Collecting Water from Aquatic Sources: Rivers, Lakes, and Ponds

Choosing the Best Collection Point

Not all locations on a river or lake are equal. Where you collect affects what you're dealing with:

Rivers and Streams

Upstream from: Human activity, campsites, trails, livestock crossings, bridges (road runoff), downstream flow from settlements

In the flow, not the edges: The central flow is cleaner than the bank zone. The bank zone accumulates organic debris, receives direct soil runoff, and often has more organic matter from adjacent vegetation.

Riffles over pools: Fast, shallow sections (riffles) are better collection points than deep pools. The turbulence aerates water and keeps organic material from accumulating. Pools are stagnant by comparison.

Below a riffle, not above: In a stream sequence, the water just below a riffle has been aerated and had some mechanical settling from the riffle itself. This is slightly better than collecting from above the riffle.

Avoid:

• Just downstream from a campsite, farm, or outhouse
• Near dead animals or animal carcasses
• Where animals actively wade (cattle crossings)
• Stagnant bank areas with heavy vegetation
• Areas with visible algal growth or discoloration

Lakes and Ponds

50+ feet from shore, 3+ feet deep: The shoreline zone has direct input from runoff, decaying shoreline vegetation, bird and animal activity, and shallow sediment disturbance. Moving out from shore improves quality.

Avoid:

• Areas with visible algal blooms (especially green, blue-green, or red discoloration — potential cyanobacteria toxins)
• Near inflows (streams entering the lake — these carry concentrated upstream contamination)
• Near developed shorelines (swimming beaches, boat launches)
• Shallow areas where sediment is easily disturbed
• Dead zones (areas with no oxygen, often deep in stratified lakes) — dark, oxygen-depleted water from these areas is particularly contaminated

Lakeside collection from shore: Use a container on a cord thrown out past the shallow zone, or wade out slightly to collect from deeper water.

Collection Technique

Collect from below the surface: Don't skim surface water, which has surface film (biofilms, insects, pollen). Submerge the container mouth 6-12 inches below the surface.

Disturb minimally: If wading to collect, let the disturbance settle before collecting. Move upstream to collect where you haven't disturbed the bottom.

Wide-mouth containers: Easier to fill than narrow-neck bottles. A wide-mouth container on a cord thrown into a river can be retrieved full.

First container for settling, second for treatment: Collect into a settling container first, let it settle, then carefully pour the clearer top portion into your treatment vessel. This two-container approach dramatically improves the quality of the water entering your filter.

Pre-Treatment: Settling and Coagulation

Turbid water clogs hollow fiber filters extremely fast. Pre-treatment extends filter life significantly.

Settling (30-120 minutes):

• Pour collected water into a clean container
• Let stand without disturbance
• Fine sediment settles fastest in containers that are taller than they are wide (less distance to settle)
• Decant the clearer top 2/3 carefully

Coagulation (optional, dramatically speeds settling):

Coagulation causes fine suspended particles to clump together and settle faster. Two options:

Alum (aluminum sulfate): A pinch (1/4 teaspoon per gallon) added to turbid water, stirred, and then allowed to settle drops the turbidity dramatically in 15-30 minutes. Alum is sold as a spice (it's used in pickling) and as a water treatment chemical. The aluminum it introduces is at levels far below any health concern at this dose.

Wood ash: A small amount of clean wood ash (not ash with chemical additives or paint residue) added to turbid water acts as a basic flocculant and can speed settling. Less precise than alum but improvised in the field.

After coagulation and settling: carefully decant the clearer top portion, avoiding the settled floc at the bottom.

Dealing with Very Turbid Water

Flood water, river water after heavy rain, and runoff water can be so turbid that standard filtering techniques clog almost immediately.

Staged pre-filtration:

1. Allow to settle 1-2 hours
2. Decant and filter through a folded cotton cloth (t-shirt material)
3. Re-filter through a coffee filter or layered fine cloth
4. Only after achieving visible clarity: run through hollow fiber filter
5. Disinfect

Assess turbidity: Dip your finger into the water in a glass. If you can see your finger clearly at 6 inches of depth, the water is clear enough for UV treatment. If not, continue pre-filtration.

Recognizing Problem Water at the Source

Visual and sensory assessment at the source isn't treatment, but it guides urgency and approach:

Avoid or use with extreme caution:

• Petroleum or oily sheen on the surface
• Unusual chemical odor (not natural organic smell, but solvent or petroleum smell)
• Blue-green, green, or red surface coloration (algal bloom — potential cyanotoxins that boiling doesn't address)
• Foam that doesn't disperse and has an oily appearance
• Dead fish or animals in or immediately near the water

These are fine:

• Brownish tint from tannins (vegetation decay) — common in wooded areas
• Clear foamy bubbles at a stream rapid (turbulence-aerated organic compounds, not pollution)
• Slight green coloring from normal algae (different from a heavy surface bloom)
• Natural organic smell (leaf litter, vegetation)

Full Treatment for Aquatic Sources

All surface water — regardless of clarity or apparent quality — requires treatment before drinking.

Standard aquatic source treatment:

1. Collect and settle (30-60 min for turbid water)
2. Pre-filter through cloth (turbid water only)
3. Hollow fiber filter (removes bacteria and protozoa)
4. Chemical disinfection or UV (adds virus coverage)
5. Optionally, activated carbon polish for taste and chemicals

This sequence handles the realistic pathogen load in most North American surface water sources reliably.