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Abstract. This paper presents the methodology used for artificial flood experiments conducted in a small artificial, trained (regulated) channel on the Nučice experimental agricultural catchment (0.5 km 2 ), central Czech Republic, and the results of the experiments. The aim was to monitor the transformation of the flood wave and the sediment transport within the channel. Two series of experiments were carried out in contrasting initial conditions: (a) in September, when the stream banks were dry, the baseflow was negligible, and the channel was fully overgrown with vegetation; and (b) in March, when the stream banks were almost water saturated, the baseflow was above the annual average, and there was no vegetation present. Within each campaign, three successive flood waves, each with an approximate volume of 17 m 3 and peak flow of ca. 40 L s −1 , were pumped into the upper part of the catchment drainage channel. The transformation of the flood wave and the sediment transport regime within an approximately 400 m long channel section were monitored by measuring the discharge, the turbidity, and the electrical conductivity in three profiles along the stream. On the basis of the results, it was concluded that there is a considerable amount of deposited sediment, even in the well-trained and straight channel that can be re-mobilized by small floods. Part of the recorded sediment therefore originates from the particles deposited during previous soil erosion events. The flood waves initiated in dissimilar instream conditions progressed differently -we show that the saturation of the channel banks, the stream vegetation and the actual baseflow had a strong influence on the flood transformation and the sediment regime in the channel. The sediment moves quickly in winter and early spring, but in the later part of the year the channel serves as a sediment trap and the resuspension is slower, if dense vegetation is present.

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Agricultural watersheds in the Czech Republic are one of the primary sources of non-point-source phosphorus (P) loads in receiving waters. Since such non-point sources are generally located in headwater catchments, streamflow and P concentration data are sparse. We show how very short daily streamflow and P concentration records can be combined with nearby longer existing daily streamflow records to result in reliable estimates of daily and annual P concentrations and loads. Maintenance of variance streamflow record extension methods (MOVE) can be employed to extend short streamflow records. Constituent load regressions are used to predict daily P constituent loads from streamflow and other time varying characteristics. Annual P loads are then estimated for individual watersheds. Resulting annual P load estimates ranged from 0.21 to 95.4 kg year -1 with a mean value of 11.77 kg year -1 . Similarly annual P yield estimates ranged from 0.01 to 0.3 kg ha -1 year -1 with an average yield of 0.07 kg ha -1 year -1. We document how short records of daily streamflow and P concentrations can be combined with a national network of daily streamflow records in the Czech Republic to arrive at meaningful and reliable estimates of annual P loads for small agricultural watersheds.

Rosendorf P., Vyskoč P., Prchalová H., Fiala D. (2016): Estimated contribution of selected non-point pollution sources to the phosphorus and nitrogen loads in water bodies of the Vltava river basin. Soil & Water Res., Eutrophication of inland waters by phosphorus as well as loads of coastal and marine waters by nitrogen is a major problem that impedes water bodies to meet the status defined by the Water Framework Directive. In order to reduce the nutrient load on the aquatic environment, first the significance of various pollution types should be thoroughly analyzed. The analysis of phosphorus runoff from agricultural land under normal rainfall-runoff conditions, and of nitrogen runoff associated with the application of manure on farmland shows their different impact on water body status in the Vltava river basin. The assessment of phosphorus indicates that annual specific phosphorus runoff ranges from 0.1 to 9.98 kg/km 2 and in the sub-basins of the Upper Vltava, Berounka, and Lower Vltava, the average values from all water bodies reach 4.08, 2.92, and 4.02 kg/km 2 , respectively. Compared with the allowable capacity of water bodies for achieving a good status, the average rate of phosphorus input on the load of water bodies comes within 20%, with a maximum value slightly exceeding 50%. This phosphorus input will not be a significant source of eutrophication of inland waters and measures will have to focus rather on other eutrophication sources. Estimating the significance of the impact of manure application on the nitrogen load of water bodies provides a completely opposite picture. The analyses showed that the load of water bodies ranges from very low values in areas without livestock to high loads in tens of kg/ha per year (max. 31.5 kg/ha/year). In the sub-basins of the Upper Vltava, Berounka, and Lower Vltava the annual specific runoff of nitrogen reaches average values for all water bodies (4.8, 3.9, and 5.7 kg/ha, respectively). The assessment of the proportion of nitrogen input on the load of water bodies showed that 25% of cases in the area of the water body may represent a critical load leading to an adverse assessment of ecological status. In many other water bodies it can, however, taking into account the load of mineral fertilizers, lead to exceeding the allowable capacity of water bodies and the risk of not achieving a good status. Nitrogen input after application of manure in soils represents an important source that threatens the good status of waters. Attention should thus be paid to all types of measures that will reduce the load of this source or restrict its transport from soil to waters.