Find and hold water

A source that cannot meet the daily demand is not a source, it is a walk. Plan on 15 litres per person per day for drinking, cooking and basic washing; 7.5 litres is the floor below which hygiene collapses and people start getting ill. Of that, only about 3 litres is drinking.

Six people therefore need about 90 litres a day — nine full 10-litre containers, carried. That is the number that decides how far away a source can be: a carry of more than a few hundred metres, twice a day, will quietly be skipped, and the nearer dirty water will be used instead.

Water collects in low ground. Work down valleys, along the base of cliffs and escarpments, and to the outside bends of dry beds.

Read the vegetation, which is the most reliable sign there is: a green line across a brown hillside is a spring or a seep. Willows, cottonwoods, poplars, reeds, rushes and sedges have roots in the water table and do not grow far from it. Follow animal tracks at dawn and dusk — they converge on water — and watch insect flight lines, since bees rarely nest more than a few kilometres from water and fly to it in a straight line.

The quality of surface water is decided by what is happening above it, not by how it looks. Walk upstream as far as is practical and look for: settlements, latrines and animal pens; dead animals in or beside the water; standing or stagnant reaches; blue-green algal scum on still water; and orange, rust-coloured or unnaturally clear staining on the bed, which means mine drainage or industrial contamination.

Clear, cold and fast-moving means less treatment, not no treatment. Nothing you can see at the bank tells you whether the water carries Giardia, Cryptosporidium or cholera.

In order, best first:

1. A spring at the point it leaves the rock — filtered through ground for years. Take it at the emergence, not thirty metres downstream where animals have stood in it.
2. A fast-running stream above all human and animal use.
3. A lake or pond with an outflow — moving water, not standing.
4. A dug seep beside a dry bed — see the next entry.
5. Standing water, last — a pond with no outflow, a puddle, a tank.

Write the ranking down and name a fallback for the day the first one fails: sources dry up, flood, freeze and get fouled, and the fallback is chosen calmly now or badly later.

In a dry riverbed, water often still runs under the sand. Dig on the outside of a bend, where the flow scoured deepest, about a metre back from the channel so the bank filters what you draw, and keep going until you are below the damp line — commonly 0.5 to 2 metres.

Make the hole 30–50 cm across, let it fill, and let it settle for 20–30 minutes. Skim from the top with a cup rather than plunging a container in and stirring the silt back up. Line the sides with stones or brush if they slump.

Every watercourse floods, and it floods higher than the day you looked at it. Read the flood line off the ground: debris and grass caught in branches and fence wire, scour marks and undercut banks, a silt line on tree trunks and rocks, and the sharp edge where vegetation changes.

Camp above that line, and above it by a margin, because the marks record the floods that happened and not the flood that is coming. Do not camp in a dry bed, a gully or the flat inside a bend, however sheltered it looks.

Before anyone forms a habit, mark and announce three places, in this order along the flow:

1. The collection point — furthest upstream. Nothing else happens here.
2. The washing point — for people, clothes and cooking pots, downstream of collection.
3. The latrine — at least 30 m from the water, downhill and downstream of both. See separating waste from water.

This costs nothing on day one and is nearly impossible to impose on day ten, once people have started washing where it is convenient.

Most water that arrives dirty was clean when it was collected. Fix the vessels:

• Narrow-necked, covered containers for carrying and storing. A vessel you cannot get a hand into cannot be contaminated by a hand.
• Dedicated containers, marked, that never hold anything else and never stand on the ground at the source.
• A dipper on a string or a tap, so nobody dips a cup or a hand into the store.
• Treated and untreated water in visibly different containers. The commonest illness in a careful group comes from mixing these two up.