Fejér László - Lászlóffy Woldemár: A hidrometria magyarországi fejlődése (1700-1945) (Vízügyi Történeti Füzetek 13. Budapest, 1986)
Idegen nyelvű összefoglalók
The completion of the Danube-mapping was at the same time the end of the first, most « important stage in the development of Hungarian hydraulic sciences. The processing of practical experiences and a wider publication of the results was started already in the late 1830s and early 1840s. It emerged that the formulae used until then for the calculation of flow velocity and discharge (Dubuat, Chézy— Eitelwein, ... etc.) could be fitted less accurately to the rapid flow of the Danube and that accurate results would be obtained only by point measurements in several verticals, down to the bottom, by means of current meters. For a due appreciation of this large-scale hydrometric survey it should be known that from among the discharge data of Europe' rivers there were very few obtained by point measurements from even at such a late period as the first decades of the nineteenth century. His study entitled „On the velocity distribution in flowing streams..." (1845) was written by Pál VÁSÁRHELYI — an outstanding engineer of the Lower-Danube regulation works — with the use of data obtained from his own measurements executed in October 1838 at the Budapest cross-section of the Danube, and on the basis of his own experiences. The principal purpose of his investigations was to establisch a relationship for practical use between water stage and the mean flow velocity of a cross-section. Since in the age when VÁSÁRHELYI lived there was a rather great uncertainty in respect of the distribution of flow velocities along the verticals, VÁSÁRHELYI's ; statement based on a great number of measurements, as to the decrease of velocities proportionate to depth described by a parabola, with horizontal axis was of great importance. The questions associated with the rules of flow were included, of course, in the curriculum of the Engineering Institute of the Pest University. In his text-book entitled „Hydromechanics and hydraulic construction" József PETZELT, professor of hydraulic engineering at the university, gave a detailed description on the different methods of flow valocity measurement and on the necessary instruments. His description enabled getting acquainted with the Kraft-made Woltman-type current meter used in Hungarian practice. It was his merit that regular exercises of hydraulic measurements were introduced at the university for students studying engineering. River regulation works started in the mid-nineteenth century primarily in the Tisza Valley, failed to bring in every case the results which were expected by those concerned, from these large-scale interventions. This outcome was explainable by the inconsequent execution of the plans of the Tisza regulation and the lack of profound knowledge on the nature of the watercourses. Beyond scientific involvement it was the potential utilization of his experiences in the regulation of the Danube that initiated Ignác HORVÁTH, professor of the Budapest Technical University to start large-scale study measurements when making use of the flood of the Danube in 1876. To reveai the kinematic rules of streaming waters he tested in sequence both the contemporary instruments for flow velocity measurements (Pitot tube, log, Woltman-type current meter) and the methods (integrating measurements as applied by German TREVIRANUS and Hungarian-born REVY, point measurements and superficial measurements). Then, on the basis of gained experience, he transformed upon his own ideas the Amsler—Laffon-made Woltmantype current meter — which was supplied with an electrical speed indicator — and continued , his measurements with this instrument.
