Vízügyi Közlemények, 1969 (51. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(44) COST-BENEFIT ANALYSIS BY RECALCULATION FOR WATER MANAGEMENT UNITS IN AGRICULTURE By Sándor Ress, Economist (For the Hungarian text see pp. 155) The term water management unit in agriculture covers usually the w ter associations, which assumed increased significance and importance with growing intensity of agricultural production and specialization of farming. The economic and to a certain extent operational analysis of their activities is for this very reason indicated. The study has been based on data made available by one of these associations, the Water Management Association of Kalocsa and Surroundings. It is of a methodological character and consequently the economical conclusions arrived at may be generalized for the operation of all water management units in agriculture. The analysis has been performed by using methods of mathematical economics (input-output model). From tiie results obtained it can be concluded that in order to meet the increased demands presented by the new economic system, the water management units in agriculture must adapt increasingly their system of management and accounting to the particular characteristics of water management. COMPUTATION OF UNSTEADY, GRADUALLY VARIED FLOW IN OPEN CHANNELS IN THE CASE OF COMPLEX WAVES By Br. Miklós Kozák, Civ. Engr. (For the Hungarian text see pp. 166) When analysing more involved, unsteady, gradually varied flow phenomena in a watercourse, the influence of branches and lateral canals cannot be neglected. In the case of complex wave forms backflow occurs in many instances and then the resulting flow conditions arc not accessible to reliable analysis, unless the wave profile is resolved into a positive- and a negative range of discharge. In the case of complex waves a new method has been developed by the author for resolving the wave profile into uniform ranges of discharge. Computation results have shown the new method to yield more reliable information. Computation checks and the analysis of the Z( T

), Q( T), Z(X), Q(X) characteristic curves obtained have demonstrated that if backflow occurs, the conventional method can be used l'or tentative estimations only. The only economic manner for computations associated with unsteady flow conditions is that involving the use of digital computers. For this purpose, further for estimating the initial conditions a mathematical program has been compiled in ALGOL code and fed into a GIER-type digital computer, which are of invaluable help in the analysis of unsteady flow phenomena. The method of computation described here is suited for the analysis of gradually varied, unsteady flow problems associated with the headwater- and tailwater reaches of hydroelectric stations built in the river bed, with lateral branches of a major stream, and generally in any canal network. The analysis can be performed even if backflow occurs. As a result of the analysis the Z=Z(T), Q=Q(T) and V=V(T) characteristic curves can be procured for any cross-section. These curves are indispensable tools for the general hydraulic dimensioning and checking of systems comprising canal networks, furthermore for planning and designing hydroelectric projects, structures and river regulation works in general. When designing river power stations with daily pondage, the optimum, most economical engineering solution cannot be selected, unless computation results relating to individual alternatives are available. The method is suited for the general dimensioning of canal networks serving irrigation, the drainage of excess surface waters and the collection of water by systems of intercepting laterals. In the case of in-, or outflow along these canal networks, the characteristic equations must be completed by a term allowing lor this lateral loading [12]. Computers are the only tools by which these computations can be performed in a realistic manner.