How to reconcile a water licence register against annual satellite imagery
Most entitlement audits start the same way: a spreadsheet export of the licence register, a shapefile of the catchment boundary, and not nearly enough field days to visit every property on it. Reconciling the two against a yearly imagery pass is how you turn that into a short list instead of a district-wide drive.
What "reconciliation" means here
This is a spatial check: whether what's physically on a property matches what the register says is licensed there. A licence record tells you the entitlement holder, the volume, the works approval number, maybe a GPS point from the original application. It doesn't tell you whether that ring tank has been widened since 2019, or whether a header pipe now runs from the river frontage to a pivot that wasn't in the original works description. Imagery does.
The register is the source of truth for what's allowed. The imagery is the source of truth for what's there. Reconciliation is just the process of lining them up and marking the gaps.
A workflow that fits one audit cycle a year
Most water regulators run this on an annual cycle tied to the licence renewal round or the water year, so the workflow should match that cadence rather than try to run continuously.
- Pull the current register for the catchment or management zone, including any conditions on storage volume or pumping capacity, not just the licence list itself.
- Get a single imagery pass over the full catchment, dated to roughly the same point each year so comparisons across years aren't confounded by seasonal fill levels. 0.5-2 m RGB resolution is enough to pick out a new dam wall, an expanded ring tank, or a pipe crossing a paddock boundary.
- Overlay licensed storages and pumping points on the imagery and flag anything that doesn't have a matching register entry, anything that looks larger than the licensed footprint, or any new infrastructure near a frontage with no corresponding works approval.
- Rank the flags by exposure: proximity to a stressed reach, size of the apparent unlicensed volume, and history of prior non-compliance on that property if you have it.
- Send the ranked list to field staff as the site-visit schedule for the year, instead of a property list generated by complaint or by rotation.
That last step is the actual payoff. An inspector who drives out to confirm a flagged structure is doing something different from an inspector doing a routine drive-by. One has a reason to be there; the other is hoping to get lucky.
What a flag is, and what it isn't
A flag from this process is a candidate, not a finding. It means a structure shows up on the imagery that doesn't have a clean match in the register. It does not mean the landholder is taking water unlawfully, and it shouldn't be written up or communicated that way. Plenty of flags turn out to be licensed works that were never properly geocoded, farm dams that predate the register and are exempt, or stock and domestic storages below the licensing threshold. The field visit is what turns a flag into a finding, one way or the other.
How you frame an unlicensed take investigation downstream depends on getting this order right. A show-cause letter built on an imagery flag alone, without a site visit behind it, rests on a desktop observation that hasn't been confirmed on the ground. The imagery layer tells you where to point the inspector; the site visit supplies the evidence.
Where this fits in the annual cycle
For catchments where the register runs to hundreds of entries and the geography makes a full property-by-property drive impractical every year, this reconciliation step is usually the difference between an audit that samples a handful of complaint-driven properties and one that actually covers the catchment. Farm Dam Detection runs the yearly imagery pass and produces the candidate-structure layer against your current register, so the desktop step above is done before the audit season starts rather than during it.
If your entitlement compliance workflow still runs on complaints and rotation, it might be worth seeing what a yearly imagery pass over your catchment would flag.