1992 年 1992 巻 23 号 p. 6-22
Irrigation in the downstream delta area of the Chao PhrayaRiver, Thailand, is based on an irrigation system aiming at water conservation;gates called regulators are installed at numerous points where canals joinrivers, for the purpose of controlling the water stage and discharge. Watermanagement involves estimation of the discharge passing through regulatorsas well as the discharge at river gauging stations, the mean daily discharge inparticular. However, since this irrigation area is a tidal area, it is difficult toreadily estimate the mean daily discharge.
The authors developed and systematized a method of estimating the meandaily discharge at the confluence and regulators of rivers in a tidal area, andapplied it to the downstream delta area of the Chao Phraya River.
A numerical simulation model of the unsteady flow was constructed which iscapable of reproducing a complicated flow condition. This model may be usedfor computing many combinations of water stages at the upstream and downstreamends, including those related to gate opening in the case of the regulator, and the discharge for each combination can be obtained. The computationresults are expressed in a multiple regression formula. When this formulacovers the mean daily water stages, and gate opening in the case of theregulator, the mean daily discharge can be estimated even in the field throughsimple calculation using a desk calculator.
