Basin precipitation based on different calculation methods

For event I, the highest total precipitation for the Brugga basin occurred using the IDW-elevation method (scenario 1) (Table 16.2). Compared to event I, events II and III are characterised by higher rain amounts and higher rain intensities. For both events, the available ground stations within or near the Brugga basin did not record as high intensities as the radar data. Thus, the resulting catchment precipitation is higher using the radar data, in particular for event II (Table 16.2). The temporal distributions of the catchment rainfall values

Table 16.2 Comparison of the two catchment precipitation values (mm) of the Brugga basin for the three investigated events

Scenario (1)

Scenario (2)

IDW-elevation

Rainfall

(80:20)

radar data

Event I (27.08.98)

25.9

22.8

Event II (22.08.98-

-23.08.98)

35.1

44.4

Event III (4.09.98-

5.09.98)

39.1

41.1

16:00

00:00

04:00

12:00

16:00

00:00

04:00

11:00 15:00 19:00

03:00 07:00 11:00

11:00 15:00 19:00

03:00 07:00 11:00

Figure 16.2 Temporal distribution of cumulative basin precipitation calculated on the basis of scenario 1 (IDW-elevation) and scenario 2 (rainfall radar data) for event II (3a) and event III (3b)

20 mm

80 mm

Figure 16.3 Spatial distribution of basin precipitation of event II: (a), calculated using the IDW-elevation method (scenario 1), and (b), calculated using the rainfall radar data (scenario 2)

calculated by the scenario 1, using the IDW-elevation method, and scenario 2, using radar data, are highlighted in Figure 16.2. For event II (Figure 16.2a), differences in cumulative total precipitation amounts based on both the rainfall data sets become obvious (see also Table 16.2). The larger temporal variability of the radar data became obvious by the temporal distribution in the cumulative curve, which is less regular than the ground station curve. Also, the radar data showed an earlier start of the event and higher rain intensities around 8 p.m. This indicates that the convective event II is an event with an isolated rain cell that was only partly detected by the ground stations, and consequently the IDW-elevation method calculated lower precipitation values. For event III (Figure 16.2b), precipitation of both data sets for both total amounts and temporal distributions show less differences. However, during the intense part of the event, the radar data showed somewhat higher rain intensities, which results in a higher total basin precipitation.

In Figure 16.3, the spatial patterns of the total precipitation for event II are shown. The spatial pattern of the basin precipitation of scenario 1 (IDW-elevation method, Figure 16.3a) is much more homogenous compared to scenario 2 (rainfall radar data, Figure 16.3b). The radar data showed that the convective cell was mainly at the upper parts in the northeast of the basin, within

Event I, 27, July 1998

Event II, 22-24, August 1998

Event III, 04-05, September 1998

Event I, 27, July 1998

Event II, 22-24, August 1998

Event III, 04-05, September 1998

5720 5740 5760 5780 5800 6350 6400 6450 6500 6680 6700 6720 6740

5720 5740 5760 5780 5800 6350 6400 6450 6500 6680 6700 6720 6740

Figure 16.4 Results of simulating the three investigated events at the outlet of the Brugga basin using the TACD model and applying the two different precipitation scenarios the sub-basin St. Wilhelmer Talbach. Here the highest intensities were recorded, which could not be captured correctly by the ground station network.

0 0

Post a comment