Effects of Anthropogenic Activities on Water Quality within Ngong River Sub-Catchment, Nairobi, Kenya

Abstract

Anthropogenic activities often compromise the water quality of natural water systems, rendering it unfit for domestic and agricultural use. This paper evaluates the effects of anthropogenic activities on the water quality of Ngong River in Nairobi County, Kenya. It aimed to assess the river’s physico-chemical parameters, identify major anthropogenic activities that act as pollutant sources and establish the relationship between the anthropogenic activities and water quality along the Ngong River. Twelve water samples were systematically collected in each of the twelve study sites in April and August 2021 and analyzed in the laboratory for various water quality parameters. The accumulation factor (AF) indicated that E. coli, total coliforms, BOD and COD were found to significantly build up downstream of Ngong River. The ANOVA test results showed that all the physicochemical parameters studied (BOD, E. coli, pH, total suspended solids, total coliforms, turbidity, conductivity, nitrates, oil and grease and TDS), except COD, were not significantly different (p ≤ 0.05) for the different sites. Measured heavy metals, such as lead (Pb) levels at different sampled points, were all found to be below the detectable limit (0.001 ppm) for both seasons. Cadmium (Cd) was detectable during the dry season with the highest levels (0.113 ppm) being recorded at Ngong Forest Boundary. The findings of this study revealed that anthropogenic activities, such as raw sewage disposal, industrial activities, solid waste dumping and small-scale agriculture, had adverse effects on Ngong River’s water quality. The study recommends a need to closely monitor anthropogenic activities along Ngong River to reduce their probable pollution of the water in the River basin. This will ensure the sustainability of the water resources.

Characterization of the Hydrochemistry, Scaling and Corrosivity Tendencies, and Irrigation Suitability of the Water of the Rivers Karawa and Iyiaji

“…Additionally, the decomposition of organic matter and free ranging cattle which come to drink water from the rivers within the area could have led to the high levels of nitrates. This observation was also made by Ngatia et al, [48]. According to Fadiran and Mamba [49], the major sources of accumulated nitrate and nitrite are non-point sources from excessive fertilizer usage or inadequate or untreated sewage.…”

“…Water samples were collected from two locations (Table 1) in each of the rivers (Aguobu Iwollo, Olo for the Karawa river and Ogbosu, Adaba for the Iyiaji river). A total of fortyeight (48) water samples were collected from the two rivers, comprising three samples from each sampling point, section, and sampling season (2019 and 2020). Water samples were collected during the early dry season (November-December) and late dry season (March-April), which are the periods when these river water are actually used by farmers for irrigation purposes (Figure 1).…”

“…Land use types can affect the spatial variation in nitrate sources [47]. Water samples are likely to have alterations in chemical composition due to microbial activities and chemical reactions [48]; hence, maintaining the pH by adding nitric acid prevents metabolic processes and adsorption within the samples. The surroundings of these rivers are dominated by informal settlements, which lack proper sewage disposal systems.…”

Sub-Liquid and Atmospheric Measurement Instrument To Autonomously Monitor the Biochemistry of Natural Aquatic Ecosystems

“…Temperature, pH, dissolved oxygen, total suspended solids, ammonia, nitrite, and nitrate concentrations have to be continuously measured to evaluate the permissible levels for aquaponic systems that provide information about the survival, growth, and food intake of fish. , Also, pH is an excellent indicator to observe the nutritional profile in freshwater fishery sectors, including calcium, magnesium, iron, manganese, and zinc, and monitoring the electrical conductivity, pH, and oxidation–reduction potential becomes vital in brackish water fish cultures . The same parameters can also be used to assess the quality of groundwater that could be compromised by anthropogenic activities, industrial effluents, , and algal bloom contamination. , …”

“… 39 , 40 Also, pH is an excellent indicator to observe the nutritional profile in freshwater fishery sectors, including calcium, magnesium, iron, manganese, and zinc, 41 and monitoring the electrical conductivity, pH, and oxidation–reduction potential becomes vital in brackish water fish cultures. 42 The same parameters can also be used to assess the quality of groundwater that could be compromised by anthropogenic activities, 43 industrial effluents, 44 , 45 and algal bloom contamination. 46 , 47 …”