Vízügyi Közlemények, 1979 (61. évfolyam)

3. füzet - Kovács György: A korszerű vízrajzi munka alapelvei. I. rész: A vízrajz célja, feladatai és az adatgyűjtő hálózat kialakítása

A korszerű vízrajzi munka. 1. rész 369 The data on major streams with cathment areas larger than 5 — 6 thousand sq.km. should indicate the changes along the stream of all transport processes, such as streamflow, ice regime, suspended sediment, bed load, dissolved substances and pollution, taking place in the channel. P'or this reason efforts should be made at obtaining continuous observation reports in the cross sections at the entrance of each major tributary, namely on the main stream and the tributary upstream of the junction, as well as downstream thereof. The remaining stations should be located between the grid points thus formed. The data on minor streams in mountain- and hilly areas are similarly expected to describe linear transport processes. The fundamental objective is accordingly to identify the catchments with comparable natural conditions and to describe by means of 10—15 stations, depending on the area, the relationship between the hydrologie parameters and the catchments. In plain- and lowland areas it is required to describe, instead of the catchments of minor streams, the conveyance in the canal networks creating artificial drainage, observing the requirements outlined before. Description according to area can be solved realistically in catchments covering more than 50—100 sq.km. For the hydrologie description of minor areas reliance can be made on representative catchments, the object of which is to explore by detailed observations the regularities of local processes. Efforts should be made at establishing at least one similar station in each hydrological unit. In the hydrologie systems influenced by human activities — and all catchments belong already to this category in Hungary — the data observed in the natural environment are alone no more adequate for assessment, and thus information is needed on the interrelations between the natural and social water cycles. For this reason the data on diversions and return discharges are equally important elements of the hydrologie information system. At the stations registering the water regime in lakes and reservoirs not only the transport processes are of interest, but data should be gathered also on the phenomena associated with water storage and extended retention, such as evaporationand seepage losses, sediment deposition, changes in quality, etc. The establishment of one data collection center along each major lake appears justified. The basic observation network on precipitation and other atmospheric phenomena, such as temperature, humidity, radiation, wind, etc., is operated within the organization of the National Meteorological Service. For this reason it is desirable that all similar data observed for operative- and research purposes within the water sector should be checked against, and processed primarily in combination with, the observations in the standard network. Only the information processed and integrated over time and area need thereafter be introduced to the hydrologie information system. The flow of vapour is not accessible to direct measurement, so that attempts should be made at approximating actual evaporation — as a major component of the natural water balance — by applying several different methods of observation. This is the function of regional stations, the primary objective of which is to describe the hydrologie processes (interception, flow- and storage of soil moisture, vertical recharge to, and losses from, ground water) taking place in the space between the atmosphere and the water table. The vapour uptake potential of the air mass is characterized by pan evaporation data, if we succeed in eliminating the disturbing influence of horizontal energy advection, or in making allowance therefor on the basis of theoretical figures. In the interest of determining full,actual évapotranspiration observations are needed on the components of the energy balance. Although the greatest number and most reliable information on the processes involved, are obtained by means of lysimeters, the construction and operation thereof is very expensive, so that their application in a network does not seem warranted. Nevertheless, a few key stations should be equipped with these. The variation in the parameters mentioned last is not a continuous one, but follows a mosaic pattern, since the relevant factors, such as plant cover, soil type, depth of the water table, vary also in an irregular manner. Efforts should therefore be made to transfer the data observed at stations in representative locations to other areas by models suitably formulated. 3 Vízügyi Közlemények