Estimation of nitrogen and phosphorus losses to surface water and groundwater through the implementation of the SWAT model for Norwegian soils

• Published in: Journal of soils and sediments 2007-08, Vol.7 (4), p.223-231
• Main Authors: Panagopoulos, Ioannis, Mimikou, Maria, Kapetanaki, Maria
• Format: Article
• Language: English
• Subjects: Agricultural research; Annual runoff; Behavior; Cereal crops; Clay; Climatic conditions; Cold; Cultivation; Fertilizer application; Grain cultivation; Infiltration; Leaching; Loam; Nitrates; Nitrogen; Phosphorus; Physical properties; River basins; Rivers; Runoff; Sediments; Snowmelt; Snowpack; Soil texture; Soil types; Soils; Surface water; Surface-groundwater relations
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1065/jss2007.04.219

It is acknowledged that diffuse sources cause the most important nitrogen (N) and phosphorus (P) losses to the river system and substantially enrich the groundwater in nitrates. These losses arise primary from agricultural activities mainly fertilizer applications, and they are determined by soil attributes. In cold climates, winter conditions and freezing of soils may influence the infiltration capacity of the soil and thereby can have a serious effect on the partitioning of excess precipitation and subsequently on the soil and nutrient transportation. The purpose of this article is to investigate the behaviour of six widespread and different textured soil types, on nutrient (N, P) losses under cold climate conditions. The investigation was conducted in the Norwegian Vansjø-Hobølv catchment through the application of a physical model named Soil and Water Assessment Tool (SWAT), taking into consideration the additional aspect of freezing soils during winter, which distinguishes Scandinavian from other European soils. SWAT is a physical river basin model that was developed for the U.S.D.A. Agricultural Research Service, by the Blackland Research Center in Texas. In the current modeling approach the catchment was divided into 43 Hydrologic Response Units (HRUs) which consist of different combinations of the existed landcover and soil types. Nitrogen and phosphorus losses arising from these HRUs were estimated for the period 1990-2001 through the simultaneous simulation of water and sediment processes that are closely linked to the nutrient processes. The model took into account soil temperature in order to quantify water and nutrient transport to deeper layers, considering negligible downward movement when the soil temperature was under 0°C. It also simulated the aboveground development of the snowpack and the snowmelt processes on a daily basis. The six different soil types were distinguished in two groups according to their similarity in texture and other physical properties, one group of fine-textured soils and a group of coarse soils. The results were evaluated for different crop cultivations (barley, oats and wheat) of the aforementioned soils. Finally, the model was calibrated and validated by comparing predicted results with measured data. Fine-textured soils caused significant runoff, sediment, total nitrogen (TN) and total phosphorus (TP) yields to the river system while coarser soils were characterized by high water drainage and nitrates leaching.