Vízügyi Közlemények, 1966 (48. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(13) PATTERN OPERATION AND STANDARD DESIGN OF IRRIGATION SYSTEMS WITH HIGH-HEAD PUMPING STATIONS By M. Gábri and L. Szikra, Engrs. (For the Hungarian text see pp. 87) Sprinkling irrigation in Hungary witnessed — as revealed by Table I — considerable development since 1960. Sprinkling irrigation fields meeting requirements of large-scale farming operations, and supplied from pressure centers (high-head pumping stations) are established in sequence. Operating systems and those under design are compiled in Table II. These fields have been built with a permanent pipe network consisting of asbestos cement pipe, while operation is accomplished using portable laterals. The two fundamental prerequisites for simplified and standardized design are the introduction of pattern operation and establishing a standard design for the permanent (buried) asbestos cement network. In pattern operation plots in the system are of an identical size, the arrangement of asbestos cement laterals and the spacing of hydrants is uniform, identical water volumes are distributed continuously through the laterals, while placing stand-by lines, transfer after operation and mounting are also performed continuously. Operation itself is continuous, where the contemplated amount of rain is distributed during the entire operating period of one day, without interruption, over individual plots. This type of operation is impossible, unless 100% stand-by portable lines are available. Standardization of asbestos cement networks implies that a predetermined number of plots, or the multiple thereof, is supplied from a single asbestos cement header line. Consequently the discharge to be conveyed by the line is also predetermined, respectively a round multiple thereof. In this respect, requirements of large scale operations are plots of as far as possible uniform size, and the possibility of growing any of the contemplated plants on any of the plots. The type of sprinkler nozzle used, technical specifications of these and the arrangement pattern to be observed are described in Chapter 2 a of the Hungarian text. The favourable side ratio for plots was found to be 1 : 2. The economical length of operating portable laterals is 240 m (Fig. 1 ). One side of the plot is consequently 480, or 960 m long (Fig. 2), while the other is accordingly 960, or 480 m. The economical plot size is thus 46 hectares. The recommended spacing of asbestos cement laterals is illustrated in Figs. 2 с and 2 d. The other dimension of the plot is governed by the spacing and number of hydrants, which depends on the arrangement of portable pipelines (Fig. 3). Plot dimensions and sizes have been compiled for different hydrant spacings, lateral arrangements and number of hydrants in Table III

. Values resulting in a 46 ha large plot of the most favourable form — at a hydrant spacing of 96 and 120 m — are framed in the table. Data contained in Table III are given a visual representation in Figs. 4, 5 and 6. Diagrams for the operation of portable laterals equipped with Hungarian sprinkler nozzles of Type T 22 and T 45 are given in Figs. 7 and 8, respectively. For establishing water demand categories in pattern operation, a hydrant spacing of 120 m and an arrangement of asbestos cement laterals according to Figs. 2b, c, or d was assumed. Consequently if the conveying capacity of a portable lateral is assumed at 13 lit/sec on the average, an asbestos cement lateral must be designed to carry 52 lit/sec, in order to be able to supply water to the four portable laterals serving a table. Each plot has then a supply rate of 104 lit/sec. Standardized designing consists of the following steps: laying out plots, selecting the site for the high-head pumping station, and drawing the most favourable trace for the asbestos cement pipe network. Closed circuit solutions offer in general uneconomical operating characteristics. Existing branches of cultivation, farm boundaries, or administration units — if conflicting with the requirements of an economical design — cannot be observed. The basic layout patterns for asbestos cement pipelines and plot arrangements are illustrated in Fig. 9. Losses over unit length in asbestos cement pipes are com-