Determination of Stream Inflow in Kwan Phayao Using IFAS on Tank Model with Geometric Information System

Abstract

Kwan Phayao is considered as important water resources in Phayao province with watershed area of 1,227 square kilometers but it just has 30 million cubic meters of storage. There are thirteen rivers flowing in and one river flowing off Kwan Phayao. This research is objective to determine the stream inflow from different sub-basins in Kwan Phayao by using IFAS program on two layers tank model with geometric information system. Therefore, the rainfalls provided by eight rain gauges stations and physical area data will be used as an input. Furthermore, the Kwan Phayao river basins are distinguished into six sub-river basins which three river basins are gauge watersheds. As a result, the water inflow can be used to examine the accuracy of the runoff measured by the model of IFAS. To clarify this, the specific parameters such as SKF, SNF and AUD will be adjusted depending on the geographical characteristics. The mentioned parameters will be firstly applied to the river basins with their rain gauges stations , then , will be applied to those sub-river basins without streamflow gauges stations. The types of parameters used will be adjusted owing to the similarity of geographical characteristics, usages of lands and the dam structures of each sub-river basins. Afterward, hourly and daily stream inflow will be calculated. Finally, the calculated stream inflow will be utilized as an important information in outflow decision-making from Kwan Phayao.