Fejér László - Lászlóffy Woldemár: A hidrometria magyarországi fejlődése (1700-1945) (Vízügyi Történeti Füzetek 13. Budapest, 1986)

Idegen nyelvű összefoglalók

By the turn of the century both the instruments and the methods of velocity measurements applied by the hydrographie service became settled in all details. Flow velocity measurement became an everyday routine work. Essential great survey works were completed. With the composition of his principal work entitled „Hydrometry" (1906) Sámuel HAJOS so to say terminated his creative activity. Further development was taken over by the department of hydraulic construction of the Technical University of Budapest. From 1903 József WEISSMAHR — later professor of this department — has begun research for the improvement of flow velocity measurements, at a workship built on the banks of the Danube (Nagymaros) for measurement exercises. In a study summarizing his activity of one and a half decades (1918) he analysed the sources of error emerging from the nature of watercourses and from the methods and instruments applied in the measurements. On the basis of experience he made further improvements on the HAJÓS-type instrument but his version has not been used often in domestic practice. Besides measurements in great rivers an increasing demand was posed by our engineering practice for an accurate assessment of flow flow velocities which, primarily in artifical canals, rarely exceeded 0.5 m/s. The construction of a suitable instrument was an important requirement. To make progress an experiment was made by Ede VICZIÁN and professor Sándor ROHRINGER but their instruments failed to be a long-lasting solution, just as well as that of WEISSMAHR's. * Due primarily to economic reasons, in the one and a half decades subsequent to World War I, the activity of the hydrographie service strongly declined. No more than 2 to 3 discharge measurements were performed annually. Other institutions of the water sector, namely the civil engineering and river agencies, were mostly in want of instruments. It was the new survey of the Tisza river between 1929 and 1931 — that couldn't postponed due to changes in the river-bed — that offered again opportunities for discharge measurements. In the second half of the 30s the nearly two-decade neglect of discharge measurements was felt oppressively. The increasing demand for discharge data could hardly be met by the hydrographie service with its instrument park diminished by overuse. Time has passed over the equipment developed by HAJÓS in the early 1890s, although an axcellent one even in international terms. As compared to the products of the foreign precision-mechanical industry specialized in the manufacture of hydrometric instruments the domestic small-scale plants were considerably backward. Because of measures taken for the reduction of payments in foreign currencies, there were no possibilities for the acquisition of instruments from abroad. This serious situation could be overcome only in a sequence of steps. A plan for a new instrument was prepared by Gábor BERÉNYI, utilizing domestic and foreign experience. The general aspects for the construction of this instrument included increased operational safety and a wide range of applicability, The first series of this instrument was manufactured in 1940, with a closed body and a vane cast from light metal. *