Analysis method

The empirical and theoretical distributions of the annual spring discharges were studied. The method for analytical approximation and multi-criterial optimization of the empirical distributions proposed by Gerassimov (1988) was used. The main ideas of the method are as follow: (i) approximation of the empirical distribution functions by regression analysis of appropriately transformed coordinates; (ii) transformation of the empirical cumulative frequencies to normal distribution quan-tiles, and taking logarithms of the random variables; and (iii) choice of the most appropriate approximation. Table 1 presents water discharges for

Table 1. Spring discharges (in m3/s) for chosen probabilities of exceedance

No.

95%

90%

50%

10%

5%

25

2.286

2.540

3.653

5.210

5.755

396

0.137

0.173

0.361

0.701

0.840

48

0.287

0.324

0.487

0.711

0.789

63

0.195

0.214

0.290

0.382

0.411

59

0.690

0.759

1.046

1.415

1.538

39a

0.434

0.492

0.736

1.052

1.158

0.01 0.050.1 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 9999.5 99.9

probability, %

0.01 0.050.1 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 9999.5 99.9

probability, %

Fig. 2. Probability distribution curves for springs 25 and 396 located in the Danube basin.

selected probabilities of exceedance. In Figures 2 and 3 the probability distributions for some springs are given.

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