4.8. Water quality and fisheries.

The trapping and trucking scheme  failed. Lay-opinion claimed that because of poor design, fish would not enter the adult fish trap. Surviving smolts migrating downstream are said to have escaped the upper traps due over-topping and blockages during flood conditions, and entered the reservoir. Rumours of anglers taking 'large trout' from Brianne, persisted.

The Towy Fishery was described by Howells and Jones in 1972. They stated:-

"The river supports an important salmon (Salmo salar L.) and seatrout (Salmo trutta L.) fishery. A total of 12 coracle net and 9 seine net licences are issued annually for use in the estuary. The average reported annual net catch for the past ten years is 418 salmon and 2,218 seatrout. The equivalent average salmon rod catch is 1,139 based on a small percentage of returns and the actual catch could well be more than double this figure. The capital value of salmon in the river Towy was estimated by the late WJM Menzies in 1966 to be not less than £150 per fish. Seatrout records are not required from anglers at present but when records were kept, e.g. in 1954, the estimated annual catch for the Towy district was 22,000 fish. The river is noted for its large seatrout, up to 18 lb (8kg), and a recent study indicated that about 20% of the rod catch were 4 lb (1.8kg) or over in weight whereas the net caught seatrout average about 3¼ lb (1.5kg.)."

4.8.1. In retrospect, it is surprising that SWWRA, and subsequently WWA, persevered for so long considering the poor production of smolts and the large numbers of ova and fry stocked out prior to construction. It would be interesting to learn the details of any capital settlements which may have been made for long term management of the scheme. Acidification was eventually identified and is well documented.

4.8.2. Mitigation for the failure of the scheme remained with WWA, and subsequently Dwr Cymru. This was originally attempted by sporadic stocking of mainly salmon parr reared at Dolbantau Hatchery, and subsequently at Cynrig Hatchery. The actual number of fish required to meet the mitigation is still a matter of conjecture. Plans were made in 1984 to build a small dedicated rearing unit on the Taf. Plans for a more ambitious unit at Nantgaredig in 1986 were frustrated by the ill-fated Aquanorse project. It was not until Llynyfan Fach Hatchery was established in 1994, under CFF’s initiative, that the mitigation stocking requirement was more adequately addressed.

4.8.3. Water temperature problems associated with the single point low-level draw-off also emerged and the upper Towy below Brianne became effectively barren. Water quality in the reservoir deteriorated and raised concern about the levels of ph, aluminium and manganese in the ouflow. Leachate from abandoned lead mines exacerbated the situation.

4.8.4. Early in 1991, lime was applied to Brianne and an immediate improvement was observed. Subsequent dosing has maintained the situation, with two automatic lime dosers now in operation. These are maintained by  DCWW Industrial who also supply the lime. They also  operate a hydro-electricity generation scheme at the Dam.

4.8.5. Water quality remains a problem in the estuary. What were originally Carmarthen Borough's planned improvements to the local sewerage, did not fully materialise until 1998, 15 years later than anticipated. Stage 2, which should have been completed by 1971, was not completed until 1986 (this involved just the partial treatment of the town's sewage). At present, the discharge consent is for 12630 M3d (2.78mgd).

4.8.6. The former joint creamery STW, no longer used for milk effluent, is now used for treatment of refuse-dump leachate (3000 BOD) activated by Llangunnor sewage, and is operating well under-capacity with a discharge BOD of 120mg/l.

4.8.7. SWWRA stated that a flow of 591 - 636 Ml/d (130 - 140mgd) would be required for dilution, even after proposed sewerage improvements - and that raised levels of BOD could still occur during increased morning discharges. It is little wonder that a situation existed until 1998 where local anglers complained of strong ammonial odours, and eyes watering, near and downstream from the discharge points. Coracle fishermen reported fish turning downstream away from discharges. Lowered levels of dissolved oxygen still occur, especially during summertime low river flows and spring tides. These have been attributed to association with sewage effluent of algal blooms and sediment disturbance.

4.8.8. An oxygenation plant installed at Parc-y-splott STW in 1986 at a cost of £250,000 proved to be totally inadequate and ineffective. It was abandoned when it was discovered that its discharge capacity should have been 17 tonnes/day instead of its actual 2 tonnes (probably enough to blow any unfortunate passing fish out of the water). Water quality was downgraded in the Carmarthen area upper tidal reach to Class 2, whilst the main river is Class 1a.

4.8.9. 8800 Ml (2000mg) of the reservoir's water was originally allocated as a 'water bank' for regulation losses and to provide 'freshets for attracting adults into the fish trap. Following the failure of the trapping and trucking scheme, the purpose of the water was described by WWA, and now by EA as being 'for river management purposes'. Anglers consider it to be 'for fishery purposes'. SWWRA appeared sceptical about the amount even for fish-attracting freshets. It certainly is not enough to provide more than one decent 4 day mini-spate in a season. The outlet valve at the dam is incapable of releasing high enough flows (2200 Ml - 500mgd) to produce a good flood unless catchment input is sufficient. SWWRA considered that 3636 - 4090 Ml (800 - 900mgd) produced best salmon catches.

4.8.10. Over the years, 'releases' of 3 - 5 days duration with flows up to maximum outlet output have been made. Although significant rises in water level occurred in the upper river, the effects were considerably reduced in lower reaches. Cold water (c.10 degC) normally confined above Llandovery flowed through the river. Angling successes during releases varied from occasionally good to bad. Fish tended to travel quickly through the lower reaches. Turbidity could well be a significant factor; release water resembles gutter water.

4.8.11. In the years immediately preceding liming, no releases were permissible before July because of acidity in the reservoir. None were made at all in 1990. Low flows in spring and early summer attracted Little Ringed Plovers to nest on shingle banks. 34 pairs were observed in 1991. The height of 'scrapes' (nests) above water level, measured outside of high flows in June, ranged from 0.2 to 2M (mean 0.96M) with 72.5% being less than 1M above the river but only 15% less than 0.5M (Tyler 1992).

4.8.12. A release planned in June 1991, the first since Brianne had been limed, was postponed because of the presence of the birds.

RSPB since optimistically recommended:- 'avoid sudden and significant releases of water from reservoirs between early May and mid August which could cause a rise in water level of more than 0.3 - 0.5M'

Other recommendations included:-

d. If possible, fence off most sensitive areas (eg stretches of river with many shoals and an aggregation of pairs of Little Ringed Plovers so that stock cannot trample on eggs or young.'

4.8.13 Apart from the continuing problems of cold water and the residual effects of acidification in the upper Towy, there have been some significant benefits from the presence of Brianne. The most important, and probably vital, to the river fishery, is the effect of damping out highly aluminised acidic flood surges from the main river. These could have had catastrophic effects on the juvenile fish population. Hopefully, this threat has been removed.

4.8.14. While much of the river can benefit from higher compensation flows, especially in drought conditions, the lower reaches downstream from Nantgaredig can be seriously affected. Diurnal variations in flow have also been identified as affecting fish migration patterns. At present, abstraction can take place at any time during the day or night, depending on the availability of cheap electricity for the pumps. There are 4 low-lift pumps which take up the river water to lagoons on site; it is then transferred via 6 high-lift pumps by tunnel and pipe the 16.5 miles to the Velindre Water Treatment Works near Swansea.

4.8.15. While the presence of Llyn Brianne in the headwaters may have a smoothing effect on flows, any reduction in flood levels in the lower valley is minimal. It was subsequently calculated  that the flood level at Carmarthen Bridge would have been reduced by just 4 cm if the reservoir was not spilling during the major floods of 1987.

4.8.16. By isolating the upper catchment from the main river, the reservoir has since been estimated to reduce the gravel yield upstream from Llandovery by one third, but any anticipated reduction in gravel mobility is undetectable. While the yield to the upper river is less,  that occurring during the late 60's and early 70's was due more  to a now dispersed mobile surge resulting from extensive forestry planting and drainage construction works during the 50' and 60's. There continues to be considerable bank erosion and gravel (and soil) mobility from Llandovery down to Carmarthen.

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