12 Dynamics, Range, and Severity of Hydrological …
239
Table 12.1 Parameters of significant linear trends in the annual series of selected hydrological
drought estimators
River
Water-gauge Annual number of days with
hydrological drought (N D )
Coefficient of severe drought
contribution (CS D )
a
R 2
a
R 2
Nysa Kłodzka Skorogoszcz −3.465
0.173 0.382
0.253
Bystrzyca
Jarnołtów
−4.146
0.191 –
–
Liswarta
Kule
−4.211
0.195 –
–
Ina
Goleniów
3.366
0.131 0.245
0.248
Reda
Wejherowo
–
–
−0.303
0.149
Vistula
NowyBieru´ n –
–
0.327
0.218
Przemsza
Jele´ n
4.149
0.168 0.378
0.280
Soła
O´ swi˛ ecim
−3.504
0.275 –
–
Raba
Proszówki
−5.622
0.404 −0.360
0.326
Dunajec
Kro´ scienko
−2.278
0.165 −0.351
0.293
Dunajec
NowyS˛ acz
–
–
−0.361
0.376
Wisłoka
Mielec
−2.472
0.140 −0.276
0.410
Wieprz
Krasnystaw −7.049
0.441 −0.265
0.211
Wieprz
Ko´ smin
−6.068
0.362 −0.303
0.200
Pilica
Przedbórz
–
–
−0.163
0.150
Pilica
Białobrzegi
−2.900
0.144 –
–
Bug
Włodawa
−3.296
0.151 –
–
Drw˛ eca
Elgiszewo
3.921
0.343 0.302
0.150
Significance level: α = 0.05, a – slope coefficient of the trend line, R 2 – determination coefficient
Water management at these facilities allows for alleviating the effects of hydrological drought, as manifested by a significant tendency to the reduced number of days
with drought. A similar observation is true for the coefficient of severe droughts
contribution, which systematically decreases as a result of guaranteed flow generated by these reservoirs. However, in the rivers downstream of the reservoirs, in
which municipal functions predominate (e.g., the Vistula – Nowy Bieru´ n, the Nysa
Kłodzka – Skorogoszcz), where water resources are stored and transported over
natural catchments, significant positive trends were noticed for the coefficient of
severe droughts contribution with relatively high fit (R
2
= 0.3). Spatial analyses do
not reveal dense or ordered zones with significant multiannual trends for hydrological drought estimators. It can, therefore, be assumed that the observed trends do not
have a hydroclimatic background and are triggered by local factors, mainly related
to water management.
239
Table 12.1 Parameters of significant linear trends in the annual series of selected hydrological
drought estimators
River
Water-gauge Annual number of days with
hydrological drought (N D )
Coefficient of severe drought
contribution (CS D )
a
R 2
a
R 2
Nysa Kłodzka Skorogoszcz −3.465
0.173 0.382
0.253
Bystrzyca
Jarnołtów
−4.146
0.191 –
–
Liswarta
Kule
−4.211
0.195 –
–
Ina
Goleniów
3.366
0.131 0.245
0.248
Reda
Wejherowo
–
–
−0.303
0.149
Vistula
NowyBieru´ n –
–
0.327
0.218
Przemsza
Jele´ n
4.149
0.168 0.378
0.280
Soła
O´ swi˛ ecim
−3.504
0.275 –
–
Raba
Proszówki
−5.622
0.404 −0.360
0.326
Dunajec
Kro´ scienko
−2.278
0.165 −0.351
0.293
Dunajec
NowyS˛ acz
–
–
−0.361
0.376
Wisłoka
Mielec
−2.472
0.140 −0.276
0.410
Wieprz
Krasnystaw −7.049
0.441 −0.265
0.211
Wieprz
Ko´ smin
−6.068
0.362 −0.303
0.200
Pilica
Przedbórz
–
–
−0.163
0.150
Pilica
Białobrzegi
−2.900
0.144 –
–
Bug
Włodawa
−3.296
0.151 –
–
Drw˛ eca
Elgiszewo
3.921
0.343 0.302
0.150
Significance level: α = 0.05, a – slope coefficient of the trend line, R 2 – determination coefficient
Water management at these facilities allows for alleviating the effects of hydrological drought, as manifested by a significant tendency to the reduced number of days
with drought. A similar observation is true for the coefficient of severe droughts
contribution, which systematically decreases as a result of guaranteed flow generated by these reservoirs. However, in the rivers downstream of the reservoirs, in
which municipal functions predominate (e.g., the Vistula – Nowy Bieru´ n, the Nysa
Kłodzka – Skorogoszcz), where water resources are stored and transported over
natural catchments, significant positive trends were noticed for the coefficient of
severe droughts contribution with relatively high fit (R
2
= 0.3). Spatial analyses do
not reveal dense or ordered zones with significant multiannual trends for hydrological drought estimators. It can, therefore, be assumed that the observed trends do not
have a hydroclimatic background and are triggered by local factors, mainly related
to water management.