Review and modernisation of dam survey frameworks

Client: Hydro Tasmania
Location: Tasmania, Australia
Date: 2025-26

Reprocessing historical spatial datasets and modernising control networks to strengthen certainty in deformation monitoring

Background

Regular deformation surveys are an important input to a dam safety program. Reliability of survey control and confidence in reported data are paramount.

Over several decades, Entura has monitored many of Hydro Tasmania’s dam assets.

In 2025, Entura was engaged to review and modernise the deformation monitoring framework at 2 concrete arch dams in Hydro Tasmania’s dams portfolio that are more than 50 years old. This work examined the survey history, equipment and methodologies used through time; assessed the relevance and adequacy of archived records; and focused on the stability and suitability of control networks that underpin deformation results.

The objective was to ensure that observed trends reflect true structural behaviour rather than artefacts of survey control, and to provide a robust foundation for ongoing monitoring.

Solution

Entura delivered a structured, methodical program to strengthen the integrity of datasets and streamline future monitoring, while keeping continuity with the long-term record.

This included:

• comprehensive desktop review of historical survey methods, instrument changes, target configurations and control strategies across both sites
• control network assessment, moving from legacy practices toward minimally constrained least-squares adjustments to reduce distortion risk and improve traceability
• reprocessing historical surveys using contemporary computation tools to validate control stability, reconcile baselines and datums, and standardise reference frames.
• target and instrumentation modernisation alignment, including correlation between historical and replacement targets so that long-term trends remain continuous
• improving field and processing governance with consistent instrument constants, pillar mounting standards, orientation practices, and clear documentation of procedures and assumptions
• practical recommendations for control redundancy, pillar selection (reference vs orientation), and sightline/access refinements to support reliable future campaigns.

This approach ensured a repeatable, transparent workflow that aligns with contemporary deformation monitoring practice while preserving the value of the historical record.

Outcome

Entura provided Hydro Tasmania with reliable, well-governed deformation datasets for each of the 2 dams, together with clear guidance to support future monitoring and interpretation – without altering the underlying character of the long-term records.

At both sites, dataset integrity was enhanced by refining control strategies, documenting reference systems, and consolidating workflows. Historical and modern observations were reconciled, enabling consistent comparisons over time and clarifying the distinction between genuine dam behaviour and control-related effects.

The program also streamlined field and processing practices, increasing certainty and improving efficiency for subsequent survey rounds.

Hydro Tasmania now has:

• trend assessments grounded in robust control and coherent reference frames
• transparent documentation of methods, assumptions and change history to support ongoing governance
• actionable, practical recommendations to maintain long-term reliability and continuity of monitoring.

Services

• Control network review
• Historical data reprocessing
• Deformation survey governance
• Target/instrument correlation
• Recommendations for control redundancy and orientation