One row per water sample (bottle) collected during the monthly monitoring of
drinking water quality from borehole sources to household storage in four
Ugandan districts (Nakaseke, Kaabong, Kumi and Luuka), November 2024 to
September 2025. Samples were taken at the borehole outlet, from the
container used to carry water home (usually a jerrycan) and from the
household drinking water storage container, and analysed for E. coli by
membrane filtration of 100 mL. Each row links to the field visit it belongs
to through visit_id (see borehole_visits and household_visits). Field
records and laboratory results were matched on district, date and bottle
number; match_status documents the outcome.
Format
A tibble with 3203 rows and 16 variables
- sample_id
Unique identifier of the water sample (one bottle). Integer.
- visit_id
Identifier of the field visit during which the sample was collected. Links to the visit_id column of borehole_visits for sample_type 'borehole' and 'borehole_duplicate', and of household_visits for 'transport_container' and 'storage_container'. NA when a laboratory result could not be linked to a field record (see match_status).
- region
Region of Uganda where the sample was collected: Central Region, Karamoja Region, Teso Region or Busoga Region.
- district
District where the sample was collected: Nakaseke, Kaabong, Kumi or Luuka. The laboratory form used the spellings 'Kaboong' and 'Kamuli' for the last two; these were harmonised to the field survey spelling.
- date_sampled
Date the sample was collected (YYYY-MM-DD). For laboratory results without a field record this is the incubation start date, which in this study is the sampling date.
- sample_type
What was sampled: 'borehole' (water from the borehole outlet), 'borehole_duplicate' (second bottle from the same borehole taken for quality assurance), 'transport_container' (water from the container used to carry water from the borehole to the household), 'storage_container' (water from the household drinking water storage container). NA when the laboratory result has no field record.
- bottle_number
Number written on the sample bottle in the field and read by the laboratory. Numbering restarts every sampling day, so it identifies a sample only together with district and date_sampled.
- date_incubation
Date on which the sample was filtered (membrane filtration) and incubation started. NA when no laboratory result is linked.
- date_result
Date on which the colonies were counted and the laboratory form was submitted, normally the day after date_incubation (18-24 h incubation). NA when no laboratory result is linked.
- petri_dish_number
Petri dish label used by the laboratory for this sample, as recorded. Some entries are placeholder values (e.g. 88888). NA when no laboratory result is linked.
- ecoli_cfu
Number of E. coli colonies (colony forming units) counted on the membrane filter after incubating volume_ml of sample. The laboratory was instructed to enter 101 when more than 100 colonies were present (too numerous to count); a few values above 101 were recorded as typed. NA when no laboratory result is linked.
- tntc
TRUE when ecoli_cfu is greater than 100, meaning the plate was too numerous to count and ecoli_cfu is a censored value rather than an exact count. NA when no laboratory result is linked.
- volume_ml
Volume of sample water filtered, in millilitres. 100 mL for every analysed sample except one, where 'Other' was selected without a value (NA). NA when no laboratory result is linked.
- contamination_category
Contamination level derived from ecoli_cfu with the thresholds used in the project: Safe (0), Slightly contaminated (1-10), Moderately contaminated (11-50), Highly contaminated (51-100), Unsafe (more than 100). Ordered factor. NA when no laboratory result is linked.
- lab_notes
Free-text notes written by the laboratory technician about the sample (e.g. field blank, duplicate sample, visible maggots, interrupted incubation).
- match_status
How the field record and the laboratory result were linked on district, date and bottle number: 'matched' (exactly one field bottle and one laboratory result share the key), 'no lab result' (field bottle without a laboratory result), 'no field record' (laboratory result without a field record), 'ambiguous key' (the key occurs more than once in the field or the laboratory data, so the rows were deliberately not linked and remain separate).