Research Article - (2020) Volume 7, Issue 1
Received: 07-Feb-2020
Published:
11-Mar-2020
, DOI: 10.37421/jreac.2020.7.264
Citation: Kitur Esther, Kotut Kiplagat and Richard Kerich. "Variations in the Physico-Chemical Characteristics of Water in Five Peri-Urban Reservoirs in Kiambu and Nairobi City Counties, Kenya". J Environ Anal Chem 7 (2020) doi: 10.37421/jreac.2020.7.264
Copyright: Esther K, et al. This is an open-access article distributed under the terms of the creative commons attribution license which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
Information on reservoirs is important as it forms a vital baseline for among others the detection of undesirable changes in water quality. Variations in the physicochemical characteristics of water were investigated in five peri-urban reservoirs Uhuru reservoir located in Nairobi City County and Ruiru, Ngewa, Comte and Kianjjibbe in Kiambu County between February 2014 and January 2015. The aim of the study was to establish the quality of water. Mean Secchi depth recorded in cm was 0.7 ± 0.9 in Uhuru, 0.9 ± 0.43 in Ruiru, 0.1 ± 0.04 in Ngewa, 0.1 ± 0.6 in Comte and 0.3 ± 1.3 in Kianjjibbe. Mean temperatures in °C were 23.8 ± 1.8 in Uhuru, 21.6 ± 2.2 in Ruiru, 24.3 ± 2.9 in Ngewa, 23.4 ± 1.6 in Comte and 24.0 ± 1.9 in Kianjjibbe. Electrical conductivity in μS cm-1 was 90.4 ± 23.81 in Uhuru, 45.8 ± 5.7 in Ruiru, 195.5 ± 37.3 in Ngewa, 113.3 ± 20.5 in Comte and 298.94 ± 41.5 in Kianjjibbe. pH was 7.4 in Uhuru and Ruiru and 7.2, 7.3 and 7.7 in Ngewa, Comte and Kianjjibbe respectively. Dissolved oxygen in mgL-1 was 7.1 ± 0.7 in Uhuru, 7.1 ± 0.26 in Ruiru, 6.2 ± 1.1 in Ngewa, 7.6 ± 1.1 in Comte and 9.0 ± 0.8 in Kianjjibbe. Total alkalinity in mgL-1 CaCO3 was 35.5 ± 8.8 in Uhuru, 18.0 ± 0.24 in Ruiru, 83.9 ± 7.9 in Ngewa, 41.1 ± 8.9 in Comte and 110.2 ± 15.9 in Kianjjibbe. Nitrate nitrogen μg L-1 was 9.8 ± 1.37 μg L-1 in Uhuru, 9.0 ± 12.5 in Ruiru 4.2 ± 0.43 in Ngewa, 7.1 ± 5.56 in Comte and 13.6 ± 1.14 in Kianjjibbe. Total nitrogen in μg L-1 was 33.1 ± 22.7 in Uhuru, 39.8 ± 3.0 in Ruiru, 34.1 ± 22.5 in Ngewa, 40.5 ± 36.9 and 32.5 ± 28.7 in Comte and Kianjjibbe reservoir respectively. Total phosphorus in μg L-1 in the reservoirs was 0.8 ± 0.14 in Uhuru, 1.0 ± 0.02 in Ruiru, 1.0 ± 0.77 in Ngewa, 1.0 ± 0.82 in Comte and 2.7 ± 0.25 in Kianjjibbe. Soluble reactive silica in mgL-1 was 3.4 ± 0.47 in Uhuru, 4.0 ± 0.64 in Ruiru, 7.3 ± 0.7 in Ngewa, 5.9 ± 0.15 in Comte and 7.0 ± 199 in Kianjjibe. Peak values of total nitrogen and total phosphorus were recorded during the wet season while high soluble reactive silica was recorded during the dry season. There was a significant difference in all measured physcio-chemical parameters between the reservoirs (p<0.001, df=59). The study concludes that the reservoirs investigated varied in levels of physico-chemical properties. The variation was attributed to differences in rainfall, volume of outflow and use dynamics of the water of the reservoir.
Reservoir • Physcio-chemical parameters • Water quality
Water is a vital element among the natural resources [1]. It is critical for the survival of all living organisms including man, food production, economic development and as the sustenance of life on earth [1,2]. Globally, today many cities are faced with acute shortage of water, 40% of food supply is grown under irrigation and a variety of industrial processes depend on water [1]. The environment, economic growth and development are highly influenced by the quality of surface water and its seasonal availability [1]. According to WHO [3], the quality of drinking water is a powerful environmental determinant of health and therefore adequate supply of safe drinking water is universally recognized as a basic human need and a main source to fulfil diversified needs such as drinking, cooking, washing, irrigation, use in industries and farming [4]. Currently more than 1.2 billion people have no access to drinking water, 1.3 billion have inappropriate sanitary services, more than 200 diseases have been associated to contaminated water while about 6,000 people mostly children die daily from diarrhea diseases in peri-urban setups [5]. The quality of water is affected by human activities and Rivers Rwaka and Ithanji are main sources of water in the area has declined due to rise in urbanization, population growth, change in land use pattern and industrial production. Polluted water is a threat to human health and aquatic organisms [1,5]. Lack of water is considered as socio-economic obstructive factor of a country [3]. Many Communities in the world are increasingly turning to reservoir water for their needs.
Reservoirs are surface water bodies which are nourished by river bodies. Pollution of rivers is critical because of the inadequacy or non-existence of surface water quality protection measures and sanitation [1]. The wastes from human activities are disposed into rivers with little regards to their assimilative capacities and pollutants may go long distances before being diluted and may end up in the reservoirs thereby threatening food production, environment and human health. The quality of water is a function of either or both natural and human activities and the continued consumption of untreated or contaminated water is expected to pose short or long term health implications [1]. Therefore the evaluation of reservoir water quality is essential for the development of civilization and to establish database for future water resource strategic planning and development, management and conservation of water [6]. Studies on reservoir water have been conducted on hydroelectric power production reservoirs in Kenya but no comprehensive study has been conducted on reservoir in pre-urban areas where water is used for domestic purposes and for urban irrigation. In the study, the physicchemical parameters of water of pre-urban reservoirs were measured. A healthy aquatic ecosystem depends on the physic-chemical and biological contaminants of water [6]. The objectives of the study were to find out the variations in water quality parameters in the pre-urban reservoirs and whether the parameters vary with seasons.
Study area
The study area covers five reservoirs located in Nairobi city and Kiambu counties. Uhuru reservoir within Nairobi city county (commercial area), is located between latitude 36°57′E and 36°58′E, longitude 1°58′S and 1°57′S. It lies at an altitude of 1800 m above sea level and receives its water from Ngong River. Ruiru, Comte and Kianjjibbe reservoirs are located in Kiambu County (an agricultural area). Ruiru reservoir lies between latitudes 1°85′S, 1°85′S and longitudes 36°65′ 36°66′E. It receives its water through Kimaiti, Ruiru, Ngeteti, and Gitindo rivers. Comte reservoir lies between latitude 1°76′S, 1°75′S and longitudes 36°, 63′ and 36° 64′ E’ and Kianjjibbe lies between latitudes and 1°, 76′S, 1°, 75′S and longitudes 36°, 63′E, 36°, 64′E. Comte and Kianjjibbe reservoirs receive their water through Kianjjibe river. Ngewa reservoir in Thika district within Kiambu county lies between latitudes 1°78′ S, 1°, and 77′S, longitudes 36°, 65′ 36° 66′ E. It receives its water through Gaia. Gaia has two tributaries, Ngewa and Choomba Rivers (Figure 1).
Figure 1. Map showing the location of Uhuru, Ruiru, Ngewa, Comte and Kianjjibbe reservoirs (Map drawn from the Map of Kenya, 2003).
Data collection and statistical data analysis
Water samples were collected from the reservoirs for a period of one year. Water was collected from a depth of 20 cm using a water scooper. In Uhuru and Ruiru reservoirs water was collected from the centre of the reservoirs, this was possible with the use of a boat, in the other reservoirs where accessibility to the centre was not possible the water was collected near the dam wall away from the influence of the inflowing rivers. The water was transferred into 500 ml plastic containers and transported to Kenyatta University environmental science laboratory for analysis. No preservatives were used as the water was analyzed within 24 hours. The physical parameters, electrical conductivity (μS cm-1), temperature, dissolved oxygen were measured in the field using a conductivity probe (Type TetraCon 325) of a multiline meter (WTW, Weilheim-Germany) with automatic temperature compensation to 25°C. Secchi depth was determined using a secchi disc [7]. In the laboratory, total alkalinity was determined titremetrically using 0.02 N standard H2SO4 and with mixed methyl red bromcresol indicator [7]. Nitrite nitrogen NO2-N, total nitrogen (TN), orthophosphate phosphorus PO4-P, total phosphate and soluble reactive silica (SRS) were determined colorimetrically using UV/VIS spectroscopy machine T80+ [7]. Data analysis was done using a computerized statistical programme (STATISTICA 8.0, 2007). The data was subjected to one way analysis of variance (ANOVA) and significant differences accepted at (p ≤ 0.001). Where significant difference was found, the mean valves were separated using posthoc Tukey’s (HSD) test. Descriptive statistics for all collected data was also obtained using STATISTICA software.
The study revealed variations in the physic-chemical parameters of water in the peri-urban reservoirs. There is a clear sign of the impacts of anthropogenic activities within the reservoirs and the impacts of the anthropogenic activities on the quality of water vary with seasons. Therefore it is concluded that good farming practices around the reservoir catchment and regular monitoring of water quality is highly recommended.
I give special thanks to Managing Director SOCFINAF Company Ltd and Director Water and Sewerage Department of Nairobi County Council and the staff for granting me access to the reservoirs, their co-operation and assistance during sample collection. Special thanks to Mr. Mwangi of the Department of Plant and Microbial Science, Kenyatta University both in the field and in the laboratory.
Journal of Environmental Analytical Chemistry received 1781 citations as per Google Scholar report
