Vízügyi Közlemények, 1937 (19. évfolyam)
3-4. szám - Szakirodalom
18 annual flooding of the basins. The replacement of this old system by free-flow perennial irrigation, i. e. irrigation from canals running at a high level throughout the year, caused a constant rise of the ground water level in the Nile valley. The deterioration of the fertile Egyptian soils observed in recent years is always associated with this artificially high water table, from wich free evaporation can take place, giving rise to salt accumulation near the surface. As the alluvial deposit of the Nile everywhere contains harmful salts in its deeper layers, the deterioration of land occurs in Upper as well as in Lower Egypt, its nature being determined only by the actual depth of the water table. Hundreds of investigations made by the Chemical Section of the Ministry of Agriculture of Egypt have shown that these infertile soils can be classified into two types : 1. „Black Alkali" soils, and 2. Gypsum veined soils, which appear to be sharply distinct, except for the common property of impermeability to water. The „Black Alkali" soil is a typical sodium-soil characterised by the very marked increase of the exchangeable sodium. It contains a comparatively small amount of soluble salts, but the carbonate and bicarbonate titration of the water extract is abnormally high. The gypsum veined soil contains a large amount of soluble salts (gypsum, magnesium- and sodium salts), which accumulate in a certain horizon, above which an impermeable layer occurs. The soil is mainly saturated with Ca and Mg, the proportion of the latter being often abnormally high. There is a direct connection between these types of infertility and the situation of the land with regards to the high level canals, as in their neighbourhood where the water table is highest the black alkali type is produced, while in the more distant parts of the infiltrated area the gypsum veined type is found. The reclamation of these deteriorated patches presents a very difficult problem. The installation of an intensive drainage system is the all-important element in the reclamation, but even good drainage is only a preventive measure, and the land already deteriorated requires some special treatment. Gypsum has some effect on the black alkali soil, but its application is obviously needless for the gypsum veined soil, where amelioration could be hastened only by deep-ploughing, which breaks through the impermeable layer. IV. DATA OF WATER SUPPLY IN HUNGARY. By R. PAPP. (Pages : 67—90.) The population of Hungary is in a very unfavourable situation concerning water supply. Most of the country is plain, sparcely crossed by small rivers of highly varying discharge, and on the other hand, in most parts of the country drinking water of unobjectionable quality can be obtained only from a depth of
