Vízügyi Közlemények, 1967 (49. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(4 3) pipeline. Rating curves for laterals and irrigation hoses are reproduced in Figs, в and 7. In sprinkler laterals a 1% change of terrain slope results in slight discharge variation only, whereas the discharge of hoses is appreciably affected by 0.2 to 0.3. already.' Brief publications and reports 1. Gábos, L., Orlóczi, 1., Civ. Engrs. and Tóth, J., Chemist : Sewage problems of Debrecen (for the Hungarian text see pp. 99) The development of Debrecen town is seriously retarded by the lack of suitable handling and treatment facilities for municipal sewage. The recently commenced enlargement of the sewer network may be regarded as an initial step towards the solution of these problems. At present only about one-third of the downtown area is served by a sewer network, which, however, accomodates about 60% of the inhabitants. Sewage collected by this network is discharged alter presettling into the open Tocó canal, which remains polluted and presents a health hazard for tens of kilometres. Studies were conducted by the authors during 1964-65 to determine both quantity and quality parameters of sewage collected by the municipal network. In the Summer of 1965, in the dry season, the average daily sewage volume was found to be 32,000 cu.m., which occurred as indicated in Fig. 3. Owing to the low proportion of industrial wastes the sewage is of fecaline, domestic character. A major source of contamination is the high salts concentration of thermal waters used. The problem of sewage and rainfall water removal from areas with no sewerage will be solved by the contemplated extension of the sewer network. Sewage from the eastern parts of the town cannot be removed and conveyed to a central treatment plant, unless a separate system of canalization is adopted and an additional main canal is built at great cost. For the solution of the problem of sewage disposal a complex, multiple-purpose system is considered most suitable. In this system storage-to accomplish water routing-would assume under the particular conditions greatest significance. Depending on soil type and operational as well as engineering conditions, part of the sewage could be utilized in agriculture, while the rest (a variable volume) would require treatment. 2. Szilvássg, Z., Civ. Engr.: Experiences gained during the investigation of flood levees along the southern reach of the Danube (for the Hungarian text see pp. Ill) "Ageing" of flood levees was repeatedly observed in practical flood control. The consequences thereof became manifest in the loss of strength and impermeability. No numerical data were available on the phenomenon, neither were the causes thereof understood and cleared in a satisfactory manner. To investigate the factors giving rise to the serious deterioration of levees during the exceptional Danube highwater in 1965, and further to determine in general the protective value of levees, explorations were started during the highwater period already. These were first of an informative character only, the main objective having been to throw light on phenomena caused by the action of water in the levee body. For this end attempts were made at determining the lines of saturation and piezometric head. The most important conclusion derived from these investigations was that levees consisted of widely differring materials and the levee body consisted of a random succession of layers of different density. Relying on this evidence, a program was started hereafter to determine the condition of levees over the southern reach of the Danube using nuclear methods of density and moisture determination and supplementary soil testing in the laboratory. In each of 7 cross sections selected on the basis of experience gained during highwater, four lined boreholes were sunk and density-, as well as moisture profiles determined. Soil properties determined at the laboratory on disturbed samples taken írom every layer penetrated during drilling included grain-size distribution, Atterberg limits and permeability. On the strength of information thus gained, the ageing of levees could be traced back to swelling phenomena and to changes in the structure of clay minerals contained in the soils. Under the influence of water the compacted density of the soil decreases, swelling occurs to an extent and at a rate depending on its swelling characteristics,