Hidrológiai Közlöny 1971 (51. évfolyam)
1. szám - Valló Sándor: Összefüggés a felszíni vizek minősége és a hidrológiai viszonyok között
12 Hidrológiai Közlöny 1971. 1. sz. Special Conference Number, Szebellédy, L. 7. Cziráky, J. (Hungary): Quality problems related to conservation areas in Hungary. For a more cornplete picture the papers by G. Öllös (Hungary): Influencing the quality of water in surface reservoirs." (Hidrológiai Közlöny, No. 5, 1970), P. Benedek and B. Hock (Hungary): "Water pollution", further L. Felföldy (Hungary): "Eutrophication of surface waters" (Both in Vízügyi Közlemények, No. 3, 1969) have been drawn upon. Material has been included alsó from reports by the VITUKI (Research Institute for W ater Resources Development, Budapest) as well as from numerous scientific works dealing either comprehensively or in detail with the subjeet and published in the domestic, or foreign literature, a list of which would, however, require too much space. II. Methods for investigating and interpreting relationsliips between water quality and hydrologieal conditions The methods used for investigations, research and computations designed to serve preventive pollution control will be dealt with first, together with the conclusions arrived from them. The methods used for the observation, data processing and interpretation of changes in the volume of water resources have been developed long ago and may be regarded as familiar. However, the observation and interpretation of data on quality changes of surface waters have assumed great importance in recent decades, owing partly to rapidly growing pollution, but alsó because surface waters are increasingly relied upon for watersupply. The first step in quality studies consists of the correct taking of water samples. This will be impossible, unless local conditions, hydrography, meteorology, fauna and flóra, as well as sources of pollution are studied carefully. The methods applied in Hungary for the processing of analytical data are described in the paper by I. Fazekas. The main stages of the method are: a) Tabulated summary of analytical results, indicating means and significant extreme values, b) preparation of graphical time records on the more important components of water quality, c) preparation of duration diagrams for individual components of water quality. In watercourses it is essential to consider rates of flow and relate quality characteristics to these. Averages weigthed according to flow rate can be calculated and represented in the form of qualitycomponent profiles along the watercourse. The next stage consists thus of d) quality diagrams along the watercourse, indicating the most and least favourable values observed, as well as those adopted as a basis of classification. Water resources management to be effective calls for the regular determination of water pollution in its relations with flow rates and the results must be evaluated comprehensively. Attention should be called in this context to the laudable trend according to which besides the familiar classification (into four categories) by quality parameters, the intended use of water is alsó included (communal, industrial, or agricultural watersupply, the latter distinguished whether irrigation, or fisheries are to be supplied). In this manner the following visual diagram is arrived at: e) Water quality uiaps. These show streamflow rates of given duration in the period under study, quality classified alsó according to uses, as well as the major sources of pollution, indicating alsó the quality and rate of discharge. The methods outlined above serve primarilv the purposes of generál water management and pollution control. Regular data collection and processing will already permit tentative forecasts on water quality to be compiled. This is essential for perspective planning, moreover it offers information of statistical reliability for particular design problems and estimates of raw-water quality for the operation of waterworks. More intense pollution of surface waters by humán factors implies the necessity of more accurately formulating the concept of the quality balance. In detailed investigations VITUKI started from the definition of the water balance, and compared actual wastes load with the load-bearing capacity of individual river sections. In this particular case the counterpart of resources is the load-bearing capacity, whereas demand corresponds to the actual load. Accordingly, the quality balance is positive if the capacity is greater than the actual load and negative in the opposite case. The quality counterpart of water resources, namely the permissible wastes load, was considered alsó in the paper by B. Hock. The permissible wastes load is a concept pertaining to a particular section of a watercourse. As a component of quality it implies a limit expressed in g/sec units, considered to cause no harm downstream of a particular point of wastes discharge. High-toxicity, industrial wastes are not included, such containing organic substances yielding to oxidation being assumed. For the self-purification of the recipient the components of oxygen household are of primary importance (dissolved oxygen, BOD 5, oxygen consumption). Oxygen household is positively influenced by a) uptake of dissolved oxygen by diffusion across the watersurface, b) uptake of dissolved oxygen owing to the photosynthetic activity of vegetation. The negative factors are: a) natural pollution in surface waters, b) organic pollution due to domestic and industrial wastes, and c) pollution due to the aerobic and an aerobic decomposition of bottom sludge. The effect of these factors is reflected primarily in changes of the dissolved oxygen content. The equation of the "oxygen line" was conceived almost half-a-century ago by Streeter and Phelps for describing self-purification. The method basecl on the classic concept of the oxygen line neglected oxygen uptake owing to the photosynthetic activity of phytoplancton, as well as the oxygen consumption by natural pollution and decav of bottom sludge. The mathematical model must therefore be viewed with criticism. Nevertheless, if an allowable limit is specified for the lowest dissolved oxygen content in a recipient, then starting from the originál oxygen saturation
