Rate each surface water source on four checks: does it flow all year (perennial flow), is its bank stable, what lies upstream that could foul it, and how does it behave across the seasons. A spring is usually the best source because ground filtration cleans it, but a spring still has to be watched through a dry season, since a stream that runs strongly in spring can shrink to a trickle by late summer.
Streams, rivers, springs and standing water judged as candidate supplies for a settlement, by reliability, stability and contamination risk.
Springs Beat Streams Only If They Survive the Dry Season
The carrier article calls springs often the best water source: water that has moved through soil and rock for a long time emerges cleaner than an open stream, and it comes out of the hillside rather than across your fields. But the carrier’s reasoning, that a hillside spring indicates a reliable aquifer, holds only for springs that are still running at the end of the dry season. Many springs are fed by a small, shallow store and stop. Reliability is measured, not inferred from the fact that water is coming out.
Streams and rivers have the opposite problem. They carry far more water than a settlement needs at their best, so quantity is rarely the issue; quality and flooding are.
What You Need
- A notebook and a dry-season visit — or a local who remembers the last drought.
- A container of known volume and a watch — for springs, see Spring Identification.
- A tape or marked stick — for streams, see River & Stream Assessment.
Method: Score Each Candidate on Four Questions
Step 1: Perennial flow Look for water-loving trees (willow, alder) that indicate year-round moisture. Look at the stones of a stream bed: algae growth or a stain line well above the present waterline shows the stream has been much higher; a dry, bleached bed shows it dries out.
Step 2: Bank stability Eroded, undercut banks suggest the stream shifts course and floods. A channel with fresh gravel bars and torn-up roots is moving. Settle away from it, and see Watershed Position & Flood Risk for how far.
Step 3: Upstream contamination Walk upstream as far as you reasonably can. Abandoned industrial sites, old dumps and dense animal populations upstream are all problems the carrier names. Add to that any settlement or herd above your intake: intake sits upstream of your own washing, latrines and livestock watering.
Step 4: Seasonal behavior Visit in more than one season. If you can only visit once, pick the end of the driest month and treat anything you see then as the real capacity.
Ponds and Standing Water
Ponds and lakes store water, which smooths the dry season, but they also hold algae, animal waste and stagnant sediment, and they breed insects. Use them as a backup, take water from moving inlets rather than the stagnant edge, and treat every drop (see Water Purification).
Common Mistakes
- Calling a spring reliable because it flows today — a wet-season flow tells you nothing about August.
- Intake downstream of your own latrine — put intakes upstream and uphill of all human and animal waste.
- Ignoring what is upstream because the water looks clear — contaminants such as industrial residue are often invisible.
Safety
Surface water carries pathogens even in remote country
A single animal carcass or upstream camp contaminates a whole reach. Always treat surface water before drinking. If you cannot walk the full upstream catchment, assume it is contaminated.
What’s Next
- Learn next: River & Stream Assessment — measure a stream’s flow
- Combine with: Water Quality Indicators — what to look for in the water itself