Many people in the Malvern area go to some trouble to collect spring water for using at home, but what is special about the water?
It is not a secret that the local springs actually show quite a variation in composition, maybe enough to taste the difference. The best-known water nationally came from Primeswell Spring on the western flank of the Hills near British Camp. This was the source of the water formerly bottled by Cadbury-Schweppes as Malvern water at the village of Colwall west of the Malverns until 2010 (the spring site is inaccessible today). Small-scale bottling is currently undertaken at the Holy Well following a long tradition dating back to the 1620s. It was the subject of the famous claim by local physician John Wall in 1757 that the water contained “nothing at all”!
The article by John Payne in the MSA’s Autumn 2020 newsletter explains the geological framework: the substrate through which the water has flowed underground. Along the Malvern ridge there are very old, fractured rocks of the Malverns complex, whereas to the west are limestones. To the east are sandstones covered by a mantle of debris which moved downslope under ice-age conditions.
Here, I have gathered together various water analyses including pH and the concentrations of inorganic species, mainly from a Reading Masters thesis by Sawyer in 2002 and an unpublished set from 1996 kindly supplied by Professor Jon Blundy. The waters were collected in the spring and summer and showed minor variation in composition.
Here, we focus on the concentrations of dissolved salts, which show characteristic differences between springs (Figure 1 overleaf). There is a variation by a factor of 10 between the purest water (55-60 milligrams per litre dissolved solids, found at St Ann’s Well) and the least pure (550 milligrams per litre as at Lord Sandys Spout and Chances Pitch).
Water flows quickly through the fractured rocks of the Malverns complex, shown in purple on Figure 1, and the purer samples rise on these rocks. The water at the Holy Well is relatively pure, although that at the nearby Eye Well is even more so.
Figure 1. Malvern Springs plotted with a star symbol. The darker the shading of the star, the higher the concentration of dissolved salts. Geological divisions from the British Geological Survey. Purple is the Malverns Complex with Silurian limestones and shales to the west and Triassic sandstones to the east. Ice age deposits not shown.
The popular Hayslad site (Figure 2) also has this characteristic. In contrast, the Primeswell site spring water, the source of Cadbury-Schweppes Malvern water, has dissolved a significant amount of limestone, having around 250 milligrams per litre total dissolved solids. This product clearly did not have the characteristic purity which originally led to Malvern water’s fame.
Figure 2. Dr. John Payne next to Hayslad Well on the western flank of the Malvern Complex. This site is extensively used as a source of water. (Photo: John Gunn)
Where the content of salts is higher, the type of salt gives clues as to its source. Hard waters arise where calcium carbonate has dissolved, and are typical where springs have contacted Silurian limestones on the western side of the Malverns complex. Sulphate levels tend to be higher in the eastern springs which could be due to traces of calcium sulphate (gypsum) in Triassic Mudstones, but sulphate also forms by oxidation of iron sulphides (pyrite, or fool’s gold) which is widespread as a trace mineral.
It is good to report that only two sites (the most salty) had nitrate concentrations above the EU suggested limit of 50 mg/litre and most are below 10, particularly on the Malvernian rocks. Nitrate in lowland areas in general tends to be high because of fertiliser application, whereas livestock are the main source on the Hills, which are a SSSI and therefore managed sensitively.
The content of sodium chloride is relatively high in springs which are located in places where they appear to be capable of being contaminated by road salt. It is notable that this saltiness is present some months after the season when salt would have been applied to the roads.
Another aspect of water quality is the presence or absence of harmful bacteria. Monitoring by the Environment Agency shows that this is not normally a matter of concern except at one or two vulnerable sites which are not normally used as water sources. Nevertheless, at times of exceptionally high or low flow the risk is heightened and, unlike tap water, the water is not continuously monitored for drinking purposes. The MSA is currently looking at how data held by the County Councils can be made more widely available.
Members of the MSA have expressed an interest in doing some citizen science research on the springs, so I suggested we might look at how the spring waters vary in composition over time which could tell us something about the natural underground plumbing system.
Researchers have found that many springs become more concentrated at low rates of water flow because the water has resided underground for longer on average and had more chance to dissolve the rock. Very rapid drops in concentration after rain flow point to active conduits of water flow which may be associated with more sediment particles and bacteria. The simplest way to do such monitoring is by measuring the salt content of the water (TDS – total dissolved solids). This is done by measuring the electrical conductance of the water with which TDS is proportional. Meters are cheap and widely used for monitoring fish tanks and ponds, so the MSA purchased several for volunteers to make measurements as time permits.
We started the project early in 2021, but because of Covid restrictions there was no chance to do any hands-on demonstrations and some problems emerged such as not measuring in still water and the instruments themselves being temperamental at times. In November last year we met at Hayslad, handed out a set of sample bottles and agreed to implement a protocol whereby water samples would be taken home and measured later at room temperature in comparison with a standard water. This would pick up on instrument problems and has the advantage that samples can be stacked up and all measured at once.
Spring water sampling initiation November 2021 (photo © Carly Tinkler)
In practice not everyone who expressed interest has been able to get going on this, but Carly Tinkler, Lucy and Peter Draper and Anna Brook have been active and their results are plotted in Figure 3. You can see how each spring has a distinctive composition, but also different variabilities and timings of change. Weather had been quite dry up until mid-February 2022 when we had much rain, but the effects on the springs’ composition seem quite muted. One of the controlling factors will be whether there is a large storage tank at a particular site, since this will dampen changes.
Figure 3. Changes in spring water composition from November 2021 to March 2022
A programme of this sort is open-ended, and in the early stages, all observations are useful. Once we know more about spring behaviour, more targeted observations will be needed to develop the topic, eg measuring more regularly in general and more frequently just after heavy rainfall. No doubt then, the distinctive character of each spring would emerge.
If you would be interested in joining in this programme do contact the MSA.
Ian Fairchild (Herefordshire & Worcestershire Earth Heritage Trust)