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Adequate and sustainable water resources are fundamental for human life to promote economic and social growth. Since the start of industrialisation, the global water demand has been growing continuously. Access to sufficient domestic water supply is a very problematic experience for the urban population of low and middle-income countries. The leading factors behind water insufficiency are urbanisation, seasonal variability, economic growth, population growth, inadequate dam capacity, and lack of experts in the sector. Aside from these factors, behaviour, patterns and household characteristics have been identified as the most important influence governing water consumption.
Many Non-Governmental Organisations working in these low and middle-income countries have tried to salvage the problem by digging wells to support these communities. However, many of these dug wells have failed to supply the necessary daily volume because of unproductive siting, poor construction practices, and lowering of the water table due to seasonality. Little research has looked at any useful information on water consumption and evaluated groundwater storage of an aquifer as a solution for sustainable seasonal domestic water consumption.
Freetown, the capital city of Sierra Leone, is the case study because of the necessity to assess the problems of meeting water demands, initiated by variability in seasons, inadequate infrastructure, lack of expertise, and the intense migration from the rural areas to settle in the city. This has subjected surface water supplies to increasing pressure from growing demand. However, groundwater sources have not been sufficiently tapped. This research aims to develop a strategy to manage groundwater in a sustainable way under the influence of seasonal variability. To achieve this, two work elements were designed and implemented as part of this thesis.
The first work element gathered information using multiple-choice format questionnaires on the factors that influence seasonal water end-use consumption patterns at a per capita scale of 398 households. The key variables investigated were income, education, number of rooms, number of vehicles, family size, collection containers, and time to fetch and distance to source. The investigated households were categorized into four household income groups and were evaluated individually to determine their daily per capita water consumption in litres per day (l/p/d). Additionally, surveyed data was used to develop statistical regression models for estimating demand as a function of household characteristics using stepwise-multiple-linear regression techniques.
The second component of this research investigated groundwater interconnectivity with other surface water bodies for the assessment of the aquifer’s suitability, pumping, recharge, and drawdown capacity for an increased abstraction of water supply. Consequently, related thematic maps have been created from digital elevation models and ASTER data downloaded from the USGS websites using a GIS format. The 3D numerical ModelMuse MODFLOW package, integrated with GIS techniques was used to understand the groundwater dynamics under varying scenarios of abstraction and wells performance for the next fifteen years.
The results of the water consumption questionnaire-based study provided quantitative evidence of daily per capita end-uses for the different household income groups. The modelled data indicated a significant variation in the volume of per capita water consumption (13 l/p/d to over 273 l/p/d). Also, the findings suggest that distance to a water source and queuing time to fetch water and return home impacts the volume of water collected. On the other hand, the groundwater simulations studies indicate managed groundwater abstraction to be the most efficient and sustainable strategy to increase daily per capita water end-use volume. Results revealed that the groundwater regional recharge rate (101 x106 m3/year) is greater than the water supply from the service provider (12.4x106 m3/year), thereby giving the possibility to increase yearly per capita water consumption. Further simulation results show water supply from infiltration galleries can produce a further 51.8×106 m3/year.
A demand-supply analysis, taking into account population projections and per capita consumption estimates and groundwater supply simulations developed in this research, showed that the annual groundwater supply is sufficient to satisfy the domestic water supply needs without causing any water stress or shortage. Therefore, this research proposes the implementation of new boreholes for densely populated areas and infiltration galleries along simulated perennial rivers to address acute urban water shortage in Freetown, Sierra Leone. |
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