Department of Civil Engineering

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Causes of delays in highway construction projects in Ghana
(Civil and Environmental Research, 2016) Aforla, B.; Woode, A.; Amoah, D. K.
Delays in construction projects are a global phenomenon, causing a multitude of negative effects on the key project participants – clients, consultants, and contractors. The main purpose of this study is to identify the causes of delay of highway construction projects in Ghana to determine the most important to the key project participants. Literature review and semi-structured interviews of 12 key players in the implementation process were conducted. Thirty five possible causes of delay were identified and further grouped into ten categories. A questionnaire survey was conducted on the resulting list of delay causes for the identification of the most important causes of delay. The relative importance of the individual causes were determined and ranked by their Relative Importance Index. The findings revealed that the five most important causes of delay in road construction projects in Ghana are 1) Delay in honouring payment certificates 2) Equipment failure 3) Shortage of materials 4) Poor site management 5) Late delivery of materials on site. It is hoped that the findings of this paper will help project participants to act on critical causes to minimize delay of their projects.
A stochastic weather generator model for hydroclimatic prevision in urban floods risk assessment in Abidjan District (Cote d’Ivoire).
(Sustainability, 2016) Danumah, J. H.; Odai, S. N.; Saley, M. B.; Szarzynski, J.; Adjei, K.; Kouame, F. K.
Flood risk occurrence is very often related to heavy precipitation; and available future weather data is a potential source for long term flood risk prediction. The aim of this paper was to determine and analyze trends in rainfall, temperature and PET under present and future climatic conditions using Long Ashton Research Science-Weather Generator (LARS-WG) software, in prediction of flood risk occurrence in Abidjan. This work was based on the integration of Hydro climatic daily data within LARS-WG software. The processing steps are: (1) calibrating and validating the model using 50 years measured data, (2) generating baseline data for 50 years, (3) processing future scenario data based on baseline already set using HADCM3 and (4) Comparing baseline and generated scenario data. The resulting statistics show that temperature will increase by 0.32, 1.36 and 2.54 °C for the periods 2011–2030, 2046–2065 and 2080–2099 respectively. Then rainfall in the same period will increase by 4 %, 6 % and 10 % respectively. The mean and high flooding risk will then increase in long term within this urban area. Thus this future large extension of flooding occurrence imposes to take future weather scenario into account in prediction and management of flooding risk in Abidjan District.
Flood risk assessment and mapping in Abidjan district using multi-criteria analysis (AHP) model and geoinformation techniques (Cote d’ivoire).
(Geoenvironmental Disasters, 2016) Danumah, J. H.; Odai, S. N.; Saley, B. M.; Szarzynski, J.; Thiel, M.; Kwaku, A.; Akpa, L. Y.
Background: Flood is one of the most destructive natural disasters of climate change effects in West Africa. Flood risk occurrence is a combination of natural and anthropogenic factors, which calls for a better understanding of its spatial extent. The aim of this paper is to identify, and map areas of flood risk in Abidjan district. Results: This work is based on the integration of multi-criteria data including slope, drainage density, type of soil, Isohyet, population density, land use and sewer system density within ArcGIS interface. The resulting AHP flood risk map shows that areas under high and very high flood risk covers 34 % of the study area. Conclusion: The Analytic Hierarchy Process (AHP) method used as a multi-criteria analysis allowed the integration of several elements under two criteria, hazards and vulnerability, for flood risk assessment and mapping. Results revealed that, Abidjan district is heavily exposed to the risk of flooding. Eight out of thirteen (8/13) municipalities within the district are at a high risk of flooding which calls for decision makers to effectively develop strategies for future flood occurrences within the Abidjan district (South of Côte d’Ivoire).
A review of water charges: customers’ perception of the quality of the levels of service in Ghana, the water charges and their willingness to pay for improved services.
(Journal of Research in Humanities and Social Science, 2016) Gyabaah, F.; Amankwah-Minkah, A.; Agbotui, P. Y.
The trade-off between full cost recovery and providing the urban poor with potable water in the right quantity, quality and at affordable prices is ever increasing especially in African countries. Ghana, not being an exception continues to struggle in its efforts to provide safe drinking water to the urban populace and Ghana Water Company Limited (GWCL), the urban water service provider stands at the centre of this ordeal. The company has been criticised for being inefficient in its management of the urban water supply due to various reasons - technical, financial and political. This report reviews the water supply management in Ghana. It further investigates by way of a survey, the perception of consumers in Ghana of the quality of the levels of service offered them regarding water quality, quantity and reliability, as well as the affordability and willingness to pay for improvements in the water services rendered by the GWCL. The survey came up with one hundred and thirty-four (134) valid respondents – 56 directly handed out printed questionnaire respondents and 78 online respondents. The survey results show that most customers perceive the water quality and reliability of the service received as being average and above, although over 78% of them have their water supply interrupted at least once every week. The quantity of water received is shown as not being adequate, since 54% of customers resort to other sources of water to supplement public supply. Even though the water quality is rated as good, customers rarely drink water from this service, as 66.4% of them prefer drinking sachet or bottled water. Most consumers (63.4%) think the current water prices are high and only about 3% are willing to pay more to achieve full cost of water service and for a significant improvement to the supply system. The water supply situation in Ghana should be recognized as a national issue and given higher priority. Major reforms need to be made in both policy and practice if the levels of service are to match up to internationally accepted standards. This would bring significant public health improvements and service improvements to wider Ghanaian society
Change and Analysis of Extreme Rainfall Indices During 1960–2010 and 2011–2100 in Abidjan District (Côte d’Ivoire).
(Climate Change Research at Universities, 2017) Danumah, J. H.; Odai, S. N.; Saley, M. B.; Akpa, L. Y.; Szarzynski, J.; Kouame, F. K.
Flood risk occurrence is very often related to heavy precipitation. The availability of analysis of weather data is a potential source for long term flood risk prediction and management. The aim of this paper was to determine and analyse trends of observed and future rainfall indices from 1961 to 2010 and 2011 to 2100 using rclimdex model in Abidjan District. This work was based on the integration of daily weather data within rclimdex model throughout quality control test, homogeneity test and indices calculation of ten (10) rainfall indices. The results showed an overall decrease trend of the rainfall indices namely through a negative trend in the annual total rainfall, maximum number of consecutive wet days, and number of extremely wet days during the period from 1961 to 2010. Exception was made from 1995 to 2010 where the same indices showed a positive trend. However, the results have showed also an increase trend of consecutive wet days (CWD), Simple daily intensity index (SDII) and Number of heavy precipitation days (R10) indices from 2011 to 2100. Thus these findings explain the nowadays flood occurrence and indicate that rainfall extreme under flood risk events will continue in the future. Therefore it call decision makers for preparedness and mitigation strategies in Abidjan District.
Big data challenges in transportation: A case study of traffic volume count from massive radio frequency identification (RFID) data.
(2017) Wemegah, T. D.; Zhu, S.
We are in an advancing stage of data acquisition and an even greater dynamic stage of dealing with big data. Data sizes have evolved over the years from a few kilobytes to Exabyte. The transportation engineer has also been caught up in the big data era and to efficiently analyze this massive data for maximum benefits, various challenges relating to data acquisition, data storage, data cleaning, data analysis and visualization has to be overcome. In this paper, we discuss these challenges and approaches to managing them with respect to massive Radio Frequency Identification data for traffic volume count in Nanjing, China. We recommended software, use analytical and visualization techniques like aggregation, graduated circular symbols and traffic count map to overcome big data challenges to produce peak hour, offpeak hour traffic volume counts and traffic count maps showing locations of low and high volume traffic. The paper, therefore, contributes to the management of big data by transportation engineers for traffic volume and congestion analysis.
Flow zone characterisation in a fractured aquifer using spring and open-well T and EC monitoring
(EGU General Assembly Conference Abstracts, 2017) Agbotui, P.; West, L.; Bottrell, S.
A quantitative groundwater resource management under uncertainty using a retrospective optimization framework.
(Sustainability, 2017) Kifanyi, G. E.; Ndambuki, J. M.; Odai, S. N.
Water resources are a major concern for any socio-economic development. As the quality of many surface fresh water sources increasingly deteriorate, more pressure is being imparted into groundwater aquifers. Since groundwater and the aquifers that host it are inherently vulnerable to anthropogenic impacts, there is a need for sustainable pumping strategies. However, groundwater resource management is challenging due to the heterogeneous nature of aquifer systems. Aquifer hydrogeology is highly uncertain, and thus it is imperative that this uncertainty is accounted for when managing groundwater resource pumping. This, therefore, underscores the need for an efficient optimization tool which can sustainably manage the resource under uncertainty conditions. In this paper, we apply a procedure which is new within the context of groundwater resource management—the Retrospective Optimization Approximation (ROA) method. This method is capable of designing sustainable groundwater pumping strategies for aquifers which are characterized by uncertainty arising due to scarcity of input data. ROA framework solves and evaluates a sequence of optimization sub-problems in an increasing number of realizations. We used k-means clustering sampling technique for the realizations selection. The methodology is demonstrated through application to an hypothetical example. The optimization problem was solved and analyzed using “Active Set” algorithm implemented under MATLAB environment. The results indicate that the ROA sampling based method is a promising approach for optimizing groundwater pumping rates under conditions of hydrogeological uncertainty.
Perceived enjoyment, concentration, intention, and speed violation behavior: Using flow theory and theory of planned behavior
(Taylor and Francis Ltd., 2017) Atombo, C.; Wu, C.; Zhang, H.; Wemegah, T. D.
Objective: Road accidents are an important public health concern, and speeding is a major contributor. Although flow theory (FLT) is a valid model for understanding behavior, currently the nature of the roles and interplay of FLT constructs within the theory of planned behavior (TPB) framework when attempting to explain the determinants of motivations for intention to speed and speeding behavior of car drivers is not yet known. The study aims to synthesize TPB and FLT in explaining drivers of advanced vehicles intentions to speed and speed violation behaviors and evaluate factors that are critical for explaining intention and behavior. Method: The hypothesized model was validated using a sample collected from 354 fully licensed drivers of advanced vehicles, involving 278 males and 76 females on 2 occasions separated by a 3-month interval. During the first of the 2 occasions, participants completed questionnaire measures of TPB and FLT variables. Three months later, participants' speed violation behaviors were assessed. Results: The study observed a significant positive relationship between the constructs. The proposed model accounted for 51 and 45% of the variance in intention to speed and speed violation behavior, respectively. The independent predictors of intention were enjoyment, attitude, and subjective norm. The independent predictors of speed violation behavior were enjoyment, concentration, intention, and perceived behavioral control. Conclusions: The findings suggest that safety interventions for preventing speed violation behaviors should be aimed at underlying beliefs influencing the speeding behaviors of drivers of advanced vehicles. Furthermore, perceived enjoyment is of equal importance to driver's intention, influencing speed violation behavior.
Study of brick mortar using sawdust as partial replacement for sand.
(Journal of Civil Engineering and Construction Technology, 2017) Sasah, J.; Kankam, C. K.
The paper reports results of study on standard masonry mortar containing sand and sawdust as aggregates in a mix proportion of 1:3 and water-cement ratio of 0.55. A modified mortar of same design mix proportion (1:3) but varying water/cement ratio and constant slump of 74.3 mm to achieve higher workability was also evaluated. Six different percentages (5, 10, 15, 20, 30 and 50%) of sand replacement were investigated. The flexural tensile strength, compressive strength, dry density, masonry wallet compressive strength, water absorption and slump were evaluated. The British code recommended masonry wallet compressive strength of 5.3 N/mm2 was achieved with 8 and 13% sawdust contents in the standard and modified mortars, respectively. Such mortars can be used as jointing and rendering materials on interior walls of buildings where water absorption by the mortar would be reduced. Key words: Sawdust, mortar, wallet, masonry compressive strength, water absorption
Biotite influence on the binding properties of bituminous materials.
(International Journal of Engineering Research & Technology (IJERT), 2017) Aforla, B.; Woode, A.; Amoah, D. K.; AY, B. S.
The effect of biotite on rheological properties of bitumen was investigated using biotite extracted from gneiss rocks. The research methodology involves two phases. The first phase involves the separation of biotite from gneiss rock. The second phase involved tests carried out on bitumen- biotite blend to determine the effect of biotite on the rheological properties of bitumen. The biotite was ground to 75Âµm size and blended with bitumen AC-10 prepared in various proportions and the rheological properties determined in the laboratory. The results of this study shows that biotite improves the binding properties of bitumen. At low temperatures, the presence of biotite in bituminous mixtures in the proportion of 2 to 3.5% by weight of bitumen improves the binding properties. Conversely, at higher temperatures of about 135oC, the biotite bitumen mix showed best result at 2%. An increase of up to 3.5% by weight of biotite resulted in a drop in the kinematic viscosity values even though there was an improvement in the binding properties over the pure AC-10 bitumen results.
Characterization of a fractured aquifer using open-well dilution tests.
(80th European Association of Geoscientists & Engineers (EAGE) Conference and Exhibition, 2018) Agbotui, P.Y.; West, J.; Bottrell, S.
An approach to characterization of multilayer aquifer systems using open well borehole dilution is described. The approach involves measuring observation well flow velocities while a nearby extraction well is pumped by introducing a saline tracer into observation wells and collecting dilution vs. depth profiles. Inspection of tracer profile evolution allows discrete permeable layers within the aquifer to be identified. Dilution profiles for well sections between permeable layers are then converted into vertical borehole flow velocities and their evolution, using an analytic solution to the advection-dispersion equation applied to borehole flow. The dilution approach is potentially able to measure much smaller flow velocities that would be detectable using flowmeters. Vertical flow velocity data from the observation wells are then matched to those generated using a hydraulic model of the aquifer system, "shorted" by the observation wells, to yield the hydraulic properties of the constituent layers. Observation well flow monitoring of pumping tests represents a cost-effective alternative or preliminary approach to pump testing each layer of a multilayer aquifer system separately using straddle packers or screened wells and requires no prior knowledge of permeable layer depths and thicknesses. The modification described here, of using tracer dilution rather than flowmeter logging to obtain well flow velocities, allows the approach to be extended to greater well separations, thus characterizing a larger volume of the aquifer. An example of the application of this approach to a multilayer Chalk Aquifer in Yorkshire, Northeast England, is presented.
Micro-level social vulnerability assessment towards climate change adaptation in semi-arid Ghana, West Africa
(Environment, Development and Sustainability, 2018) Badmos, B. K.; Adenle, A. A.; Agodzo, S. K.; Villamor, G. B.; Asare-Kyei, D. K.; Amadou, L. M.; Odai, S. N.
This study determined the social vulnerability index (SoVI) of households to climate change impacts for three identified locations (upper, mid and lower) in the Vea catchment, semi-arid Ghana. This study adapted the social, economic and demographic indicator approach. The data used were obtained from a survey of 186 randomly sampled farm households and direct field measurements of 738 farm plots belonging to the same sampled farm households. Information from the literature, expert judgement and principal component analysis were useful for computing and analysing the SoVI. The variables were normalized, weighted and subsequently recombined to determine the index of the three locations towards climate change. Although the SoVI to climate change was highest (0.77) for the upper part of the catchment, the mid- and lower parts of the catchment show a high SoVI of 0.72 each. The overall SoVI for the catchment is 0.73. The study re-emphasizes the high vulnerability level of dry areas to climate change. Moreover, it shows there is variability at micro-scale. There is a need to put appropriate measures to address the vulnerability of households to climate change in the semi-arid areas of West Africa. Factors aggravating dry land’s vulnerability towards climate change should be prevented with implementable policies. Furthermore, it is important to identify conditions that have made some areas less vulnerable to climate change, and then, we can work out the possibility of adapting such to the vulnerable places.
Explorative analysis of vehicular movement patterns using RFID-based transport data: An eulerian perspective
(Gioacchino Onorati Editore, 2018) Wemegah, T. D.; Zhu, S.; Yeboah, G.; Atombo, C.
The advancement in technology on data capture procedures has overcome many of the challenges associated with data acquisition for transportation studies. The use of Radio Frequency Identification (RFID) technology is increasingly becoming significant in transport application domains where there is the need to track and analyze patterns of vehicles movement. In this paper, we explore the efficacy of RFID technology, a eulerian perspective on movement, to extract spatial and temporal rhythms of vehicular movements in, Nanjing, China for road traffic analysis. Data mining and geo-computation methods were used to mine and extract vehicular movement. The count data, statistical, visual analytics and Geographic Information System (GIS) methods were used to determine spatial and temporal patterns of vehicular movement. Global Moran’s I, hot spot analysis and kernel density estimations were the spatial statistical methods used to determine spatial patterns of vehicular movements. The study reveals the efficacy of the usage of massive RFID data, which uses a eulerian perspective of movement for determining spatiotemporal patterns for traffic analysis. The study revealed morning peak and evening peak vehicular movements, for weekdays with Thursdays and Fridays displaying the most vehicular movements. Spatial patterns revealed a clustering of low and high vehicular counts for weekdays, weekends, off-peak and peak hours. This explorative study using RFID technology to determine spatial and temporal patterns in vehicular counts has important application for traffic analysts. This study approach supports traffic congestion monitoring, traffic flow statistics and traffic planning as well as helps to determine low and high traffic locations to evaluate the performance of a traffic system.
Local level impacts of climatic and non‐climatic factors on agriculture and agricultural land‐use dynamic in rural northern Ghana
(Singapore Journal of Tropical Geography, 2018) Badmos, B. K.; Villamor, G. B.; Agodzo, S. K.; Odai, S. N.; Badmos, O. S.
This study investigated the local level impacts of climatic and non-climatic factors on the agricultural land-use dynamic in rural northern Ghana. Data was collected by means of household questionnaires and interview. The data collected relates to farmer's knowledge about climate change, response to the impact of climate change, dynamics in the area cultivated for crops, and the climatic and non-climatic factors that affect agricultural land-use dynamics. The data collected was subjected to simple descriptive statistics and chi-square tests. Farmers indicated that the weather patterns have affected their cropping activities. Delay in the start of rainfall, fluctuation and cessation before the growing season ends have affected them. Also, inadequate access to farm inputs has affected them. In the face of unfavourable conditions, the farmers may respond by increasing or decreasing the land area cultivated for some crops, they may continue to cultivate their crops, or they may abandon the crop(s) for the season. Jobs outside of the farm are being taken up to support household needs. Climate change has been interacting with non-climatic (socio-economic) factors, and a holistic approach would be the best to address the local or regional change. Intensification of research within the study region and nearby regions would improve preparedness for future local/regional change.
Study of recycled polyethylene plastic waste as binder in building block for greener construction.
(International Journal of Trend in Research and Development (IJTRD), 2018) Kankam, C. K.; Ansa-Asare, K.; Meisuh, B. K.; Sasah, J.
Plastic production has overtaken most man-made materials including metals and has long been under environmental scrutiny. Most plastic wastes are accumulated in landfills, natural environment and oceans. It is estimated that with the current trend of global production and waste management, approximately 12000 million metric tons of plastic waste will accumulate in landfills and in the natural environment by the year 2050. Plastics have very poor recycling rates, and their inherent menace is most pervasive in low-income, developing countries. This paper presents results of study on plastic waste as binder in mixtures of sand (fine aggregates) to produce building blocks for construction. Melted polyethylene plastic was mixed with sand (sandplast) in different proportions of 1:1, 1:1.5, 1:2, 1: 2.5 and 1:3 (plastic: sand). Test results include compressive, tensile and impact strengths, stress-strain response, fire resistance, water absorption and permeability of sandplast. The optimum mix ratio for the compressive, tensile and impact strength was 1:2. The compressive and tensile strength of sandplast blocks ranged from 4.8 to 7.4 N/mm2 and 3.3 to 7.2 N/mm2 respectively. These are greater than the respective values for sandcrete blocks produced in Ghana that generally vary from 1.4 to 3.5 N/mm2 and 0.1 to 0.3 N/mm2 . The static modulus of elasticity of sandplast averaged approximately 89.0, 311.5 and 197.7 N/mm2 for mix proportions of 1:1, 1:2 and 1:3. At temperatures below 80oC the strength properties and stability of sandplast blocks remained unchanged. When immersed in water, sandplast blocks were found to be insoluble in water. The coefficient of permeability of sandplast averaged 4.6 x 10-4 , 8.2 x 10-4 and 21.8 x 10-4 cm/sec for mix proportions 1:1, 1:2 and 1:3 respectively.
Greywater in the drains of a sewered community in Ghana
(Water Practice & Technology, 2018) Dwumfour-Asare, B.; Nyarko, K.B.; Essandoh, H.M.; Awuah, E.; Anim, K.K.; Quaye, A.
With less than 5% sewerage coverage and abysmal greywater management, Ghana’s environment could be highly polluted, especially water resources. The few sewered communities may be guilty of pollution from greywater discharge into stormwater drains. In this study, Asafo, Ghana, was used as a case study to assess greywater characteristics in the major drains in a sewered community. The approach involved desk study reviews and laboratory analysis of greywater samples. The findings showed some inhabitants discharge greywater into neighbourhood drains instead of sewers. Most greywater sources from reviews and sampled drains failed the discharge limits for major contaminants including turbidity (39.4–2,880 NTU), BOD5 (64–700 mg/L), COD (207– 2,308 mg/L), TSS (70–4,720 mg/L), TDS (420–2,860 mg/L), nutrients – TKN, NH3-N, NO3 -N, NO2 -N (0–218.5 mg/L), total P and PO4 3 (1.24–26.18 mg/L), elemental species – Na, K, Mg, etc (0–1.6 mg/L), and microbiological – total and faecal coliforms, and E. coli (2.95–10.4 log CFU/100 ml). High strength greywater accounted for odour emissions where flows stagnated. Greywater characteristics are highly variable but have potential for biological treatment as the BOD5:COD ratios 0.5. Ghanaian greywater, including flows from a sewered community, is untreated and polluted, and our environment is unsafe.
Modeling the effect of days and road type on peak period travels using structural equation modeling and big data from radio frequency identification for private cars and taxis
(Springer Verlag, 2018) Wemegah, T. D.; Zhu, S.; Atombo, C.
Hole-to-hole fuel injection characteristic differences that occurs during injection, results in non-uniform fuel distribution and compromised combustion and emission in direct injection IC engines. Hence the instantaneous determination of these differences could help in understanding and the improvement of combustion characteristics. In this paper, a hole-to-hole transient measuring method based on the spray momentum flux theorem was developed and used to determine the fuel injection rate from each nozzle hole of a multi-hole diesel injector. The customized measuring method, was further used to study the characteristics of injection from multi-hole nozzle. Injection rates from the multi-hole nozzle, were compared with those measured with an EFS IFR-600 which is widely used to measure the total injection rate of diesel injector. And about 1% discrepancy in terms of cycle fuel injection quantity, was obtained. Additionally, the fuel injection rate from each nozzle hole of a double layered eight-hole diesel injection nozzle were measured and analyzed. It was found that the cycle fuel injection quantities of the lower layered nozzle holes (4 holes) were 5–15% greater than the cycle fuel injection quantities of the upper layered nozzle holes (4 holes). This was attributed to the different degrees of flow resistance encountered by the nozzle holes. The lower layered nozzle holes encountered relatively less flow resistance than the upper layered ones. This result validates the experiment results obtained from the same nozzle, where the mean fuel injection quantities from eight fuel tunnels connected to the holes, showed the same trend.
Simulation of climate characteristics and extremes of the Volta Basin using CCLM and RCA regional climate models
(Theoretical and Applied Climatology, 2019) Darko, D.; Adjei, K. A.; Appiah-Adjei, E. K.; Odai, S. N.; Obuobie, E.; Asmah, R.
The extent to which statistical bias-adjusted outputs of two regional climate models alter the projected change signals for the mean (and extreme) rainfall and temperature over the Volta Basin is evaluated. The outputs from two regional climate models in the Coordinated Regional Climate Downscaling Experiment for Africa (CORDEX-Africa) are bias adjusted using the quantile mapping technique. Annual maxima rainfall and temperature with their 10- and 20-year return values for the present (1981–2010) and future (2051–2080) climates are estimated using extreme value analyses. Moderate extremes are evaluated using extreme indices (viz. percentile-based, duration-based, and intensity-based). Bias adjustment of the original (bias-unadjusted) models improves the reproduction of mean rainfall and temperature for the present climate. However, the bias-adjusted models poorly reproduce the 10- and 20-year return values for rainfall and maximum temperature whereas the extreme indices are reproduced satisfactorily for the present climate. Consequently, projected changes in rainfall and temperature extremes were weak. The bias adjustment results in the reduction of the change signals for the mean rainfall while the mean temperature signals are rather magnified. The projected changes for the original mean climate and extremes are not conserved after bias adjustment with the exception of duration-based extreme indices.
Evolutional characteristics of hydro-meteorological drought studied using standardized indices and wavelet analysis
(Modeling Earth Systems and Environment, 2019) Gyamfi, C.; Amaning-Adjei, K.; Anornu, G. K.; Ndambuki, J. M.; Odai, S. N.
The study presents a more recent historical analysis of hydro-meteorological droughts in the Olifants Basin, South Africa from 1980 to 2013 using the Standardized Precipitation Index (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI) and the Streamflow Drought Index (SDI). Time series of SPI, SPEI and SDI were analyzed for drought intensity and duration using wavelet analysis. Results indicate different periodicity and temporal variability of drought with significant meteorological drought incidence in 1991–2004 within the 2–8-year band and hydrological drought in 1996–2004 within the 3–5-year band. Spearman correlation analysis revealed a significant correlation (p < 0.01) between SPI and SPEI irrespective of the timescale. However, the strongest correlation occurred at the same timescale for SPI and SPEI: 3-month timescale (r = 0.904, p < 0.01), 6-month timescale (r = 0.936, p < 0.01), 9-month timescale (r = 0.946, p < 0.01) and 12-month timescale (r = 0.947, p < 0.01). A significant relation also existed between SDI and SPI (r = 0.731, p < 0.01) as well as between SDI and SPEI (r = 0.631, p < 0.01). Findings further indicate varying degrees of drought ranging from near normal to extremely dry conditions during 1980–2013. It is expected that strategies and policy actions on drought factor in the recurring nature of droughts so as to minimize the negative impact on water resources and other human–hydro-ecological systems.

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