A true spring still runs in the driest part of the year and stays close to the same temperature all year, while a rain seep disappears within days of dry weather. Time how long a bucket of known size takes to fill: 10 litres in 60 seconds is 10 litres per minute, 14,400 litres per day.
Recognizing and confirming a natural spring on a candidate site, and measuring its yield before committing a settlement to it.
A Spring Is Ground Water Coming Out; a Seep Is Rain Still Draining
Water soaks into the ground and moves downhill until something makes it come out: a layer of rock or clay it cannot pass through, a cut in the hillside, or a fault. Where that happens a spring appears. Springs fed by a large, deep store flow all year. Springs fed by a thin, shallow store flow only after rain. The carrier says to estimate flow by timing how long it takes to fill a known container; do this at the right moment, which is the end of the dry season, or the number is meaningless.
For finding springs in the first place, see Spring Location: Finding Natural Springs. This page is about confirming and judging them.
What You Need
- A bucket or jug of known volume — a marked 10 L bucket is ideal.
- A watch — or count seconds aloud.
- A thermometer, if you have one — otherwise your wrist will do for comparison.
Method: Confirm It, Then Measure It
Step 1: Look for the signs Lines of green, wet ground on a hillside in dry weather; rushes, watercress or willow clustered on one spot; a small pool that never drains; a place where several small trickles meet. A line of seeps along one level on a slope often marks a layer of rock or clay that stops water going deeper.
Step 2: Check it is not just rain draining Return after at least a week without rain. A seep that has dried is not a supply. A spring that is still running, and of similar volume, is.
Step 3: Compare temperature Spring water from deep ground stays close to the same temperature all year, cooler than the air in summer and often warmer than the air in winter. Surface runoff follows the weather. If you have no thermometer, a spring feels distinctly cold in summer and mild in winter.
Step 4: Measure the yield Hold the bucket at the outflow, or build a small lip of clay or stone to collect the whole flow. Start timing as water enters and stop when full. Volume / time = yield.
Worked Example
Ten litres fill in 60 s.
- 10 L / 60 s = 0.167 L/s = 10 L per minute.
- 10 L/min x 60 x 24 = 14,400 L per day.
- At the 15 L per person per day survival standard, that supports 14,400 / 15 = 960 people, but only if the flow holds at that rate through the dry season, which is why the measurement is repeated at the worst time.
For the larger design of capturing a spring, see Spring Capture and Springhouse.
Common Mistakes
- Measuring once in spring — flow then can be several times the late-summer figure.
- Measuring only the part of the flow you catch — if half the water runs past the bucket, you under-read; build a collecting lip.
- Assuming cleanliness — water that has crossed pasture, a latrine or a limestone fissure can still carry pathogens, because fissures let surface water through with little filtering.
Safety
A spring below human or animal waste is contaminated
Check the ground uphill of the spring for latrines, grazing, dumps and old buildings before drinking. Treat spring water the first time you use it and test it by sight and smell afterwards, but keep boiling or filtering the supply.
What’s Next
- Learn next: Water Quality Indicators — judging the water itself
- Combine with: Groundwater & Well Potential — the same aquifer, reached from above