Domestic and Irrigation Water Quality on the Southern Slopes of Mount Kilimanjaro

Abstract

This study assessed the quality of water for drinking and irrigation purposes on the southern slopes of Mt. Kilimanjaro during the dry season under low flow conditions. Fifty-one samples covering 8 different water types were collected in a snapshot sampling campaign over 10 days in February 2023. First, physical, chemical and biological parameters were analysed and compared with Tanzanian and international requirements for drinking and irrigation water quality. The samples were then ranked according to their suitability for drinking and/or irrigation using water quality indices (WQI). All drinking water quality parameters except for E. coli and turbidity were within the reference standards. A generalized problem of faecal contamination was found in the study area, including in domestic water, which highlights the need to identify sources of contamination and remediate before distribution. The drinking water quality index (DWQI) classified 77% of the samples as unsuitable, 4% as poor or very poor and 19% as good or excellent for drinking. Irrigation water quality parameters were within the guidelines of restriction of use except for pH in 5 samples. All samples were classified as safe for irrigation according to the irrigation water quality index (IWQI). However, five other irrigation indices (Kelley’s Index, Soluble Sodium Percentage, Permeability Index, Residual Sodium Bicarbonate and Magnesium Ratio) showed potential problems with excess of sodium and magnesium. A combination of indices is recommended for assessing water quality for irrigation use.