**
RIVER RUNOFF EXTREMES AND
TENDENCIES: **

**
FACTORS OF RISK LIKELY RELATED TO
GLOBAL CLIMATE**

*
G. PÁNDI., J. MIKA.*

**
ABSTRACT. **-** River Runoff
Extremes And Tendencies:Factors Of Risk Likely Related To Global Climate. **
River runoff data** **are analysed at different sub-catchments in the
Transylvanian Basin of the Carpathian Mountains. Spatial and temporal
variability, as a source of hydrological risk, are first quantified for the 19
gauging stations. Temporal variability of decadal time-scales are statistically
related to the hemisferical warning trend
(0.26 K/decade)
observed in the 1974-1998 period. Method of instrumental variables is used to
estimate linear regression coefficients between regional rainfall and
hemispherical mean temperature for this period. The sequence of consecutive
years is defined for instrumental variable, that fulfil the main criterion i.e.
the non-zero correlation to the independent variable (r=0.825). Regression
analysis is also performed for parallel 9 precipitation stations for independent
validation, and for the monthly absolute extremes of the 25 years. Another
validation of the terults applies independent hydrological parameters in
Hungary. Both spatial and temporal variability are about one decimal magnitude,
that makes existence of continuous observations rather important. Trends of the
runoff are mainly decreasing parallel to the global warming-up tendency of the
investigated 25 years. For 0.5 K hemisferical warming the local order of runoff
changes spreads from several percents to tens of percents. The largest area-mean
decrease of runoff is analysed for the July-August period, with average decrease
of 75 %. Although there are two further independent estimations in the study,
that support the discovered relation between drying-out of the Basin and the
warming tendency of the Hemisphere, this relation of the robust part of the
runoff sample may not be extended to the tails of the distribution.