2227
    Watsonville, CA 95077
  • 831-761-8644 (phone)
  • 831-761-8695 (fax)
For a full list of contacts please
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