Glossary.
Plainly stated.

EU-wide rules for the monitoring and classification of bathing waters. Mandatory parameters are E. coli and intestinal enterococci; cyanobacteria are monitored separately. Municipalities are the implementing body, the German Environment Agency provides the annual assessment. Real-time monitoring complements mandatory sampling with an early-warning layer.

Spatial mapping of the depth structure of a lake, river or coastal section. Classically done by sonar from a boat, today also satellite-supported for shallow, clear waters (Satellite-Derived Bathymetry, SDB). Bathymetric maps are the basis for volume calculation, sediment budgets and understanding stratification processes.

The entire area from which precipitation flows to a water body above and below ground, bounded by the watershed. It determines which substances arrive: land use, soil type, sealed surfaces and discharges explain a large part of the nutrient load. Anyone looking for causes will rarely find them in the lake itself. In its consulting work, e.Ray therefore always relates measured values to the area that produces them.

A green pigment found in all photosynthetically active algae and cyanobacteria. Its concentration is the standard proxy for phytoplankton biomass in water and thus a key parameter for trophic assessment. Captured optically via fluorescence probes – also in the WAMO sensor stack.

A measure of the concentration of dissolved salts and ions in water. Rising conductivity indicates discharges, leaching from soils or salt input. In freshwater, typical values lie between 50 and 800 µS/cm – abrupt spikes are an early-warning signal for substance inputs.

Photosynthetically active bacteria that can form mass developments (“blooms”) in nutrient-rich waters. Some strains produce toxins (microcystin, anatoxin) that are a health hazard for humans and animals. Early warning via phycocyanin probes and satellite-supported detection is a core application of WAMO and SWIM.

Consolidation of heterogeneous sources – official monitoring programmes, gauge and weather data, satellite scenes, sector registers, own sensors – into a shared format aligned in time and space. The work rarely lies in the volume of data but in comparability: reference systems, units, measurement intervals and quality information all have to fit together. e.Ray connects existing holdings with its own measurements without replacing established specialist systems.

Removal of deposited sediment layers by excavator, suction dredging or with the water body drained. It takes out nutrient stocks and recovers water depth, but it is the most expensive item in the measures catalogue and raises the question of what to do with the sludge. Whether the effect lasts depends on whether inputs from the catchment fall at the same time. e.Ray supplies the before-and-after values from which this can be read.

Technical mixing of a stratified lake so that oxygen-rich surface water reaches the deep zone – usually by compressed-air circulators or impellers. In the 18-point catalogue this is measure 8. The intervention is effective but not harmless: it lifts nutrient-rich deep water into the epilimnion and may promote algal growth in the short term. e.Ray accompanies such installations with depth profiles of temperature and oxygen.

The concentration of O₂ dissolved in water – the most important vital parameter of a water body. Values below 4 mg/L stress fish, below 2 mg/L mass mortality begins. Summertime hypoxia in the deep zone of eutrophic lakes is a typical warning signal. WAMO measures continuously at multiple depths.

Genetic material that organisms leave behind in the water as cells, mucus or excretions. A single water sample can show which species occur in a water body without catching or observing them – helpful for shy, rare and invasive species. Limits: eDNA proves presence but says little about population size, and currents can shift the apparent location. e.Ray is evaluating the method as a complementary biological layer alongside sensors and satellite data.

The mixed, sun-warmed upper water layer of a stratified lake. Wind and convection keep it in motion, and contact with the atmosphere holds it close to oxygen saturation. Most of the primary production takes place here, which is why algal blooms become visible in the epilimnion first. From the temperature spread between the epilimnion and the deep zone, a WAMO sensor chain reads how stable the stratification currently is.

Enrichment of a water body with plant nutrients – primarily phosphorus and nitrogen from agriculture, wastewater and the atmosphere. The consequences are algal blooms, oxygen depletion in deeper layers and loss of biodiversity. Eutrophication is the most common driver of ecological deficits under the EU Water Framework Directive.

Umbrella term for global satellite-navigation systems: GPS (USA), Galileo (EU), GLONASS (Russia), BeiDou (China). WAMO stations use GNSS receivers for precise position and time synchronisation of every measurement series. EUSPA funding for e.Ray refers to Galileo integration.

Introduction of oxygen into the deep zone while the summer stratification is deliberately preserved – the essential difference from destratification. Common methods are hypolimnetic aerators with gas separation, pure-oxygen injection or Nano-Bubble systems. They can ease oxygen deficits at the bed and limit the release of phosphate, but they do not replace a reduction of nutrient inputs. At the Backhausteich, e.Ray applies the same technique close to the bed in a shallow water body and monitors operation with measurements.

The cold, low-light deep layer of a stratified lake, cut off from the surface water. During summer stagnation it has no contact with the atmosphere: the oxygen present is consumed and not replenished. If the reserve does not last until autumn turnover, the hypolimnion becomes anoxic and phosphate is released from the sediment. This is precisely why WAMO measures at several depth horizons rather than at the surface alone.

A sub-discipline of hydrology dealing with physical, chemical and biological processes in lakes, rivers, ponds and wetlands. Limnologists provide the expert interpretation behind measurement and satellite data – at e.Ray this expertise is part of the consulting package.

Aquatic plants visible to the naked eye: submerged meadows, floating-leaf stands and reed beds. They stabilise the sediment, compete with algae for nutrients and provide spawning grounds and refuge. Their species composition is a biological quality component under the EU Water Framework Directive. Whether light conditions are still sufficient for them is shown by turbidity and Secchi depth – both parameters from the WAMO data set.

A laboratory method that identifies many species at once from a mixed sample: a short, species-specific DNA section is amplified, sequenced and matched against reference databases. Together with eDNA, this produces species lists for fish, invertebrates or algae from a few litres of water. Its reliability stands or falls with the completeness of the reference database. For e.Ray, metabarcoding is a development stage of the data platform, not a product available today.

A standard framework for traceable environmental reporting – originally from climate policy, increasingly also used in water management and biodiversity reporting. “Monitoring” measures, “Reporting” documents, “Verification” checks independently. Robust MRV is a prerequisite for funding programmes, certificates and official recognition of measures.

Sensors that capture reflection in several discrete spectral bands – typically visible light, near-infrared and short-wave infrared. Indices such as NDWI or NDVI are derived from band combinations. Sentinel-2 provides 13 bands at 10–60 m resolution and is the operational data source for SWIM.

Gas bubbles in the nanometre range which, unlike coarse air bubbles, barely rise and instead remain in the water column for a long time. They can therefore make oxygen available close to the bed as well, where it is needed most urgently in biological and chemical terms. Effect and persistence depend strongly on the equipment, the water chemistry and the installation site; blanket performance figures should be read with caution. At the Backhausteich, e.Ray is trialling a 70 m Nano-Bubble aeration line.

A spectral index used to delineate water surfaces from satellite data. Calculated from the ratio between the green and near-infrared bands: (Green − NIR) / (Green + NIR). Values above 0 indicate open water surfaces, negative values vegetation or land. The basis for water-extent analyses in SWIM.

Consumption of dissolved oxygen during the microbial breakdown of organic matter as well as through respiration and chemical oxidation. Depletion rises with water temperature and concentrates where dead biomass accumulates: close to the bed and in the sediment. Where it exceeds resupply, hypoxia develops first, then anoxia with all its consequential processes. The depletion rate can be read from the slope of the oxygen curve in the deep water.

A logarithmic measure of the concentration of hydrogen ions, from 0 (acidic) through 7 (neutral) to 14 (alkaline). Natural freshwaters mostly lie between 6.5 and 8.5. Diurnal fluctuations show photosynthetic activity – strong deviations may indicate discharges.

Addition of iron, aluminium or calcium compounds that convert dissolved phosphate into poorly soluble forms and precipitate it. In the 18-point catalogue it appears as mineral phosphate binding and is often combined with sediment capping in order to suppress release permanently. It remains effective only for as long as resupply from the catchment stays limited. Phosphate and oxygen curves before and after application show whether the binding holds.

Under oxygen-free conditions, iron-phosphate complexes in the sediment are reduced and give bound phosphate back to the water. This internal load can exceed the external input and explains why lakes remain eutrophic for decades after wastewater treatment has been successfully upgraded. The decisive factor is the redox potential immediately above the sediment. Oxygen and redox measurements close to the bed make this tipping point visible.

Unlike classical grab sampling (weekly or monthly grid), real-time monitoring delivers readings in minute- to hour-cadence directly to the dashboard. A prerequisite for early warning of algal blooms, oxygen deficiency or substance inputs – and for traceable MRV reports.

An electrochemical measure of whether oxidising or reducing conditions prevail in the water, expressed in millivolts. High positive values indicate oxygen-dominated conditions. As the potential falls, nitrate, manganese, iron and finally sulphate serve in turn as substitute oxidising agents; only sulphate reduction lies reliably in the negative range. For sediment chemistry this is more informative than oxygen concentration alone. In the WAMO sensor stack the value complements the oxygen measurement close to the bed.

An artificial basin that takes up stormwater or flood runoff and releases it with a delay. Hydraulically proven, ecologically demanding: shallow depth, a high nutrient load from sealed surfaces and long residence times encourage warming, algal growth and oxygen deficits. Operators therefore face questions otherwise familiar from lake management. e.Ray treats retention basins as an application case of their own for monitoring and restoration.

A black sediment layer, frequently smelling of hydrogen sulphide, that forms when organic material is broken down without oxygen. It binds large amounts of nutrients, continues to consume oxygen and, where oxygen remains absent, releases phosphate and methane. Sapropel is therefore less a cause than a self-reinforcing consequence of oxygen demand at the lake bed. Oxygen profiles from several depths show when this zone is expanding.

Data transmission via communication satellites instead of mobile networks. Necessary where mobile coverage is missing or too unreliable – remote lakes, mountain reservoirs, marine stations. WAMO stations can optionally be equipped with a SatCom module, making them independent of terrestrial infrastructure.

The depth at which a white disc of 20 to 30 cm diameter just ceases to be visible – the oldest limnological measurement method and still one of the most informative. It combines turbidity and algal density into a single, easily communicated value and feeds into several trophic indices. The drawback: the reading depends on the observer and is only possible in daylight. From turbidity, chlorophyll and satellite values, Secchi depth can be modelled forward.

A zone only a few millimetres to centimetres thick in which the water body and the sediment exchange substances. It is here that it is decided whether phosphate, ammonium, iron and methane stay bound in the sediment or reach the lake; across this short distance the oxygen concentration often falls from saturated to zero. Small in scale, yet controlling for the entire nutrient budget. Measures for oxygen supply close to the bed target precisely this boundary layer.

A satellite mission of ESA under the Copernicus programme – two satellites deliver multispectral imagery with a 5-day revisit over every point on Earth. Data is free, which makes Sentinel-2 the standard data basis for operational water monitoring across Europe. SWIM processes Sentinel-2 scenes automatically.

In summer, many deeper lakes form a warm surface layer (epilimnion) and a cold deep zone (hypolimnion) with a sharp thermocline between. Stratification determines whether oxygen reaches the depths – and thus how stably the ecosystem responds to eutrophication.

e.Ray's satellite-supported remote-monitoring platform. Processes Sentinel-2 and partner data streams into layers for water extent, turbidity, algal probability and temperature. Provides area-wide trend information even where there is no WAMO station.

The transition zone between the warm epilimnion and the cold hypolimnion, technically the metalimnion. Over a few metres the temperature drops steeply; the density difference acts like a barrier and almost entirely suppresses vertical exchange. The position and sharpness of the thermocline determine how much oxygen reaches the depths and when autumn turnover sets in. Temperature sensors at several depth horizons record its depth directly.

Classification of water bodies by nutrient richness: oligotrophic (nutrient-poor, clear, oxygen-rich), mesotrophic (medium nutrient level), eutrophic (nutrient-rich, turbid, prone to hypoxia) and hypertrophic (algal blooms dominate). The trophic stage governs which measures from the 18-point catalogue are sensible.

A measure of the light transmission of water, recorded as scattering by suspended matter. High turbidity may indicate sediment inputs after rainfall, algal blooms or bioturbation. Measured optically via scattered-light sensors – a standard parameter on WAMO, derived from spectral analysis on SWIM.

e.Ray's on-site sensor platform. A floating body with a modular sensor stack (temperature, oxygen, pH, conductivity, turbidity, chlorophyll, phycocyanin), solar power, mobile or SatCom uplink. Measures continuously at multiple depths and sends data straight to the SWIM dashboard.

Measures that hold precipitation in the land and the water system for longer instead of draining it away quickly: retention spaces, ponds, storage, rewetting, unsealed surfaces. This is central to adapting to longer dry periods. Water that stands for a long time in slow-moving systems does, however, warm up and can develop oxygen deficits. Water quantity and water ecology therefore belong in the same plan – e.Ray supplies the measurements that connect both sides.

Umbrella term for interventions intended to improve the ecological condition of an impaired lake, pond or retention basin – from nutrient reduction in the catchment through sediment management to targeted oxygen supply. Which measure works only becomes clear once it is known which process is limiting the water body. e.Ray therefore begins with measurement and analysis and accompanies measures through to verification of their effect.

Directive 2000/60/EC – obliges all EU member states to bring their surface waters into a “good ecological status” and their groundwater bodies into a good quantitative and chemical status. Assessment is based on biological, chemical and hydromorphological quality components in 6-year management plans. The cornerstone of water-management regulation in Germany.