Abstract
Human exposure to water contaminated with faeces is a leading cause of worldwide ill-health. Contaminated water can be transmitted rapidly in karst terrain as a result of the connectivity of surface and groundwater systems, high transmissivity of aquifers over large areas, and well-developed underground conduit systems. Faecal indicator organisms (FIOs) are the most widely-used indicator of faecal contamination and microbial water quality; however, the conceptualisation of FIO risk and associated sources, pathways, and survival dynamics of FIOs in karst landscapes requires a degree of modification from traditional conceptual models of FIO fate and transfer in non-karst systems. While a number of reviews have provided detailed accounts of the state-of-the-science concerning FIO dynamics in catchments, specific reference to the uniqueness of karst and its influence on FIO fate and transfer is a common omission. In response, we use a mixed methods approach of critical review combined with a quantitative survey of 372 residents of a typical karst catchment in the southwest China karst region (SWCKR) to identify emerging research needs in an area where much of the population lives in poverty and is groundwater dependent. We found that the key research needs are to understand: 1) overland and subsurface FIO export pathways in karst hydrology under varying flow conditions; 2) urban and agricultural sources and loading in mixed land-use paddy farming catchments; 3) FIO survival in paddy farming systems and environmental matrices in karst terrain; 4) sediment-FIO interactions and legacy risk in karst terrain; and 5) key needs for improved hydrological modelling and risk assessment in karst landscapes. Improved knowledge of these research themes will enable the development of evidence-based faecal contamination mitigation strategies for managing land and water resources in the SWCKR, which is highly vulnerable to climate change impacts on water supply and quality of water resources.
Highlights
Exposure to water resources contaminated with either human, livestock or wildlife faeces can pose a potential risk to human health (Kay et al, 2007)
In response to growing awareness of the challenge of karst-related Faecal indicator organisms (FIOs) pollution, we have identified five key themes and a series of research priorities that would support a critical advance in our knowledge of FIO behaviour in the southwest China karst region (SWCKR), as related to key processes and features of this terrain (Fig. 1)
The population of the SWCKR is highly vulnerable to water contamination issues, with mitigation challenged with a combination of climatic conditions, population pressures, and land-use regimes that can strongly influence FIO behaviour
Summary
Exposure to water resources contaminated with either human, livestock or wildlife faeces can pose a potential risk to human health (Kay et al, 2007). The SWCKR is characterised by well-developed karst geology, high intensity precipitation events, population pressure, intensive agriculture and animal husbandry, and the highest national poverty rates, which have all been identified as causes of increased microbial contamination risk (Balbus and Embrey, 2002; Curriero et al, 2001; Dangendorf et al, 2002; Guo et al, 2009; Howard et al, 2003; Luffman and Liem, 2014) This combination of factors makes this geographical area a high priority for considering the challenges and opportunities of FIO research needs in karst terrain. The aims of this critical review are to identify research needs for advancing our understanding of FIO fate and transfer in the SWCKR, and to extrapolate from this region to identify a broader, more generic set of research priorities needed to better define our understanding of karst-related FIO behaviour
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