The Integrated Catchments model of Phosphorus dynamics (INCA-P) was applied to the River Lugg to determine the key factors controlling delivery of phosphorus to the main channel and to quantify the relative contribution of diffuse and point sources to the in-stream phosphorus (P) load under varying hydrological conditions. The model is able to simulate the seasonal variations and inter-annual variations in the in-stream total-phosphorus concentrations. However, difficulties in simulating diffuse inputs arise due to equifinality in the model structure and parameters. The River Lugg is split into upper and lower reaches. The upper reaches are dominated by grassland and woodland, so the patterns in the stream-water total-phosphorus concentrations are typical of diffuse source inputs; application of the model leads to estimates of the relative contribution to the in-stream P load from diffuse and point sources as 9:1. In the lower reaches, which are more intensively cultivated and urbanised, the stream-water total-phosphorus concentration dynamics are influenced more by point-sources; the simulated relative diffuse/point contribution to the in-stream P load is 1:1. The model set-up and simulations are used to identify the key source-areas of P in the catchment, the P contribution of the Lugg to the River Wye during years with contrasting precipitation inputs, and the uptake and release of P from within-reach sediment. In addition, model scenarios are run to identify the impacts of likely P reductions at sewage treatment works on the in-stream soluble-reactive P concentrations and the suitability of this as a management option is assessed for reducing eutrophication.

The President. especially qualified to speak on the subject of the prevention of pollution by trades waste, because his professional avocations brought under his inspection a great many manufactories. But however desirable it was to prevent the pollution of streams, it was necessary to be careful not to harass the manufacturers to such an extent as to ruin their trade. Manufacturers often had but a small margin of profit, and were in competition with foreigners who were not subject to the restrictions which obtained in England. Happily the utilization of trades waste sometimes led to profit. An admirable instance of the profits arising from trades waste might be found in gasworks. I n former days the tar and ammoniacal liquors had been got rid of as best they might be, with no thought of utilizing them. Now those refuse products were a great aid in lowering the price of gas.

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