Locating springs

There are telltale signs to look for when locating springs. Vegetation is a great help to identify spring lines. Rushes and sedges that grow in wet places are often a darker green than the surrounding grass. Clumps of these plants can often be seen at intervals, thereby clearly taking your eye to the spring line. Where springs are used for a water supply, be on the look out for spring collection chambers and storage tanks. Sometimes a hydraulic ram is used to pump the water up to the farm. These make characteristic 'clunking' noise at regular intervals and act as a signal for both the ram and spring.

Not all water that issues from the ground is spring-water. It may be water discharging from a land drainage pipe or culvert and consisting largely of surface water. Other alternatives include leaking water supply pipes and sewers that can be identified from their chemistry. All true springs consist of groundwater and may be identified by their chemical or physical characteristics. Springs will have a similar chemical composition to local groundwaters, and a comparison of chemical analyses will help separate springs from land drains or leaking pipes. Leaking mains water is likely to have a different chemical character than the groundwater and when it has been treated with chlorine is likely to contain trihalomethanes that are proof positive that the flow contains mains water. Sewage in groundwater can often be identified by the presence of faecal bacteria.

Most groundwater discharges have a fairly constant temperature throughout the year that is around 8-15oC in the UK depending on where you are. This property can be used to identify springs at times when there will be a contrast with the temperature of surface waters. Groundwater seepages and springs are easy to identify during the winter, because they are unlikely to freeze and will support plant growth at a time when there is none elsewhere. Look for green plants in the water as a sign that it is relatively warm. During the summer, spring waters will appear cold, but a thermometer will be required to compare water temperatures. For the best results take the readings during the afternoon of warm or hot days when surface waters will have had the opportunity to warm up.

A third way to distinguish a spring from a land-drain discharge is by measuring flows over a period of several weeks. Several readings will be required each week and the results should be plotted up as a hydrograph for each 'spring'. You will find that the flow at some spring sites hardly seems to change at all, while others fluctuate markedly with a clear response to rainfall. Groundwater springs often show little change in flow over short periods. Those 'springs' that fluctuate greatly are likely to be fed by land-drains and consist largely of surface-water runoff.

This Handy Hint is based on information in my book Field Hydrogeology.

Copyright © 2004 by Rick Brassington

Eur Geol Eur Ing Professor F.C. Brassington BSc MSc CGeol FGS CEng MICE FCIWEM