Look, smell and walk upstream before choosing a water source, because clarity, colour, odour, algae, stream-bed life and nearby land use can rule a source out. They can never rule one in: the worst hazards, including disease organisms, nitrate and arsenic, have no colour, smell or taste, so every source still needs treatment.
Field signs of water quality for a candidate settlement source, what each sign suggests, and what field inspection cannot detect.
The Senses Can Reject a Source but Cannot Approve One
The carrier says water quality “can be treated but adds labor”, weighting it just below reliability. This page is about the cheap part: using your eyes, nose and feet to decide which candidate is worth treating and which to drop. A source that fails these checks is one to avoid. A source that passes is only one that has not yet been disqualified.
What You Need
- A clear glass jar or bottle — to hold a sample against the light.
- Time at the site — at least one visit after rain, one in dry weather.
- A willingness to walk upstream — most contamination is found there, not at the site.
Method: Five Checks
Step 1: Clarity and colour Fill the jar and hold it up. Cloudy water carries suspended soil, which protects germs from treatment. Let it stand for a day: if it clears, the cloudiness was coarse silt; if it stays cloudy, fine clay or organic matter is present. An orange-brown stain on stones suggests dissolved iron, which is harmless to health but tastes of metal. Green growth suggests nutrient-rich water.
Step 2: Smell and surface Rotten egg smell means oxygen-poor, decaying matter or sulphur compounds. Oily films that break up when you touch them, versus natural iron films that crack like glass, can distinguish fuel contamination. Foam that persists is suspicious. Fresh clean water has little smell.
Step 3: Life Larvae of mayflies, stoneflies and caddisflies living under stones tend to indicate well-oxygenated water with little organic pollution. A bed of red worms in mud, or no life at all in a stream that looks otherwise suitable, suggests the opposite. These are tendencies, not proof.
Step 4: Land upstream Walk upstream. Look for dead animals, livestock crossing points, camps, abandoned industrial sites, old dumps or mine workings. The carrier lists abandoned industrial sites, old dumps and dense animal populations as the problems to look for.
Step 5: Seasons Quality varies. Rain washes manure and soil into streams, so a source can be worst just when you most need it. Check after a storm.
What the Senses Cannot Find
- Disease organisms — bacteria, viruses and parasites give no sign. Treatment is the answer: see Water Purification, Boiling Purification and Sand Filters.
- Nitrate — from manure and fertilizer, a risk to infants. The WHO guideline value is 50 mg/L as nitrate. Boiling does not remove it; it concentrates it as water evaporates.
- Arsenic and other metals — natural arsenic in some groundwater. The WHO guideline value is 10 micrograms per litre. Boiling does not remove it.
If your settlement lies in a region with known mineral or industrial legacy, treat unexplained illness among those drinking from a source as a signal to change source.
Common Mistakes
- “It is a mountain spring, so it is safe” — springs can pick up contamination from pasture and fissures. See Spring Identification.
- Relying on a taste test — taste can detect iron and salt, not germs.
- Treating only the intake — contamination can enter after collection, in dirty buckets and storage.
Safety
Boiling does not cure every kind of bad water
Boiling kills germs but concentrates nitrate and leaves metals and chemicals in place. Do not give water from a suspected nitrate, industrial or mining source to infants even after boiling. Change the source.
What’s Next
- Learn next: Water Purification — making a source safe
- Combine with: Surface Water Sources — choosing between candidates