Assessment of water quality in Wales 2024
Updated water quality data across Wales can be downloaded in Excel and viewed as maps.
View the data on Water Watch Wales
View the maps on the Wales Environmental information Portal
Download the maps from Data Map Wales
Water Framework Directive (WFD) Regulations
The 2024 interim classification has remained steady with 40% of water bodies at good or better overall status. This is the same as the previous classification in 2021 but an improvement of 3% from 2015 and 5% since 2019.
Under the Regulations we divide the water environment into water bodies. These include lakes, rivers, groundwater, transitional waters (estuaries) and coastal waters. In total there are 933 water bodies in Wales.
We monitor water bodies for different things which we call elements. This includes chemical, physical and biological elements. We then apply a set of rules to classify every water body into one of five status classes (high, good, moderate, poor or bad) based on the worst of its ecological or chemical status.
The Regulations use a ‘one out all out’ approach for the overall status assessment, which means if one assessed element fails, the whole water body fails overall. If we look separately at each individual element, 93% of water bodies reach good or better status.
A breakdown for the number of water bodies for each status class in each water body type is shown below as well as the percentage at good or better. Note rivers type also includes canals and surface water transfers.
|
Water body type |
High |
Good |
Moderate |
Poor |
Bad |
% Good or better |
|---|---|---|---|---|---|---|
|
Groundwater |
0 |
21 |
0 |
17 |
0 |
55 |
|
Rivers |
0 |
311 |
323 |
78 |
14 |
43 |
|
Lake |
1 |
27 |
69 |
15 |
2 |
25 |
|
Estuaries and Coastal |
1 |
11 |
42 |
1 |
0 |
22 |
|
Total |
2 |
370 |
435 |
110 |
16 |
40 |
Water quality assessment of rivers in Special Areas of Conservation (SAC)
In total, 122 out of 127 water bodies have enough data to be assessed for phosphorus and of those 50% pass their targets. This is an 11% improvement compared to the previous assessment.
There are failures for the Gwyrfai, Eden, Teifi, Dee, Cleddau, Usk and Wye SACs. The failures for the Gwyrfai and Eden SACs are new in 2024 with one water body in each catchment failing. The Eden failure is due to one high sample.
At an individual SAC level there has been no change in the percentage of water bodies passing for two SACs (Tywi and Glaslyn, part of the Meirionnydd Oakwoods SAC), a deterioration in four SACs (Eden, Gwyrfai, Dee and Cleddau) and an improvement in three SACs (Usk, Wye and Teifi).
We have assessed eight more water bodies compared with the previous assessment. If we only compare the water bodies assessed in both 2021 and 2024, then five have deteriorated from a pass to a fail (in the Gwyrfai, Eden, Dee and Wye SACs) and 17 have improved from a fail to a pass (in the Teifi, Usk and Wye SACs).
For ammonia, which is also a nutrient, 98% of water bodies assessed pass the total ammonia targets and 100% the unionised ammonia target, an improvement since the previous assessment.
Dissolved Oxygen (DO) (96%) and Biochemical Oxygen Demand (BOD) (77%) have improved however, pH (98%), Acid Neutralising Capacity (ANC) (95%) and Trophic Diatom Index (TDI) (45%) have declined.
The table below summarises the percentage of assessed water bodies passing for the SAC river water quality attributes.
|
River SAC |
Phosphorus |
TDI |
DO |
BOD |
Total ammonia |
Unionised ammonia |
pH |
ANC |
|---|---|---|---|---|---|---|---|---|
|
Afon Eden – Cors Goch Trawsfynydd |
75 |
0 |
100 |
100 |
100 |
100 |
100 |
100 |
|
Afon Gwyrfai a Llyn Cwellyn |
50 |
- |
100 |
100 |
100 |
100 |
50 |
50 |
|
Afon Teifi |
75 |
0 |
88 |
100 |
100 |
100 |
100 |
100 |
|
Afon Tywi |
100 |
100 |
100 |
100 |
100 |
100 |
100 |
100 |
|
Afonydd Cleddau |
28 |
8 |
94 |
47 |
89 |
100 |
100 |
100 |
|
Meirionnydd Oakwoods and Bat Sites (Afon Glaslyn) |
100 |
0 |
100 |
100 |
100 |
100 |
100 |
100 |
|
River Dee & Bala Lake (Wales) |
38 |
0 |
88 |
100 |
100 |
100 |
100 |
100 |
|
River Usk |
54 |
89 |
100 |
92 |
100 |
100 |
100 |
100 |
|
River Wye (Wales) |
42 |
43 |
98 |
66 |
98 |
100 |
96 |
91 |
For the assessment river water quality monitoring data for the 127 water bodies in the nine SAC rivers has been assessed against the targets published in the Conservation Objectives.
The Conservation Objectives can be found in the Core Management Plans.
Condition assessments are undertaken for the attributes stated in the Conservation Objectives. This water quality compliance assessment will form part of the condition assessment alongside other attributes such as flow, morphology and, for species, population. Where the water quality targets apply these are reported as pass, fail or not assessed. For cross-border sites with England, the assessments are for the stretch of river in Wales only.
Water quality data combined across Wales
Under the WFD Regulations other legislation important for the protection of water, such as the Habitats Regulations, is also considered when looking at what need to be achieved. In general targets for the SAC rivers can be more stringent. There are overlaps for Phosphorus, Total Ammonia, DO, ANC and TDI and we can combine to show if the most stringent standard has been met.
View a spreadsheet on Water Watch Wales.
Further information
For further information contact WFDWales@cyfoethnaturiolcymru.gov.uk.