Table 2 The ranges for electrical conductivity values and the concentration ranges {or average values} for nitrate, fluoride, thermotolerant coliforms (TTC) andE. coli in the surface and groundwaters in the case study regions. The GNA and LA regions have high groundwater dependency for piped water supplies. In the MA, the Ramisi River has a several-kilometre-long tidal reach so concentrations of the parameters are given separately in square brackets
Parameter | Site type | Case study region | ||||
|---|---|---|---|---|---|---|
KRA | GNA | LA | WTA | MA | ||
Electrical conductivity (μS/cm) | River | 61.0–110.0 | 97.0–1,057.0 | 143.0–300.0 | No river | 80.0–404.7 [5,647.0–35,300.0] |
Well | 280.0 ≥ 2,500.0 | – | – | 1,124.0–3,900.0 | 67.0–5,000.0 | |
Borehole | 160.0–1,280.0 | 230.0–3,420.0 | 380.0–538.0 | – | 200.0–7,000.0 | |
Nitrate (mg/L) | River | 1.2–8.2 | 0.0–20.6 | 0.03–25.5 | None | 0.9–6.0 [52.0–268.0] |
Well | 1.2–188.3 {18.1–70.3} | 5.9 | 0.01–0.07, Turkana central | 78.0–222.0 in town; 0.0–106.0 in county | 0.2–68.0 | |
Borehole | 1.7–8.4 | 0.1–36.0 | 3.3–6.8 | 0–443 in county | 0.2–32.2 | |
F (mg/L) | River | 0.3–0.5 {0.8} | 0.3–3.4 {0.8} | <0.01–1.32 | None | 0.0–0.6 [1.3–5.4] |
Well | 0.9–3.5 {3.5–6.2} | – | 0.1–3.8, Turkana Central | 0.2–0.8 | 0.0–0.2 | |
Borehole | 0.3–7.3 | 0.6–20.0 {6.2–6.7} | 0.1–0.4, town; 0.2–1.2, Turkana Central | 0.2–8.2 | 0.1–0.4 | |
TTC (cfu/100 ml) | River | 152–210 | – | 24, 2,400 (two samples) | None | 3–37 [123–1,150] |
Well | 894–2,183 | – | – | 3 ≥ 1800 {1048} | 5–10 | |
Borehole | 0–144 | – | – | – | 3.3–81.0 | |
E. coli (cfu/100 ml) | River | – | – | 2,000 (one sample) | None | 8–22 [13–817] |
Well | <10.0 to >100,000 {654a} | – | – | 0–275 {41} | 0 | |
Borehole | – | – | – | – | 0 (majority)−18 | |
Data sources | DHV1988; Orwa2001a; Wright et al.2013; Okotto-Okotto et al.2015; Wright et al.2013; Ong’or and Long-Cang2007; AfriWatSan Project | LOWASCO (REACH Project Partner); unpublished data | Chalala et al.2017; Gro-for-GooD Project | |||
- TTC range < 10 to >100,000 in Okotto-Okotto et al.2015 datasets. Average F concentration in the water supplied from Nakuru Water and Sanitation Services Company (NAWASSCO) taps was 7.05 mg/L (Njeru and Alukwe2017). In Msambweni area only the groundwater sources of Milalani Primary School Borehole and Tuliani Borehole were contaminated with faecal coliform. High nitrate concentrations relate to the downstream portion of the Ramisi River (Chalala et al.2017). Pb in the town of Wajir is a major issue (0.00–0.03 mg/L vs WHO guideline of 0.01)
- aE. coli in Manyatta Estate