Compliance Assessment of the River Wye SAC Against Phosphorus Targets
River Wye
The Wye is the largest Welsh SAC (Special Area of Conservation) river, with a catchment covering much of southern Powys and part of the Brecon Beacons National Park before crossing the border into England near Hay-on-Wye. It is divided into 43 water bodies in Wales, with two water bodies straddling the border. There are an additional four water bodies entirely in England.
Targets for the river were incorporated into the SAC management plan in 2017 (NRW 2017c), and range from 10 µg l-1 (micrograms per litre) in headwater areas increasing progressively downstream to 50 µg l-1 (micrograms per litre) in the more nutrient-enriched English sections.
The management plan update erroneously omitted the ‘Wye - conf Afon Tarenig to conf Afon Bidno’ water body target. This water body has been assessed here using the Near Natural target for its type. Additionally, an assessment has been carried out for Welsh parts of the cross-border water body ‘Wye - Scithwen Bk to Bredwardine Br’ as approximately 22km of this lies within Wales. The near natural target has been applied here in line with CSM guidance. Targets for these two water bodies should be viewed as draft, and the Wye Core Management Plan updated accordingly.
Much of the Upper Wye catchment is rural and until recently has been predominantly farmed for sheep and beef cattle. More recently there has been a rapid expansion of chicken farms, which has been the source of considerable public concern.
Comparison of phosphorus concentrations in the Wye against targets indicate widespread failures, some of them large in magnitude. Fourteen water bodies passed their targets, 28 failed and three were unknown. Water bodies achieving their orthophosphate targets were in the Upper Wye above Rhayader, about half of the Ithon, and two water bodies in the Irfon. All of the middle Wye tributaries, the remaining Irfon and Ithon and the Llynfi failed their targets. The largest failures were the Wye near Newbridge, the Cammarch, Clettwr Brook, Mithil Brook, lower Irfon, Garth Dulas and the three water bodies in the Llynfi catchment.
Map of phosphorus concentration targets in the Wye SAC
Map of phosphorus targets for the River Wye SAC. All concentrations are annual means and growing season means in µg l-1 (micrograms per litre). Inset shows the Wye – Walford Brook to Bigsweir water body in the lower Wye. Cross-border water bodies have been cropped to the Welsh border.
Map of annual mean phosphorus concentrations in the Upper Wye
Map of annual mean phosphorus concentrations (µg l-1) in the Upper Wye. Inset shows the Wye – Walford Brook to Bigsweir water body in the lower Wye. Cross-border water bodies have been cropped to the Welsh border. Greyed out water bodies could not be assessed due to lack of data.
Map of phosphorus compliance for Welsh sections of the Wye SAC
Map of phosphorus compliance for Welsh sections of the Wye SAC.Water bodies shaded green pass their target. Other colours fail the target with different colours representing the magnitude of failures in µg l-1, expressed as the larger of annual means and growing season means. Inset shows the Wye – Walford Brook to Bigsweir water body in the lower Wye. Cross-border water bodies have been cropped to the Welsh border. Greyed out water bodies could not be assessed due to lack of data.
Compliance for the River Wye SAC
Compliance for the River Wye SAC
|
Waterbody Name |
Sample Point |
Target (µg l-1) |
N Samples |
Annual Mean (µg l-1) |
Growing Season Mean (µg l-1) |
Assessment |
|---|---|---|---|---|---|---|
|
Wye - conf Afon Tarenig to conf Afon Bidno |
50361 |
10* |
29 |
2 |
2 |
Pass |
|
Wye - conf Afon Bidno to conf Afon Marteg |
50004 |
10 |
33 |
2 |
2 |
Pass |
|
Afon Bidno - source to conf R Wye |
50003 |
10 |
29 |
1 |
1 |
Pass |
|
Wye - conf Afon Marteg to conf Afon Elan |
50177 |
20 |
34 |
11 |
14 |
Pass |
|
Afon Marteg - source to conf R Wye |
50005 |
13 |
33 |
7 |
6 |
Pass |
|
Afon Elan - Caban-coch Rsvr to conf R Wye |
50008 |
10 |
- |
- |
- |
Not Assessed |
|
Wye - conf Afon Elan to conf R Ithon |
50010 |
10 |
29 |
37 |
38 |
Fail |
|
Ithon - source to conf Llaethdy Bk |
51354 |
10 |
29 |
8 |
8 |
Pass |
|
Llaethdy Bk - source to conf R Ithon |
51352 |
10 |
16 |
7 |
6 |
Pass |
|
Gwenlas Bk - source to conf R Ithon |
51353 |
10 |
23 |
24 |
22 |
Fail |
|
Ithon - conf Llaethdy Bk to conf Gwenlas Bk |
50086 |
10 |
29 |
13 |
13 |
Fail |
|
Camddwr Bk - source to conf R Ithon |
50820 |
13 |
17 |
20 |
17 |
Fail |
|
Ithon - conf Gwenlas Bk to conf Camddwr Bk |
50086 |
10 |
29 |
13 |
13 |
Fail |
|
Aran - source to conf R Ithon |
50084 |
15 |
- |
- |
- |
Not Assessed |
|
Mithil Bk - source to conf R Ithon |
50825 |
15 |
18 |
40 |
37 |
Fail |
|
Howey Bk - source to conf R Ithon |
50089 |
15 |
16 |
25 |
23 |
Fail |
|
Nantmel Dulas - source to conf R Ithon |
50821 |
10 |
17 |
21 |
17 |
Fail |
|
Ithon - conf Camddwr Bk to conf R Wye |
50085, 50090 |
25 |
31 |
17 |
16 |
Pass |
|
Clywedog Bk - source to conf Bachell Bk |
50823 |
10 |
17 |
9 |
8 |
Pass |
|
Bachell Bk - source to conf Clywedog Bk |
50824 |
10 |
8 |
4 |
- |
Pass |
|
Clywedog Bk - conf Bachell Bk to conf R Ithon |
50087 |
10 |
26 |
15 |
16 |
Fail |
|
Wye - conf R Ithon to conf R Irfon |
50813 |
15 |
29 |
8 |
8 |
Pass |
|
Afon Gwesyn - source to conf R Irfon |
57103 |
10 |
15 |
12 |
10 |
Fail |
|
Irfon - conf Afon Gwesyn to conf Cledan |
57712 |
10 |
27 |
8 |
7 |
Pass |
|
Cledan - source to conf R Irfon |
50818 |
10 |
21 |
18 |
11 |
Fail |
|
Tirabad Dulas - source to conf R Irfon |
50077 |
10 |
19 |
8 |
8 |
Pass |
|
Afon Cammarch - source to conf R Irfon |
50078 |
10 |
27 |
46 |
13 |
Fail |
|
Garth Dulas - source to conf R Irfon |
50079 |
10 |
28 |
15 |
22 |
Fail |
|
Chwefru - source to conf R Irfon |
50081 |
10 |
29 |
22 |
26 |
Fail |
|
Irfon - conf Cledan to conf R Wye |
50080 |
10 |
27 |
24 |
38 |
Fail |
|
Builth Dulas Bk - source to conf R Wye |
50501 |
15 |
16 |
16 |
19 |
Fail |
|
Duhonw - source to conf R Wye |
50012 |
15 |
29 |
15X |
15X |
Fail |
|
Edw - source to conf Colwyn Bk |
51355 |
15 |
28 |
30 |
39 |
Fail |
|
Camnant Brook - source to confluence R Edw |
50510 |
15 |
24 |
24 |
32 |
Fail |
|
Edw - conf Camnant Bk to conf Clas Bk |
50815 |
15 |
|
|
|
Not Assessed |
|
Edw - conf Clas Bk to conf R Wye |
51305 |
15 |
28 |
20 |
23 |
Fail |
|
Clettwr Bk - source to conf R Wye |
50015 |
15 |
21 |
41 |
50 |
Fail |
|
Bach Howey Bk - source to conf R Wye |
50016 |
15 |
22 |
29 |
36 |
Fail |
|
Scithwen Bk - source to conf R Wye |
50017 |
15 |
21 |
19 |
21 |
Fail |
|
Wye - conf R Irfon to Scithwen Bk |
50440 |
16 |
29 |
23 |
29 |
Fail |
|
Triffrwd - source to Dulas |
50811 |
15 |
14 |
70 |
40 |
Fail |
|
Dulas Bk - source to conf Afon Llynfi |
50094 |
25 |
9 |
74 |
- |
Fail |
|
Afon Llynfi - conf Dulas Bk to conf R Wye |
50098 |
25 |
26 |
77 |
90 |
Fail |
|
Wye - Scithwen Bk to Bredwardine Br (Wales) |
50018[1] |
30 |
34 |
<21[2] |
<23 |
Pass |
| Wye - conf Walford Bk to Bigsweir Br |
50032 |
39 |
34 |
52 |
55 |
Fail |
[1] This is a cross-border unit.
[2] Most of the data for this sample point was collected using the ‘Low’ method. The mean concentration for 2019, when sampling switched to ‘Very Low’ was 9 µg l-1.
Sensitivity Testing for Failing Water Bodies on the River Wye SAC.
|
Waterbody Name |
Sample Point |
Target (µg l-1) |
Median (µg l-1) |
Annual Mean (µg l-1) |
Outlier (µg l-1) |
Mean Excluding Outlier (µg l-1) |
BOD / N / NH3 confirm outlier |
Failure Type |
|---|---|---|---|---|---|---|---|---|
|
Wye - conf Afon Elan to conf R Ithon |
50010 |
10 |
29 |
37 |
- |
- |
- |
Consistent |
|
Gwenlas Bk - source to conf R Ithon |
51353 |
10 |
23 |
24 |
57 |
- |
- |
Consistent |
|
Ithon - conf Llaethdy Bk to conf Gwenlas Bk |
50086 |
10 |
10 |
13 |
58 |
- |
- |
Consistent |
|
Camddwr Bk - source to conf R Ithon |
50820 |
13 |
12 |
20 |
95 |
15 |
- |
Episodic |
|
Ithon - conf Gwenlas Bk to conf Camddwr Bk |
50086 |
10 |
10 |
13 |
58 |
- |
- |
Consistent |
|
Mithil Bk - source to conf R Ithon |
50825 |
15 |
22 |
40 |
188 |
- |
- |
Consistent |
|
Howey Bk - source to conf R Ithon |
50089 |
15 |
24 |
25 |
77 |
- |
- |
Consistent |
|
Nantmel Dulas - source to conf R Ithon |
50821 |
10 |
10 |
21 |
112 |
- |
- |
Consistent |
|
Clywedog Bk - conf Bachell Bk to conf R Ithon |
50087 |
10 |
7 |
15 |
100 |
12 |
- |
Episodic |
|
Afon Gwesyn - source to conf R Irfon |
57103 |
10 |
6 |
12 |
61 |
9 |
>Q3 (N) |
Episodic |
|
Cledan - source to conf R Irfon |
50818 |
10 |
12 |
18 |
152 |
- |
- |
Consistent |
|
Afon Cammarch - source to conf R Irfon |
50078 |
10 |
8 |
46 |
747 |
19 |
- |
Episodic |
|
Garth Dulas - source to conf R Irfon |
50079 |
10 |
5 |
15 |
239 |
6 |
>Q3 (BOD, NH3) |
Episodic |
|
Chwefru - source to conf R Irfon |
50081 |
10 |
17 |
22 |
- |
- |
- |
Consistent |
|
Irfon - conf Cledan to conf R Wye |
50080 |
10 |
7 |
24 |
355 |
12 |
- |
Episodic |
|
Builth Dulas Bk - source to conf R Wye |
50501 |
15 |
15 |
16 |
35 |
15 |
- |
Episodic |
|
Duhonw - source to conf R Wye |
50012 |
15 |
14 |
15 |
70 |
13 |
>Q3 (All) |
Episodic |
|
Edw - source to conf Colwyn Bk |
51355 |
15 |
15 |
30 |
369 |
17 |
- |
Episodic |
|
Camnant Brook - source to confluence R Edw |
50510 |
15 |
16 |
24 |
183 |
- |
- |
Consistent |
|
Edw - conf Clas Bk to conf R Wye |
51305 |
15 |
14 |
20 |
145 |
15 |
Outlier (BOD, NH3); Q3 (N) |
Episodic |
|
Clettwr Bk - source to conf R Wye |
50015 |
15 |
24 |
41 |
172 |
- |
- |
Consistent |
|
Bach Howey Bk - source to conf R Wye |
50016 |
15 |
21 |
29 |
99 |
- |
- |
Consistent |
|
Scithwen Bk - source to conf R Wye |
50017 |
15 |
17 |
19 |
46 |
- |
- |
Consistent |
|
Wye - conf R Irfon to Scithwen Bk |
50440 |
16 |
10 |
23 |
223 |
15 |
Outlier (BOD, NH3); Q3 (N) |
Episodic |
|
Triffrwd - source to Dulas |
50811 |
15 |
36 |
70 |
115 |
- |
- |
Consistent |
|
Dulas Bk - source to conf Afon Llynfi |
50094 |
25 |
46 |
74 |
241 |
- |
- |
Consistent |
|
Afon Llynfi - conf Dulas Bk to conf R Wye |
50098 |
25 |
64 |
77 |
193 |
- |
- |
Consistent |
|
Wye - conf Walford Bk to Bigsweir Br |
50032 |
39 |
45 |
52 |
- |
- |
- |
Consistent |