Geoelectric Evaluation of Groundwater Potential and Vulnerability of Overburden Aquifers at Onibu-Eja Active Open Dumpsite, Osogbo, Southwestern Nigeria

Electrical resistivity method was used to assess groundwater potential and vulnerability of overburden aquifers at Onibu-Eja active open dumpsite, Osogbo, Southwestern Nigeria. Eighteen Vertical Electrical Sounding (VES) points and five 2-D imaging profiles established in five traverses at the periphery of the dumpsite were surveyed and analysed. The subsurface comprised of thin topsoil (resistivity 65 - 998 Ωm);heterogeneous weathered layer with resistivity 63 - 333 Ωm and thickness 0.7 - 8.5 m;weathered basement (resistivity 31 - 1253 Ωm and thickness 0.7 - 27.0 m) and fractured/fresh basement (resistivity 36 - 6213 Ωm). The 2-D inverse model of the profiles delineated low resistivity values ranging from 5 to 100 Ωm at a depth range of 10 - 20 m along traverses TR1-TR3 which is attributed to leachate percolation close to the dumpsite. The weathered basement was inclined relative to the dumpsite. The total overburden thickness varies from 6.9 to 33.7 m, with 20 and 40 m generally recommended as productive for groundwater abstraction in Southwestern Nigeria occurring in 61% of the area. Further, about 85% of the weathered layer resistivity values fall within medium groundwater potential (100 - 250 Ωm) and high groundwater potential (>250 Ωm). The ranking of groundwater potential as a function of saprolite (weathered basement) resistivity showed that 72% of the study area is characterized by optimum weathering (20 - 100 Ωm) and is classified as good groundwater potential. Fractured basement covered <30% of the study area. The evaluation of aquifer protective capacity has helped to classify the area into moderate, weak and poor protective capacities with moderate protective capacity zone covering 72%.

Comparison of a Soil Vulnerability Map for Tetracycline Soil Contamination at a Global and Local Scale

Recently, de la Torre[1] provided an approach for assessing the vulnerability of European soils for tetracyclines, fluoroquinolones and sulfamides contamination using a spatial risk assessment. It allowed identifying areas where vulnerable soil more occur, providing useful information for policies designed to reduce contamination. In the current study, this approach was applied to a local level, the autonomous region of Castile and León (C&L), located in the north-west part of Spain. High accurate and reliable source data were employed to generate a soil vulnerability map for tetracyclines in the study area, attempting to improve the release and consequence risk prediction. More specifically, pig density, temperature and soil use risk estimators were improved using data from national or local databases. Result comparison between the European and the present approach showed a good agreement demonstrating the utility of the European vulnerability map to be employed not only at global level but also for deciding how to allocate limited resources on national or subnational environmental surveillance programs of antibiotics. The model application at local level using more accurate data from national or local sources, afforded a better understanding of the spatial distribution of the risk, mainly associated with the higher accuracy of the national land use database SIOSE. It could offer a useful tool for local management of the risk, such as the management of animal manures fertilization on soil.

Blind Spots on Achilles’ Heel:The Limitations of Vulnerability and Resilience Mapping in Research

The mapping of vulnerability and resilience has become an important tool for vulnerability and resilience research.By definition,maps are selective representations.However,the predominant methods of mapping also have constraints.When addressing vulnerability and resilience,these limitations,barriers,and blind spots have to be taken into account.Some aspects cannot be easily mapped,such as specific forms of knowledge and interpretation,the processuality of vulnerability and resilience,the dynamics of social processes,the context of origin,the establishment of contingent interpretations,and so on.These limitations are not only theoretically important,but also are practically significant,since maps themselves become dispositifs.They are regarded as representations of reality,shape particular interpretations of vulnerability and resilience,and are used as a basis for decision-making.If the unmapped preconditions of mapping remain unconsidered,this can lead to problematic side effects.

Assessment of Community Based Climate Change Risk Focusing Agriculture and Fisheries Sector in Haor Areas of Bangladesh

The research paper aims at understanding the level of climate change risk of the Haor areas of Bangladesh. It follows a participatory approach, using Focus Group Discussion (FGD) and Key Informant Interview (KII) to identify important climate change induced hazards, assess the probability of occurrences of the hazards and level of their consequences. Using geo-spatial techniques, the paper prepares hazard risk maps and risk hotspot maps. Policy documents, previous researches, and Government statistics and reports helped to develop the concepts and planning of the research. The unparalleled hydro-ecological attributes of Haor areas pose both opportunities and constraints for the local population. Poverty, lack of basic infrastructure and amenities, awareness and external support have already put the people in Haor areas in a vulnerable situation while the recurring natural hazards and shifting pattern of climate are making the constraints nearly unmanageable. Excessive rainfall in the monsoon and drought in the dry season is affecting the farming and fishery-based communities the most. The community perceptions on hazards, their occurrences, consequences and relative importance of each hazard for the agriculture or fisheries sector in the study area have been collected from the FGDs and subsequently analyzed to produce individual and multi-hazard risk maps for the area based on scoring. This information is also used to rank the Upazillas in the study area depending on risk level. The community people were also asked to select the important elements or structural facilities at risk in their area needed for their life and livelihood. Based on this selection, risk hotspot map for the study area has been prepared using GIS based weighted overlay methods. The final risk hotspot map identifies about hundred unions in the area as hotspots. This paper might encourage the local government organizations to make choice on the intervention as well as intervention needs for protecting livelihoods in the study area. The results of the study will be helpful in planning adaptation options for future for the study area as well as effectively allocate resources/investments to protect population and livelihoods from possible climate change induced hazards.