Impact of land use types on Nsooba stream: case study of Bukoto I to Bwaise III

Abstract

A study was conducted to determine the impact of land use type on water quality in Nsooba stream. The objectives of the study were: 1) to map the different land use types along Nsooba stream, 2) to assess the water quality in the stream and 3) to determine the relationship between the measured water quality parameters and land use type along the stream. GIS was used to map out the various land use types around Nsooba stream and this was supported with ground trothed data. A total of 72 samples were collected over a 12 weeks’ period from 6 sampling sites along Nsooba stream and tested in the laboratory for levels of COD, BOD, TSS, TP and TN; and Feacal coliforms using APA standard methods. Another 72 samples were collected and measured in-situ to determine the physico-chemical characteristics of water (TDS, DO, pH, Temperature and EC) in Nsooba stream. The relationship between water quality parameters and land use type was determined using redundancy analysis (RDA) and nonparametric Spearman rank correlation. Results showed that the built-up area was the most dominant land use type along the stream and was comprised of roads, settlements, commercial facilities like retail shops, abattoirs, markets, bakeries hospitals and banks. The physic-chemical parameters were TDS (187.16 mg/l), DO (6.17 mg/l), pH (6.96), and Temperature (21.330C) and EC (377.18μS/cm). For chemical parameters, the levels were COD (169.77mg/l), BOD (21.87mg/l), TN (4.32 mg/l), TP (1.9 mg/l) and TSS (0.44mg/l). For microbiological parameters, Feacal Coliforms were 6.292 log10 cfu/100ml.The water quality parameters were significantly different between the dry and wet season (p<0.05). The concentration was higher downstream (Bwaise III) compared to upstream (Bukoto 1). Sampling site 1 upstream in Kisilamu zone recorded the lowest levels of concentration of water quality parameters while sampling site 5 downstream in Kibe zone recorded the highest concentrations. Sampling sites located where there is intensive landuse, the concentration of water quality parameters was also high signifying that there is a relationship between the measured water quality parameters and land use type along the stream. The RDA showed that commercial and industrial developments influence temperature, BOD, COD, and TDS while residential development influences TP, DO, and TN. Infrastructural development mainly influences pH. The study concluded that the impact of land use type on water quality parameters in Nsooba stream is high. The study recommends sensitization, designation of waste collection points and enacting on or enforcing already existing bye-laws.