NRW Freshwater River Macroinvertebrates

Freshwater macroinvertebrates are used as an indicator of water quality and river flow requirements due to the relative immobility and abundance. This dataset contains site, sample, metric and taxa information from freshwater river macroinvertebrate surveys carried out across Wales by Natural Resources Wales and former Environment Agency Wales since 1978 and onwards. These surveys are conducted as part of on-going monitoring of river water quality for legislative requirements and to meet business drivers.

A strict methodology is applied when sampling for freshwater river macroinvertebrates. There is a core network of sites which are monitored on a three-yearly rolling programme. These sites are located where risk assessment has shown significant risk of failure of WFD ecological quality standards. In addition sites may be sampled for investigative work, or on an ad hoc basis. Sampling areas are located with a larger survey area and must be representative of the overall survey area. A three-minute kick-sample is the most commonly used sampling method, although where necessary alternative methods are used, for example in deeper water or for investigative work. Once samples are collected they are sent NRW ecology laboratories for identification using standard methodologies, employing a strict Analytical Quality Control (AQC) procedure.

Once the data is collated in the central database, it has then been extracted and QA'd before being published. It is important to note that this dataset will include some sampling events from recent months where sampling has been undertaken but laboratory analysis has not been completed, therefore the full complement of taxa for that sampling event will not yet be uploaded. These records will be completed in future data uploads from NRW to the NBN Atlas. This dataset also includes records for some non-macroinvertebrate species, such as birds and fish, that were either observed or collected during sampling. Any non-target organisms collected during sampling were immediately returned to the river.

Redactions

Some information has be redacted to make the data openly available. This includes

Third party data
Data collected for ongoing investigations
Cancelled or incomplete surveys
Location of protected species where releasing details of their location could have a detrimental effect e.g. freshwater pearl mussels.

Update Frequency

This data is continually updated with the most surveys undertaken in the spring and autumn. Data from survey seasons is often not enter at the time of capture and can be several months before its is entered into the system. The external dataset is updated monthly to include new data, and may also contain corrections to previously published data due to quality assurance work.

Information Warnings

We do our best to avoid data quality problems, but as these datasets reflect the data we hold, they may contain errors
The data is provided as a set of related data tables due to the quantity and structure of the data. A basic understanding of ecology and relational data is assumed.
Data related to pollution incident investigations or protected species information is not released as locational information of these sites may be detrimental to ongoing investigations or species protection.
Not all sites have environmental base data listed.
Much of the data collected prior to 2002 was recorded using a logarithmic scale 3=A, 33 = B etc.
Prior to 2012, most taxa were only recorded to family level, we moved to mixed-taxon level at this time. For this reason, some early samples may show blanks for some of the indices which required a higher level of taxonomic detail eg. LIFE species.

Further Information:

Please see the following documents for further information

Attribution statement

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Please refer to the licence to understand the conditions of using this data.

OWS endpoints

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Spatial data (3)

Spatial data download

River Macroinvertebrates Sample Metrics
River Macroinvertebrates Taxa
River Macroinvertebrates Site Details

Metadata download

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Type:

Spatial data

Publication date:

22 April 2025

Licence:

Open Government Licence for Public Sector Information (OGL)

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