A field‐based study of soil water and groundwater nitrate release in an Adirondack forested watershed

Abstract.A data mining, regression tree algorithm M5 was used to review the role of mutual hydrological and seasonal settings which control the streamwater nitrate flushing during hydrological events within a forested watershed in the southwestern part of Slovenia, characterized by distinctive flushing, almost torrential hydrological regime. The basis for the research was an extensive dataset of continuous, high frequency measurements of seasonal meteorological conditions, watershed hydrological responses and streamwater nitrate concentrations. The dataset contained 16 recorded hydrographs occurring in different seasonal and hydrological conditions. Based on predefined regression tree pruning criteria, a comprehensible regression tree model was obtained in the sense of the domain knowledge, which was able to adequately describe most of the streamwater nitrate concentration variations (RMSE=1.02 mg/l-N; r=0.91). The attributes which were found to be the most descriptive in the sense of streamwater nitrate concentrations were the antecedent precipitation index (API) and air temperatures in the preceding periods. The model was most successful in describing streamwater concentrations in the range 1-4 mg/l-N, covering large proportion of the dataset. The model performance was little worse in the periods of high streamwater nitrate concentration peaks during the summer hydrographs (up to 7 mg/l-N) but poor during the autumn hydrograph (up to 14 mg/l-N) related to highly variable hydrological conditions, which would require a less robust regression tree model based on the extended dataset.

Section: Introductionmentioning

confidence: 99%

Assessment of hydrological and seasonal controls over the nitrate flushing from a forested watershed using a data mining technique

Rusjan

Mikoš

2008

“…Subsurface lateral flow is generally initiated when rainwater percolates through a soil profile, meets an impeding layer of soil, regolith or bedrock on hillsope, forms saturated condition and then is diverted laterally downslope (Luxmoore, 1991;Newman et al, 1998). Subsurface lateral flow has been intensively studied in natural ecosystems as it is a major hydrological process (Cirmo and McDonnell, 1997;DeWalle et al, 1988;Burns et al, 2001;McHale et al, 2002;Inamdar and Mitchell, 2007) and it is linked to spatial pedogenetic variations of nutrients and pollutants (Schlichting and Schweikle, 1980). In agriculture, soil structure within a soil profile can be altered by natural soil water erosion and by soil tillage.…”

Section: Introductionmentioning

confidence: 99%

Subsurface lateral flow from hillslope and its contribution to nitrate loading in streams through an agricultural catchment during subtropical rainstorm events

Zhang

Tang

Gao

et al. 2011

Abstract. Subsurface lateral flow from agricultural hillslopes is often overlooked compared with overland flow and tile drain flow, partly due to the difficulties in monitoring and quantifying. The objectives of this study were to examine how subsurface lateral flow generated through soil pedons from cropped hillslopes and to quantify its contribution to nitrate loading in the streams through an agricultural catchment in the subtropical region of China. Profiles of soil water potential along hillslopes and stream hydro-chemographs in a trenched stream below a cropped hillslope and at the catchment outlet were simultaneously recorded during two rainstorm events. The dynamics of soil water potential showed positive matrix soil water potential over impermeable soil layer at 0.6 to 1.50 m depths during and after the storms, indicating soil water saturation and drainage processes along the hillslopes irrespective of land uses. The hydro-chemographs in the streams, one trenched below a cropped hillslope and one at the catchment outlet, showed that the concentrations of particulate nitrogen and phosphorus corresponded well to stream flow during the storm, while the nitrate concentration increased on the recession limbs of the hydrographs after the end of the storm. All the synchronous data revealed that nitrate was delivered from the cropped hillslope through subsurface lateral flow to the streams during and after the end of the rainstorms. A chemical mixing model based onCorrespondence to: B. Zhang (bzhang@caas.ac.cn) electricity conductivity (EC) and H + concentration was successfully established, particularly for the trenched stream. The results showed that the subsurface lateral flow accounted for 29 % to 45 % of total stream flow in the trenched stream, responsible for 86 % of total NO − 3 -N loss (or 26 % of total N loss), and for 5.7 % to 7.3 % of total stream flow at the catchment outlet, responsible for about 69 % of total NO − 3 -N loss (or 28 % of total N loss). The results suggest that subsurface lateral flow through hydraulically stratified soil pedons have to be paid more attention for controlling non-point source surface water pollution from intensive agricultural catchment particularly in the subtropical areas with great soil infiltration.

“…Woods and Rowe, 1996;Tani, 1997;Buttle and McDonald, 2002;Troch et al, 2003;Tromp-van Meerveld and McDonnell, 2006a, b;Kampf and Burges, 2007;Fiori and Russo, 2007) because of its importance in runoff generation and controlling the export of leached mineral and nutrient species (e.g. van Verseveld et al, 2008;McHale et al, 2002). The hillslope was designed to facilitate the occurrence of this process.…”

Section: Design Criteriamentioning

confidence: 99%

Hillslope hydrology under glass: confronting fundamental questions of soil-water-biota co-evolution at Biosphere 2

Hopp

Harman

Desilets

et al. 2009

Abstract. Recent studies have called for a new unifying hydrological theory at the hillslope and watershed scale, emphasizing the importance of coupled process understanding of the interactions between hydrology, ecology, pedology, geochemistry and geomorphology. The Biosphere 2 Hillslope Experiment is aimed at tackling this challenge and exploring how climate, soil and vegetation interact and drive the evolution of the hydrologic hillslope behavior. A set of three large-scale hillslopes (18 m by 33 m each) will be built in the climate-controlled experimental biome of the Biosphere 2 facility near Tucson, Arizona, USA. By minimizing the initial physical complexity of these hillslopes, the spontaneous formation of flow pathways, soil spatial heterogeneity, surface morphology and vegetation patterns can be observed over time. This paper documents the hydrologic design process for the Biosphere 2 Hillslope Experiment, which was based on design principles agreed upon among the Biosphere 2 science community. Main design principles were that the hillslopes should promote spatiotemporal variability of hydrological states and fluxes, facilitate transient lateral subsurface flow without inducing overland flow and be capable of supporting vegetation. Hydrologic modeling was used to identify a hillslope configuration (geometry, soil texture, soil depth) that meets the design objectives. The recommended design for the hillslopes consists of a zero-order basin shape with a 10 degree overall slope, a uniform soil depth of 1 m and a loamy sand soil texture. The sensitivity of the hydrologic response of this design to different semiarid climate scenarios was subsequently tested. Our modeling showed that the timing of rainfall in relation to the timCorrespondence to: L. Hopp (luisa.hopp@oregonstate.edu) ing of radiation input controls the spatiotemporal variability of moisture within the hillslope and the generation of lateral subsurface flow. The Biosphere 2 Hillslope Experiment will provide an excellent opportunity to test hypotheses, observe emergent patterns and advance the understanding of interactions.