Observations on the spatial variability of the Prut river discharges

Andrei-Emil BRICIU, Dumitru MIHĂILĂ, Liliana Gina LAZURCĂ, Luciana-Alexandra COSTAN, Viorica NAGAVCIUC, Carmen Andreea BĂDĂLUȚĂ


Liquid and solid discharges of the Prut River were analysed based on measurements
performed in 7 points from the Romanian national network of water monitoring during a
period of 30 years. The analyses were performed on flows for the period after the
construction of the Stânca-Costeşti dam and show the influence of the dam for the entire
analysed time. The analysis from upstream to downstream of the spatial variability of the
Prut River annual discharges showed their steady increase downstream and then a
decrease in the sector next to Oancea station. A statistical minority of the annual
discharges showed a continuous increase of them until the flowing of Prut into Danube.
Knowing that the lower basin of the river is characterized by a low amount of rainfall and
a higher evapo(transpi)ration than the remaining basin, the decreasing flows to the river
mouth is explicable; but the increasing flows to the river mouth cannot be justified, under
these conditions of water balance, than by certain climatological parameters of thermodynamical
nature which generate, with increased frequency, more intense and rich
rainfall, with a torrential character. The analyses on couples of three months showed that
the Oancea flows are higher than the upstream stations (opposite than usual) in years
when the flows of the upstream hydrometrical stations are lower than the multiannual
average and that supports the mentioned pluviometrical character. A plausible cause for
"Oancea phenomenon" is the increase and the decrease of the sunspots number, whose
cycles are relatively well fold on the increase and decrease of annual average flow at
Oancea hydrometrical station. The strongest increased discharges of the Prut River over
the discharges at the upstream stations occur from May to July (MJJ), the months with the
highest amount of rainfall. Seasonal analysis of MJJ and other couples of 3 months
showed that there are also growing flows at Prisăcani station relative to the adjacent
stations, but only in MJJ. This increase at Prisăcani is due to the local influx of water, not
to the decrease of the flow at the upstream and downstream stations. Prisăcani influx of
water is due to the large volume of rainfall in early summer on Iaşi Coast caused by the
numerous orographic convections, volume found then in the permanent flow. The Stânca
section has a contrasting variability too, but here is an explicit anthropogenic cause,
namely the upstream dam. We conclude the analysis of the Prut river runoff spatial
variability by showing that the river doesn’t have a linear model, but one with local
deviations whose manifestations can be attributed to the climate and anthropic specificity
of the considered sector


uneven spatial variation, sunspots, torrential rainfall, spatial analyses, monthly analyses

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