Assessment of the Water Quality of the Oti River in Ghana
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Assessment of the Water Quality of the Oti River in Ghana A. Abdul-Razak1*, A. B. Asiedu2, R. E. M. Entsua-Mensah1 and K. A. A. deGraft-Johnson1 1 CSIR-Water Research Institute, P. O. Box M.32, Accra, Ghana 2 Department of Geography and Resource Development, University of Ghana, Legon, Accra, Ghana *Corresponding author; E-mail: [email protected] Abstract Oti river, an important tributary of the Volta lake in Ghana, was chosen as a case study to investigate the variations in the quality of its water at different locations. This was necessitated by the people’s reliance on the river for their domestic and agricultural water use. Composite water samples drawn from some sections of the Oti river were analysed in the laboratory for certain parameters to enable assessment of water quality. The observed results of the laboratory analyses are compared with the 2003 Ghana Raw Water Criteria and Guidelines for domestic use. The results indicated that turbidity, total iron, faecal coliforms and total coliforms were above the limits set out by the 2003 Ghana Raw Water Criteria and Guidelines for domestic use. Thus, the water from Oti river was considered unsuitable for direct human consumption at the sampled locations. Using the Water Quality Index (WQI) Calculator 1.0, the WQI for Oti river was calculated to be 39.3. The WQI indicates that water quality in the Oti river was poor. This implies that the water quality is almost always threatened or impaired; conditions usually depart from natural or desirable levels. Public awareness with respect to the need to boil and/or filter the water before drinking is called for. Sanitary facilities to control river pollution and appropriate water treatments techniques are required in the area to improve the welfare of the riparian dwellers. Introduction Water quality monitoring is an essential tool used by environmental agencies to gauge the quality of surface water and to make management decisions for improving or protecting the intended uses. The Oti-arm of the basin contributes up to about 40% of the total volume of water in the Volta lake (Moxon, 1968; GEF-UNEP, 2002.). Evaluations of Oti river water quality conditions are often limited in scope and spatial extent due to the length and size of the river, insufficient monitoring resources, and its multi-jurisdictional nature. The Oti basin is affected mainly by both domestic and agricultural activities. Pollution is generally slight and localized along the banks owing to indiscriminate disposal of untreated faecal matter and garbage, because of lack of adequate sanitary and waste disposal facilities (WRC, 2000). The environmental issues arise from the improper management and control of domestic, municipal, agricultural and industrial wastes which find their way into the water bodies, as well as from erosion in river catchments as a result of clearing for farming, timber, and extraction of firewood, among others (WRC, 2000). The ever-increasing demands that the society places on the ecosystem of the Oti river basin, coupled with the need to generate useful and convincing information in the design of socially optimal decisions for public intervention give good reason for the study. The overall aim of the study was to determine the status of the Oti river water quality. The specific objectives of the study were: 1. To study the physico-chemical and bacteriological characteristics of the Oti river; 2. To propose recommendations for the efficient management of the river ecosystem. Materials and methods Study area The study was conducted in the Oti arm of the Volta river basin. The Oti river begins in the Atakora Mountains at Boom, a forest reserve in Northern Benin, as River Pendjari. It passes through, and flows along, the border of Burkina Faso with Benin, Northern Togo highlands to Ghana, and finally drains into the Volta lake to the east of Kete Krachi (Fig. 1). West African Journal of Applied Ecology, vol. 15, 2009 Fig. 1. Map of Ghana showing the Oti arm of the Volta basin The Oti basin is found along the eastern fringes of the Northern Region of Ghana, across the middle belt to the northern portions of the Volta Region. Latitudinally, it extends from about 10o 50’ N to around 7o 30’ N. It covers parts of Nalerigu, Gushiegu, Cheriponi, Yendi, Bimbila, Salaga and the whole of Saboba and Zabzugu townships in the Northern Region, and parts of Kete-Krachi Local Council in the Volta Region. The total area of the basin is 17,942 km2 and a total length of 936.7 km. The Oti basin in Ghana falls mainly in the Rural Savanna Geographic Division, which contributes up to 45.5% to national poverty levels (GSS, 2000). The mean annual inflow of the river into Ghana is about 276 m3/s (Opoku-Ankomah, 1998; WARM, 1998). It has a permanent flow, though most of its tributaries dry up during the dry season. The tributaries in Ghana include So, Mo and Kpasa rivers. Land-use is mainly extensive bush fallow and grazing (GEF-UNEP, 2002). The study district was the Zabzugu-Tatale District of the Northern Region of Ghana. The Sabari and Oti townships were the sampling locations. Climate and vegetation The climate of the Northern Region is relatively dry, with a single rainy season that begins in May and ends in October. The amount of rainfall recorded annually varies between 750 mm and 1050 mm. The dry season starts in November and ends in March/April, with maximum temperatures occurring towards the end of the dry season (March-April) and minimum temperatures in December and January. The harmattan winds, which occur during the months of December to early February, have considerable effect on the temperatures in the region, which may vary between 14 ºC at night and 40 ºC during the day. Humidity, however, which is very low, mitigates the effect of the daytime heat. The main vegetation is classified as vast areas of grassland, interspersed with Guinea savanna woodland, characterized by drought-resistant trees such as the acacia, baobab, shea, dawadawa, mango and neem (GSS, 2005). West African Journal of Applied Ecology, vol. 15, 2009 A reconnaissance survey of the sa were earmarked, namely upstream and major activities in the sampling area whilst downstream Water samples were collected on a bimonthly basis for a period of 6 months (December–May). At each sampling point, a clean 1-litre polyethylene sample bottle in the laboratory for off site analysis. For dissolved collected into 300 ml plain glass bottles and thempling DO fixedpoints using was thecarried azide out modification in November of Winkler’s2005. Two method. sampling sites Samples for biological oxygen demand (BOD) were co downstream. Upstream site was suppo subsequent DO determination. Samples for bacteriological bottles. The water samples were kept at 4 ºC in ice chest and tr CSIR-Water Research Institute, Tamale, on the same point was after most of the major activities. appropriate labels on them, and record was made of in the laboratory, to avoid external contamination oxygenwas (DO)filled withdeterminations, water. Thissed separatewas, to be subsequently, the samples point beforewere used any All the analyses were based on standard methods as prescribed in the APHA turbidity with a HACH 2100 P Turbidimeter. Sodium llected into dark glass bottles for incubation and photometry, trace metals by atomic absorption spectrophotometer, calciumanalyses andwere magnesiumcollected into by sterilized EDTA plain glass titration, sulphate by the turbidimetric met et al ansported to the laboratory of the field station of the Other analyses included alkalinity. (1998). by Conductivitystrong acid wastitration measured daymethod. of with collection Nutrients for (nitrate-nitrogen analysis. Sampling and bottles had phosphate-phospho-rous) were determ each bottle. The samples were refrigerated, upon receipt nesslerisation and spectrophotometric determination at 410 ornm. deterioration, Fluoride was until determined the time of by the the analysis. SPADNS method. Total and faecal coliforms were determined by membrane filtration method using M-Endo-Agar Les (Difco) at 37 °C and on MFC Agar at 44 °C, respec appropriate to each water quality parameter, as establish relations between parameters in the Densu b executed by SPSS (version 12 for Windows, year 2003).hod, and chloride byand argentometric potassium were titration. measured by flame emission Each sample was analyzed for the following inedparameters: using Dionex-80 ion analyzerCybersan and ammonium 510 conductivity by direct meter and sulphate, nitrate-N, phosphate, fluoride, total hardness, coliform and faecal coliform. The values of these parame and Guidelines (WRC, 2003). The physico-chemical and bacteriological characteristics tively. Pearson’s rank correlation was also used to Tables 1 and 2. asin. All tests were two-tailed. The analyses were variations during the sampling months. The parameters are discussed based on varia dissolvedpH, oxygen,conductivity, BOD, turbidity,total iron, alkalinity, manganese, chloride, total ters were compared to the Ghana Raw Water Criteria Results and discussion 80 70 of Oti river are presented in Fig. 2a and 2b, and 60 Physical Parameters tions upstream and downstream, as well as 50 40 Value 30 20 10 0 pH Conductivity (µS/cm) Turbidity (NTU) West African Journal of Applied Ecology,December vol. upstream February upstream May upstream Alkalinity (mg/l) Total Hardness (mg/l) Fig. 2a. Physical parameters of the Oti river DecemberDis downstreamsolved Oxygen (mg/l) February downstream May downstream 15 , 2009 Chemical Parameters 2.5 2 1.5 1 Concentration (mg/l) Concentration 0.5 0 D e 0 0 -N te on e O rid /1 /1 te a Ir es B o de te ra ph al an lu ri ha it os ot g F hlo lp N h T an C Su P M December upstream December downstream February upstream February downstream May upstream May downstream Fig.