Modelling the hysteretic patterns of solute concentration-discharge relationships and their significance for hydrological pathways at the farm-scale
Eludoyin, Adebayo Oluwole
PublisherUniversity of Exeter
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Recent researches on the effects of environmental degradation on food security suggest that a better understanding of the relationship between agricultural intensification and pollutant transfer is urgently required to support the implementation of sustainable agricultural policies, globally. Poor understanding of the hydrological behaviour of clay-rich soils in intensively managed agricultural regions is highlighted as an important problem. The study therefore evaluated precipitation-soil water chemistry relationships, soil variability and concentration-discharge relationships at the farm-scale based on datasets from the North Wyke Farm Platform between 2011 and 2013. The three main hypothesis were that (1) precipitation and soil water chemistry are significantly related (2) significant relationships exists between the distribution of soil physiochemical characteristics and the managments of the fields, and that (3) hydrological behaviour of fields underlain by certain dominant soils in the study area are different from that of other fields. The basis of this work was to elucidate links between sources of pollutants and water quality, further understanding of the effect that management of the soil may have upon the quality of the water and improve understanding of the pathways of pollutants within intensively managed landscapes. Precipitation chemistry of the study area was chemically different from that of the other regions in the United Kingdom, and was influenced by contributions from sea salts and terrestrial dusts. The soil chemistry was rich in organic matter which contributed significantly (r2>0.60; p<0.05) to the distribution of total carbon and total nitrogen in the fields. Mean total carbon and nitrogen stocks ranged 32.4 - 54.1 t C ha-1, and 4 - 6.2 t Na ha-1, respectively in the entire farm platform while runoff coefficient at four selected fields (Pecketsford, Burrows, Middle and Higher Wyke Moor, and Longlands East) varied between 0.1 and 0.28 in January and November, 2013. The study rejected the first and third hypotheses, and concluded that the study area is largely influenced by contributions from the surface runoff mechanisms. The study also noted that sodium and chloride ions were dominant in the precipitation chemistry, and therefore suggests their further investigation as conservative tracers in the soil and runoff chemistry.