Vízügyi Közlemények, 1979 (61. évfolyam)

4. füzet - Mistéth Endre: Mezőgazdasági öntözőrendszer biztonsága

596 Mistéti

г Endre K

1

0 Ft/ha/èv 4. ábra. Az öntözés fajlagos költségei (Kw), 1 0,75 kielégítettség esetén, az öntözendő к terület (То) nagyságának függvényében Fig. 4. Unit costs of irrigation (Kw) at a supply level 1 - — = 0.75, in terms of the magk nitude (To) of the area to be irrigated Figure 4. Frais spécifiques de l'irrigation ( Kw) en cas de l'assouvissement de 1 = к = 0,75, en fonction de l'importance de la superficie à irriguer (То) principal canals have only been included in the optimization computations. The costs of supply, storage and principal canals are quadratic functions of the area to be irrigated. The annual maintenance costs are proportionate to the construction costs, just as the annual operating costs. To these latter the cost of filling once the reservoirs must also be added. The annual water demands must be determined for a particular crop pattern assumed in terms of the potential évapotranspiration value. To this water demand the needs of flooding irrigation and fish ponds, further the seepage and evaporation losses in the distribution network must be added. This water demand is evidently a random variable, the distribution of which within the growing season has been neglected in the study. The water demand follows a normal distribution, as it depends mainly on the meteorological conditions prevailing in the river valley. The water demand can be met from precipitation, by direct diversion from the river, further from artificial storage reservoirs. The volume of the latter is also a random variable, following evidently a skew distributions, as it is related to the annual streamflow in the river. The skewness can be assumed to approximarte a distribution fitted to the annual highest streamflow rates. The unsatisfied water demands, periodical water shortages result from inadequate storage volume. By adding the volumes of all reservoirs the annual average