This article gives an estimation of minimum river water flow of the Prut River and the Siret River basins. There are two special periods of low flow between floods. The first one runs from August to November (summer-autumn period) and the second one runs from December to February (winter period). These periods were separated because of different genetics of runoff formation.
It was found that 7 days is an optimal period with a stable minimum water flow. Physical and geographical features of the river basin, comparative flow and precipitation graph, scientific works of American scientists became the confirmation for giving preference to 7-days period.
All series of observations are homogeneous according to the calculations in the program StokStat. In general, all samples are homogeneous for at least one criterion with 1% level of significance and can be used for further research.
The samples of the average 7-day minimum water runoff from the beginning of observations until 2018 became the basis for the construction of maps of the distribution of the minimum water runoff across the study area. The result of this work represents two current maps of the distribution of runoff modules (l*s / km2) of the summer-autumn and winter low water periods.
There was conducted the research of the connection between the actual values and the values taken from the maps. The connection between calculated and cartographed minimum modules of water flow showed a close correlation, the approximation coefficients are R2 = 0.9731 and 0.986 for two maps. In this case, the connection line is at an angle close to 45°.
We can see a decrease of minimum water flow modules in the direction from west to northeast and a parallel decrease in the density of the distribution of isolines. The altitude has a similar distribution in this area, so there was evaluated a correlation between these two parameters. It is close, the approximation coefficients are R2= 0.5618 and 0.6661 for winter and summer-autumn periods.
Consequently, the constructed maps are reliable and can be used in the future to determine the value of minimum flow modules from other parts of the basins for practical and scientific purposes. In particular, this concerns the estimation of the minimum runoff of the river basins, for solving various water management tasks: planning water supply and water intake works, designing and constructing hydrotechnical structures, performing reclamation works, drought assessment.
Expansion for the Moments of a Nonlinear Stochastic Model
