Water supply

1Why WASH saves lives

In camps and affected areas, diseases related to water, sanitation and hygiene (diarrhoea, cholera, hepatitis E, typhoid) are among the leading causes of illness and death, especially among young children and malnourished people. WASH acts on faecal-oral transmission: through contaminated hands, water, food, flies and soil.

This is often summarised by the “F-diagram”: barriers (latrines, handwashing, treated water, food protection) break the transmission routes.

2Quantity and access: the Sphere benchmarks

• At least 15 litres per person per day for drinking, cooking and personal hygiene (an indicative benchmark to be adapted to the context, and higher in health facilities).
• A water point less than 500 metres from households.
• A queuing time at the water point of less than 30 minutes.
• As a benchmark, around 250 people per tap (depending on flow rate), 500 per hand pump, 400 per open hand-dug well.
• Clean containers for collection and storage at home (for example two 10- to 20-litre jerrycans per household).

These benchmarks are indicators, not quotas: they are discussed with communities, in particular women and girls, who often collect the water.

3Water supply options

• Water trucking: fast but expensive, to be replaced by sustainable solutions as soon as possible.
• Rehabilitation of existing boreholes, wells and networks: often the most cost-effective option.
• Surface water treatment (river, lake) with treatment units, or new boreholes after surveys.
• Management by trained water point committees (maintenance, cleanliness, minor repairs, possible user contribution).

4Treating water and monitoring its quality

• Chlorination: the most common method in emergencies. Benchmark: a free residual chlorine concentration of 0.2 to 0.5 mg/l at the point of delivery (higher, around 0.5 to 1 mg/l, during a cholera outbreak), after a contact time of at least 30 minutes, with low-turbidity water (ideally below 5 NTU).
• Measurement of residual chlorine with a comparator or photometer (DPD) several times a day at water points and in a sample of households.
• Bacteriological testing: 0 faecal coliforms (E. coli) per 100 ml at the point of delivery.
• Household water treatment (tablets, filters, boiling) when water cannot be treated at source, with demonstrations and follow-up.

5Assessing and planning water supply: a method from the first 72 hours to the first 3 months

The benchmark of 15 litres per person per day is not a plan. A water supply plan answers four quantified questions: how much water is needed, for whom and where; where it will come from and at what reliable yield; how it will be made safe and monitored; and how the response will move from emergency solutions to durable ones. The method below follows the sequence used by most experienced WASH teams.

Step 1: rapid assessment (days 1 to 3)

• Who: a pair made up of a WASH technician and a hygiene promoter, ideally one man and one woman, accompanied by a community member or an officer from the government water department. The project manager validates the planning assumptions.
• What: population and trend (arrivals per day), existing sources and their condition, distance and collection time, quantities actually collected (estimated from the number and volume of containers), treatment in place, water containers available in households, protection risks around water points, and early health signals (acute watery diarrhoea, child deaths) obtained from health actors.
• How: direct observation, key informant interviews, separate focus group discussions with men and women, on-site measurement of residual chlorine and turbidity, sanitary inspection of sources. The WASH Cluster rapid assessment tools or the Multi-Cluster/Sector Initial Rapid Assessment (MIRA) provide a common framework; it is better to use them than to design an NGO-specific questionnaire, so that data are comparable.

Step 2: calculating actual demand

Demand is not limited to households. Institutional needs must be added, and then system losses. The benchmarks below are those commonly used on the basis of the Sphere Handbook and the sector's technical guidance; they are starting points, to be adjusted to climate and practices.

Losses are then added: 10 to 20% for a well-built new network, often 30% or more for a rehabilitated network or poorly controlled water trucking. The design demand is therefore: (household needs + institutional needs) × (1 + loss rate).

Step 3: source inventory and safe yield

For each source, you need to know the safe yield, not the claimed yield. For a borehole, this requires a pumping test (a step-drawdown test followed by a constant-rate test, often 24 to 72 hours, with recovery monitoring) carried out by a hydrogeologist or a qualified driller. Prudent rule: do not pump for more than 16 to 18 hours a day and stay below the constant-rate test yield. For a surface source, you need to estimate the low-flow (dry season) yield, not the yield on the day of the visit. For an urban network, you need to obtain from the utility the actual supply hours and pressure.

Step 4: transition scenario

The plan is written in three phases, each with its cost per cubic metre and its exit date:

1. Acute phase (weeks 1 to 4): water trucking, bladder tanks, in-tank chlorination, distribution of containers and household water treatment products if the water cannot be controlled.
2. Stabilisation phase (months 2 and 3): rehabilitation or drilling, simple distribution network, gradual reduction of trucking.
3. Consolidation phase (from month 4): solar or hybrid pumping, management committees, maintenance handed over to local actors, involvement of the utility or the government technical service.

A credible water supply plan states, from the first week, the date on which water trucking must stop and the conditions that will make this possible. Water trucking without an exit strategy can cost ten times more per cubic metre than an equipped borehole, and quickly becomes the project's largest budget line.

6Chlorination and water treatment: calculations, protocols and monitoring

Chlorination is simple in principle and often poorly executed. Typical mistakes are doses calculated "by eye", turbidity too high so that it shields bacteria, contact time not respected, and monitoring limited to the tank while the water becomes recontaminated between the tap and the cup. This section provides the calculations and protocols to master.

Conditions for effectiveness

• Turbidity below 5 NTU, ideally below 1 NTU. Above that, a pre-treatment step is needed (sedimentation, flocculation, filtration). Above roughly 20 NTU, chlorination alone is not reliable.
• pH below 8. Above this, the proportion of hypochlorous acid, the most effective disinfecting form, drops sharply: the dose and contact time must be increased, or the upper end of the residual chlorine range targeted.
• Contact time of at least 30 minutes before distribution.
• Free residual chlorine of 0.2 to 0.5 mg/l at the point of delivery under normal conditions, 0.5 to 1 mg/l during a cholera or diarrhoea outbreak. The WHO health-based guideline value for chlorine is 5 mg/l, but the water becomes unpleasant to taste well before that, which pushes households towards untreated sources.

The chlorine demand test

The dose to apply is the sum of the water's chlorine demand (the chlorine consumed by organic matter and other substances) and the desired residual. It is determined by a simple test:

1. Prepare a 1% active chlorine stock solution (10 g of active chlorine per litre, i.e. about 14 g of 70% calcium hypochlorite or 15 g of 65% dissolved in 1 litre of water; calibrate a measuring spoon and check the solution with the comparator).
2. Fill three to five 20-litre buckets with the water to be treated.
3. Add increasing volumes of the 1% solution: 1 ml, 1.5 ml, 2 ml, 2.5 ml (i.e. 0.5; 0.75; 1; 1.25 mg/l for 20 litres, since 1 ml of 1% solution contains 10 mg of chlorine).
4. Wait 30 minutes, then measure the free residual chlorine in each bucket with a DPD comparator.
5. Select the lowest dose that gives between 0.4 and 0.5 mg/l after 30 minutes (to keep a margin up to the point of consumption), then extrapolate to the tank volume.

The test must be repeated at every change of source, after heavy rain and at least once a week for surface water.

Calculating the dose for a tank

Formula: mass of product (g) = volume (m³) × dose (mg/l or g/m³) ÷ active chlorine concentration of the product (as a fraction).

Example: 10 m³ tank, selected dose of 1.5 mg/l, 70% calcium hypochlorite (HTH). Active chlorine required: 10 × 1.5 = 15 g. Mass of HTH: 15 ÷ 0.70 = 21.4 g, rounded to 21 g. Dissolve the product in a bucket of water, let the insoluble residue settle, and pour the clear part into the tank while it is being filled to ensure mixing.

HTH loses concentration with heat, humidity and time. A stock that has been opened for several weeks under a corrugated iron roof may have lost a significant share of its active chlorine. The residual chlorine reading, not the theoretical dose, is what counts.

Pre-treatment: sedimentation and flocculation

For turbid river water, aluminium sulphate is used as a coagulant. The dose is determined by a jar test: several 1-litre containers receive increasing doses (for example from 20 to 80 mg/l), are stirred rapidly for one minute, then slowly for 15 to 20 minutes, and left to settle for 30 minutes. The lowest dose that gives clear water is selected. pH strongly influences the result; water that is too acidic after coagulation may require correction with lime. Compact treatment units (such as the emergency kits of the Red Cross or the large WASH NGOs) integrate these steps but require a trained operator and a constant supply of chemicals.

Household water treatment

WHO assesses the performance of household water treatment products through an international evaluation scheme: give preference to products that have been tested under it. Any distribution must be accompanied by a demonstration and household follow-up: field studies regularly show rates of correct use well below distribution rates.

Water quality monitoring plan

• Residual chlorine and turbidity: at each tank after the contact time, at each distribution point at least once a day in the acute phase (two to three times a day during an outbreak), and in a sample of households every week.
• Bacteriological analysis (E. coli or thermotolerant coliforms): by membrane filtration with a field kit, on non-chlorinated sources and on a sample of water points and households. The commonly used risk grid classifies results as 0 (compliant), 1 to 10 (low risk), 11 to 100 (intermediate risk), more than 100 CFU per 100 ml (high risk).
• Chemical parameters: for any new borehole, at least one laboratory analysis. The WHO guideline values most often at issue are arsenic (10 µg/l), fluoride (1.5 mg/l) and nitrate (50 mg/l); conductivity or total dissolved solids indicate taste acceptability (above about 1,000 mg/l, the water is often rejected).
• Sanitary inspection: standard WHO form for each type of source (borehole with handpump, dug well, spring protection, tank, tap), which gives a risk score and corrective actions.

7Worked example: water supply for the Kalimbé site, from the first week to the third month

Fictional context: following clashes in Sarandi district, some 18,000 displaced people have gathered on communal land in Kalimbé, in the dry season. The only nearby source is a half-dry open well; a perennial river flows 9 km away, and a functional municipal borehole, managed by the Doro town council, is located 11 km away. The fictional NGO "Eau Solidaire" is designated by the cluster as the site's lead WASH partner. The first health data report 210 cases of acute watery diarrhoea in one week among children under 5, with no confirmed cholera cases.

Step 1: design demand

Step 2: acute phase with water trucking (weeks 1 to 5)

Realistic target agreed with the cluster: 7.5 l per person per day by the end of the first week, 15 l by the end of the fourth week. For the first week: (18,000 × 7.5 l) + 13.6 m³ institutional = 148.6 m³, increased by 20% for transport-related losses, i.e. about 178 m³ per day.

• Source: the Doro municipal borehole, after a written agreement with the town council on volumes, hours and compensation for generator fuel. The river is ruled out in the acute phase (turbidity measured at 60 NTU, no treatment unit available for three weeks).
• Trucks: 12 m³ tankers, a 2 hour 30 minute round trip (11 km, filling, unloading), 10 working hours a day, i.e. 4 round trips and 48 m³ per truck per day. Requirement: 178 ÷ 48 = 3.7, so 4 trucks plus 1 in reserve.
• On-site storage: 10 m³ bladder tanks; the aim is at least half a day of storage, i.e. 9 to 10 tanks, each connected to a 6-tap stand.
• Chlorination: in each bladder tank after filling, based on the demand test carried out on the borehole water (low demand of 0.3 mg/l, selected dose 0.8 mg/l), with residual chlorine checked at each tapstand three times a day.
• Cost: all-inclusive hire (driver, fuel, maintenance) negotiated at 360 US dollars per truck per day, i.e. 1,800 dollars per day for 5 trucks and about 10 dollars per cubic metre delivered. Over five weeks: 63,000 dollars.

With 10 tapstands of 6 taps each, the site has 60 taps, i.e. 300 people per tap: above the benchmark of 250. The team reports this to the cluster as a temporary gap and plans 2 additional tapstands in week 3 (72 taps, 250 people per tap).

Step 3: the durable solution (from week 4)

A geophysical survey (vertical electrical soundings) identifies four favourable sites. Three productive boreholes are drilled; the constant-rate pumping tests (48 hours) give safe yields of 7.5, 5 and 9 m³/h.

Reasoning: 344 m³ covers the demand of 330 m³ with a margin of only 4%. The team therefore decides to keep one truck in reserve for two more months, to rehabilitate the existing open well (fitted with a handpump, for non-drinking uses), and to include active loss reduction in the plan (leak detection, self-closing taps). The pumps are solar-powered with generator back-up for overcast days. Two elevated 95 m³ tanks provide half a day of storage and the pressure for 12 tapstands of 6 taps each.

Step 4: chlorination consumables

Demand test on the borehole water: 0.7 mg/l. Selected dose: 0.7 + 0.5 = 1.2 mg/l. Active chlorine per day: 330 × 1.2 = 396 g. 70% HTH: 396 ÷ 0.70 = 566 g per day, i.e. 17 kg per month. Three-month stock with a 20% margin for degradation: 61 kg, ordered in 45 kg drums stored in the shade, in a dry place and away from fuel.

Step 5: cost comparison

Calculation: (156,000 + 24 × 2,500) ÷ (330 × 730 days) = 216,000 ÷ 240,900 = 0.90 dollar per m³. This argument, presented together with the pumping tests, convinces the donor to reallocate the "trucking" budget lines to investment from the second month.

Step 6: indicators monitored

How this table is read matters as much as the figures: residual chlorine is good at the tap but insufficient in households in month 3. The likely cause is recontamination during transport and storage (open containers, water drawn with cups). The answer is not to increase the dose at the tank, but to distribute containers with a spout and a lid, and to focus hygiene promotion on safe water handling.

8Reusable tools and templates

The following tools can be adapted directly. They are deliberately simple: a form that teams actually fill in is worth more than a comprehensive form abandoned after two weeks.

Daily water point monitoring sheet

Water quality monitoring schedule in the acute phase

Checklist for a water trucking contract

• Authorised and monitored source, with written agreement from the authority or operator.
• Tankers reserved for drinking water, cleaned and disinfected before first use (concentrated chlorine solution, rinsing), with no history of carrying fuel or chemicals.
• Delivery note signed at each trip by the water point attendant (time, volume, residual chlorine on arrival).
• Payment by verified volume, not by the number of trips declared.
• Penalty or termination clause in case of non-compliant delivery, and spot checks by the logistics team.
• Contingency plan if a truck breaks down or the road is cut off.

Model terms of reference for a water point management committee

• Composition: 5 to 9 elected members, at least half of them women and at least one woman in a key position (chair or treasurer), with representation of the different groups on the site, including persons with disabilities.
• Tasks: cleanliness of the water point and its drainage apron, management of opening hours and queues, reporting breakdowns within 24 hours, relaying complaints, minor repairs after training.
• Resources: toolkit, common wear parts, documented training, direct telephone contact with the technical team.
• Limits: the committee is not responsible for "sanctioning" users or restricting access; any financial contribution is discussed with the cluster to remain consistent with other sites.

Questions for a focus group discussion with women on access to water

1. Who collects water in your household, at what time, and how many trips a day?
2. How long do you wait at the water point? What happens while you wait?
3. Are there times or places where you or your daughters do not feel safe going to fetch water?
4. Does the water have a taste or smell that bothers you? Do you use other sources, and for what purposes?
5. Do you have enough containers? How do you store water at home?
6. If a problem occurs at the water point, who do you tell? Did you get a response?

9Common mistakes and what donors, evaluators and auditors look at

The costliest mistakes in the field

1. Confusing water produced with water consumed. Dividing the volume pumped by the population gives a flattering figure that ignores losses, institutional uses and unequal access between areas of the site. The quantity indicator must be verified through a household collection survey (number and volume of containers filled the previous day), disaggregated by area.
2. Checking chlorine only at the tank. A compliant residual at the tank says nothing about the water people drink. Monitoring must extend to the household container.
3. Drilling without a survey or authorisation. A borehole sited without a hydrogeological survey, without authorisation from the water resources department and without a pumping test is a high-risk expense. Dry or low-yield boreholes are common in crystalline basement areas; the contract with the driller must provide for payment of dry boreholes according to a pre-agreed schedule and an independent supervisor present at key stages (depth, casing, gravel pack, development, test).
4. Letting water trucking become permanent. Without an exit date, trucking becomes the default solution, with high costs, a risk of fraud (fictitious trips) and total dependence on the road and on fuel.
5. Ignoring operation and maintenance. A handpump without spare parts or a pump mechanic breaks down within months. Studies of handpumps in sub-Saharan Africa show high non-functionality rates after a few years; maintenance must be planned and budgeted from the design stage.
6. Designing without women. Taps too high or too low, water points far away or isolated, opening hours incompatible with other tasks: all reasons why a "compliant" facility is little used or becomes a site of violence.
7. Neglecting competing use with the host population. A displacement site pumping from the same aquifer as the neighbouring village, or receiving free water while villagers pay, creates tensions. Conflict sensitivity analysis and the inclusion of host communities are expected by donors.

What donors look at

What an evaluator or auditor checks

• The traceability of volumes: delivery notes, meters, pumping logs, reconciliation with payments to transporters.
• The traceability of supplies: stock movements of chlorine and coagulant, consistency between theoretical and reported consumption.
• Raw water quality data, dated and signed, and the documented response to non-compliant results.
• The functionality of infrastructure several months after the end of works, and the existence of an actor responsible for maintenance.
• Accountability: existence and use of a complaints mechanism, changes made in response to feedback, participation of women and marginalised groups, in line with the Core Humanitarian Standard (CHS).

The Global WASH Cluster's Quality Assurance and Accountability Framework offers a simple logic that evaluators apply: is the response compliant with agreed standards, appropriate to the needs expressed by affected people, and documented in a verifiable way? Preparing your data along these lines makes every review easier.

10Adapting water supply to different contexts

Sudden-onset or protracted crisis

In a sudden-onset crisis, the priority is minimum quantity and water safety within a few days: prepositioned contingency stocks (bladder tanks, tapstands, chlorination kits, tablets), framework agreements with transporters, lists of pre-qualified drillers. In a protracted crisis, the logic changes: solarised networks, support to utilities and government technical services, social tariffs, management delegated to private or community operators, and life-cycle cost analysis. The shift from one logic to the other must be explicit in the proposal to the donor, and funding modalities follow suit (short-term humanitarian funding, then transition or development funding).

Camp or urban setting

• Camp: the WASH actor designs the whole system; site planning (with the CCCM cluster and the camp manager) must reserve space for tanks, networks and drainage areas.
• Urban setting: the population is dispersed across neighbourhoods and host families. The response supports the existing system (repairing pipes, fuel or spare parts for pumping stations, treatment chemicals for the utility), uses market-based approaches (water vouchers with monitored vendors, cash transfers), and monitors quality at vendor level. Water market analysis (prices, vendors, quality) is a prerequisite.

Remote management

When the international team or the coordination cannot access the site, monitoring relies on: local partners trained and equipped with comparators and field kits; geotagged, time-stamped photos of works and readings; meters and, if the budget allows, remote sensors on pumps; independent third-party monitoring; random phone calls to users and committees. The contract with the partner specifies the thresholds that trigger an alert (for example non-compliant residual chlorine in more than 20% of a week's readings).

Insecurity and armed conflict

Water infrastructure is protected under international humanitarian law as objects indispensable to the survival of the civilian population, but it is regularly damaged or used as a means of pressure. The ICRC documents the cumulative impact of protracted conflict in urban areas on essential services: a pumping station deprived of electricity or spare parts for months can cause more deaths than the fighting itself. In practice: stocks of critical spare parts, back-up energy sources, risk mapping of collection routes, adapted distribution hours, and dialogue with the authorities and parties to the conflict on access for maintenance teams.

Local partners with limited capacity

Localisation is a Grand Bargain commitment, not a transfer of risk. Realistic capacity strengthening combines: hands-on training on site (chlorination, demand test, sanitary inspection), equipment provided and maintained, joint supervision that tapers off over time, an adequate operating budget (including the partner's overheads), and gradual delegation of responsibilities based on a shared capacity assessment.

Specific situations

• Floods: wells and boreholes become contaminated. Standard protocol: dewater the well, clean it, shock-disinfect with a concentrated chlorine solution (around 50 to 100 mg/l, contact time of 12 to 24 hours), pump until the residual returns to normal, then carry out bacteriological testing.
• Drought: priority to rehabilitating and deepening water points, managing competing use with livestock, targeted water trucking, salinity monitoring.
• Extreme cold: frost protection (buried pipes, insulated tanks), increased need for hot water for hygiene.
• Cholera outbreak: residual chlorine raised to at least 0.5 mg/l at the point of delivery, more frequent monitoring, priority to the neighbourhoods and facilities where cases appear (see day 3).

11Interview questions and key references

The following questions are common in interviews for WASH engineer, manager or coordinator positions. The expected content of a strong answer is given for each.

1. "You arrive at a site with 10,000 displaced people and no water. What do you do in the first 72 hours?"

A good answer is sequenced and quantified: rapid assessment with the community and health actors; calculation of minimum demand (75 m³ per day for 7.5 l, 150 m³ for 15 l, plus institutions and losses); identification of a safe source and agreement with its operator; water trucking with chlorination and monitoring; distribution of containers; immediate coordination with the cluster and the site manager; a transition plan towards a durable solution from the first week.

2. "Residual chlorine is compliant at the tap, but zero in 40% of households. What do you do?"

The candidate explains recontamination between collection and consumption, proposes checking containers (opening, cleanliness, how water is drawn), distributing appropriate containers, focusing hygiene promotion and possibly adding household water treatment. They do not propose increasing the dose at the tank without limit, and recall the taste acceptability threshold.

3. "How do you justify to a donor an investment in boreholes in the middle of an emergency?"

The candidate compares the cost per cubic metre over the foreseeable duration of the crisis, presents the results of hydrogeological surveys and pumping tests, shows the reduction in risk (dependence on the road and on fuel) and the operation and maintenance strategy, and anticipates the required permits.

4. "How do you monitor the quality of a water programme under remote management?"

The candidate cites concrete means (time-stamped photographic records, meters, third-party monitoring, calls to users, raw residual chlorine data), contractual alert thresholds, and strengthening of the partner's capacity with a realistic budget.

5. "Why is 15 litres per person per day not a sufficient target?"

The candidate explains that the benchmark is a minimum for survival and basic hygiene, that needs vary with climate, health and cultural practices, that an average volume hides inequalities between areas and households, and that access (distance, waiting time, safety) and quality matter as much as quantity.

6. "What is your experience of pumping tests, and what do you do with the results?"

The candidate distinguishes between step-drawdown and constant-rate tests, explains drawdown and recovery monitoring, and derives from them the safe yield, the pump installation depth and the choice of pump (flow rate, total dynamic head).

Key references

• The Sphere Handbook: Humanitarian Charter and Minimum Standards in Humanitarian Response (2018 edition), Water Supply, Sanitation and Hygiene Promotion chapter: Sphere Association.
• Guidelines for Drinking-water Quality (fourth edition and addenda) and sanitary inspection forms: World Health Organization.
• Technical notes on drinking-water, sanitation and hygiene in emergencies: WHO and WEDC, Loughborough University.
• Engineering in Emergencies (Jan Davis and Robert Lambert): field technical reference.
• Public Health Engineering in Precarious Situations: Médecins Sans Frontières.
• ICRC water and habitat technical manuals, in particular on protracted armed conflict in urban areas and essential services.
• Quality Assurance and Accountability Framework and rapid assessment tools: Global WASH Cluster.
• Humanitarian WASH thematic policy: DG ECHO, European Commission.
• Emergency Application Guidelines, WASH technical requirements: USAID Bureau for Humanitarian Assistance (BHA).
• Core Humanitarian Standard on Quality and Accountability (CHS): CHS Alliance, Sphere and Groupe URD.