Water research round-up

This is a collection of links to articles that have been recently published that I find relevant to my work or just interesting from a content or methods perspective.

Intermittent supply-related 

Coulibaly, L., Jakus, P. M., and Keith, J. E. (2014) Modeling water demand when households have multiple sources of water. Water Resources Research (just accepted).
Abstract: A significant portion of the world’s population lives in areas where public water delivery systems are unreliable and/or deliver poor quality water. In response, people have developed important alternatives to publicly supplied water. To date, most water demand research has been based on single-equation models for a single source of water, with very few studies that have examined water demand from two sources of water (where all non-public system water sources have been aggregated into a single demand). This modeling approach leads to two outcomes. First, the demand models do not capture the full range of alternatives so the true economic relationship amongst the alternatives is obscured. Second, and more seriously, economic theory predicts that demand for a good becomes more price-elastic as the number of close substitutes increases. If researchers artificially limit the number of alternatives studied to something less than the true number, the price elasticity estimate may be biased downward. This paper examines water demand in a region with near universal access to piped water, but where system reliability and quality is such that many alternative sources of water exist. In extending the demand analysis to four sources of water we are able to (i) demonstrate why households choose the water sources they do, (ii) provide a richer description of the demand relationships among sources, and (iii) calculate own-price elasticity estimates that are more elastic than those generally found in the literature.
My notes: The study was conducted in the Zarqa Governate of Jordan, where piped water was delivered 41 hours/week and households also rely on tanker trucks, water filled at shops, and bottled water. They found that households chose to consume from sources other than piped water because of limited hours, undesirable water aesthetics , and perceptions of illness.

Venkatachalam, L. (2014) Informal water markets and willingness to pay for water: a case study of the urban poor in Chennai City, India. International Journal of Water Resources Development, 1–12.
Abstract: The present study analyzes the role of informal markets in fulfilling the water requirements of poorer households in Chennai City, India. The results of a survey reveal that a significant number of poor people purchase water from informal markets and that they incur a sizeable expenditure on water purchases; some of these households are also willing to pay additional amounts for improved water supply from public sources. The results suggest that improvements in public water supply would significantly increase the welfare of the poor. The informal markets need to be regulated and monitored so that they can serve the households in a better way.

Water quality in distribution systems 

World Health Organization (2014), Water safety in distribution systems, Geneva.

Chowdhury, S. and Al-Zahrani, M. (2014) Modeling Heterotrophic Bacteria in Plumbing System of Drinking Water. Water Environment Research, 86(6), 504–512.Abstract: This study investigated occurrences of heterotrophic (HPC) bacteria and developed predictive models for HPC bacteria in plumbing pipes (PP) and hot water tanks (HWT) of two houses in Dhahran (Saudi Arabia). Heterotrophic bacteria in PP and HWT were observed to be 2.4 to 5.3 and 0.4 to 5.9 times the HPC bacteria in water distribution system (WDS), respectively. Three linear, one nonlinear, and one neural network models were investigated to predict HPC bacteria in PP and HWT. Significant factors for bacteria regrowth in PP and HWT were identified through numerical and graphical techniques. The R2 values of the models varied between 0.57 and 0.96, indicating moderate to excellent predictive ability for HPC bacteria in PP and HWT. The models were found to be statistically significant, which were also validated using additional data. These models can be used to predict HPC bacteria regrowth from WDS to PP and HWT, and could help to predict exposure and risks.

Water Quality Monitoring

Jung, A.-V., Le Cann, P., Roig, B., Thomas, O., Baurès, E., and Thomas, M.-F. (2014) Microbial Contamination Detection in Water Resources: Interest of Current Optical Methods, Trends and Needs in the Context of Climate Change. International Journal of Environmental Research and Public Health, 11(4), 4292–4310.
Abstract: Microbial pollution in aquatic environments is one of the crucial issues with regard to the sanitary state of water bodies used for drinking water supply, recreational activities and harvesting seafood due to a potential contamination by pathogenic bacteria, protozoa or viruses. To address this risk, microbial contamination monitoring is usually assessed by turbidity measurements performed at drinking water plants. Some recent studies have shown significant correlations of microbial contamination with the risk of endemic gastroenteresis. However the relevance of turbidimetry may be limited since the presence of colloids in water creates interferences with the nephelometric response. Thus there is a need for a more relevant, simple and fast indicator for microbial contamination detection in water, especially in the perspective of climate change with the increase of heavy rainfall events. This review focuses on the one hand on sources, fate and behavior of microorganisms in water and factors influencing pathogens’ presence, transportation and mobilization, and on the second hand, on the existing optical methods used for monitoring microbiological risks. Finally, this paper proposes new ways of research.

Modeling – Water-borne diseases and environmental drivers

Finger, F., Knox, A., Bertuzzo, E., Mari, L., Bompangue, D., Gatto, M., et al. (2014) Cholera in the Lake Kivu region (DRC): Integrating remote sensing and spatially explicit epidemiological modeling. Water Resources Research (just accepted).
Abstract: Mathematical models of cholera dynamics can not only help in identifying environmental drivers and processes that influence disease transmission, but may also represent valuable tools for the prediction of the epidemiological patterns in time and space as well as for the allocation of health care resources. Cholera outbreaks have been reported in the Democratic Republic of the Congo since the 1970s. They have been ravaging the shore of Lake Kivu in the east of the country repeatedly during the last decades. Here we employ a spatially explicit, inhomogeneous Markov chain model to describe cholera incidence in eight health zones on the shore of the lake. Remotely sensed datasets of chlorophyll concentration in the lake, precipitation and indices of global climate anomalies are used as environmental drivers in addition to baseline seasonality. The effect of human mobility is also modelled mechanistically. We test several models on a multi-year dataset of reported cholera cases. The best fourteen models, accounting for different environmental drivers, and selected using the Akaike information criterion, are formally compared via proper cross-validation. Among these, the one accounting for seasonality, El Niñno Southern Oscillation, precipitation and human mobility outperforms the others in cross-validation. Some drivers (such as human mobility and rainfall) are retained only by a few models, possibly indicating that the mechanisms through which they influence cholera dynamics in the area will have to be investigated further.

Integrated Watershed Management

Nerkar, S. S., Tamhankar, A. J., Khedkar, S. U., and Lundborg, C. S. (2014) Quality of Water and Antibiotic Resistance of Escherichia coli from Water Sources of Hilly Tribal Villages with and without Integrated Watershed Management—A One Year Prospective Study. International Journal of Environmental Research and Public Health, 11(6), 6156–6170.
Abstract: In many hilly tribal areas of the world, water scarcity is a major problem and diarrhoea is common. Poor quality of water also affects the environment. An integrated watershed management programme (IWMP) aims to increase availability of water and to improve life conditions. Globally, there is a lack of information on water contamination, occurrence of diarrhoea and antibiotic resistance, a serious global concern, in relation to IWMP in hilly tribal areas. Therefore, a prospective observational study was conducted during 2011–2012 in six villages in a hilly tribal belt of India, three with and three without implementation of an IWMP, to explore quality of water, diarrhoeal cases in the community and antibiotic resistance of Escherichia coli from water sources. The results showed that physico-chemical quality of water was within limits of safe consumption in all samples. The odds of coliform contamination in water samples was 2.3 times higher in non-watershed management villages (NWMV) compared to integrated watershed management villages (IWMV) (95% CI 0.8–6.45, p = 0.081). The number of diarrhoeal cases (18/663 vs. 42/639, p < 0.05) was lower in IWMV as compared to NWMV. Overall E. coli isolates showed high susceptibility to antibiotics. Resistance to a wider range of antibiotics was observed in NWMV.


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