Vízügyi Közlemények, 1932 (14. évfolyam)
2. füzet - XII. Kisebb közlemények
23 together lasting nearly 400 years (from about 1450 to 1850). This is why the systematic work of control was not begun earlier than the commencement of the last century. The detailed topographic and hydrographie survey of the river was first carried out in the years 1833—1841. The flood control works were begun in 1846, according to the proposals of Paul Vásárhelyi, a Hungarian engineer, whose project consisted of a series of cutoffs and the construction of levees. The fall of the river in its original stage was extremely slight, 1—2 centimetres per kilometre (0-05 to 0-1 ft per mile), so that the duration of the flood was too long. In order to shorten the time of downflow, cutoffs were applied and the levees were conducted as close as possible to the river banks. The levee constructions were carried out by and at the expense of autonomous levee companies composed of the interested landowners. This system, though found good in several respects, involved unsystematic levee lines in many places. Figs. 8 and 9 show that considerable improvement is now to be seen from this point of view. At first the levee dimensions proved insufficient. Fig. 10 shows the gradual rising of high water levels and the increase of levee dimensions. Table VIII summarizes the changed conditions in the river bed along the whole course of the stream divided into 12 characteristic zones, as indicated in Fig. 12. (The heads of Table VIII are : Number, Zones, Elevation of low water level, Length of zones before and after regulation, Shortening in percentage, Number and length of cutoffs, Slope). 112 cutoffs were made, which resulted in a shortening of 453 kilometres (281 miles), as is shown in the longitudinal section in Fig. 11. Table IX —XI give data as to the reduction of flood-duration, the acceleration of the downflow of floods, the rising of flood flow line owing to constriction by levees, the sinking of low water level produced by cutoffs, and the increase in range of fluctuations in water levels. The tributaries of the Tisza River were also floodcontrolled on the same principles, as is shown in Table XII. (Heads : Name of tributary, Watershed, Min. and max. discharge, Number of cutoffs, Length before and after regulation, Shortening in percentage). In the Tisza basin an area of 2-6 million hectares (6-4 million acres) was flood-controlled by constructing levees of 3555 kilometres (2210 miles) ; thus this system is by far the most extensive in Europe. For the purpose of surface drainage, up to 1914, there were built 9183 kilometres (5700 miles) of open drainage canals, and 4230 sluice gates and culverts. At the time of high water 93 pumping stations with a total output of 120 cubic metres per second (4240 cu.ft per sec.) hoist the drained water into the river. Just before the world war projects for constructing impounding reservoirs in the districts of upland streams, serving the purpose of flood control, were being planned. At present only about 45,000 hectares (110,000 acres) are not protected by levees, mostly on stretches where the plains exposed to floods are relatively narrow and the expenses of levee construction would impose too great a burden on the parties interested. Fig. 13 shows part of such an area of 30,000 hectares (74,000 acres) situated just below the Sajó mouth and overflowed only by excessive high waters every 10—15 years. This airplane photo taken in the spring of 1932, gives us some idea of the conditions prevailing in the Tisza basin 100 years ago for 2—3 months every year. Works for the purpose of protecting these areas are now in progress. In addition to the flood control system an extensive net-work of surface drainage canals is now almost completed. The matter of irrigation would be the next step, but under prevailing conditions this presents enormous difficulties, because it requires great
