TOWARDS EFFECTIVE PLANNING, DESIGN AND MONITORING OF DAMS IN NIGERIA

Besides serving as a center of tourist attraction, creating jobs for the unemployed, a rich source of fish and a fallback in times of drought, a dam also creates electricity from nothing other than the falling of water through its turbines. In Nigeria, like in many other parts of the world, dam projects are often seen as key to economic solution through hydroelectric power supply. The technology of dam construction in Nigeria is still experimental. There are so many unknown factors in dam design, construction and operation that may affect dam’s safety and performance. Relying on field experience from various parts of Nigeria, this paper examines the essential details necessary for consideration in dam planning and design using the complete and accurate information on the important variables such as technical, environmental, socio-cultural, economic or cultural factors. The results of these examined factors indicated that most of dam projects in Nigeria are not properly planned. The basic planning flaws include hydrologic, environmental and social factors which are seen by dam builders as obstacles to be ignored, covered up or surrogated to engineering in the project planning. Incorrect calculation of flood flows has lead to dam failures and reservoir siltation has drastically reduced the lifespan of dams, making one to conclude that the entire concept of dam safety as a design criterion is a new one. It appears that Nigeria will have to live with these flaws and some of these cost for sometimes to come. There is, therefore, the need for us to reduce these through proper planning, design and monitoring of our dams. It is recommended that a comprehensive dam safety study of all old dams (i.e. ≥ 20 years) be carried out. &nbsp

HUMAN HEALTH AND ENVIRONMENTAL RISK ASSESSMENT OF THE ALAKIA INDUSTRIAL DISTRICT OF IBADAN, SOUTH WEST NIGERIA

A scientific survey was conducted in February 2002 in three communities (Majawe, Osun-Abolowojaiye and Papa Adogba) communities of Alakia Industrial district of Ibadan to determine the extent of the damages caused by the negative impact of the industrial effluent discharges into the Elesin stream and emissions of gaseous pollutants into the atmosphere within the three communities. A socio-economic survey was also carried out to establish the impact(s) on human and livestock populations of the study area. A sample of non-affected areas served as control for comparison. The degree of pollution was established by the determination of the concentrations of the metals including Pb, Ca, N, K, Cd, Fe, Zn, Ca, Cr, Mn, Na, Mg, a specific non metal phosphorus as well as chlorides (Cl-) and Nitrates (N03-). The study established the presence of metals in concentrations higher than the recommended limits in effluent discharges in all the samples in the study area and a clear link between the effluent discharges and pollution with its severe damages in the area

QUALITATIVE AND QUANTITATIVE ASSESSMENT OF RAINWATER HARVESTING FROM ROOFTOP CATCHMENTS: CASE STUDY OF OKE-LANTORO COMMUNITY IN ABEOKUTA, SOUTHWEST NIGERIA

Quantitative and qualitative assessment of Rainwater harvesting system from rooftop runoff from acatchment at Oke-Lantoro Community in Abeokuta, Southwest Nigeria was determined using eightroof designs in respect to slope and six selected roofing sheet materials respectively. The resultshowed that the steeper the roof slope the more the rainwater harvested irrespective of rainfall amountand duration. The roof pattern with a large and steep slope designed with gutter tends to harvest morewater and at a higher rate. Physico-chemical analysis of the harvested water samples gave resultswhich varied from various drinking water quality regulatory standards. Sample from galvanized roofingsheet was influenced by zinc and lead in quantity beyond human consumption level, while the asbestosroofing sheet water sample gave higher calcium and magnesium contents which reflected in thetotal hardness value. Sample from the aluminum roofing sheet gave the best result but it was alsoaffected by the influence of atmospheric dust particles and faecal materials of birds, lizards and othersmall organisms. Considering the results of the physico-chemical tests, the harvested water samplescould be put to other domestic uses, as they cannot be consumed directly

Spatial Variation of Throughfall in Two Tree Plantations in Abeokuta, South-Western Nigeria

Abstract This paper determined the variability of throughfall in two tree plantations on the campus of University of Agriculture, Abeokuta, South Western Nigeria. It involved the use of experimental plots consisting of Tectona Grandis and Gmeliba Arborea. Gross precipitation and thoughfall were measured and determined for a month. The data obtained was analysed using simple descriptive statistics such as means, percentages and frequency counts. Correlation analysis was used to determine the relationship between gross precipitation and throughfall under each tree plantation. Results show that Tectona plantation had more throughfall throughout the period of study than that of Grnelna plantation. Also there is a strong relationship between gross precipitation and throughtfall in the two plantation. The implication of the results for the management and use of water resources in the study area were discussed and recommendations made as to how water trapped through interception can be better managed

Assessment of Problems Affecting Public Water Distribution in a Humid Tropical Zone

Abstract The paper determined the extent to which residents in Iju-Ishaga southwest, Nigeria (a rapidly developing fringe settlement in Lagos) differ in their assessment of major problems affecting the distribution of public water supply based on some socio-demographic variables such as gender, marital status and socio-economic background. The study made use of 240 respondents (133 males and 107 females) spread over the eight wards in the local government. Data collection involved the use of a questionnaire while its analysis employed the use of frequency counts and t-test statistic in the assessment of the respondents about the problems affecting the distribution of public water in the study area. The implications of the findings were identified and recommendation made on how to ensure effective public water supply in Iju-Ishaga

Analytical Investigation of Pollutants in Lagos Coastal Waters, Nigeria

Abstract This paper deals with pollution aspect of environmental management and monitoring of the continental shores of the Lagos Lagoon for its sustainable development. The water quality assessment of coastal waters, at the principal locations of the lagoon susceptible to high level of pollution in the Ebute-Metta and Eti-Osa axis of the Lagos Lagoon was performed. Assessment was undertaken according to different physical and chemical parameters including biological oxygen demand (BOD), Dissolved oxygen (DO), electric conductivity (EC), total suspended solids (TSS), Alkalinity, Acidity, Total hardness (TH), grease content, major cations and anions, and some heavy metals. Results showed that the Shores of the Lagos lagoon at the Iddo and C.M.S axis becomes progressively polluted by the waste materials discharged along its course. Thus, Lagoon at these locations currently faces a number of serious environmental and ecological challenges. Urbanization and high commercial activities at this axis of the Lagoon contributed to the water quality deterioration with regional consequences on the aquatic ecosystem and on the health of the down stream's user groups. This synergetic effect is of concern for the sustainable use of the resources

Estimation of Water Balance of Oyan Lake in the North West Region of Abeokuta, Nigeria

The paper presents results related to water balance of the Oyan Lake in the North West in Nigeria. The catchment covering an area of 9000 km2 includes a small dam called Oyan dam having an effective watershed area of 40 km2 with a gross storage of 270 million cubic meters. Hydrology of the area was characterized on the basis of land use, rainfall, temperature, evaporation, evapotranspiration, and runoff using meteorological data. Different methods like rainfall coefficient method is used to determine monthly distribution of rainfall including rainy and dry months; Penman method to calculate evaporation from the reservoir; Thornthwaite method and Thornthwaite water balance model to determine potential and actual evapotranspiration; and runoff coefficient method to estimate runoff. The catchment is characterized by one rainy season and two dry seasons during the year. The rainy season has five months duration and dry season seven months. The mean annual rainfall of the catchment is 1015.09 mm, out of which rainy season accounts for 96.% and the dry season for 3.9%. The total annual water loss by evaporation from the reservoir is 1178.5 mm. The mean annual actual evapotranspiration for the catchment is 899.3 mm. The mean annual runoff generated from the catchment is estimated to be 822.2 million cubic meters. The amount of water that percolates into the ground in the catchment as groundwater is estimated to be about 219.9 million cubic meters, and the same at the reservoir site is 826.9 million cubic meters. The total amount of water which is actually available to recharge the groundwater within the catchment is 1046.8 million m3