Stratified random sampling was used. The study area was
divided into 5 sampling strata based on catena position (Fig. 1).
The 5 strata were southern upland wells (village 1), shallow wells
in the southern dambo gardens (village 1 gardens), stream,
shallow wells in the northern dambo gardens (village 2 gardens)
and northern upland wells in village 2. For the upland and dambo
garden strata, water samples were collected from 15 randomly
selected wells. Water samples were also colleted from fifteen
randomly selected sampling positions within a distance of about a
kilometre along the river. These gave a total of 75 samples per
sampling session.