title: Identification of phosphorus export from low-runoff yielding areas using combined application of high frequency water quality data and MODHMS modelling.
abstract: In basins combining flat-sandy valleys and hilly-bedrock sub-catchments, the assessment of nutrient (phosphorus) exports from low-runoff yielding environments is difficult. To overcome this issue hydrological modelling and high frequency phosphorus measurements were simultaneously employed. A coupled surface water-groundwater interaction model (MODHMS) was used to determine runoff from the low-runoff yielding part of the catchment. The modelling results indicated that the lower catchment contributed less than 10% of annual catchment discharge over a number of weeks during mid-winter. High frequency phosphorus (P) measurements showed a threefold increase in P concentration during this period in 2008, which lasted for 3 weeks. Concentration-discharge analysis suggested that the increase in P concentration was associated with runoff generation processes in the low-runoff yielding sub-catchment. It was estimated that this area contributed 32% of the annual P load though only 2% of total annual discharge in 2008. Both runoff and P contributions occurred during the period when the water table rose to the surface causing inundation. It was shown that the P concentrations in discharge from the low-runoff yielding sub-catchment were similar to those observed in the shallow groundwater layers.
authors.affiliation: CSIRO Land and Water, Floreat, Western Australia, Private Bag 5, Wembley, WA 6913, Australia. Michael.Donn@csiro.au
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Donn
authors.forename: Olga V
authors.initials: OV
authors.lastname: Barron
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Barr
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments / Q000737:chemistry; D060587:Groundwater / Q000737:chemistry; D008956:Models, Chemical; D010758:Phosphorus / Q000032:analysis*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus