Vízügyi Közlemények, 1966 (48. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(45) The product (H

) yields the loss in crop resulting from all damages caused by draught and excess water. The maximum crop which can be expected in the case of ideal water supply is obtained by adding this loss to the actual crop. The largest possible crop to be expected in the case of ideal water supply, and serving as reference is thus Qj max = Qj+ H. A similar parameter /'was introduced to represent all engineering facilities improving waterhousehold on agricultural areas. In this case the numerator represents the crop resulting or becoming available as an increment from the operation of that particular facility. The denominator remains as before. Values characterizing waterhousehold, or waterhousehold facilities in different periods are calculated from a model in which data on precipitation and potential évapotranspiration are averages representative for the particular area. As an illustrative example, waterhousehold of arable lands in the south-eastern part of the Hungarian Plains, in Békés county, is investigated. Main conclusions are summarized as follows: The waterhousehold coefficient is readily handled and well defined. Quantitative analysis revealed the following facts: 1) The role of water in agricultural production increases with the standard of farming methods. The objectives of waterhousehold are therefore subject to wide variations in time. Engineering structures cannot be designed correctly, unless the interrelation between water and farming methods is known. 2) Potential development must be allowed for already in the design stage of engineering structures. This holds especially true in the present age of rapid technical development, where appreciable changes may ensue even within the amortization period in the scope of objectives as well as in the type of interference. 3) Extreme values of water quantities to be drained, or supplied can be measured by physical units and arc constant for individual areas. "Within these areas it is the economical quantity to be drained, or supplied which is subject to variations. For this reason standard amounts of application are valid under the given set of conditions only and any change in farming methods entails a change in these as well. 4) Experimental techniques relying on long-term, empirical observations are no more effective in waterhousehold investigations. In periods of rapid development these data give virtually no information for development planning. Factors influencing phenomena and interrelations existing between these should rather be determineif jiy fundamental research to provide the foundations from which long-range lorecats can be compiled with any degree of reliability.! The above conclusions have been verified by modern practice. No attempt could however be undertaken for clearing the causes of deficiencies, until no unit suitable for measuring the dynamical development of waterhousehold, and for exploring ratios and trends, was available. The waterhousehold coefficient was found suitable for establishing a sound dynamical approach to the development of waterhousehold and for permitting the investigation of relationships between waterhousehold and agricultural productions. As such it is a valuable tool in shaping a new philosophy and gaining new knowledge. The following notations have been used in this paper: = periodical (monthly) deficiency, or surplus of water in the model characterising waterhousehold [mm]; bi = regression coefficient appyling to peried "i" (month) [q/ha, mm]; x = Emount of crop recorded during the years under consideration [q/ha]; y i — precipitation in individual periods "i" during the year of crop records considered [mm/month]; H = total crop loss in the model [q/ha]; Qj trix — nux'mvm crcp attaineble at a given standard (j) of farming (series of years) when all crcp reducing effects of water can be eliminated [q/ha]; Qj = average crop attained at a given standard (j) of farming (series of vears) [q/ha];