Bath - Hot Springs
Protection and Water Monitoring
To view Hot Springs Flow Data
To view Hot Springs Temperature Data
To view Hot Springs Pressure
Bath exists because of the emergence of three natural springs in
the heart of the city which deliver over 1 million litres of
mineral-rich water every day. Uniquely in the UK, the mineral water
is hot - it rises to the surface at a constant temperature of at
least 45° C. These springs have been, and continue to be, at
the centre of economic, social and cultural developments in the
City. As such, their protection is of paramount importance locally
Bath was, in fact, charged with responsibility for the Hot
Springs in a Royal Charter of 1591 granted by Elizabeth I – this
duty has passed to Bath & North East Somerset Council. The
springs are further protected by the 1982 County of Avon
Mineralogy of Bath's Hot Springs
The analyses show that the thermal waters all contain sodium,
calcium, chloride and sulphate ions in high concentrations.
The chemical composition of the spring waters has been examined
over time. Although there are some small variations, in general,
allowing for changes in analytical methods it has been concluded
that composition has remained constant over the past century.
From: Kellaway, GA 1991
Concentration (Hetling Spring)
Water Monitoring Systems
The temperature and flow of the springs has been monitored for
many years by the local authority (firstly Bath City Council, and
currently Bath and North East Somerset Council). The data is used
for monitoring the potential impact on the Springs of any
development within the City of Bath. The monitoring system also
provides essential data for ongoing research into the origins of
In addition to written reports, the water flow and temperature
data is now gathered in a format appropriate for publishing on the
Internet, so meeting the Council's desire to provide information in
an accessible way to the public.
The information here is a summary report of monitoring data
collected on behalf of B&NES with the technical assistance of
Zenith International. The information is updated each month.
Zenith International is based in Kingsmead Square, Bath - little
more than a stone's throw from the hot springs. The Water &
Environment group is one of the UK's leading teams of
hydrogeologists with expertise in a whole range of groundwater and
water resources projects. Their experience with the hot
springs dates back to 1998 when they reviewed the old
monitoring system, leading to recommendations for a much-improved
and more reliable replacement. They then managed the
procurement and installation of the new system and have since
provided monitoring services and advice to Bath & North East
Somerset Council over a number of years.
The graphs above display flow, temperature and other physical
properties of the water collected from the three Hot Springs in
Bath. Namely the Kings spring, Hetling spring and Cross Spring. The
data displayed is collected at 10-minute intervals by the data
logging system located within the Roman Baths. The data shown for
the Kings Spring is broken down into two components - The Kings (or
Great) Bath and the Great Drain. The Stall Street borehole
intercepts groundwater rising in the Kings Spring. The Hetling and
Cross Springs are displayed separately.
The flow and temperature of the Hot Springs are known to be
relatively constant.However, all of the data exhibits variations to
a small degree. Most short-term changes in the recorded flows and
temperatures are naturally occurring. Spring flows and temperatures
also exhibit other variations. The main ones are described
- The Stall Street Borehole shows frequent changes in flow and
temperature. This occurs when flow to the Pump Room fountain is
manually reduced or stopped, usually during concerts or other
functions in the Pump Room.
- The Great Bath flow exhibits a slow decline with time. This
happens because the pipework through which water flows to the Great
Bath becomes coated with sediment from the springs. The overflow
from the Kings Spring through the Great Drain shows a corresponding
rise. The sum of the two flows is relatively constant as these
constitute the total Kings Spring output. The flow to the Great
Bath increases again whenever the pipework is cleaned.
- The temperatures of the Great Bath and Great Drain show
variations due to daily and seasonal changes of ambient air
temperature. Furthermore, if the flow rate reduces then so does
temperature as the water has had more time to cool as it moves away
from the spring.
- The Great Drain flow data exhibits "spikes" caused by rainfall.
Rain also affects the temperature, pH and conductivity data
recorded at some sites. Rainfall is measured and recorded so these
"spikes" can be correlated with rainfall.
Other changes in the flow and temperature occur from time to time.
Any significant variations are detailed and explained in the
accompanying notes for each month's graphs.
Monthly Data: September 2007
The data for September 2007 is now available by
following the links to the graphs above.
There are a number of points in the data that require brief
explanation and these are detailed below:-
- Gradual increase in Great Drain flow throughout the month in
response to a decrease in flow through GB1.
- Occasional short lived apparent decreases in Hetling Spring
flow, due to sensor error.
- Pump Room Fountain flow diverted during the evening of
23/09/07, resulting in an increase in flow overnight.
- Variations in GB1, GB2 and Great Drain flows and temperatures
between 24/09/07 and 26/09/07 in response to drain down of King’s
Spring for cleaning and subsequent flow alterations.
- Incorrect Hetling Borehole temperature data recorded throughout
- The Great Drain, Hetling Spring and GB1 temperatures decrease
in response to heavy rain events.
- Fluctuations in Hetling Borehole pressure due to sensor error.
Apparent decrease in Hetling Borehole pressure on 19/09/07 due to
- Slight decrease in pressure seen at Kingsmead Borehole, Hetling
Borehole, Stall Street Borehole and Cross Bath Inclined Borehole on
24/09/07 in response to drain down of King’s Spring.
- Gradual slight decrease in Cross Bath Inclined Borehole
pressure throughout the month.
- Minor variations in flow, temperature and pressure at Hetling
Borehole, Cross Bath, Cross Bath Inclined Borehole and Stall Street
Borehole are due to Spa cleaning in place programs and regular