Update to phosphorus targets for water bodies in Special Area of Conservation (SAC) rivers in Wales
As part of the focus on water quality in SAC Rivers in Wales, we have reviewed the waterbodies in scope for SAC targets, and also made changes to the phosphorus targets for six water bodies. This review is part of the water quality target setting process for SAC Rivers and implements recommendations in the Compliance Assessment of Welsh River SACs Against Phosphorus Targets (Hatton-Ellis and Jones 2021).
In the future the aim is to do a full review of all water quality targets for water bodies which are part of SAC rivers, therefore it was decided to implement these minor changes immediately rather than wait. The changes are detailed below (Table 1).
As a result of the review, two water bodies have been removed and four have been added due to minor inconsistencies in mapping. This has largely been due to water bodies which do not align with the SAC boundary and also due to updated information about the location of the relevant SAC features.
In addition, targets for five water bodies have been tightened and for one water body the target has been relaxed. The phosphorus targets are based on a typology using thresholds for altitude, alkalinity and river size. The changes are due to the water body having been assigned either an incorrect altitude, alkalinity or river size or incorrect phosphorus data used during the original target setting process.
Change |
Water Body ID |
Water Body Name |
SAC |
Phosphorus target (µg l-1) |
---|---|---|---|---|
Water body removed |
GB110064048730 |
Mawddach - middle |
Afon Eden - Cors Goch Trawsfynydd |
n/a |
Water body removed |
GB110065053960 |
Glaslyn – upstream Colwyn |
Coedydd Derw a Safleoedd Ystlumod Meirion |
n/a |
Additional water body |
GB111067051980 |
Tryweryn - Mynach to Llyn Celyn |
Afon Dyfrdwy a Llyn Tegid |
10 |
Additional water body |
GB110064048740 |
Wen (Mawddach) |
Afon Eden - Cors Goch Trawsfynydd |
10 |
Additional water body |
GB110064054610 |
Crawcwellt South |
Afon Eden - Cors Goch Trawsfynydd |
5 |
Additional water body |
GB109056040000 |
Grwyne Fawr - source to conf Grwyne-Fechan |
River Usk |
7 |
Phosphorus target tightened |
GB111067051610 |
Ceiriog - upstream of Teirw |
Afon Dyfrdwy a Llyn Tegid |
10 (previously 28) |
Phosphorus target tightened |
GB111067051910 |
Ceiriog - confluence Dee to Teirw |
Afon Dyfrdwy a Llyn Tegid |
25 (previously 28) |
Phosphorus target tightened |
GB110064048750 |
Eden - lower |
Afon Eden - Cors Goch Trawsfynydd |
5 (previously 10) |
Phosphorus target tightened |
GB109056039960 |
Grwyne-Fechan - source to conf Grwyne Fawr |
River Usk |
15 (previously 28) |
Phosphorus target tightened |
GB110064048710 |
Mawddach lower |
Afon Eden - Cors Goch Trawsfynydd |
10 (previously 13) |
Phosphorus target reduced |
GB110061030690 |
Deepford Brook - headwaters to conf with Syfynwy |
Afonydd Cleddau |
40 (previously 39) |
Table 1. Changes to waterbodies and phosphorus targets since the publication of the Compliance Assessment of Welsh River SACs Against Phosphorus Targets (Hatton and Jones 2021).
Following these changes, there are now 127 water bodies within SAC rivers with a defined single phosphorus target
Find a full list of phosphorus targets for each SAC river in Wales
Re-assessment of waterbodies following changes to the phosphorus targets
The additional water bodies and water bodies with revised targets have now been re-assessed for compliance, using data from the same time period as the original phosphorus compliance report (2017-2019) and the results are shown in Table 2 below.
One waterbody is now assessed as failing, which was previously assessed as passing, the ‘Ceiriog - confluence Dee to Teirw’ (GB111067051910) in the River Dee SAC. This is only failing for the growing season mean. Compliance assessment results for water bodies in the River Dee SAC in the 2021 report and with the revised targets (which cause the water body on the Ceiriog to fail) are shown in figures 1 and 2 respectively, below.
Change |
Water- body ID |
Waterbody Name |
Site |
Target µg l-1 |
Sample point ID |
---|---|---|---|---|---|
Additional water body |
GB111067051980 |
Tryweryn - Mynach to Llyn Celyn |
Afon Dyfrdwy a Llyn Tegid |
10 |
288 |
Additional water body |
GB110064048740 |
Wen (Mawddach) |
Afon Eden - Cors Goch Trawsfynydd |
10 |
20228 |
Additional water body |
GB110064054610 |
Cracwellt South |
Afon Eden - Cors Goch Trawsfynydd |
5 |
28902 |
Additional water body |
GB109056040000 |
Grwyne Fawr - source to conf Grwyne-Fechan |
River Usk |
7 |
- |
Phosphorus target tightened |
GB111067051610 |
Ceiriog - upstream of Teirw |
Afon Dyfrdwy a Llyn |
10 |
28038 |
Phosphorus target tightened |
GB111067051910 |
Ceiriog - confluence Dee to Teirw |
Afon Dyfrdwy a Llyn Tegid |
25 |
578 |
Phosphorus target tightened |
GB110064048750 |
Eden - lower |
Afon Eden - Cors Goch Trawsfynydd |
5 |
20064 |
Phosphorus target tightened |
GB109056039960 |
Grwyne-Fechan - source to conf Grwyne Fawr |
River Usk |
15 |
- |
Phosphorus target tightened |
GB110064048710 |
Mawddach lower |
Afon Eden - Cors Goch Trawsfynydd |
10 |
20003 |
Phosphorus target relaxed |
GB110061030690 |
Deepford Brook - headwaters to conf with Syfynwy |
Afonydd Cleddau |
40 |
86005 |
Table 2. Information about additional water bodies and water bodies with changed phosphorus target
Waterbody Name |
Target µg l-1 |
No. samples annual |
Annual Mean µg l-1 |
No. samples growing season |
Growing Season Mean µg l-1 |
Previous Status 2021 |
Result Status 2022 |
---|---|---|---|---|---|---|---|
Tryweryn - Mynach to Llyn Celyn |
10 |
26 |
8.55 |
18 |
9.57 |
not included |
pass |
Wen (Mawddach) |
10 |
no data |
- |
no data |
- |
not included |
not assessed |
Cracwellt South |
5 |
21 |
2.34 |
14 |
2.78 |
not included |
pass |
Grwyne Fawr - source to conf Grwyne-Fechan |
7 |
no data |
- |
no data |
- |
not included |
not assessed |
Ceiriog - upstream of Teirw |
10 |
no data |
- |
no data |
- |
not assessed |
not assessed |
Ceiriog - confluence Dee to Teirw |
25 |
31 |
22.25 |
19 |
25.9 |
pass |
fail |
Eden - lower |
5 |
21 |
0.77 |
14 |
0.86 |
pass |
pass |
Grwyne-Fechan - source to conf Grwyne Fawr |
15 |
no data |
- |
no data |
- |
not assessed |
not assessed |
Mawddach lower |
10 |
28 |
0.85 |
18 |
0.74 |
pass |
pass |
Deepford Brook - headwaters to conf with Syfynwy |
40 |
28 |
44.25 |
17 |
50.2 |
fail |
fail |
Table 3. Phosphorus compliance for additional water bodies and water bodies with changed phosphorus target
Figure 1. Orthophosphate compliance map for the River Dee SAC from the 2021 Compliance assessment. Water bodies shaded green pass their target. Other colours fail the target with different colours representing the magnitude of failures in µg l-1-1, expressed as the larger of annual means and growing season means. Greyed out water bodies could not be assessed due to lack of data.
Figure 2. Orthophosphate compliance map for the River Dee SAC based on the updated targets. Water bodies shaded green pass their target. Other colours fail the target with different colours representing the magnitude of failures in µg l-1-1, expressed as the larger of annual means and growing season means. Greyed out water bodies could not be assessed due to lack of data.
Summary of phosphorus compliance for all 127 water bodies within SAC Rivers in Wales
A total of 109 water bodies in nine different SACs were assessed (Table 3 below). Overall, 43 (39.4%) water bodies passed their targets and 66 (60.6%) water bodies failed. This varied in each SAC river with no water bodies assessed as failing in the Afon Eden - Cors Goch Trawsfynydd, Afon Gwyrfai a Llyn Cwellyn, River Tywi and the Meirionnydd Oakwoods and Bat Sites SACs (Table 4 below).
Assessment |
Pass |
Fail |
Total |
Not assessed |
Grand Total |
---|---|---|---|---|---|
Number of water bodies |
43 |
66 |
109 |
18 |
127 |
% of water bodies assessed |
39.4 |
60.6 |
85.8 |
14.2 |
100 |
% by length (km) of water bodies assessed |
44 |
56 |
88.1 |
11.9 |
100 |
Table 3. Summary of SAC river phosphorus compliance results expressed as number and length of water bodies.
SAC River |
Pass (no. water bodies) |
Pass (% of water bodies assessed) |
Fail (no water bodies) |
Fail (% of water bodies assessed) |
Total no. water bodies |
Not assessed |
Grand Total |
---|---|---|---|---|---|---|---|
River Dee & Llyn Tegid |
4 |
50 |
4 |
50 |
8 |
1 |
9 |
Afon Eden - Cors Goch Trawsfynydd |
4 |
100 |
0 |
0 |
4 |
1 |
5 |
Afon Gwyrfai a Llyn Cwellyn |
2 |
100 |
0 |
0 |
2 |
0 |
2 |
Afon Teifi |
8 |
50 |
8 |
50 |
16 |
2 |
18 |
Afon Tywi |
2 |
100 |
0 |
0 |
2 |
1 |
3 |
Afonydd Cleddau |
5 |
33 |
10 |
67 |
15 |
4 |
19 |
Meirionnydd Oakwoods and Bat Sites |
2 |
100 |
0 |
0 |
2 |
0 |
2 |
River Usk / Afon Wysg |
2 |
12 |
15 |
88 |
17 |
7 |
24 |
River Wye / Afon Gwy |
14 |
33 |
29 |
67 |
43 |
2 |
45 |
Table 4. Summary of SAC river phosphorus compliance results for the nine SAC Rivers in Wales.
Sample point correction
In the Compliance Assessment of Welsh River SACs Against Phosphorus Targets (Hatton-Ellis and Jones 2021), the report mentions an ‘additional sample point from near Waunfawr Sewage Treatment Works (STW) (55219 Waen STW)’ on page 34. This should read sample point 22519.