Catchment News

Assessing the impact of the Bellawaddy River on the microbiological quality of the bathing waters of Enniscrone Beach, Co. Sligo

The Bathing Water Directive (2006/7/EC) was transposed into Irish law in 2008. Its objective is to improve the protection of bather’s health and introduced stricter standards for water quality and a new method of assessment. It has established a more pro-active approach to the assessment of possible pollution risks, and to the management of bathing waters. It also places considerable emphasis on promoting increased public involvement, and for improved dissemination of information on bathing water quality to the general public.

Bathing waters are now classed into four quality categories; ‘Excellent’, ‘Good’, ‘Sufficient’, or ‘Poor’ with a minimum target of ‘Sufficient’ required to be achieved for all bathing waters. The new standards are almost twice as strict as those previously applied and assessment is undertaken on a 4 year data set rather than annually.

Bathing water categories are determined by levels of indicator bacteria in the water called E. coli & intestinal enterococci. This is because they indicate conditions where pathogens harmful to human health are present (usually called Short- Term Pollution). Bathers can become ill as a result of such contamination.

There are two aspects to this contamination.

1. 1. Source of bacteria &
2. 2. The management of bathing

Source:

Up to recently focus has been on urban wastewater treatment plants. However studies have shown that despite major investment in local wastewater infrastructures, bathing waters can still fail to achieve acceptable water quality standards. €5 million was spent on upgrading Enniscrone’s waste water infrastructure in 2008. Subsequent audits of the treatment plant have shown good compliance. However, at the time

of this study the EPA had warned that previous monitoring results signalled that the bathing water was at high risk of failing to achieve Excellent quality status (it has since failed to attain this status). Some focus is now turning to other aspects like riverine inputs as a source of short-term pollution.

The Bellawaddy River discharges to the bathing water at the bottom left of Fig. 2. It rises in the forested area in the centre background. The River Catchment is small at 18.6 km², but the picture shows that there is a substantial area of intensely farmed countryside that can influence the quality of the river water before it discharges to the bathing water.

The aims of this project were to determine if the river was a clear source of short-term pollution at Enniscrone’s bathing waters and to evaluate if any environmental aspect can be used to indicate conditions associated with a high risk of short- term pollution.

The project, using local rainfall data, hydrometric data (river level and flow produced from an automatic data-logger installed), microbiological results, loadings and statistical analysis proved that the Bellawaddy River was the main source of short-term pollution events at Enniscrone Beach.

It is important to note that this pollution effect to rainfall intensity (in other words the effect of intense local rain on the water flowing through the river catchment).

Management of bathing:

Bathing management was the other aspect considered with regard to this short-term contamination of bathing water. New bathing water regulations (2015) have broadened the focus from the retrospective management of water quality to a more predictive/proactive approach in order to protect bathers’ health. This prediction or forecasting is difficult to do as microbiological results can take from 18 – 36 hours to produce from the time of sampling. Water contamination may have been present at the sampling time and bathers’ health thus compromised. A different metric to indicate periods where water quality may be compromised is therefore required.

The concept adopted for this project was taken from economists who were discussing why they missed predicting the last recession. These were some of their observations:

“One of the many paradoxes facing the practical economist is insatiable demand for economic forecasts alongside overwhelming evidence that forecasting is a complete waste of time.”

“One of the few really interesting innovations in forecasting methods has been the development of something called Now-casting. The future is all very well, but we have an equally tough task in figuring out where the economy is right now – or what it has been doing over the recent past.”

The “Now-casting” metric formulated here involved using the combined sewer network servicing Enniscrone town to measure rainfall intensity (Fig. 4). If a locally intense rainfall event occurs, any extra water in the sewer is diverted and collected in a storm-water tank located at the treatment plant. The water level in this tank is recorded continuously.

Spikes in the level of the storm-water tank were plotted against levels of indicator bacteria in the bathing water for the summer of 2014.

The resultant graphs and analysis were able to demonstrate strong covariance between breaches of water quality standards in the bathing water, and peaks in the water level of this storm-water tank.

(Control results showed that any storm-water that may have discharged to the sea did not affect water quality). Similar results were obtained for all three types of indicator bacteria monitored.

This reproducible method using local data could clearly indicate conditions where there was a current risk of short-term pollution at Enniscrone Beach.

The link between the Environment and Public Health is now to the fore in public policy. From the EPA’s Strategic Plan “Our Environment – Our Wellbeing” the Director-General Laura Burke states:

“Clear, accurate and timely information is a vital component in raising awareness about the environment among the public and key policy and decision makers. As part of our strategic priorities we will be accelerating the development of new approaches and tools, with a particular emphasis on the provision of accessible information to allow people to make informed choices for themselves, their families, their communities and their businesses.”

Further research is currently underway by the author to devise an early warning system for this bathing water using data from the river catchment. This new project is trying to obtain relevant upstream catchment data in real-time, so as to identify potential short-term pollution incidents before they reach the bathing water area. Newly generated Pollution Impact Potential maps from the EPA Catchment Unit were used to identify likely zones of pathogen contribution to the river and thus help identify locations in the catchment for monitoring stations

The use of technology like telemetrised hydrometric data-loggers (Fig.6) and automatic rain gauges etc. along with detailed knowledge of the catchment, should produce data that may lead to more effective tools for managing bathing at Enniscrone Beach.

Wayne Egan, Hydrometric & Groundwater Section, EPA Regional Inspectorate Castlebar

This article is a summary of Wayne Egan’s project for his recently completed undergraduate degree, which was awarded the Undergraduate Awards Gold Medal (Global) in the Earth & Environmental Section 2016.

A huge congratulations to Wayne for this achievement.

http://www.undergraduateawards.com/year/winners-2016/