{"id":"river-macroinvertebrates","slug":"river-macroinvertebrates","name":"River Macroinvertebrate Community Dataset","description":"Four community indices from the Environment Agency’s standardised freshwater invertebrate sampling in England, at the 2,611 river sites with a record long enough to show change — at least thirty samples across at least fifteen years, from 1965. WHPT scores the community for organic pollution, LIFE for flow, PSI for fine sediment, and the taxon count for richness. The animals in a riverbed cannot leave, so what persists at a site integrates everything the river did between visits, including the pollution incident nobody sampled and the drought that ended before anyone arrived.","methodology":"Collected from the Agency’s Ecology and Fish Data Explorer bulk download. Indices are taken as the Agency computes and publishes them rather than recomputed. Sites are published as British National Grid eastings and northings with no latitude or longitude, and are converted by inverting the transverse Mercator projection of the Airy 1830 ellipsoid and then applying a Helmert datum shift to WGS84; omitting the second step would leave every site about a hundred metres out. Where a sample was reanalysed the latest version is held; field replicates sharing a site, date and version are dropped rather than averaged, because their mean is a statistic the Agency never published. Sites whose grid reference falls outside the National Grid are not held rather than placed approximately.","domains":["ecosystem","quality"],"metricIds":["whpt-aspt","whpt-ntaxa","life-family-index","psi-family-score"],"subjectScope":"Environment Agency river macroinvertebrate monitoring sites in England with a long record","cadence":"irregular","version":"1.0.0","released":"2026-08-27","changelog":[{"version":"1.0.0","date":"2026-08-27","summary":"First release.","additions":["WHPT ASPT, WHPT NTAXA, LIFE and PSI at 2,611 long-record English river sites, from 1965."]}],"limitations":["An index is not a count. It scores which taxa were present against a table of sensitivities, so two samples with identical indices can differ tenfold in the number of animals, and a rising index is a community shifting towards sensitive taxa rather than a population recovering.","Strongly seasonal. The Agency samples in spring and autumn and the communities differ substantially between them, so a year-on-year comparison that mixes seasons will find changes that are the calendar rather than the river. Each observation carries its own sample date so the two can be separated.","Not comparable with biological indices from other countries. WHPT, LIFE and PSI are British indices built on British taxon tables and a British sampling protocol, and a European or American index with a similar range does not mean the same thing.","Sites with short records are excluded, not missing. Of 30,693 sites the median has three samples; the 2,611 held are those with at least thirty samples across at least fifteen years. Any national picture drawn from this describes long-monitored sites, which the Agency chose for reasons — often known pressures — and which are not a random sample of English rivers.","Describes the sampled reach and not the river. Conditions can differ sharply above and below a discharge, a weir or a confluence.","NTAXA is sensitive to analytical effort and to the taxonomic level the analyst worked at, so a change in laboratory practice can move it without the river changing.","The full taxon lists are not held. Anyone needing which species were present, rather than what the community indicates, needs the publisher’s taxon archive."],"context":{"hydrionisClass":"water-dependent-system","biologicalBasis":"ecological-index","whyHeld":"Chemistry describes the water at the instant a bottle was filled. Invertebrates describe the year. Holding both lets a reader see whether a river that looks clean on paper actually supports the community a clean river supports — and the two disagreeing is itself the finding. None of this measures water: an index is what the animals indicate about conditions, not a concentration, a flow or a volume.","waterRelevance":["Biological condition of rivers, as an integrator of what chemistry samples miss","The ecological signature of low flow, which LIFE was built to detect","Fine sediment pressure on riverbeds, which PSI responds to","Whether ecological condition moved with a drought, a discharge or a change in land use"],"suitableUses":["Tracking biological condition at one river site over decades","Comparing sites sampled under the same Environment Agency protocol","Showing LIFE beside a river flow or drought record on a shared time axis, within one season","Contrasting the four indices at one site to see which pressure moved"],"unsuitableUses":["Reading an index as a count, a density or a population of anything","Comparing these with biological indices from other countries or other protocols","Comparing spring and autumn samples as though they were repeated readings of one quantity","Treating the held sites as a representative sample of English rivers; they are the long-monitored ones","Attributing an index change to a cause — low flow, a discharge, siltation — on the strength of the two moving together. LIFE falling is consistent with low flow and is not evidence of it: impoundment, siltation and channel works move it too.","Inferring anything about a river reach that was not sampled"],"joinDimensions":[{"kind":"publisher-stated","on":"The Environment Agency’s own WFD water body identifier, carried on every held site","limitation":"Places a site in the water body the Agency assigns it to, which is a publisher’s statement and not a geometry Hydrionis has checked. It does not establish that two sites in one water body are hydrologically connected, or which is upstream of the other."},{"kind":"time-only","on":"Sample dates, against any other Hydrionis series for the same period","limitation":"A kick sample reflects the months before it, not the day it was taken, so aligning it to same-day flow or rainfall compares an integrated signal with an instantaneous one. The lag is real, unmeasured here, and varies by taxon."}],"relationshipConfidence":"contextual","eligibility":{"api":true,"download":true,"overlay":true,"publicPage":false}},"observationCount":470453,"seriesCount":10444,"subjectCount":2611,"from":1965,"to":2026,"sourceIds":["uk-ea-ecology"],"units":["%","count","index"],"redistributable":true,"commerciallyReusable":true,"citation":"Hydrionis (2026), River Macroinvertebrate Community Dataset, version 1.0.0. Retrieved from https://hydrionis.com/data/datasets/river-macroinvertebrates/","downloads":[{"file":"/downloads/observations-ecosystem-uk-ea-ecology.csv","format":"CSV","label":"ecosystem observations from EA ecology (637,594 rows)"}],"apiPath":"/api/v1/datasets/river-macroinvertebrates.json","lastFetched":"2026-08-27","fields":[{"id":"whpt-aspt","name":"WHPT average score per taxon","definition":"Mean pollution-sensitivity score of the scoring macroinvertebrate taxa found in a standardised sample, under the Walley Hawkes Paisley Trigg system.","unit":"index","nativeGeography":["monitoring-station"],"comparabilityNotes":"A community index, not a count. It scores the taxa present against a sensitivity table, so two samples with identical scores can differ tenfold in the number of animals found. Comparable only between samples taken under the same protocol — the Environment Agency’s standardised three-minute kick sample. Not comparable with indices from other countries, which use different taxon tables and different sampling, even where the numeric range looks similar. Strongly seasonal. Spring and autumn samples from one site are not two readings of the same quantity, and a comparison that mixes them will find differences that are the calendar rather than the river. Describes the sampled reach, not the river. Conditions can differ sharply above and below a discharge, a weir or a tributary confluence. The scale is not anchored at zero: WHPT assigns negative scores to the most pollution-tolerant taxa, so a badly degraded sample can return a negative average."},{"id":"whpt-ntaxa","name":"WHPT number of scoring taxa","definition":"Count of macroinvertebrate taxa in a standardised sample that carry a WHPT sensitivity score.","unit":"count","nativeGeography":["monitoring-station"],"comparabilityNotes":"A count of taxa, not of animals: finding one mayfly and finding four hundred both count as one taxon. Comparable only between samples taken under the same protocol — the Environment Agency’s standardised three-minute kick sample. Not comparable with indices from other countries, which use different taxon tables and different sampling, even where the numeric range looks similar. Strongly seasonal. Spring and autumn samples from one site are not two readings of the same quantity, and a comparison that mixes them will find differences that are the calendar rather than the river. Describes the sampled reach, not the river. Conditions can differ sharply above and below a discharge, a weir or a tributary confluence. Sensitive to analytical effort and to the taxonomic level the analyst worked at, so a change in laboratory practice can move it without the river changing."},{"id":"life-family-index","name":"LIFE flow index (family level)","definition":"Lotic-invertebrate Index for Flow Evaluation: mean flow-preference score of the macroinvertebrate families found in a standardised sample.","unit":"index","nativeGeography":["monitoring-station"],"comparabilityNotes":"A community index, not a count. It scores the taxa present against a sensitivity table, so two samples with identical scores can differ tenfold in the number of animals found. Comparable only between samples taken under the same protocol — the Environment Agency’s standardised three-minute kick sample. Not comparable with indices from other countries, which use different taxon tables and different sampling, even where the numeric range looks similar. Strongly seasonal. Spring and autumn samples from one site are not two readings of the same quantity, and a comparison that mixes them will find differences that are the calendar rather than the river. Describes the sampled reach, not the river. Conditions can differ sharply above and below a discharge, a weir or a tributary confluence. Designed to respond to flow, but it responds to anything that shifts the community towards still-water taxa — impoundment, siltation and channel works among them. A fall is consistent with low flow and is not evidence of it, and pairing it with a flow record shows whether the two moved together, never that one caused the other."},{"id":"psi-family-score","name":"Proportion of sediment-sensitive invertebrates","definition":"Share of the macroinvertebrate community made up of families sensitive to fine sediment, on a scale of 0 to 100.","unit":"%","nativeGeography":["monitoring-station"],"comparabilityNotes":"A community index, not a count. It scores the taxa present against a sensitivity table, so two samples with identical scores can differ tenfold in the number of animals found. A proportion of the community, not a measurement of sediment: it says what the animals indicate, not how much silt is present, and no depth or mass of sediment can be inferred from it. Comparable only between samples taken under the same protocol — the Environment Agency’s standardised three-minute kick sample. Not comparable with indices from other countries, which use different taxon tables and different sampling, even where the numeric range looks similar. Strongly seasonal. Spring and autumn samples from one site are not two readings of the same quantity, and a comparison that mixes them will find differences that are the calendar rather than the river. Describes the sampled reach, not the river. Conditions can differ sharply above and below a discharge, a weir or a tributary confluence. Zero and one hundred are both genuinely reported."}]}