Special Publication of the Nigerian Association of Hydrological Sciences

Cover Page

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Title Page

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Table of Content

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Reviewers

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Citation

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Preface

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FLOOD MANAGEMENT

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An Assessment of Flood Risk Perception and Response in Jalingo Metropolis, Taraba State, Nigeria

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Flooding is now an annual occurring event in Jalingo metropolis especially after heavy rainstorm which is further worsened by the nature of topography of the area. The study area consist of undulating plain interrupted in places by low rising hills as well as poor/inadequate drainage network. The knowledge of the public flood risk perception is considered a crucial aspect in modern flood risk management as it steers the development of effective and efficient flood mitigation strategies. This study examines the level of individual flood risk perception and behavioral response in Jalingo Metropolis. The survey design method was employed in this study. This involves interviewing people living in the study area using structured questionnaires. 252 respondents were randomly selected from three of the most affected areas in the Metropolis. These include Mallam Gabdo, Mafindi and Low cost areas. In each ward/unit, 84 structured questionnaires were administered. Descriptive statistics were used to analyze the data. The result of the findings shows that 23.7% of the respondents were aware that the area was prone to flooding, while 76.3% were not aware. Also about 67.6% of the respondents said that they have evacuated their houses and shops to flooding in the area while 32.4% have never evacuated their houses or shops to flood problems in the area. This study recommends the need to educate the people living in the flood plain on the dangers of continuous occupation of the area.

Assessment of Urban Flood Disaster: A Case Study of 2011 Ibadan Floods

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Increase in both precipitation due to climate change and imperviousness due to urbanization coupled with encroachment in to areas liable to floods have continued to increase the frequencies and risk to floods in urban centres of the world. In the developing countries indiscriminate dumping of refuse and siltation in waterways and drainage system are common practices, which reduce the carrying capacities of the stormwater channels and increase the risks of flooding and associated hazards. Ona River and its tributaries in Ibadan city was hit by floods in 2011, the University of Ibadan, the Eleyele and IITA dams were at the receiving end. Many communities downstream suffer serious damages and over 100 lives were lost. This paper reviews the immediate causes and possible measures to prevent further occurrence.

Development of Intensity Duration Frequency (IDF) Curve for Parts of Eastern Catchments using Modern Arcview GIS Model

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The hydraulic and structural design of control structures have failed in many years due to lack of geodetic and reliable hydrologic analysis of rainfall and discharge data in some catchments. Hydrologists are often faced with the task of using a limited number of quantitative observations, together with a conceptual understanding of the operation of processes involved in the movement of water through the hydrological cycle, to estimate the occurrence of water at various locations. This is usually done with the assistance of hydrological models which not only have to consider the precipitation and runoff at a certain point, but also other variables such as topography, vegetation cover, rooting characteristics, etc. The Intensity Duration Frequency (IDF) relationship is a mathematical relationship between the rainfall intensity, the duration and the return period. This relationship is determined through statistical analysis of samples of records at proper meteorological stations. This are typically performed based on specified design storms derived from the rainfall intensity-duration-frequency (IDF) estimates and an assumed temporal distribution of rainfall. Use of inappropriate data or design storms could lead to malfunctions of the infrastructure systems: over-estimation may result in costly over design, or under-estimation may be associated to risk of human safety.The hydrologic design of flood storage structures is done by computing the discharge rate for 2, 5, 10, 25, 50 or 100 years return period, which indicate that the heaviest rain occurred once in either 2, 5, 10, 25, 50 or 100 years period respectively as the case may be. The development of IDF curve is of paramount importance in the determination of design discharge. This paper analysed rainfall data from four different gauged rainfall stations that are homogenous and applied to ArcView GIS model to generate regional rainfall intensity (RRI) map using the “inverse distance weighting method” for the interpolation of the stations values.

Geostrategic Plan for Mitigation of Flood Disaster in Nigeria

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Nigeria is geographically located downstream river Niger and Benue that takes their sources from Guinea and Cameroun respectively. Both rivers discharge into the country by forming a confluence at Lokoja. The Niger basin has a total active catchment area of about 1.5 million km² and usually subdivided into the Upper Niger, Inland Delta, Middle Niger and the Lower Niger basins. Nigeria is located in the latter covering about 30% of the Niger basin total catchment area. There are two types of floods in the Niger basin; the first is known as the White floods which usually occur during the rainy season with a peak flood flow occurring between July and September and the second is the Black flood emanating from Guinea with maximum flood flows occurring between December and January. Consequently Nigeria with over 80% of the population of the Niger basin that represents about 60% of the country’s population and located downstream has been continually inundated by the persistent floods from both the Niger and the Benue with many loss of lives and properties. However, the Niger Basin Authority (NBA) in Niamey, created by its 9 member countries including Nigeria, established a satellite controlled Data Collection Platform (DCP) located along the river Niger and the Benue catchment areas in the country. The DCP collects flow data at every station every 1 hour of a day and transmit every 3 hours through the EUMETSAT satellite. Flood flows can therefore be monitored and downloaded from these hydrological network stations as well as disseminated through the Internet. This paper therefore, takes critical analyses on the use of the satellite controlled DCP to mitigate the impact of the persistent flood disaster that is causing loss of lives and properties in the country.

Monitoring of Groundwater Recharge for Flood Management

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This paper proposes regular groundwater recharge estimation as a viable process capable of revealing possible occurrences of flooding in drainage basins for emergency actions and future water planning. Flooding is often monitored by considering the surface water flow/stream flow level. However, changes in groundwater levels can be a source of flood forecasting information. We inferred from results obtained from hydrograph separation and water table fluctuations methods carried out from stream flow and twenty (20) groundwater level monitoring in Ogun River basin that regular estimation of groundwater recharges in the basin area can assist in establishing the peaks of fluctuations, which can be a vital flood prevention mechanism.

Flood Management in an Urban Setting: A Case Study of Ibadan Metropolis

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This paper revisits flooding problems in Ibadan Metropolis, in the past fifty years, especially the most recent flood of August 2011. Flood disasters can be attributed to the unnecessary risks people take when they encroach on flood plains. There will be no flood disasters if human beings stayed away from the flood plains.

The methodology adopted for the flood investigations includes site visits, interviews of affected inhabitants, and analyses of flood data collected during the field investigations. These investigations were complemented with review of past records of flooding, and interpretation of satellite imagery of flood affected areas, especially for inaccessible areas, to produce flood hazard maps.

Results of the spatial analysis of flooding in the 11 local government areas of Ibadan indicate that 26,553 buildings were constructed within the statutory set back to the rivers and streams while 2,105 were flooded. Large scale encroachment into the river floodplains was observed throughout the area. The major cause of flooding in Ibadan Metropolis is due to uncontrolled urbanization of the area.

The Nigerian Meteorological Agency (NIMET) predicted that there will be very heavy rains and flooding in a number of states in Nigeria in 2012. In Oyo State, Ibadan is specifically mentioned as a city to experience flooding. This emphasises the urgent need to put in place measures to facilitate effective management of the anticipated floods to prevent the re-occurrence of the damage and losses of the 2011 disaster.

Social-Economic Indicators and Public Perception on Urban Flooding in Lagos, Nigeria

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Urban flooding is a serious disaster in the world, which not only causes serious damage, disturbs normal life and working conditions, but also pollutes the city and causes sanitary problems. It often also leads to loss of lives. In Lagos, urban flooding has largely become the focus of development initiatives. This paper examined the socio-economic impact and public perceptions of flooding in Lagos using questionnaire survey, personal observation, In-depth Interview (IDI) and Focus Group Discussions (FGD). The findings show that urban flooding has led to the damage of personal and public properties ranging from house utensils, foods, books to cars, buildings and schools. About 39% of the respondents have their economic activities affected by flood and the monetary value of loss in business due to flooding from single storm event range from $84.75 to $8474.58. Loss of goods and properties is more severe for the low income earners than the high income ones and the ratio of those that have benefited from flooding to those that have lost goods and properties is 1:7. The public perceive urban flash flood to be harmful, but other issues, such as acquisition of landed property in any part of Lagos are perceived to be more significant than the seasonal inconveniences and losses, which accrued from urban floods hazard. Involvement of all stakeholders in decision making process on the issue of de-flooding Lagos is recommended.

Social Impact and People’s Perception of Flooding in Makurdi Town, Nigeria

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This study assesses the social impacts and people’s perception of flooding events in Makurdi town which has almost become a yearly occurrence. Data for this study were obtained from questionnaires, interviews, personal observation, archival records of ministries and newpaper reports. A total of 219 respondents, drawn from residents in flood prone areas, were sampled for this study. Descriptive statistics and Likert Rating System were used in the analyses of the data. The results of analyses show that floods in Makurdi occur mostly at the event of rainfall intensity and amount and especially at the peak of rainy season (August/September). And it takes 1 and 2-3days flood water to recede depending on the magnitude of event. Factors other than rainfall identified to substantially influenced flooding in the study area are: Lack of and poor drainage networks, dumping of wastes/refuse in drainage and water channels, topographic characteristics, overflowing of river banks, low infiltration due to high water table and degree of built up areas leading to increased runoffs, and climate change. Despite the flood hazards, occupants in flood prone have remained on the basis of having no alternative, cultural ethnic affinity, family home place where parent were buried, used to flooding as the whole area suffers from flooding, nature of occupation, and cheaper houses to rent. Personal properties and public infrastructures suffer all forms of flood damages. Flood mitigation measures include river rechannelisation, raising house foundations, use of sand bags, bridges and neighbor community efforts. Public enlightenment and necessary legislation and enforcement are recommended to checkmate activities aiding flooding.

Tectono-Hydrological Study of Akure Metropolis, Southwestern Nigeria

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An integrated approach was applied in studying the tectonics and their hydrological implications in Akure metropolis, using remote sensing, structures and secondary geophysical information. Structural geological information was extracted from Landsat ETM⁺ imagery covering Akure area. Since the study area is densely built-up, a systematic approach was employed in delineating the fractures which are characteristic of the underlying Basement Complex geology. Based on the fact that drainage system on such terrain is structurally controlled, the lineament trends on the few rock outcrops observable on satellite imagery were correlated with the trends of rivers draining the area. Results highlight specific fracture pattern that is most probable for hydrogeological exploration. The influence of tectonism in defining the basement aquifers underlying the study area as well as their implications for hydrological hazards were also underscored.

The methodology adopted in this study may be used for hydrogeological exploration in urban areas underlain by Basement rocks in view of the challenge encountered in lineament detection in built-up areas.

Towards effective Hydrological Measurements downstream of Oyan dam

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In 2011 the National Water Resources Institute (NWRI), Kaduna developed a Concept Note on Reservoir Sedimentation Study for Bakolori, Goronyo and Oyan dams. The study thrust is in five areas: Reservoir depth sounding, Downstream Studies, Hydrological Studies, Remote Sensing/GIS Applications and Environmental/ Socio-economic impacts assessments. A focus group on each area of the Reservoir Sedimentation study was constituted. NWRI held collaborative meetings with participating staff of selected organizations in Nigeria that are to implement the study. NWRI Management had undertaken a planning visit to these dams and the supports of the River Basin organizations that own the dams was secured. On 24^th– 27^th. May, 2011, the author participated in the Downstream Study group planning visit to Oyan Dam. During the visit, the downstream study group had a meeting with the Management of the Ogun-Oshun River Basin Development Authority (OORBDA) to discuss the study and obtain relevant documents like rating curves of existing gauging stations, maps etc. Also there was a visit to Oyan Dam reservoir, the GPS readings of benchmarks at the dam site were taken and the Oyan river system downstream of the dam was explored to determine along the main channel suitable sections for discharge measurement and Sediment sampling for onsite determination of sediment concentrations. Ten sites on the Oyan and Ogun rivers system were visited noting their hydro-environmental peculiarities. A brief overview of some of the sites is highlighted in the paper. Five locations were identified as suitable for discharge measurement and sediment sampling.

DROUGHT AND DESERTIFICATION

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Biogeochemical Consequences of Hydrologic Conditions in Isolated Stands of Terminalia Cattapa in the Rainforest Zone of Southern Nigeria

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Nutrient cycling is vital to the sustenance and productivity of trees and other plants. Farmers incorporate stands of exotic trees into their farms to provide shade and fruits thereby, contributing to the rural economy. Despite the importance of these isolated trees in the environment, the biogeochemical implications of hydrologic processes of isolated exotics have not been adequately documented in southern Nigeria. This study examined biogeochemical implications of hydrologic processes under isolated stands of Terminalia cattapa (T. cattapa) in Orogun, southern Nigeria. Throughfall and stemflow were collected from 15 stands of T. cattapa between February 2010 and January 2011; while soil samples were collected underneath the trees. Throughfall and rainfall were collected with funnel-type collectors; stemflow was collected with ¾ mm hose wound round tree trunks; and soil samples collected with a core sampler. Samples collected were analysed in the laboratory using standard methods. Data obtained were statistically analysed with both descriptive and inferential techniques using the SPSS 15.0 version. Annual throughfall and stemflow volumes were 89.2% and 6.5% of the incident rainfall (4325mm). Nitrogen, phosphorus and potassium returned to the soil via throughfall and stemflow varied, with marked similarity between the isolated tree stands and adjoining rainforest used as control. Potassium returned to the soil via throughfall in T. cattapa and rainforest were 62.5 kg/ha/yr and 65.4 kg/ha/yr; while the corresponding values for calcium were 30.6 kg/ha/yr and 31.3 kg/ha/yr. More nutrients were returned via throughfall between November and March while peak nutrient returns via stemflow occurred between May and October. Soil nutrients (N, P, K) correlated with throughfall and stemflow at r ≥ 0.23 and r ≥0.45 respectively. The isolated exotic tree stands were not observed to deplete soil nutrients. Their gradual returns of nutrient elements to the soil through hydrologic processes overtime help to improve soil nutrient status in the rainforest ecosystem.

Challenges of Continued River Niger Low Flow into Nigeria

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Over the last 4 decades River Niger has continuously been affected by the impact of climate change and abuse from human activities to the extent that in June 1985, the river was completely dry in Niamey (Niger Republic) for the first time in history. Similar low flow was recorded 2003 that was among the lowest in 50 years and the month of April, May and June are its most critical low flow periods.

The continued low flow, which is as a result of the impact of climate change coupled with the enormous negative human activities is now increasing the rate of movement of Sahara desert southward towards the Atlantic Ocean. The low flow has also lead to the continued reduction in storage of reservoirs (e.g Kainji and Jebba dams) and also reduction in food crop production, water shortages due to increasing water demand, river pollution, weed encroachment, increasing water borne diseases, mortality rate, famine, urban migration and poverty.

According to the 1995 UNESCO Study Report No. 52 on the hydrology of selected discharge of rivers in Africa, the river Niger 'loses' nearly two-thirds of its potential flow due to seepage and evaporation in the Inland Delta, the latter being aggravated by the fact that the river here touches the southern flanks of the Sahara desert. The Inland Delta, located in Mali, is swampy with the sandy soil that has a network of tributaries, channels, swamps and lakes covering about 30,000 km² during the wet season which also extends into the Sahara Desert.

Experts have been particularly worried by the proposed construction of a dam at the downstream of the Inland Delta at Taoussa in Mali that was approved by all the 9 NBA member countries (including Nigeria) for the NBA Shared Vision and Sustainable Development Action Plan. The location of Taoussa dam just downstream of the Inland Delta could technically aggravate the tremendous inundation in the Inland Delta deeper into the Sahara desert. On the other hand, the approval the Fomi dam in Guinea and Kandaji dam in Niger are regarded by experts as the most effective measures for sustainable water resources and ecosystem conservation of the river Niger.

Today, Lake Chad has almost completely disappeared from its basin, with many unfolding tragic consequences for victims in the affected region of Nigeria and Chad. Unlike the case of Lake Chad, however, it is believed that the consequences of the disappearance of River Niger in Nigeria will have all the makings of the proverbial Armageddon, in terms of its cataclysmic socio-economic and political effects on the nation.

FOOD SECURITY

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Assessment of Shallow Groundwater Quality for Irrigation Purposes in Basement Complex Terrain of Southwestern Nigeria

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This research attempts the investigation of shallow groundwater quality for suitability in agriculture (irrigation) and other uses. Samples were investigated for sodium adsorption ratio, magnesium hazard, Kelley’s ratio, residual sodium bicarbonate, and alkalinity hazard and permeability index. The methodology involves sampling of hand dug wells <30m for laboratory analyses. ICP-MS was used in determining the major metals present in the water samples while titrimetric method was employed for anions determinations. Physico-chemical results revealed a midly acidic pH of mean value 6.3, TDS of 329mg/l, E.C of 427uS/cm, Ca of 25mg/l, Mg of 8.5mg/l, and Na of 42.5mg/l. Calculated indices such as MAR, RSBC, PI indicate that majority of the water are suitable for irrigation. Kelley’s ratio shows that 31% of the water samples are above permissible limit of good irrigation waters while 69% fall within. Calculated SAR and EC classify 69% of the samples into medium salinity to low sodium hazard (C2S1), 25% within low salinity and low sodium hazard (C1S1) and 3% each within the high salinity and low hazard (C3S1) and medium salinity and medium hazard (C2S2) respectively. The groundwater qualities satisfy the condition for use in industry and livestock farming.

Chemical and Physical Properties of Harvested Rainwater from Different Roofing Sheets in Abeokuta, Ogun State

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Access to a regular supply of safe water is a basic human right but many people are denied. Rainwater is available for everybody use. This study investigated the physical and chemical properties of rainwater harvested from different catchment roofs in Abeokuta, Ogun Sate. Sterilized buckets were used to collect runoff from five (5) different roofing materials (metal sheets(pan), painted metal sheets, galvanized metal sheets, asbestos(slate) and anodized alluminium) and direct source (control) from June to October, 2010. Sample collection was replicated three times. The runoffs were analyzed for pH, temperature, Electrical Conductivity (EC), Total Dissolved Solid (TDS), chromium (Cr), lead (Pb) and zinc (Zn). pH, temperature, EC, TDS were determined immediately in the sample. Analysis of the heavy metals was done using Flame Atomic Absorption Spectrophotometer. Data obtained were subjected to descriptive statistics, analysis of variance and means were separated using Least Significant Difference (LSD). All the physical and chemical properties investigated except pH, Cr and Pb decreased from the month of June to October. Cr and Pb were not detected in all the roofing sheets throughout the five months. Control had the least concentration of Zn throughout the months while galvanized metal sheets had the highest concentration. Zn concentration in the month of June ranged from 0.09 – 3.39 mg/l with coated pan having significantly (p < 0.05) higher Zn concentration. Provision of potable water to the entire population is necessary to avoid taken water contaminated with metals.

Determination of Groundwater Availability in Parts of Ilesha, Osun State - An Effort to alleviate the Challenges of Food Insecurity

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This paper is aimed at studying the hydrogeological and geophysical characteristics of some parts of Ilesha using the electrical resistivity method, with the intention of identifying locations where water can be abstracted for irrigation purposes and to ameliorate water supply, and thereby improve food security in the areas.

The available surface water resources are inadequate to meet the entire water requirement for various purposes. Therefore, the demand for groundwater has increased over the years. Generally, groundwater is less prone to pollution in comparison to surface water. Hence, groundwater serves as an important source of water for various purposes in rural and urban areas.

Groundwater is suspected to be available in the weathered, fractured, joints and cracks of the crystalline basement. This study clearly shows that most of the areas within the sixteen sampled locations have geological rock types that contain water or has good groundwater potential.

Implications of Trends and Cycles of Rainfall on Agriculture and Water Resource in the Tropical Climate of Nigeria

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Trends and cycles of rainfall over Nigeria, as well as their implications for water resources and agriculture, have been studied since 1960 on annual, seasonal and monthly bases. Rainfall data of 47 years (1960 – 2006) were obtained for twenty stations over Nigeria for the evaluation of trends using the Mann-Kendall test. Auto correlation spectral analysis was also used to detect cycles of rainfall. The result showed dominant peaks in rainfall return at various rates. For instance, Akure, Benin, Calabar, Maiduguri and Yola stations had decreasing trends of annual rainfall at rates of 1.084, 0.03, 1.80, 0.75, and 0.12 mm/month/yr, respectively with return periods between 1-2 years and 7-10 years. Rainfall trends increased in about 75 % of the locations with return period of dominant peaks varying between 1-2 years and 15 years. Abuja recorded the highest peak of rainfall in the month of October at the rate of 4.7 mm/month/yr with return period of 1-2 years. These results indicate different spatial effects on ecosystem and agriculture. Some of the implications of these trends on agriculture and water resources vary from one station to another, depending on the trends and magnitude of return period of rainfalls. Bauchi and Minna cities are expected to experience serious desertification and complete depletion of underground water due to the effects of no change in trend of rainfall. Meanwhile, agricultural activities are expected to thrive in places like Ibadan, Gusua, Osogbo and others that have moderate increase in trends of rainfall and temperature.

Quality Assessment of Direct Harvested Rainwater in parts of Anambra State, Nigeria

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Rainwater harvesting has become an alternative water source especially in developing countries where many people lack access to pipe borne water. The build-up of greenhouse gases (GHGs) in the atmosphere has had negative impacts on the quality of rainwater and poses great risks to people who depend on this source of water resources. Hence this study assess the physico-chemical and microbiological parameters of rainwater collected in the open in Oko, Orumba North L.G.A. of Anambra State. In the study, direct harvested rainwater were collected from three stations in Oko community and analyzed to investigate the quality of harvested rainwater within the region. Thirty-one water quality parameters were considered and analyzed in the laboratory. The laboratory results were compared to permissible water quality level as recommended by NAFDAC. The comparative parameters analysis shows that the sample collected rainwater were within the permissible limit except for pH which was slightly acidic.

Total and Exchangeable Metals in Groundwater of Ile-Ife, Southwestern Nigeria

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The groundwater samples of Ile-Ife obtained from ten different locations were analysed for their total and exchangeable heavy metals in order to determine their potability status. Water samples collected for two months were analyzed for pH, conductivity, temperature, total and exchangeable heavy metal values using standard methods. The ion exchange chromatographic extraction of the exchangeable metals was carried out with anionic trimethylhyroxyammonium resin. Atomic Absorption Spectrophotometer analysis for total and exchangeable Cu, Pb, Zn, Cd and Mn was performed. The mean pH, conductivity and temperature values, measured insitu, were 6.0 ± 0.5, 340 ± 244 µS/cm and 27.5 ± 0.3^oC respectively. Total mean levels (µg/mL) of Cu, Pb, Zn, Cd and Mn were 8.275 ± 0.912, 0.179 ± 0.041, 31.858 ± 3.635, 0.090 ± 0.010 and 76.789 ± 12.889 respectively while 1.484 ± 0.228, 0.040 ± 0.008, 5.911 ± 1.002, 0.017 ± 0.003 and 20.151 ± 5.845 (µg/mL) were detected as the respective mean values (µg/mL) of the exchangeable metal fraction in the samples. Comparing the levels of heavy metals in the samples to the WHO provision for drinking water, the groundwater was capable of constituting serious health hazards.

Water Quality Evaluation of Spring Waters in Nsukka, Nigeria

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Water samples were collected and analyzed from five different spring water sources in Nsukka (Asho, Iyi-Nsukka, Ajie and Ikwoka-Obimo springs) to ascertain their portability for drinking, since they are consumed directly without treatment. Reports from hospitals in Nsukka metropolis indicate rampant cases of water borne diseases like typhoid fever. After analyzing the samples, it was found that most of the water parameters tested for was within WHO/NIS standard except in biological tests of coliforms, which have high concentration levels especially at Ajie and Iyi - Nsukka springs with 150MPN and 280MPN per 100ml. The springs also have E. coli of 3MPN/100ml each while Asho and Ikwoka- Obimo springs have <3MPN/100ml

Water Quality Evaluation of Hand-dug Wells in Ibadan, Oyo State, Nigeria

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In many countries around the world, including Nigeria, access to potable water has become a mirage. Exploitation of groundwater through the construction of hand-dug wells is a major source of drinking water for majority of the populace. The need to assess the quality of water from this source to ascertain the role of well construction methods has now become imperative because of the health impacts on individuals. Random surveys of three classifications of hand-dug wells were done between June and October 2010, in Ibadan, Nigeria. One hundred and one (101) hand-dug wells were selected. A standard form was used for capturing data used for the classification of the wells into protected, semi protected and unprotected. Standard laboratory methods were employed for the analysis of electrical conductivity, pH, Temperature, Chlorides, Nitrate, E. coli and Total Coliform Count. Results show that nitrate concentration, E. Coli and total coliform counts are more pronounced in wells that are installed close to domestic refuse waste, abattoir, pit latrine, stagnant water, and drainages. The pronounced concentrations decreased with increasing distance from the pollution sources irrespective of well classification. Protected wells gave better water quality relative to semi-protected and unprotected wells. The paper recommends regular monitoring of groundwater quality, abolishment of unhealthy waste disposal practices, and regulation of self supply well construction and design.

Water Quality Management Efficiency of Biofilteration in a Recirculating Aquacultural System

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One of the major challenges of recirculating aquaculture technology is the maintenance of water parameters at levels safe for the healthy growth of the aquatic life being reared. A biofilter is an indispensable component of a recirculating aquacultural system (RAS). It improves the biochemical qualities of the system water for re-use. In this study a fully designed and constructed recirculating aquacultural system was stocked with eighteen thousand catfish fingerlings and run for one complete rearing cycle of seventeen weeks using plastic as the biofilter media. Total ammonia nitrogen (TAN) concentration of the system was measured at the inlet and outlet points of the biofilter during the culture period. The results indicated that for the untreated water, the concentration showed a general increase through the culture cycle while for the treated water there was a marked drop in concentration values for the first four weeks, followed by a fairly constant value for the rest of the period. These values for the treated water were significantly (p < 0.05) below the critical value for safe fish culture. The maximum TAN value obtained for the untreated water was 12.770 x 10^-1mg/l, while that for the treated water was 4.226 x 10^-1mg/l. The minimum TAN values were 6.214 x 10^-1mg/l and 1.396 x 10^-1mg/l for the treated and untreated water respectively. Statistical analysis indicated significant (p < 0.05) difference between TAN values for treated and untreated water. Based on the TAN concentrations of inflow and outflow of the trickling filter, its efficiency was determined over time and result showed that the plant reached at average efficiency of 79% in three weeks, having started with an efficiency of 32% at the beginning of operation.

Water Quality Management in Aquacultural Production using Aquasmat

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This paper introduces a newly developed model, AQUASMAT, and its potential applications, especially in the tropical environment. AQUASMAT can help identify and quantify the cause, effect and relationships between water quality parameters, the physical environment and aquatic ecosystem. It is well suited for production ponds and other water bodies, as well as for predicting general pond dynamics. AQUASMAT is a valuable tool for water quality modeling and aquacultural management. In this overview, the model is shown to have the following capabilities: (1) a graphical user interphase and management data capability; (2) identification and quantification of cause and effect relationships of feed with respect to chemical water quality parameters, the physical environment, and aquatic ecosystem; (3) analysis of complex relationships in impaired production ecosystems and suggestion of cause and management of the various causes of impairment; (4) prediction of feed wastage and economic viability of the production system; (5) presentation of the effect of different management operations on fish yield; (6) tracking of more than 40 parameters which are not easily obtainable from conventional measurement procedures. The model can thus help to fill the knowledge gap and also explore cost-effective and appropriate management measures for ailing aquacultural production systems.

EROSION CONTROL

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An Assessment of Rainfall Erosivity in Parts of Eastern Nigeria: A Case Study of Owerri and Enugu

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Information on the aggressiveness and erosive power of rains received within eastern Nigeria is necessary for the proper management of soil erosion hazard within the region. In recognition of the role of rainfall as an inceptor and facilitator of soil erosion, rainfall erosivity of Owerri and Enugu was estimated using the Modified Fournier Index (MFI). The results showed that the rains received between 1974 and 2011 were highly erosive, with the annual rainfall erosivity computed of the study period being consistently greater than 160 mm.

The degree of relationship between annual rainfall and annual rainfall erosivity for the study period which was established using the Karl Pearson’s Coefficient of Correlation revealed a moderate (r = 0.609) and a high (r = 0.795) degree of positive relationship for Owerri and Enugu, respectively. In the light of the results obtained, an improved understanding of the climatic and hydrologic regime of the area is advocated in order to evolve better soil protection and management strategies.

Comparison of Soil Erosion Models for Application in the Humid Tropics

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Soil erosion by water has contributed significantly to the degradation of lands and impoverishment of the lives of people, especially those living in the humid tropics. Soil erosion models coupled with geographical information systems have a major advantage in that they can represent the spatial variability of catchment characteristics. This study compared the performances of three erosion models, namely, AGNPS, WEPP and SWAT, applied on different watersheds based on model predictions and efficiency. WEPP applications were found to provide good capability to simulate sediment yield followed by SWAT as shown by the high values of E_NS and R², while AGNPS applications were satisfactory as shown by the average values of E_NS and R². Therefore, the application of these models is highly recommended in the humid tropics to reduce environmental degradation due to soil erosion.

Hydraulic Performance of Flow over Normal and Inclined Compound Crested Weir Models

2012-11-12T09:28:39+01:00

The overflow characteristics of Compound crested weir models were investigated experimentally using a laboratory flume. The crests of these weir models consist of two parts; the upstream part has a quarter round shape while the downstream part has standard sharp crested weir shape. Series of experiments were conducted by measuring discharges and water heads over the weir models for different weir crest radii of R = 2.5 cm, 3.5 cm, 4.5 cm and angles of weir inclination α = 300, 45°, 60⁰ and 90° respectively to the direction of flow with a constant weir height P = 15 cm. It was observed that increase in the ratio of water head over the crest (h) to weir height (P) resulted in the corresponding increase in the discharge coefficient for all the weir models. The hydraulic performance for each of the weirs was determined in terms of the flow magnification factor. Hence, the model with R = 2.5 cm and α = 30⁰ was selected as the best model because it had the highest discharge coefficient and flow magnification factor of 1.326 and 1.555 respectively.

Analysis of Selected Failed Gully Erosion Control Works in Imo State

2012-11-12T09:28:39+01:00

Gully erosion constitutes the major ecological problem in southeastern Nigeria and requires adequate scientific and proper technical competence in the prevention and control of this menace. An effective control of any phenomena is not possible unless and until the principles and mechanics underlying its behaviour and distribution over time and space are fully understood. The objective of this paper is to present some examples of gully erosion control works and the effectiveness of the corrective measures put in place in Imo State. The study revealed that the initiation and development of erosion gullies is facilitated by natural processes (rainfall, topography engineering-geological properties of soils, especially texture, etc) and the activities of man, especially road construction. However, incorrect information, incomplete data or wrong concepts in the application of either method of erosion control have aggravated gully erosion problems. Many of the erosion control measures put in place in Imo State show that hydrological variables (e.g. runoff) which constitute major factors in soil erosion, were not considered in the design and has resulted in deep gullies, instead of checking erosion.

COASTAL ZONE MANAGEMENT

2012-11-12T09:28:39+01:00

Assessment of Groundwater Quality in the Lower Coastal Plain Sand Aquifer for Varied Uses

2012-11-12T09:28:39+01:00

The study assessed the water quality of lower coastal plain sand (LCPS) aquifers for varied uses. 44 samples were collected from hand dug wells. pH, electrical conductivity, total dissolved solids, total hardness, alkalinity, calcium, magnesium, sodium, potassium, chloride, bicarbonate, carbonates and sulfate were determined using standard methods. Result shows that about 95.4% of the measured EC accounts for low enrichment of salts while 2.3% accounts for both medium and high enrichment of salts. The TDS values show that about 95.5% of the samples are fresh water while 4.5% are brackish. Factor Analysis extracted four factors and explained 91.71 % of total variance. The RSC value shows that about 18.2%, 13.6% and 15.9% of the samples represent suitable, marginal and unsuitable water, respectively, for irrigation purpose. Furthermore, computed MR values indicate that about 75% of the samples are suitable while the remaining 25% are not suitable for irrigation purpose. PI values also show that 63.6% of the samples are not suitable for irrigation while 34.1% and 2.3% are marginally suitable and suitable, respectively. For industrial water uses, 6.8% of the samples exceed the prescribed WHO HCO₃limit while 2.3% and 11.4% exceed the SO₄and TH limits, respectively. 93.2% of the samples exceed the prescribed pH limits, while TDS and Cl exceed the standard limit in about 4.5% and 2.3% of the samples, respectively. The WQI ranged between 21.59 to 550.97mg/L with about 31.8% representing excellent water quality while 50%, 15.9% and 2.3% indicate good, poor and water unfit for drinking purposes, respectively. The paper recommends adequate protection and thorough treatment of the water for human consumption.

Could Ocean-land Invasion be detected using Multi-temporal Images of Landsat?

2012-11-12T09:28:39+01:00

One of the most certain consequences of global sea level rise is ocean – land invasion and is likely to increase in the near future. The coastal rural fishing communities are mostly at risk of the invasion. To address the menace spatially through scientific research interventions, different coastal mapping techniques have been adopted over the years for different research problems e.g. shoreline erosion studies, barrier island migration, coastal erosion vulnerability assessment etc. The methods adopted varied from simple analysis, manual analysis of uncorrected topographic maps and aerial photo, digital interpretation of corrected multi-temporal images of low and high resolution images (e.g. Landsat, spot, Ikonos), and hyper-spectral images (e.g. AVIRIS, CASI, hyperion). In complimenting previous studies, this study provides answer to the question “Could ocean-land invasion be detected using multi-temporal images of Landsat?” Orthorectified Landsat remotely sense datasets of MSS (1984), TM (2000), combination of TM & ETM+ (2012) were acquired from GLS portal. The study demarcated 704km² around the Eastern Obolo LGA shoreline and processed it using ENVI maximum likelihood and change detection techniques. The classes invaded by ocean were not well revealed due to Landsat low resolution; nevertheless, between 1984 and 2012, ocean invaded about 1.39km² of the vegetal class. Ocean downturns which may result to serious invasion in future were also detected. This 28years demonstration shows that Multi-temporal Landsat Images are useful for ocean – land invasion study, but increased spatial resolution may be needed for detecting more subtle changes.

Modelling Seawater Intrusion into Multi-layered Aquifer System of Lagos Area, Nigeria

2012-11-12T09:28:39+01:00

Investigation as indicated that in the immediate vicinity of Lagos metropolitan, four separate aquifers are tapped. Over-exploitation of these aquifers through boreholes for both domestic and industrial water supply has resulted in salt water intrusion occurring in the confined aquifers. Monitoring and management of salt water intrusion is not done in Nigeria hence there is a need to study and ascertain the extent of sea water intrusion along the coastal region of Nigeria.

Data were collected from the boreholes within the studied area to model a two-dimensional advection-dispersion problem. The basic differential equation was solved for two-dimensional transport in an incompressible porous medium and transport in the absence of sources. The velocity flow was solved as a separate problem, independent of the solution for the concentration. A computer program was developed to solve the two dimensional dispersion problems by the finite element method. The model was calibrated in two steps, with the transient runs modelling Chloride concentration for the three aquifers. The runs simulated the 1982 and 1996 chloride concentration and predicted what condition it will be in 2010.

The result indicated that the area of chloride concentration increased from 13km² in 1996 to 38km²for upper coastal plains sands while the concentration increases from 68mg/L to 83mg/L. Comparing the simulated chloride for all the three aquifers Abeokuta formation has the lowest value of chloride concentration. This confirms that Abeokuta formation is freshwater aquifer. Generally the results obtained for chloride concentration agrees with report of Coode Blizard Ltd.

Streamflow Variability in Ossiomo River Catchment and Implications for Basin-wide Water Resources Management

2012-11-12T09:28:39+01:00

Time series analysis of streamflow data from gauges installed in the main rivers of the Ossiomo River catchment has been undertaken using the Australian Cooperative Research Centre for Catchment Hydrology’s Time Series Analysis computer code. The results show that all the rivers are perennial, receive groundwater contribution all the year round throughout their entire lengths and that this groundwater contribution is on the average, responsible for more than 70 per cent of total flow. This large percentage contribution also modulates the response of the rivers to the higher flows in the wet season, and as such, mitigates flood risks. The results also show that there are tremendous groundwater reserves available for development in the Benin Formation that releases the groundwater to the rivers from only its upper layers. The Flow Duration Curve for the Ikhowan River, the smallest river with a gauge, shows that Q50 is on the average about 5.5 m³ s^-1, and thus, has good potential for small hydropower development. Finally, while flow characteristics have been determined from the very short and patchy records that are available, they give an insight into the water resources potential of Ossiomo River catchment and could have application, in some respects, for other rivers that flow on the Benin Formation but are ungauged.

WATER RELATED CLIMATE CHANGE ADAPTATIONS

2012-11-12T09:28:39+01:00

Linkages Between Changes In Climate Elements, Institutional Capacity and Community Access to Water In Iju, Lagos

2012-11-12T09:28:39+01:00

Synergies between climate elements, institutional capacity and percieved community access to water based on the current effect of climate change appears complex since such synergy are often times informed by multiple factors such as social, economic, political and environmental. Better understanding of the complexities as it relates to the multiple natural and political drivers if well adopted could inform change in action and further reduce water stress. This paper examines the relationships between micro climatic elements, institutional (iju water works) capacity and community perception on access to portable water in Iju. Seasonal rainfall and temperature data were collected and analysed. Available seasonal information on water levels and abstraction activities were determined. Structured interviews were conducted with officials of water works while questionnaires were administered to communities to ascertain community access to portable water supplied by the institution. The result shows direct correlations between rainfall pattern and the water level but not with water abstraction activities. However the ability of the institution to abstract water was found to be influenced by varied factors such as the state of the pumping machines , absence of power plant and obsolate equipments in the face of rising water demand due to increasing population.

Effect of Climate Change on Water Balance of Lower Ogun River Basin

2012-11-12T09:28:39+01:00

The lower Ogun River is highly vulnerable to climate change due to its geographic location at the southern edge of western Nigeria and water management planners are facing considerable uncertainties on future demand and availability of water. This study was carried out to investigate the effect of climate change on water balance of lower Ogun River basin. The procedure of Ayoade (1976) water balance bookkeeping model was followed in computation. The temperature and water balance components were compared using descriptive statistics. The result showed that climate change influences the water balance components: rainfall, evapotranspiration, runoff and change in storage. Recurrent dry spells were encountered in the years 1988, 1990, 1998, 2006 and 2009. However, in the recent years increasing rainfall amount have been observed to cause flood that displaces most inhabitance of the lower basin area. Rainfall variability, land degradation and desertification are some of the factors that may also contribute to variation in the component of the hydrologic cycle in the river basin. The recurrent dry spells and flood encountered in the basin represented a particularly trying episode for the area, with massive losses of agricultural production and its consequence on human lives and domestic economies. Thus, climate change may become a great obstacle to the achievement of the Millennium Development Goals (MDGs) to which the Government of Nigeria is committed.

Combating Climate Change Impacts on Water availability and Energy Production

2012-11-12T09:28:39+01:00

Energy and water systems are closely inter-connected and need each other. Hydroelectric power (HEP) generation remains an important source of energy in Nigeria. Notable inefficiencies and deficiencies in cash generation have compelled the Power Holding Company of Nigeria (PHCN) to rely on fuel subsidies and government subvention for funding of capital projects with the resulting ever accumulating energy supply deficits. Incidentally, the energy sector is one of the main drivers of GHG emissions, hence of global warming and climate change. It contributed 140% increase during 1970-2004 to the growth of GHG emissions. Climate variability and change caused reduced inflows into dam reservoirs resulting in the drastic and steady drop in the hydroelectric power generated by dams the Kainji and other dams in Nigeria between 1973 and 1994 and in 2003. The phenomenon has exacerbated competition for water between energy and other sectors of the economy such as agriculture. Projected temperature increases during the 21st century are expected to increase the energy demand for cooling.

The national energy mix regime with less carbon intensive economy and with a decisive transition from crude oil to gas and, increasingly renewable, is the pathway to be pursued vigorously. An integrated water resources management (IWRM) approach should be followed. In particular, climate proofing of infrastructure should be applied at all stages in the project cycle: planning, design, construction, operation, and decommissioning. It will apply relevant adaptation and risk-management strategies as a necessary component of sustainable socio-economic development. The country’s policy makers should make renewable energy development a priority policy of government at all levels. Lawmakers should also develop appropriate legal, regulatory and institutional frameworks that de-emphasize over-dependence on fossil fuels and promote demand management for water and energy.

Climate Variability and River Benue Discharge in Jimeta, Yola Area, Nigeria

2012-11-12T09:28:39+01:00

It is glaring that climate change is true and has become a monster that every effort must be targeted towards its elimination. Every sector of the economic has been affected by climate change. The impact has been intensified of recent, with the increase in world’s population and her quest for survival. In northern Nigeria, its effect among others range from increase in dry spells, heat stress, drop in water tables and consequent shortage of water. To overcome the problems, many have resulted in planting on the river bed, diging of river bed and sinking of bore hole on the bed not only for agricultural purposes but for domestic need. Using climatic (rainfall and temperature) and hydrological data (river discharge) for the period of 49 years, an attempt was made to examine the response of river Benue discharge to climate change. The result shows great fluctuations of the elements about the mean. Both runoff and rainfall total has decreased but the rate of decrease of rainfall is about 14 times that of runoff. Monthly analysis of runoff in some years of the study revealed increase in runoff above the mean but this additional runoff do not add to water availability for use because they occur during the wet season and there are no specific storage to hold the water through to the dry season. For every 0.01mm increase in rainfall there is 1 Million m³ increase in discharge and vice versa. The discharge between 1980 and 1999 decreased noticeably, because the discharge was well below actual mean of 20.419 Million m³. The simple correlation analysis revealed that, 24% and 31% association strength to the variation was accounted for by rainfall and temperature respectively. There was an inverse relation between the temperature and runoff as expected from 1980-1990, when pronounced increase in temperature above the mean coincided with the sharpest drop in runoff. The paper recommended that effort should be geared towards programs that will bring to the consciousness of the community as regard the changing climate pattern so as to prepare for the challenges and the right adaptation techniques to the impacts of climate change on water resources.

Precipitation Concentration Changes in Owerri and Enugu

2012-11-12T09:28:39+01:00

The precipitation concentration index (PCI) of Owerri and Enugu for 1974 to 2011 was computed. The PCI was estimated on an annual and seasonal scale. The seasonal estimation were based on the categorisation of the seasons in eastern Nigeria into long wet season, short wet season, short dry season and dry season.

The results of the PCI computed for Owerri showed that 87% of the years for which annual PCI was computed fell within the moderate concentration category range, while for Enugu 71% of the years fell within the moderate concentration category. For the long wet season for the study period, 74% and 66% of the years fell within the uniform precipitation concentration category at Owerri and Enugu, respectively, while 13% of the years at Owerri, and 16% of the years at Enugu fell within the moderate precipitation category.

Information derived from the PCI computation can be used for hydrological, water resources and environment management programmes, as well as serve as a warning tool for disaster preparedness in relation to flooding and erosion.