Physicochemical limnology of Lake Kubanni, Zaria-Nigeri

C.E. Mbah (7230077)

J.A. Adakole (7230074)

M.A. Dalla (7230080)

English

Loughborough University Institutional Repository

ADAKOLE, MBAH and DALLA16529th WEDC International Conference Abuja, Nigeria, 2003Physicochemical limnology of Lake Kubanni, Zaria-NigeriaJ.A1 Adakole, C.E. Mbah,  and M.A. Dalla, NigeriaTOWARDS THE MILLENNIUM DEVELOPMENT GOALSTHE QUALITY OF any water body is governed by its physi-cochemical factors. The monitoring of physicochemicalcharacteristics of a water body is vital for both long termand short analysis (Wood, 1995). Distribution and produc-tivity levels of organisms are largely determined by physi-cochemical factors (Ashton and Schoeman, 1983; Adakoleet al., 1998).The direct effect of interactions of many frequentlymeasured water quality parameters with biotic compo-nents that affect productive potentials of fish species havebeen demonstrated (Kemidirin, 1993; Adakole et al., 1998;Adakole, 2002).Kubanni lake, constructed primarily for domestic watersupply, receives various domestic and agricultural effluentsthrough its major tributary (Samaru stream) and this couldaffect the water quality. Variations in physicochemicalparameters of a water body could significantly influencethe water’s treatment processes, portability of the watersupply as well as have long term effects on the biota in theaquatic environment(WHO,1971; Adakole et al.,1998).The objective of the present study is therefore to investigatethe physicochemical variations of lake kubanni and itstributaries.Materials and methodsStudy area and sampling stationsKubanni lake, also called Ahmadu Bello University dam, isconstructed on river Kubanni and supplies water to theUniversity community. The lake (reservoir) catchment’sarea is 57Km2, its width is 122 meters (400 feet), and themean depth is 6 meters. The lake is located approximatelywithin latitude 11O11’N and longitude 7O38’E in Samaru-Zaria, Kaduna state. It is located within the premises ofAhmadu Bello University, main campus. The lake’s twomajor tributaries are the Kampagi and Samaru streams.Kampagi stream, which originates from a rural settlement,has a seasonal flow whereas Samaru stream that originatesfrom a semi-urban settlement has an all-year-round flowdue to its sustenance by urban runoffs and seepages.Five sampling stations were chosen for the study, two oneach stream at 500m apart before discharging into theLake. The fifth station was located below the dam’s dyke.Physicochemical analysisSurface water samples were collected in plastic bottlesbiweekly from each station for a period of 4 months (Aprilto July, 1999) for determination of those physicochemicalparameters that could not be determined on the field. Thetemperatures of the air (2m above water level), surfacewater (1cm below water surface) and water depth (1mbelow water surface) were determined in the field using amercury thermometer. Transparency was determined us-ing a Secchi disc. Hydrogen ion concentration (pH) andelectrical conductivity by using Kent Eil 7055 pH meter andJenway 4010 conductivity meter models respectively. Totaldissolved matter was analyzed as described by Lind,(1979).Dissolved oxygen, BOD, total alkalinity and total hardnesswere determined by burette titration (APHA, 1985).The statistical analysis was carried out using the Gensatrelease 4.03 package. Statistical procedures used includesummary statistics and analysis of variance (ANOVA).ResultsThe atmospheric, water surface and water depth tempera-tures, ranges were 24 – 30OC, 24 – 28OC and 22.50 –27.0OC respectively (Table 1). Analysis of variance for allthe temperatures revealed that there were high significantvariations (P < 0.01) among the weekly means, however,among the stations, the variations were not significant (P >0.05). The mean transparency of the lake was27.27±18.40cm, with the Lake water mean showing ahigher transparency values throughout the study period.There was a significant variation (P < 0.05) among theweekly values while a highly significant variation (P < 0.01)exists between the stations. The least total dissolved matter(65.00mg/l) was recorded in station 1 in week 1, whereasthe highest value (293.80mg/l) was recorded in station 3 inweek 4.  The variations in both biweekly and station meansof total dissolved matter values were highly significant (P <0.01). The electrical conductance of the sampling stationsis in this order of increasing magnitude: station 1 < station2 < station 5 < station 4 < station 3. The fluctuations inelectrical conductivity correlate positively with the totaldissolved matterDuring the study period, the biweekly mean pH valuesrevealed acidic conditions (pH6.6 to 6.91), whereas thestation mean range was circumneutral (pH6.34 to 7.12.There was no significant variation (P > 0.05) among thebiweekly means. However, a high significant variation (P <0.01) was observed among the station means. The meandissolved oxygen for Kubanni lake was 7.04±1.80mg/l.Both the least (2.70mg/l) and highest (9.40mg/l) dissolvedoxygen concentrations were recorded in station 5 in weeks1 and 5 respectively. The biweekly mean ranges between3.30 to 9.10mg/l There were high significant variation (P <ADAKOLE, MBAH and DALLA1660.01) in both station and biweekly means of dissolvedoxygen. The station mean biochemical oxygen demandranged between 1.00 to 3.90mg/l. The mean biweeklytotal hardness ranged from 95.20 to 210.40mg/l.CaCO3in weeks 1 and 5 respectively while the station mean valuerange from 118.90 212.80mg/l. CaCO3 for stations 1 and3 respectively. The peak total alkalinity (180.00mg/l.CaCO3) was recorded in station 3. All the other station valueswere generally below 130.00mg/l.CaCO3.DiscussionFluctuations in surface and water depth temperaturesclosely follow air temperatures in all the sampling stations.Certain taste and odor producing organism grow morereadily at a temperature range of 16 to 20OC. Hencerecommendation for any acceptable limit should be guidedby the temperature requirement at a specific localitynecessary to preserve normal species diversity and preventundesirable growth of nuisance organism (WHO, 1971;Patra and Azadi, 1985; Umeham,1989; Jonnalagadda andMhere, 2001). The measured temperature of the waterreflected the rainy season, which undoubtedly affected thetemperature probably by lowering the solar radiationduring the cloudy rainy months. The significant correla-tion in both the biweekly and station means of transpar-ency showed that the materials that determined the trans-parency level of the lake originated from the disturbanceof the lakes basin. The persistent high transparency ofstation 5 is attributed to its depth, large water volume andlow velocity. Turbidity caused by the hydrous oxides of Feand Mn is objectionable in domestic water and may requirespecial treatment for removal (Krenkel, 1974). Turbidity isnot necessarily harmful to fish (Ayodele and Ajani, 1991);however, the resulting reduction of sunlight intensity in thewater decreases the productivity of a water body. The higherdissolved matter loading of Samaru stream (stations 3 and4) than Kampagi stream (stations 1 and 2) is due to thedischarge of various domestic and agricultural effluents intoSamaru stream in contrast to Kampagi stream that passesthrough relatively undisturbed vegetation. The variations inelectrical conductivity and total dissolved matter were simi-lar.). The electrical conductance of Kampagi stream (126.88± 6.82mS/cm) was lower than that of Samaru stream(330.31± 31.37mS/cm). At low levels of electrical conduct-ance, major ions may determine the nature of the fauna(Moss, 1993).The lake’s mean pH (6.78 ± 0.03) makes the lake waterquite suitable for fish production and for domestic uses.Freshwaters with a pH range of 6.0 to 9.0 have been notedto be productive and thus recommended for fish culture(Adeniji, 1986). Outside this range water may have sourtaste and could be corrosive to metals. Unpolluted waterbodies normally show a near neutral or slightly alkaline pH.Dissolved oxygen increases the palatability of water becauseof its ability to remove undesirable taste. A dissolved oxygenconcentration of not less than 5.0mg/l is required to sustainTable 1. Statistical summary of results obtained for kubanni lake and its tributaries Parameters Grand  Mean   Standard Deviation   Standard Error   Minimum Maximum Median Atmospheric temperature (OC) 26.63 1.53 0.24 24.00 30.00 26.00 Water surface temperature (OC) 25.91 1.17 0.19 24.00 28.00 26.00 Water depth temperature (OC) 25.32 0.94 0.15 22.50 27.00 25.00 Transparency (Cm)  27.27 18.40 2.90 5.00 65.00 20.00 Total dissolved matter (mg/l) 165.10 69.21 11.00 65.00 293.80 149.73 Electrical conductivity (µS/cm) 256.80 107.80 17.00 100.00 452.00 236.50 pH 6.78 0.30 0.05 6.16 7.50 6.80 Dissolved oxygen (mg/l) 7.04 1.80 0.29 2.70 9.40 7.85 Biochemical oxygen demand (mg/l) 2.14 0.64 0.10 1.00 3.80 2.10 Total hardness (mg/l.CaCO3) 172.50 61.18 19.70 72.00 288.00 180.50 Total alkalinity (mg/l.CaCO3) 78.90 34.00 5.40 19.00 179.00 83.50 ADAKOLE, MBAH and DALLA167fish and other aquatic life in water bodies (Adeniji, 1986;Ayodele and Ajani, 1991; Adakole, 2000). Thus the 7.04± 1.80mg/l dissolved oxygen concentration of the Kubannilake points to the relatively clean condition of its waterquality. Presence of dissolved oxygen in good quantity inwater bodies have the tendency of improving the waterquality by oxidizing poisonous gases such as hydrogensulphide and ammonium into their non poisonous forms.BOD values indicate the extent of organic pollution in anaquatic system, which adversely affect the water quality(Jonnalagadda and Mhere, 2001). The BOD of unpollutedwaters is less than 1.00mg/l ; moderately polluted (BOD 2.0– 9.0mg/l) while heavily polluted waters have BOD morethan10.0mg/l(Adakole,2000). Consequently Kubanni lake andits tributaries is regarded to be moderately polluted duringthe study period. Pollution by organic maters is verycomplex as it involves not only the deoxygenation of thewater but also the addition of suspended solids, the organicmatter itself and poisons such as ammonia (Adakole,2000;Jonnalagadda and Mhere, 2001). Based on water hardnessclassification by Lind (1979), the waters of the lake (119.75± 13.87mg/l.CaCO3) and those entering the lake fromSamaru stream (171.56 ± 28.26mg/l.CaCO3) and  Kampagistream (147.50 ± 54.49mg/l.CaCO3) were all moderatelyhard. The mean alkalinity obtained for Kubanni lake(78.90 ± 5.40mg/l.CaCO3) compares unfavorably with themean(212.67 ± 37.69mg/l.CaCO3) recorded by Umeham(1989).Since it is recognized that in-lake processes can generatemore alkalinity in dilute, oligotrophic lakes than can besupplied from the lake’s catchments (Psenner, 1988;Schindler, 1988), the low alkalinity recorded during thisstudy may be attributed to size and temperature differenceof the two lakes. Alkalinity in excess of alkaline earth metalconcentrations is significant in determining the suitabilityof water for irrigation while an alkalinity range of 20 – 40mg/l.CaCO3 is recommended for domestic purposes (WHO,1971; Dillon et al., 1997)ConclusionKubanni lake water quality is influenced by its tributaries.The lake water quality is suitable for irrigational, aquacultural and domestic purposes in terms of most of thephysico-chemical parameters analyzed. However, consid-ering that the lake is a source of drinking water, thepollution potential of the tributaries gains significance.Hence, there is need for an effective pollution controlprogram of the tributaries.ReferencesAdakole, J.A. (2000). The effects of domestic, agriculturaland industrial effluents on the water quality and biota ofBindare stream, Zaria – Nigeria.  PhD Thesis, Depart-ment of Biological Sciences, Ahmadu Bello University,Zaria, Nigeria.  256pp.Adakole, J.A., Balogun, J. K and Lawal, F.A. (1998). 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Constructed wetland in water pollutioncontrol fundamental to theirs understanding. Water sci-ence and Technology. 32(3): 21 –29Adakole, J.A1.,Mbah, C.E.Dalla, M.A. (drjaadakole@yahoo.com)Footnote1Department of Biological Sciences, Ahmadu Bello Univer-sity, Zaria

Physicochemical limnology of Lake Kubanni, Zaria-Nigeria

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Physicochemical limnology of Lake Kubanni, Zaria-Nigeria

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