J. Abell and colleagues at the University of Waikato and National Institute of Water and Atmospheric Research, New Zealand, have quantified nutrient and sediment inputs to a large eutrophic lake. They draw conclusions on how hydrological and landscape factors interact to produce pollutant flux.
Pollutant concentrations after a rain event such as a storm vary greatly and therefore high-frequency sampling is needed. The amount of pollutant must be measured as a function of the stream discharge. The relationship between the two parameters can provide insights into sources and transport mechanisms in a catchment area. A catchment area can act as a filter, regulating downstream transport. Therefore changes over time that occur after a rain event give insights into upstream hydrological and landscape factors.
The team looked at two streams flowing into a large eutrophic lake, focusing on levels of suspended sediment, nitrogen and phosphorus over a range of discharge values. One stream flowed through a mainly forested area, the other through pasture land. They conducted high frequency sampling over two years for both streams, taking over 900 samples. Comparison of two streams allowed spatial conclusions to be drawn.
This article includes an in-depth discussion of the factors related to suspended sediment and nutrient levels of the two streams, and how all of these factors contribute to the eutrophic nature of the lake. The researchers examine how these results could to lead to improved management of lake water quality.
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Quantifying temporal and spatial variations in sediment, nitrogen and phosphorus transport in stream inflows to a large eutrophic lake
J. M. Abell, D. P. Hamilton and J. C. Rutherford
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