Quantifying risks to microbial water quality in Guizhou province and the South West China karst region

Overview

Exposure to microbial hazards in contaminated waters are a serious human health risk in rapidly-developing countries such as China where there is also high vulnerability to climate change impacts on water supply and quality. Further, in China, infectious disease due to unsafe water is often concentrated in low-income provinces with young children being particularly susceptible. Understanding the fate and transfer of pathogens and their pathways of exposure to human populations (e.g. via drinking water, crop irrigation, household food preparation) is therefore important in areas of China where water sources are vulnerable and prone to contamination, e.g. karst landscapes & peri-urban agricultural land. However, this urgent need to explore microbial pollution issues in the Chinese karst region is driven by more than climate-change concerns. The Chinese Ministry of Agriculture stipulated (2015) that there must be zero growth of chemical fertiliser consumption by 2020, meaning that the world’s top producer of rice and wheat will need to secure nutrient inputs from alternative sources other than mineral fertilisers. The anticipated response will be a significant increase in use of organic fertiliser, currently under-utilised, to help boost agricultural output. This raises concerns for human health of the prevalence of emerging contaminants entering soil and water, including increased concentration of human pathogens. Inhabitants of rural catchments where the use of organic fertiliser is common, such as much of SW China, may be particularly affected. This risk may be further compounded by the highly transmissive nature of the karst, with fast channel flow resulting in rapid contamination of drinking water aquifers and recycling of contaminated water onto food crops through abstraction and irrigation practices.

From 2016-2018, a large multi-partner NERC-NSFC funded project linking Glasgow, Stirling and Aberdeen Universities & colleagues in China undertook an integrated assessment of hydrology and water quality in the Houzhai catchment to identify strategies to sustain the ecosystem services of karst landscapes under increasing land use change pressures and to build resilience to climatic change in the SW-China karst region. Data on nutrient export from the catchment was complemented with microbial water quality monitoring as part of an IAPETUS PhD now nearing completion. An opportunity now exists to further develop our understanding of microbial risks to water quality in this sensitive landscape of the SW-China karst region through the use of models of hydrological connectivity (such as SCIMAP) and landscape E. coli loading (ViPER), and the newly developed SCIMAP-FIO, which linked SCIMAP & ViPER to extend the capability of SCIMAP to enable assessment of the microbial risk to water quality by faecal indicator organisms (FIOs), e.g. E. coli. This studentship will therefore build on our new understanding of this catchment and develop a spatial modelling approach to couple with and extend previous fieldwork campaigns. Members of the supervisory team are now involved in a 2nd phase of follow-on funding in China that is exploring the development of decision support tools for environmental management, which would further complement this PhD.

Research objectives: This studentship will use a combined laboratory, field and modelling-based approach to further our understanding of the vulnerability of karst terrain in contributing to microbial contamination of surface and groundwater due to rapid recharge from the land surface. The overall aim is to provide critical advances in hillslope to catchment scale modelling of E. coli delivery from land to water in typical cone & depression karst landscapes of SW China. The student will address the following research objectives:

1. Identify challenges and opportunities for translating existing modelling capability to the karst landscape of the Houzhai catchment;
2. Derive E. coli die-off values relevant for organic wastes and livestock typical of the Chines karst terrain;
3. Parameterise, test & verify the ViPER model of E. coli loading to land at plot to subcatchment scales using newly derived die-off coefficients;
4. Adapt and deploy SCIMAP-FIO to model spatial and temporal risks to microbial water quality across the Houzhai catchment and ground-truth outputs at multiple scales.

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Image Captions

The karst landscape of Guizhou province, where this PhD project will focus (Photo by David Oliver)

Methodology

The field site
Field work and modelling will be carried out in the SW-China karst terrain. Guizhou province is in the centre of the SW karst terrain and is the location of the primary field site, the Houzhai Catchment (HZ) (81 km2, nested within Sancha river basin, SRB, 5542 km2). The catchment has a typical cone and depression karst landscape and this dictates land use: the valley bottom contains larger flatter plains primarily used for oil seed rape and rice production and some hillslope cultivation, which uses narrower, more restricted terraces for cereal crops such as maize. This terracing has resulted in deforestation and areas of karst desertification, which has reduced vegetation cover from 25% to 9%. The population of this catchment is ~38,000, with 30% living in poverty and directly dependent on the environment for provisioning of potable & irrigation water, food and often fuel. Their farming activity is heavily dependent on fertiliser application (chemical, manure, sewerage), with no buffer zones between fields and watercourses. The mesoscale HZ captures the full landscape aggregation and is typical of a karst system where funnels, sinkholes, and surface and underground channel networks are well-developed. The HZ catchment is a ‘CERN’ catchment (Chinese Ecological Research Network) so existing research & infrastructure will enhance the support for the studentship.

A programme of field work in China will focus on how different land uses and hydrological drivers impact on microbial fate & transfer in the karst terrain. The student will link on-the-ground data collection and experimental results with modelling efforts to explore how land use and seasonality influences FIO source loading and subsequent transfer from land to water. Experimental investigation in China will include: (i) small plot studies of FIO persistence and mobilisation from different organic sources (livestock faeces, manures); and (ii) assessment of FIO loading in emergent waters further down the catchment continuum to compare with modelled outputs. Modelling will be driven by two existing platforms, but will be modified to reflect the local and challenging conditions typical of the Houzhai catchment: (1) SCIMAP – a risk-mapping tool designed to identify the origins of diffuse pollutants in the landscape through combined assessment of spatial patterns of source risks with hydrological connectivity. The underlying philosophy of SCIMAP is built on the well-established concept of critical source areas within agricultural landscapes whereby ‘risky’ land is produced when a pollutant source coincides with an opportunity for connectivity to a watercourse. The connectivity treatment will be updated to reflect the karst conditions. SCIMAP was originally developed for fine sediment and extended to explore pollution risks from diffuse phosphorus and nitrogen, and has recently been extended to account for FIOs; (2) ViPER – a model to map spatial patterns of E. coli accumulation on land. ViPER has evolved as an empirical model first reported as part of a cross-disciplinary toolkit for assessing farm-scale contributions to E. coli risk and has been integrated with SCIMAP for predicting risks to microbial water quality in UK catchments.

This project also includes a collaboration with Dr Tao Peng (Chinese Academy of Sciences) and Dr Phil Bartie (Heriot-Watt University).

Project Timeline

Year 1

The first 8 months will focus on developing a critical literature review and a programme of model familiarisation. The first field season in China including SCIMAP testing and field site reconnaissance will be undertaken. The student will also participate in key training opportunities.

Year 2

Year 2 will involve laboratory & field studies of FIO persistence in a range of different typical organic sources used in the SW China karst region. A second field season in China will be scheduled. The student will undertake field testing of SCIMAP & ViPER predictions of in-stream microbial water quality risk. You will be encouraged to begin to draft chapters as you progress.

Year 3

Year three will integrate data collected from both field seasons into an analysis of model performance, including comprehensive model evaluation and uncertainty assessment.

Year 3.5

The final 6 months will be used to interpret the outputs from the modelling and to finalise the thesis with respect to writing up remaining chapters and refining drafts of chapters completed thus far.

Training
& Skills

This studentship will provide a platform to build an interdisciplinary research career in applied microbiology and hydrology in the context of diffuse pollution with human health impact. The studentship will broaden the scope of the applicant’s skills base by providing specialist training in the safe handling of Hazard Group 2 microorganisms & microbiological methods, and by developing expertise in the use of a wide range of laboratory and modelling techniques. Extensive skill development in fieldwork will include comprehensive training in sampling & monitoring techniques, while the student will also benefit from working closely with experienced field researchers in China. The student will also be exposed to GIS modelling methodologies including computer code writing and risk & uncertainty analysis, with a focus on Python and the effective use of web based technologies, such as cloud computing and web services, for effective scientific research.

References & further reading

Buckerfield SJ, Quilliam RS, Waldron S, Naylor L, Li S-L & Oliver DM (2020). Rainfall-driven E. coli transfer to the stream-conduit network observed through increasing spatial scales in mixed land-use paddy farming karst terrain, Water Research, 100038, doi.org/10.1016/j.wroa.2019.100038

Buckerfield SJ, Waldron S, Quilliam RS, Naylor L, Li S & Oliver DM (2019). How can we improve understanding of faecal indicator dynamics in karst systems under changing climatic, population and land use stressors? – research opportunities in SW China, Science of the Total Environment, 646, 438-447

Porter, K.D., Reaney, S.M., Quilliam, R.S., Burgess, C. and Oliver, D.M., 2017. Predicting diffuse microbial pollution risk across catchments: The performance of SCIMAP and recommendations for future development. Science of the Total Environment, 609, 456-465.

Reaney, S.M., Lane, S.N., Heathwaite, A.L. and Dugdale, L.J., 2011. Risk-based modelling of diffuse land use impacts from rural landscapes upon salmonid fry abundance. Ecological Modelling, 222,1016-1029.

Further Information

For informal enquires: Dr David Oliver (david.oliver@stir.ac.uk tel: 01786 467846)

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