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Create an Alert Rule

An alert rule tells Nereus when to fire an alert: a condition on a specific metric, for a specific asset or asset class, that triggers at a chosen severity level. This guide walks through creating a threshold rule (the most common type) and covers the other comparators.

Prerequisites

Section titled “Prerequisites”
  • Owner, Admin, or Engineer role in the project
  • At least one asset with telemetry — the rule targets that asset (or its class)
  • Know which metric you want to alert on (e.g. level_m for a reservoir, pressure_kpa for a pump station, battery_v for any device)

Steps — threshold rule

Section titled “Steps — threshold rule”

A threshold rule fires when a metric crosses a fixed value. This example creates a warning alert when any reservoir’s level drops below 0.5 metres.

  1. Navigate to the Alerts screen from the project sidebar.

  2. Click the Rules tab to switch to the rule list.

  3. Click Create rule to open the rule editor.

  4. In the Target section, choose Class scope and select Reservoir — this applies the rule to every reservoir in the project (a live “applies to N assets” preview shows the blast radius). Alternatively, choose Asset scope and pick one reservoir, or Group scope to cover a region, zone, or site.

  5. In the Condition section, build the sentence Alert when …:

    • Metric: choose Level (level_m). The picker shows the metrics the target reports.
    • Comparator: choose falls below (lt). Other options: gt (rises above), outside_band (moves outside a band), rate (changes faster than), pct_over_baseline (exceeds a baseline by), min_over_window (stays above — flow only), and stale (reports no data for).
    • Trip value: enter 0.5. The rule fires when level_m falls below 0.5 m.

  6. In the Reduce false alarms section:

    • Confirm over: set 2 consecutive readings before the alert opens — transient dips are ignored.
    • Clear value (optional): enter 0.7. The alert resolves once the level recovers above 0.7 m — the gap prevents flickering around the threshold.

  7. In the Classification section, set Severity to Warning and pick a Category (e.g. “Reservoir level”) to group related alerts in the feed.

  8. Click Save. The rule appears in the list immediately with an Active status.

Other comparator types

Section titled “Other comparator types”

Band rules — outside_band — monitor a metric against a low–high band. Use them for pressure zones: configure a band rule on pressure_kpa with a trip value of 150 and a high value of 700 on the pressure point class. The rule fires when pressure strays outside 150–700 kPa.

Continuous-flow rules — min_over_window — evaluate a flow’s minimum over a time window (flow metrics only). Use a 24-hour window to detect a continuous leak: if a meter’s minimum flow over 24 h never drops below 3 L/min, a suspected-leak alert fires. Set Window (24 h) alongside the trip value.

Offline rules — stale — fire when a sensor stops reporting for a chosen window, raised as an offline alert. They watch for the absence of data rather than a value.

Section titled “Related”