title: The seasonal dynamics of the stream sources and input flow paths of water and nitrogen of an Austrian headwater agricultural catchment.
abstract: Our study examines the source aquifers and stream inputs of the seasonal water and nitrogen dynamics of a headwater agricultural catchment to determine the dominant driving forces for the seasonal dynamics in the surface water nitrogen loads and concentrations. We found that the alternating aquifer contributions throughout the year of the deep and shallow aquifers were the main cause for the seasonality of the nitrate concentration. The deep aquifer water typically contributed 75% of the total outlet discharge in the summer and 50% in the winter when the shallow aquifer recharges due to low crop evapotranspiration. The shallow aquifer supplied the vast majority of the nitrogen load to the stream due to the significantly higher total nitrogen concentration (11 mg-N/l) compared to the deep aquifer (0.50 mg-N/l). The main stream input pathway for the shallow aquifer nitrogen load was from the perennial tile drainages providing 60% of the total load to the stream outlet, while only providing 26% of the total flow volume. The diffuse groundwater input to the stream was the largest input to the stream (39%), but only supplied 27% to the total nitrogen load as the diffuse water was mostly composed of deep aquifer water.
authors.affiliation: Centre for Water Resource Systems, Vienna University of Technology, Vienna, Austria; Institute of Water Quality, Resources and Waste Management, Vienna University of Technology, Vienna, Austria. Electronic address: exner@waterresources.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Exner-Kittridge
authors.affiliation: Federal Agency for Water Management, Institute for Land and Water Management Research, Petzenkirchen, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Strauss
authors.affiliation: Centre for Water Resource Systems, Vienna University of Technology, Vienna, Austria; Institute of Hydrology and Water Resource Management, Vienna University of Technology, Vienna, Austria.
authors.forename: Günter
authors.initials: G
authors.lastname: Blöschl
authors.affiliation: Federal Agency for Water Management, Institute for Land and Water Management Research, Petzenkirchen, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Eder
authors.affiliation: Institute of Water Quality, Resources and Waste Management, Vienna University of Technology, Vienna, Austria.
authors.forename: Ernis
authors.initials: E
authors.lastname: Saracevic
authors.affiliation: Centre for Water Resource Systems, Vienna University of Technology, Vienna, Austria; Institute of Water Quality, Resources and Waste Management, Vienna University of Technology, Vienna, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Zessner
keywords: Catchment hydrology; Diffuse agricultural pollution; Flow pathways; Nitrate; Seasonality; Source separation