Jacqueline Frizenschaf

Investigating source water Cryptosporidium concentration, species and infectivity rates during rainfall-runoff in a multi-use catchment

Protozoan pathogens present a significant human health concern, and prevention of contamination into potable networks remains a key focus for drinking water providers. Here, we monitored the change in Cryptosporidium concentration in source water during high flow events in a multi-use catchment. Furthermore, we investigated the diversity of Cryptosporidium species/genotypes present in the source water, and delivered an oocyst infectivity fraction. There was a positive and significant correlation between Cryptosporidium concentration and flow (ρ = 0.756) and turbidity (ρ = 0.631) for all rainfall-runoff events, despite variable source water pathogen concentrations. Cell culture assays measured oocyst infectivity and suggested an overall source water infectious fraction of 3.1%. No infectious Cryptosporidium parvum or Cryptosporidium hominis were detected, although molecular testing detected C. parvum in 7% of the samples analysed using PCR-based molecular techniques. Twelve Cryptosporidium species/genotypes were identified using molecular techniques, and were reflective of the host animals typically found in remnant vegetation and agricultural areas. The inclusion of molecular approaches to identify Cryptosporidium species and genotypes highlighted the diversity of pathogens in water, which originated from various sources across the catchment. We suggest this mixing of runoff water from a range of landuses containing diverse Cryptosporidium hosts is a key explanation for the often-cited difficulty forming strong pathogen-indicator relationships.

Future climate and land uses effects on flow and nutrient loads of a Mediterranean catchment in South Australia

Mediterranean catchments experience already high seasonal variability alternating between dry and wet periods, and are more vulnerable to future climate and land use changes. Quantification of catchment response under future changes is particularly crucial for better water resources management. This study assessed the combined effects of future climate and land use changes on water yield, total nitrogen (TN) and total phosphorus (TP) loads of the Mediterranean Onkaparinga catchment in South Australia by means of the eco-hydrological model SWAT. Six different global climate models (GCMs) under two representative concentration pathways (RCPs) and a hypothetical land use change were used for future simulations. The climate models suggested a high degree of uncertainty, varying seasonally, in both flow and nutrient loads; however, a decreasing trend was observed. Average monthly TN and TP load decreased up to -55% and -56% respectively and were found to be dependent on flow magnitude. The annual and seasonal water yield and nutrient loads may only slightly be affected by envisaged land uses, but significantly altered by intermediate and high emission scenarios, predominantly during the spring season. The combined scenarios indicated the possibility of declining flow in future but nutrient enrichment in summer months, originating mainly from the land use scenario, that may elevate the risk of algal blooms in downstream drinking water reservoir. Hence, careful planning of future water resources in a Mediterranean catchment requires the assessment of combined effects of multiple climate models and land use scenarios on both water quantity and quality.

Three criteria reliability analyses for groundwater recharge estimations

There is a broad variety of methods to estimate groundwater recharge, but tools to assess the reliability of particular methods are not available. This paper introduces three distinct criteria to assess the reliability of recharge: applicability of the method used, availability of reliable data, and spatial coverage. Weightings of each criterion are assigned using key attributes present to total attributes required under each criterion. A reliability assessment was applied to two point-recharge and two diffuse-recharge dominated groundwater basins in South Australia. We show that the use of groundwater age based on chlorofluorocarbon and the conventional chloride mass balance method gives unreliable estimates of recharge in karstic aquifers, primarily due to inappropriate assumptions concerning the nature of recharge in these systems. Among the methods evaluated, watertable fluctuation, numerical groundwater modelling, Darcy flow calculation and the water budget method are applied to both point and diffuse recharge dominant groundwater basins. The reliability of these methods depends primarily on the quality of data and spatial coverage of the basin. Once the reliability level is known, water resources planners and managers assess the level of risk to aquifers, the environment, and the socio-economic development required for sustainable management of groundwater.