| Dual challenges of water scarcity and acid rain attract great attention in the context of climate change and serious air pollution in developing African countries,such as in Niger delta region of Nigeria.On one hand,water scarcity in Niger delta has progressed to pathetic states in some cities,with less than 50%of the urban areas having access to enough water supply for daily uses.On the other hand,the prevalent acid rain in the Niger delta region that is resultant from SO2 and NOx emission of local gas flaring and oil production has further complicated the issues of water supply.Rain water harvesting(RWH)has been proven to be a major water supply alternative to local residents by previous studies,but the failure predicting harvest potential hinders the harvesting practice.Thus,this study seeks a reconciled way,to achieve the dual-win goals of both improving water supply and controlling acid rain simultaneously.The multiplicity of factors that interplay in making informed decisions makes multi criteria decision analysis model(MCDA)needed,which has been widely used for non-conventional water supply options.However,influenced by subjective nature of human rationality,it is hard task to arrive at the best option of alternative water supply from sustainable aspects.From available experiences,previous studies highly depends on opinions from a limited experts,and barely included full stakeholder participation and social sustainability factors,in addition to the difficulty to express expert's opinion in a quantitative way.Here,we on the basis of sustainability criteria used fuzzy technique for order preference with similarity to ideal solution(i.e.fuzzy TOPSIS belonging to MCDA models)to reduce regional water scarcity and acid-rain simultaneously.A total of 40 experts at both government and non-government levels were surveyed in this study.The study results are as follows.(1)Based on the analysis of local situation of water sources,we explored various available alternative water supply options extensively,including borehole water,RWH,reclaimed water,imported water and desalination.Following a deductive procedure,we formulated a fuzzy TOPSIS model to bring into social,economic,technical,environmental and institutional factors by making for full stakeholder participation.This method ranks the importance of all covered factors by converting uncertain expert' s opinion into crisp scores supported by triangular fuzzy numbers,to compare the feasibility of all available water supply options for achieving sustainability.Referring to local popular water supply method of borehole,our study result shows that performance of RWH is comparable,with just a slight difference existing between the two methods.Revelations of our study are apt to all stakeholders in the water delivery sector and would deepen the public understanding on conservation of water resources by adopting RWH method.(2)Acid-rain significantly influenced RWH for water supply purpose in high harvesting potential regions of the Niger delta of Nigeria,where gas flaring during oil exploration is a major cause of acid rain.Based on previous available six options to control acid-rain,via flue gas desulphurization,liming,natural gas replacing coal power,catalytic converters for vehicular emission,and coal washing to reduce sulphur,this study brings to perspective the use of NOx burners,as well as proposing four options of hydro power and solar as alternative energy sources,quitting gas flaring and raising environmental awareness on acid rain.For all the ten options of acid-rain control,fuzzy TOPSIS method was used to aid selecting multiple economic,environmental,social,technical,and institutional factors.Results indicated that solar energy replacing coal power ranked the first to control acid-rain,while hydro energy and NOx burners ranked second and third,respectively.Hence beyond totally quitting gas flaring,enforcing the use of NOx burners and a shift to promoting investment in solar plants is considered as optimal environmental policy to control acid-rain and improve the quality of RWH.(3)The RWH served an effective option in alleviating regional water problems from the perspective of alternative water supply modes.Based on monthly rainfall data for a 22 years,this study used the simple water balance model to obtain the optimal results of RWH,by simulating the maximum volume of harvestable rain water from various tank sizes and roof areas.Result showed that the annual maximum RWH potential in Benin City reached up to 745.9 m3 per household on average.According to field survey in Niger delta region,a household cluster usually include six households that share one tank to store water form RWH for daily uses.Simulation results further found that a combined system of roof catchment area of 400 m2 and storage tank size of 400 m3 for one household cluster was optimal for the high demand scenario of 65.88 m3 monthly with a reliability of 86%.Generally,water scarcity is gradually becoming a looming danger,and pose serious challenge to human society now and in the future.This is particularly so for developing oil producing countries like Nigeria delta region where the situation is further worsened by the acid rain phenomenon which further influence the regional sustainable development.Therefore the revelations of this study(i.e.RWHS of 400 m2 and 400 m3 roof and tank sizes coupled with an investment shift in alternative energy sources such as solar power),we expect can enrich practical experiences in the foreseeable future of the region,in achieving dual-win resolutions to reconcile the preferred alternative water supply by RWH and regional acid-rain control. |
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