Turbidity & suspended solids instrumentation, historically based in Port Townsend, WA Product line now supported through Campbell Scientific, Inc.
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D & A Instruments
Turbidity monitors & water-quality instrumentation

Groundwater Profiling Permafrost Thaw Subsidence Effects

Permafrost thaw changes more than the shape of the ground. As ice-rich soil warms, pore water is released, depressions form, drainage pathways shift, and previously isolated groundwater can connect with surface water. These changes influence turbidity, suspended sediment, salinity, temperature, dissolved oxygen, and the movement of dissolved contaminants.

A groundwater profiler helps researchers map those changes through the water column and along transects. Rather than relying only on satellite imagery or isolated boreholes, a profiling system can reveal how physical subsidence corresponds with vertical water-quality gradients. This is valuable for identifying taliks, thaw lakes, seepage zones, and sediment-rich flow paths beneath or beside thermokarst features.

For Australian organisations, the subject is especially relevant when supporting Arctic field programmes, international environmental research, defence logistics, and remote sensing projects. Australia has no extensive natural permafrost comparable with northern Canada or Siberia, although alpine and subantarctic environments provide useful cold-region research settings. Australian engineering teams also contribute instrumentation, data systems, and environmental assessments to overseas projects.

The same measurement principles apply closer to home. Groundwater profiling can assist with mine-site rehabilitation in Western Australia, coastal aquifer studies near Perth and Darwin, and wetland investigations around Melbourne or the Murray–Darling Basin. In each case, the objective is to understand how changing ground conditions alter water movement and sediment transport.

How Thaw Subsidence Reshapes Groundwater

Ice-rich permafrost can act as a low-permeability boundary, separating shallow surface water from deeper groundwater. When thawing removes that barrier, water may infiltrate more deeply or rise through newly opened pathways. Ground subsidence can also create ponds that concentrate runoff, organic matter, fine sediment, and dissolved nutrients.

The result is rarely uniform. A thaw slump may contain warm, oxygen-poor water near the base, while a nearby channel carries colder, more oxygenated groundwater. Conductivity can rise where mineralised groundwater enters a thaw depression, while turbidity increases after bank collapse or intense rainfall. Vertical profiles expose these transitions more clearly than a single sample collected at the surface.

A profiler moved through a lake, flooded depression, stream reach, or borehole can record depth-dependent measurements at regular intervals. Pressure provides depth, while temperature, conductivity, turbidity, and other parameters describe the water mass. Repeated transects can show whether a subsidence feature is stabilising, expanding, or developing a new groundwater connection.

Mapping Taliks, Ponds, And Seepage

A talik is an unfrozen zone within or beneath permafrost. Some taliks remain isolated, while others connect permanently with groundwater systems. Their location matters because they can transport dissolved carbon, nutrients, metals, and fine sediment through ground that was previously relatively sealed.

Groundwater profilers are suited to locating the water-quality signatures associated with these zones. A warm anomaly may indicate groundwater exchange, although temperature must be interpreted with season, solar heating, and mixing in mind. Conductivity and dissolved oxygen can strengthen the interpretation, especially when a talik links a pond to deeper mineralised water.

Suspended-solids data add a physical dimension to the investigation. A sharp turbidity increase near the bottom may indicate sediment resuspension, a seepage plume, or material entering through a subsurface opening. Optical measurements should be selected for the expected particle size and water colour; guidance on optical wavelength selection is useful where dissolved organic matter gives thaw-affected water a tea-brown appearance.

Building A Multi-Parameter Survey System

A practical system begins with the question being tested. If the objective is to map groundwater exchange, temperature and conductivity may be central. If the focus is erosion or sediment delivery, turbidity and suspended solids become more important. Pressure, depth, dissolved oxygen, pH, oxidation-reduction potential, and fluorescence can provide supporting evidence where power, payload, and maintenance capacity allow.

The sensors should be mounted so that they experience representative water rather than turbulence created by the survey vessel. A streamlined frame, stable lowering point, and controlled descent rate help produce comparable profiles. In shallow thermokarst ponds, a small boat or tethered platform may be appropriate. In deeper or hazardous water, a winch, remotely operated platform, or autonomous vehicle can reduce exposure to unstable banks.

Data logging needs the same attention as sensor selection. Each record should include time, geographic position, depth, instrument status, and calibration information. A multi-parameter architecture should also account for sensor response times, because a fast pressure reading may change before a slower optical measurement has equilibrated. The principles described in this guide to estuarine profiling design transfer well to cold-region groundwater and surface-water studies.

Relating Water Profiles To Ground Movement

Water-quality observations become more valuable when matched with measurements of ground deformation. Interferometric synthetic aperture radar can identify broad subsidence patterns, while drone photogrammetry or terrestrial surveys can document local scarps, pond margins, and drainage channels. The profiler then helps determine what those physical changes mean for groundwater pathways.

For example, a subsiding polygon may develop a shallow pond without a strong groundwater connection. Another may show a persistent conductivity and temperature anomaly at depth, indicating exchange through a talik. Comparing several profiles across the same feature can distinguish a local seep from a wider hydraulic gradient.

Survey timing is important. Seasonal thaw depth changes through the summer, and freeze-back can isolate water bodies again. Repeating the same transects during early thaw, late summer, and autumn freeze-up creates a time series rather than a single snapshot. Permanent benchmarks, accurate GNSS positioning, and consistent instrument settings are essential when comparing results between campaigns.

Managing Optical And Field Conditions

Optical turbidity sensors measure light scattering or attenuation caused by particles in the water. Their readings can be affected by particle shape, colour, organic matter, bubbles, fouling, and sensor geometry. Permafrost thaw ponds may contain dark dissolved organic carbon as well as mineral sediment, so a calibration based on one site may not transfer reliably to another.

Field teams should collect representative water samples during profiling for laboratory suspended-solids analysis. Those samples support site-specific calibration and help separate changes in particle concentration from changes in particle type. A clean-water reference, field blank, and post-survey check can identify drift or contamination.

Cold conditions create additional operational concerns. Batteries lose capacity, connectors can become brittle, and ice crystals or slush can obstruct optical windows. Instruments should be checked for pressure ratings, operating temperature limits, cable flexibility, and anti-fouling provisions. In remote campaigns, spare wipers, seals, desiccant, cleaning materials, and a second calibrated sensor may be more valuable than a wider sensor suite.

Using Drones And Remote Platforms

Aerial surveys provide a broad view of subsidence, drainage, exposed sediment, and pond development. A drone can map the changing outline of a thermokarst lake or locate surface expressions of groundwater discharge before a profiling team selects transects. It cannot, by itself, determine the depth of a plume or distinguish suspended sediment from coloured dissolved material.

A coordinated workflow links aerial observations with in-water measurements. A drone may identify a plume entering a pond, after which a profiler follows the plume from its inlet toward open water. In some settings, a drone can also support water sampling or carry a lightweight sensor to otherwise inaccessible margins. Practical considerations for drone water sampling include payload stability, sensor exposure, georeferencing, and safe operations near people and wildlife.

Australian operators must also consider aviation and environmental requirements. Civil Aviation Safety Regulations and CASA operational rules govern many drone activities, while access to Indigenous land, national parks, and restricted defence areas may require separate permissions. In Arctic work, equivalent local aviation, wildlife, and land-access rules apply, and approvals should be secured before equipment is shipped.

Designing A Reliable Australian Project

An Australian-led project may involve equipment purchased through a local distributor, a manufacturer-supported product line, and a research partner responsible for field deployment. Clear responsibility for calibration, repairs, firmware, data formats, and replacement parts prevents delays when a campaign is operating far from a service centre. Campbell Scientific support is relevant where product-management and technical contact arrangements need to be coordinated for D & A Instruments systems.

Procurement should account for the realities of the Australian market. Equipment may be ordered in Australian dollars, shipped from overseas, and held for months before an Antarctic or Arctic deployment. Customs documentation, lithium-battery transport, export controls, and cold-weather packaging should be planned at the start rather than immediately before mobilisation.

Local compliance also matters when the work is carried out in Australia or connected to an Australian research programme. The Environment Protection and Biodiversity Conservation Act 1999 may apply to impacts on protected matters, while the Water Act 2007 is important for projects involving Commonwealth water resources. State and territory groundwater licences, environmental approvals, cultural heritage obligations, and landholder permissions can apply separately.

For field teams based in Perth, Darwin, Brisbane, or Melbourne, a staged test in a local water body is a sensible validation step. A Perth coastal wetland can expose conductivity and fouling issues; a Darwin wet-season site can test high sediment loads and rapid deployment; a Melbourne catchment can support repeatable calibration and data review before equipment is sent overseas. Australian habits such as relying on mobile connectivity, ute-based field access, and scheduled site visits should be adjusted for Arctic work, where communications, roads, and resupply may be limited.

Turning Profiles Into Defensible Evidence

The strongest interpretation combines several lines of evidence: profiler transects, suspended-solids samples, ground elevation, satellite deformation, meteorological records, and site photographs. A temperature anomaly alone does not prove groundwater inflow, and a turbidity peak alone does not establish subsidence-related erosion. Agreement between independent measurements gives the interpretation greater weight.

Quality assurance should be documented with the data. Record calibration standards, instrument serial numbers, sensor warm-up time, deployment depth, GPS accuracy, weather, ice conditions, and any cleaning performed between stations. Flag readings collected during winch movement, vessel disturbance, or visible bubbles rather than treating every value as equally reliable.

A well-designed monitoring programme can then track whether thaw subsidence is changing water exchange, sediment mobilisation, or contaminant transport. The resulting evidence supports environmental baselines, infrastructure risk assessments, restoration planning, and long-term climate research without treating the ground surface as a complete proxy for what is happening below the water.

Practical Priorities For Field Teams