docs: document BernCo HydroVu source schema (ST2DAT-129)

[crawson-icasa]

Why

• BernCo HydroVu is one of the next sources to onboard and had no required source mapping doc

How

• Added docs/sources/bernco_hydrovu.md based on _mapping_template.md.
• Confirmed the credentials. hydrovu_bernco is in Secret Manager and its {id, secret} payload already matches what _resolve_hydrovu_credentials() expects, so no credential code has to change
• Surveyed all 53 locations against the live tenant instead of sampling one, covering device profiles, parameter and unit inventory, cadence, and history depth
• Mapped all six entities, with every fixed value traced to sources/hydrovu/adapter.py and canonical/canonical_constants.py
• Documented the unit conversion. parameterId="4" arrives as unitId="35" (metres) at every location, so PVACD's × 3.28084 carries over unchanged
• Split the Sensor section into "exists in canonical_constants.py" and "applies to this source", because 11 of the template's 13 names are not yet defined in canonical_constants.py
• Included sanitized, JSON-validated response examples for all three endpoints

Notes

Any special considerations, workarounds, or follow-up work to note?

• deploy/30_dagster_gcp_auth.sh grants secretAccessor on hydrovu_pvacd only. The Dagster service account needs the same grant on hydrovu_bernco before this runs in production
• Found two code discrepancies: dlt_pipeline.py:191-193 logs 404 as "no data endpoint" when it means no data at or after startTime, and 13 of BernCo's 14 404s return full history at startTime=0. dlt_pipeline.py:130-137 says the API has no endTime parameter, but the OpenAPI spec lists one
• Three locations sit at In-Situ's Fort Collins factory-default coordinates, and one of them carries live DTW data. Two more return sentinel timestamps at epoch 0 and 960
• A location's parameter set changes over time. 35 locations have carried DTW against 29 today, so any backfill allowlist has to come from historical coverage
• Ten locations are VuLink gateways reporting only their own telemetry. Exclude them from the allowlist rather than filtering them at transform time
• initial_start_date is still open. History runs back to 2009-05-18, so someone has to pick how much of it to load
• Multi-tenant HydroVu stays unmodeled: one flat [sources.hydrovu] block, one registry entry. Open Questions Scaffold dagster_dlt(ST2DAT78) #1 proposes a design, this PR implements none of it

[github-actions]

Your pull request is automatically being deployed to Dagster Cloud.

Location	Status	Link	Updated
aqueduct_dagster_defs_definitions		View in Cloud	Aug 25, 2026 at 01:02 AM (UTC)

[chasetmartin]

I would probably remove project and number from this doc, otherwise looks good