title: A hydrodynamics-based approach to evaluating the risk of waterborne pathogens entering drinking water intakes in a large, stratified lake.
abstract: Pathogen contamination of drinking water lakes and reservoirs is a severe threat to human health worldwide. A major source of pathogens in surface sources of drinking waters is from body-contact recreation in the water body. However, dispersion pathways of human waterborne pathogens from recreational beaches, where body-contact recreation is known to occur to drinking water intakes, and the associated risk of pathogens entering the drinking water supply remain largely undocumented. A high spatial resolution, three-dimensional hydrodynamic and particle tracking modeling approach has been developed to analyze the risk and mechanisms presented by pathogen dispersion. The pathogen model represents the processes of particle release, transport and survival. Here survival is a function of both water temperature and cumulative exposure to ultraviolet (UV) radiation. Pathogen transport is simulated using a novel and computationally efficient technique of tracking particle trajectories backwards, from a drinking water intake toward their source areas. The model has been applied to a large, alpine lake - Lake Tahoe, CA-NV (USA). The dispersion model results reveal that for this particular lake (1) the risk of human waterborne pathogens to enter drinking water intakes is low, but significant; (2) this risk is strongly related to the depth of the thermocline in relation to the depth of the intake; (3) the risk increases with the seasonal deepening of the surface mixed layer; and (4) the risk increases at night when the surface mixed layer deepens through convective mixing and inactivation by UV radiation is eliminated. While these risk factors will quantitatively vary in different lakes, these same mechanisms will govern the process of transport of pathogens.
authors.affiliation: Water Research Institute, University of Granada, C/ Ramón y Cajal 4, 18071 Granada, Spain. Electronic address: abhoyer@ugr.es.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Hoyer
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA; Tahoe Environmental Research Center, University of California, Davis, 291 Country Club Dr., Incline Village, NV 89451, USA. Electronic address: gschladow@ucdavis.edu.
authors.forename: S Geoffrey
authors.initials: SG
authors.lastname: Schladow
authors.affiliation: Water Research Institute, University of Granada, C/ Ramón y Cajal 4, 18071 Granada, Spain; Department of Civil Engineering, University of Granada, Campus Universitario de Fuentenueva (Edificio, Politécnico), 18071 Granada, Spain. Electronic address: fjrueda@ugr.es.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Rueda
mesh_terms: D002140:California; D003458:Cryptosporidium / Q000302:isolation & purification* / Q000502:physiology; D060766:Drinking Water / Q000469:parasitology*; D004784:Environmental Monitoring / Q000379:methods*; D057446:Hydrodynamics; D060106:Lakes / Q000469:parasitology*; D008962:Models, Theoretical; D009505:Nevada; D018570:Risk Assessment; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D060766:Drinking Water
keywords: Back-tracking algorithm; Body-contact recreation; Cryptosporidium; Drinking water contamination; Individual-based model; UV inactivation