Groundwater monitoring data and SGMA annual reporting

Reference article · 5 min read

A groundwater sustainability agency carries an unusual data burden for its size. Many GSAs are run by a few staff at a water district, county, or joint powers authority, yet must keep a monitoring record that holds up over decades, supports a judgment about whether the basin is sustainably managed, and reaches the state in structured form each year.

This article covers the data a GSA has to carry and the choices that make the spring submission routine. Report content, formats, and deadlines are set by state regulation and change over time, so confirm current rules with your state agency and your counsel.

The well registry is the foundation

Everything attaches to a well, and a vague registry produces a record nobody can defend. Carry at least:

Identifiers. A stable local identifier plus any state well number, well completion report number, and identifiers used elsewhere. Keep a crosswalk; never overwrite one with another.
Location and datum. Latitude and longitude with the horizontal datum and how they were obtained. A coordinate without a datum is ambiguous.
Reference point elevation. The surveyed elevation of the measuring point, the vertical datum, and a history of changes. Groundwater elevation is computed from it, so losing that history shifts the whole time series.
Construction and status. Total depth, casing diameter, screened intervals, the aquifer or model layer monitored, well use, and whether the well is active, destroyed, or inaccessible. Nested wells need each interval treated as its own monitoring point.

Manual soundings and transducer telemetry

Manual and continuous records are different data types and should not be blended into one column. A sounding is one value with a stated method; a transducer produces a dense series that needs processing before it means anything.

Barometric compensation. Non-vented sensors need a barometric record. The compensation step and the source used belong in the stored data.
Drift and time. Schedule manual soundings alongside the transducer and keep both; record the offsets the check reveals rather than quietly applying them. Use a consistent standard time without daylight shifts.
Pumping influence. A level measured in or near a pumping well is not a static level. Capture that as a condition on the reading.

Quality control on suspect readings

Adopt a short list of checks and run them identically every time: impossible values, readings deeper than the well, implausible rates of change, flatlines, duplicate timestamps, and readings that disagree with neighboring wells.

Flag rather than delete. Keep the raw value, attach a qualifier, and record who reviewed it and when. State programs generally distinguish provisional from reviewed data, and your system should do the same, so a report cites a stable version while newer readings are still in review.

Extraction records and confidentiality

Extraction data is usually the weakest part of the record and the most sensitive data the agency holds.

Metered volumes. Store meter identity, units as read, raw totalizer values, and the computed volume. Rollovers, meter replacements, and unit changes must stay visible rather than smoothed over.
Estimated volumes. Where wells are unmetered, record the method, whether evapotranspiration, power consumption, or land use survey, and its inputs, so the estimate can be reproduced later.
Attribution. Tie each volume to a well, a parcel or field, and a water use sector, because reporting is organized by sector.

Settle confidentiality before collection begins, not after a records request arrives. Treatment of individual extraction reports varies by state; aggregate figures are commonly public while parcel-level detail may be protected. Decide with counsel what is disclosable, then build the system to publish aggregates without exposing individual values, and limit access by role.

Subsidence, water quality, and surface water

Subsidence. Vertical displacement may come from satellite interferometry datasets published by the state, continuous GPS stations, extensometers, or benchmark surveys. Each carries its own reference period, processing vintage, and accuracy, so store those with the value.
Water quality. Carry sample date, depth, laboratory, method, and reporting limit with each result. Store a non-detect as a non-detect with its reporting limit, not as a zero, and keep substitution rules in the analysis layer.
Interconnected surface water. Stream gages, shallow piezometers near streams, and model output all contribute. Label modeled values so they are never mistaken for observations.

Thresholds and the annual report

Sustainable management criteria are set at named representative monitoring sites: minimum thresholds, measurable objectives, and interim milestones. Hold those values as data attached to the site, with effective dates, so each new reading is compared automatically and an approaching exceedance is caught in season.

Annual reports are generally built on a water year rather than a calendar or fiscal year, are due in the spring, and are filed through the state's online portal. Expect basin conditions, elevation data and contour maps, change in storage, extraction by water use sector with the method of measurement, and total water use. The report is both narrative and structured upload, so build the export first and let the narrative draw on the same numbers.

How to start

Inventory monitoring sites and verify reference point elevations and construction records before evaluating software. Bad metadata defeats good software.
Make loading and exporting the state's current schema an acceptance test, demonstrated on a year of your real transducer files and lab deliverables, malformed records included.
Require in the contract full export of all data and metadata in open formats at any time and at termination, with the agency owning the data.
Require role-based access, the ability to withhold or aggregate extraction detail in published outputs, and an audit history in which corrections preserve the original value.

HQT builds and integrates data systems for public agencies, including monitoring data management, telemetry ingestion, quality control, and regulatory reporting.

Frequently asked questions

What data does a groundwater sustainability agency need for its annual report?

Annual reports typically draw on groundwater elevation measurements at monitoring sites, groundwater extraction by water use sector with the method of measurement noted, surface water supply and total water use, and an estimate of change in groundwater storage, along with narrative basin conditions and maps. The underlying records that make those numbers defensible are the well registry, reference point elevations, measurement methods, and quality control flags. Exact content requirements are set by state regulation and are revised over time, so check the current rule and reporting guidance before building your submission.

Do we need pressure transducers, or are manual water level measurements enough?

Manual soundings alone can satisfy many monitoring objectives, particularly where seasonal high and low conditions are what matters. Transducers add value where you need to see short-term response, pumping influence, or conditions at sites that are hard to reach in winter. Most agencies run both, using periodic manual soundings as the check on transducer drift, and they store the manual readings as their own record rather than folding them into the sensor series.

Is individual groundwater extraction data a public record?

It depends on the state and on how the data was collected. In many places aggregate extraction figures are clearly public while reports tied to an individual landowner or parcel may carry some protection, and the boundaries are fact specific. Decide the question with your agency counsel before you begin collecting, tell reporting parties what you decided, and configure your system so it can publish aggregates and restrict parcel-level detail by user role.

When is the SGMA annual report due and how is it submitted?

Annual reports are generally prepared on a water year basis and are due in the spring, with submission through the state agency's online groundwater management portal. The submission usually includes both a narrative report document and structured data files for elements such as groundwater elevations and extraction. Deadlines, file formats, and portal modules change, so confirm the current schedule and templates with the state agency well before the due date.

Should we build our own database or buy a monitoring data system?

Either can work, and the deciding factor is usually staff capacity to maintain it over decades rather than initial cost. What matters most is that the system holds site metadata, measurement methods, quality flags, and version history, and that it can export everything in open formats on demand. Whichever route you take, make the state's required export a written acceptance test and keep data ownership and full export rights in the contract.