SEPA Bathing Waters Signage

Calum McPhailEnvironmental Quality

Unit manager

Ruth Stidson

Bathing Waters Signage

Officer

Contents

SEPA beach signage – overview and results

Development of the SEPA Signage Prediction Tool

Development of future modelling systems

Background on Bathing Waters

Scotland has had problems of poor quality bathing water in some areas

Combination of diffuse pollution, especially on the west coast, and CSO discharges

For some sites meeting the potential new Directive will be challenging

Signage Overview

SEPA makes a daily water quality prediction, relating to the EU standards for bathing water, at the 10 signage sites throughout the bathing season

This is based on relevant environmental (mainly rainfall) events from the previous two days

This information is then displayed at the beach via an electronic variable message sign and on the web and phone line.

  

Example of electronic beach sign (at Prestwick) and alternative sign face legends

EC Bathing Water with signage

EC Bathing Water

SEPA Bathing Waters Signage

• Scottish Executive initiated & funded

• Run as a project in 2003 & 2004

• Now in place at 10 beaches 2005 - 2007

2004 Signage Validation Results

Signage good and good

water quality80%

Signage poor and poor

water quality5%

Signage good but poor water

quality2%

Signage poor but good

water quality13%

Based on 683 samples

Exceedances of Mandatory water quality within 2004 bathing season

0 1 2 3 4 5 6 7 8 9

Ayr

Prestwick

Troon

Irvine

Saltcoats

Ettrick

Brighouse

Sandyhills

Aberdeen

Portobello C

Events

Failssuccessfullypredicted

Could bepredicted

Hydrologicallyunpredictable

Signage validation results 2003 - 2005

0

10

20

30

40

50

60

70

80

90

100

20035 sitesn = 399

1% ~ 4 samples

200410 sitesn = 683

1% ~ 7 samples

200510 sitesn = 200

1% = 2 samples

%

Signage good andgood water quality

Signage poor andpoor water quality

Signage good butpoor water quality

Signage poor butgood water quality

Aberdeen Signage results 2004 & 2005(excellent, good, or poor status predictions)

0

10

20

30

40

50

SignageEXCEL,Microb.EXCEL

SignageGOOD,Microb.GOOD

SignagePOOR,Microb.

FAIL

SignageGOOD,Microb.EXCEL

SignagePOOR,Microb.GOOD

SignagePOOR,Microb.EXCEL

SignageEXCEL,Microb.GOOD

SignageGOOD,Microb.

FAIL

SignageEXCEL,Microb.

FAIL

%

2004 Solid fill2005 Striped fill

First year - 2003 sign management

Signs set to predict poor quality if: 24 hr rain greater than 10 mm or 48 hr rain greater than 15 mm

These were known as ‘decision trigger levels’

This worked well but there was scope for improvement

Development of the SEPA Signage Prediction Tool

Known relationship between rainfall and coliform levels

SEPA archives for historical datasets (e.g. water quality results and environmental drivers)

Understanding site response to inputs, or recent infrastructure improvements/schemes

Predicting diffuse pollution: rain events run-off from fields increased coliform levels

Further developing the relationship between rain & coliforms

For each of the signage sites: Relevant rain and river gauging stations

were identified At each raingauge, 1 to 5 days rain was

correlated against faecal and non-faecal coliforms and faecal streptococci

Strongest relationships at each site were identified

Conversion into a useful tool

Possible to use relationship to predict coliform levels on any given day

Use this information to predict if the coliform levels will be in exceedance of EC guidelines

Development of signage prediction tool to refine decision trigger levels

What does the tool do?

Site specific Enables the testing of potential decision

trigger levels against actual data from 2000/1 onwards

Instantly allows the user to see the outcomes of trial decision trigger levels

Allows the user to alter the coliform exceedence limits in anticipation of the new Directive

Irvine rainSaughall

rainAmlaird

rainBlackdyke

rain

2001 Y 10 x 10 x TC <= 100002002 Y 15 15 15 15 FC <= 20002003 Y 40 40 40 40 FS <= x2004 Y x x x x

x x x x

Irvine Garnock8 8

Results

Signage GOOD, Microb. PASS

Signage POOR, Microb.

FAIL

Signage GOOD, Microb.

FAIL

Signage POOR, Microb. PASS

Results

Signage GOOD, Microb. PASS

Signage POOR, Microb.

FAIL

Signage GOOD, Microb.

FAIL

Signage POOR, Microb. PASS

2001 14 1 1 4 2001 70 5 5 202002 20 3 0 4 2002 74 11 0 152003 58 6 0 5 2003 84 9 0 72004 54 10 0 18 2004 66 12 0 22Total 146 20 1 31 Average 73 9 1 16

Date TC FC FSIrvine rain

24 hrIrvine rain

48 hrIrvine rain

72 hrIrvine rain

96 hrIrvine rain

120 hr

Saughall rain

24 hr

Saughall rain

48 hr

Saughall rain

72 hr

Saughall rain

96 hr

Saughall rain

120 hr

1-Jun-01 13500 1400 150 0.2 8 12.4 13 13.4 1.2 12.1 13.9 18.5 20.85-Jun-01 2500 1200 260 0 0 0 5.2 5.4 0 0.2 0.2 10 11.212-Jun-01 500 70 5 0 0 4 10.4 10.4 0 0.5 4.2 13.6 14.415-Jun-01 50 10 10 4.2 4.2 4.2 4.2 4.2 2.5 2.5 2.5 2.5 3

Microbiology testvalue or x

as %

Years to includeY or N

Hydrology test details

value or x

24 hour rain =>48 hour rain =>72 hour rain =>96 hour rain =>120 hour rain =>

Hydrology test detailsFlow >=

Enter criteria

Results as numbers

Copy and paste in data set:

Coliform values (up to 3 types)

Rainfall (up to 4 gauges and 5 time periods)

River flow (up to 2 gauges)

Years to includeMicrobiology values

Start testing rain and river values

SEPA Signage Prediction Tool

Immediately see past results

Strengths of the current tool

Very effective at predicting compliance against mandatory standard in Scotland 98% correct or precautionary in 03 & 04,

99% in 05 Simple to:

Use Update Apply to additional sites

Transparent

Easy adaptations

Very easy to adapt for other factors IF they can be considered as a single variable E.g. if sunshine is a major driver can add in

test as per river flow Input sunshine (eg) as hours Use test such as ‘if sunshine < x hours

predict poor’ Use tool to test different values of x Can use similar technique for wind, tide,

telemetered CSO spills etc

More challenging adaptations

It is possible to consider combined factors IF rain > 10 mm → poor IF rain > 8 mm AND

Wind = onshore OR tide = incoming

→ poor

Rapidly becomes more complex !

Bathing Water Future Models

Colin GrayData Analyst Modeller, SEPA

Aim: To try and improve current models To develop models for future, more

stringent EU directive To utilise new developments and

software within SEPA

Data Available to Models

Rainfall data for relevant gauges per beach River flow data High tide times & sample times Weather Salinity

Can not be used in predictions currently due to sampling methods

Wind direction and speed Beach usage

Conclusions from Data Analysis No clear cut splits between all fails and passes for current or future

EU rules

Although more extreme levels of rain fall and river flow tend to be failures, there is a large amount of overlap at more moderate (normal) levels

Similar results from several beaches Important factors are:

Rain fall over time periods Total rain River flow High tide time Salinity

No trends seen in weather, wind speed or direction, beach usage or other miscellaneous data

Very difficult to visualise multiple factor data and trends E.g. if x is over this, and y is under this while z is this, then

beach will fail IMiner and S-plus modelling techniques can assist

Software and Techniques

SEPA Statistical and Modelling software S-plus

ideal for data manipulation and graphing Insightful Miner (IMiner)

designed for producing work flows and modelling large amounts of data

Both are closely integrated

Models Used Scoring Method Classification Trees (a.k.a. Decision Trees) Neural Networks Classification Regression Naïve Bayes

General Principles

Performance will be very dependant on true trends being present

Lack of failure data can lead to models using incorrect assumptions

Computers know nothing of science! All models need human validation and

adjustment to ensure making sensible assumptions and relationships

Decision trees

Uses method called RPART (recursive partitioning) Builds braches which represent relationships between

factors Helps highlight key factors affecting a bathing water

Easy to interpret and adjust Very fast to generate and utilise Widely used in other industries e.g. pharmaceutical Easy to implement as an everyday prediction tool Suited well to bathing water predictions

Uses predefined conditions to determine prediction

Decision Trees Irvine, current EU Directive

Performance for Irvine

For Current EU directive:

Perfect prediction Tree is very simple and scientifically reasonable

Performance for Irvine For Future EU directive:

Tree becomes very complex

Performance for Irvine

For Future EU directive:

Although performs well: No way of controlling the fact that it is preferable to predict

a ‘Pass’ as a ‘Fail’ instead of vice versa as in above Have altered the method to allow for weighting

Some final splits in the tree are likely not to be based on actual reason for failing

Splits will highlight difference in data for results and may have no scientific relevance

Summary of Decision Trees

Decision trees appear to provide a good method of modelling beaches Easier to interpret and adjust than other methods Better performance than scoring, neural networks or

logistic regression

However careful manipulation of the weighting may be required

Care needed to ensure final splits are scientifically valid

Missing data needs to be handled in a standard method

Future Work

Decision tree models Derive models for all bathing waters using

2003 and 2004 data Then use 2005 data to assess

performance

Ongoing project to assess usage of rain radar to improve predictions

Potential network expansion to new sites

A View from the Sun - Nov 2004

Models Developed

Scoring Method Attempt to score factors Add scores at the end and if over a certain number then it is predicted a fail Very similar to current method but more flexible Could improve predictions at Irvine but more difficult at Saltcoats Very time consuming to develop and very ad-hoc

Neural Networks Uses IMiner internal neural network method Produces very complex relationships between factors Can be very powerful and highly predictive Is very dependant on quality of training data Almost impossible to adjust or interpret Is unlikely to perform well in new circumstances

Logistic Regression Produces an equation to represent the bathing water Can weight the outcome of pass or fail May over generalise factors as applies one coefficient to each

Signage Roles

2003 – 2004

Scottish Executive initiated and funded the project as a pilot

SEPA determined the daily water quality predictions

2005 - 2007

SEPA to run beach signage

Faber Maunsell

Installing and maintaining the electronic signs and communication linkages

Local Authorities, Clean Coast Scotland,

Public involvement and understanding of the signage project

BW Signage working: SEPA systems

WEBSITE

PHONELINE

PHONE TEXT

Incorporating into predictive tool

If tide / wind / sunshine is to be incorporated into the tool, it needs to be a secondary consideration to rainfall

Say statistical tests show that an onshore wind at Irvine significantly increases coliform concentrations

If the trigger level for Irvine is set at 12 mm of rain within 24 hours, can code into Excel that: IF rain is x % lower than the trigger level AND the

wind is onshore, then OVERRIDE to POOR IF rain is x % above the trigger level AND the wind

is NOT onshore, then OVERRIDE to GOOD Can potentially code for tide, wind and sunshine for

multiple triggers, however this does considerably increase the complexity of the tool