Vízrajzi Évkönyv 88., 1983 (Budapest, 1984)

Tartalomjegyzék

The stages read while the water surface was partly, or entirely covered with ice, or with open water in the gaging cross-section but with the waterlevel influenced by a more distant ice jam are distinguished by a special symbol. The headings of the tables show the size of the catchment area above the gaging cross section,further the elevation of the "gage zero" above the Baltic level.

In order to characterize the water regime of the stream, the typical monthly and annual stages for a several-year period, where possible for a decade with normal water regime, and for a recent period, further the extreme stages on record are also indicated at each gage for the sake of comparison.However,when examining the stages over an extended period of time, any occasional change in bed geometry over the particular river section must also be taken into account. For this reason, instead of historical data of little practical interest the extreme values entered are stages which are likely to occur under the present bed conditions. /Thus for instance,the highest highwater level LNV indicated for the Budapest gage is not the 1063 cm reading observed during the ice jam flood of 1838, since as a consequence of river training measures the probability of occurrence of such stages is very slight.Also,the lowest low-water level LKV on the Dunaremete gage is the lowest stage observed during the past 20 years, since the lowest reading of 40 cm on the 1st January, 1888 is precluded from recurring by the rise of the bottom during the intervening period./

The elevation of the zero point had to be changed on some gages over the time. The last modifications of the gage zeros were carried out in 1943 and 1946.For the details thereof reference is made to the earlier volumes of the Hydrographic Yearbook. The past stages entered in the Yearbook for the sake of comparison are related invariably to the current gage zero elevations.

The stages observed on the gages included in the standard network, but not published in the Yearbook are preserved in the data files of the Hydrographic Institute, while those registered on other gages are to be found in the files of the competent district water authority.

The data tabulated as daily discharges are -daily mean discharges.The data related to ice cover conditions are indicated by the symbols used in the tables of stages. At the bottom of the daily data the monthly and annual typical data of the current year and the reference period have been grouped separately, indicating also the extreme values.

Some of the stage-discharge curves have been modified on the basis of more recent,or a larger number of measurement data, but such modification has not been extended to the previous years. The bivariate stage-discharge curves apply to the streamflow rates passing at peak stage conditions.

In some gaging cross sections,such as the reaches influenced by dams and tributaries on the Tisza River and in the Tisza Valley, the streamflow rate is influenced significantly by the surface slope as well. For such gages the relationship between the streamflow rate,the stage and the surface slope has been determined from the results of streamflow measurements. The daily mean discharges have b^en estimated using the relationship determined. For such calculations the I and Q values pertaining to the particular stage have been obtained from the tabulation containing0the corresponding values of the stage /h, cm/,^ the surface slope under steady flow conditions /I , cm/km/ and the streamflow rate /Q , m /s/ under similar conditions. Hereafter, in the kSowledge of the simultaneous stage data on the auxiliary gage also indicated in the table,the actual surface slope /I,cm/km/ for the given instant over the reach included by the two gages has been determined. These data have then been entered into the formula Q = Q /I/I to find the actual streamflow rate Q /in /s/ passing the gaging cross section under considiration.

For estimating the streamflow rates through the Szeged gaging cross section on the Tisza River, allowance had to be made, besides the stages on the Mindszent gage, also for the stages on the Makó gage on the Maros River. Consequently, the value of I had to be found from the auxiliary table in terms of the stages at Szeged and at Makó. The streamflow rates through the cross sections, for which three-, or multi-variate relationships are published can be calculated only by taking the other two /or three/ variables simultaneously into consideration /no variable must be omitted, or neglected in the calculations/.

Typical water temperature data are given for the gages which are representative for longer river sections controlling the variations in water temperature. Where the water temperatures are observed but once, in the morning only, the extreme values are the data selected from the readings taken in the morning. The water temperatures are measured at 20 to 40 cm depth below the water surface.

The hydrological particulars /stages, streamflbw rates etc./ over some streams, or sections of streams, such as the Sió Canal, some sections in the Tisza River System, are influenced by human activities, such as the operation of weirs, diversions, discharges. The extent of these influences varies with time, and the length of the river section affected depends on stage. The duration in time and range of these effects can be identified by a detailed analysis of the observation data alone.

The data on sediment transport - both for the current year and for the longer period - are values estimated from observation data. The values corresponding to the highest stages on record and observed during the year of report have been entered as extreme values.-23-