Abstract: In order to measure water in open channels in an irrigation district, a new type of flow measuring meter, a portable long-throated flowmeter, has been developed. The flowmeter consists of a long throated flume, a portable indicator rod for measuring the height of water, and a digital display for flow rate. The meter has remote transmission capability. In field tests the device has proven to be accurate, mechanically reliable, and easy to use and maintain. In addition, computer software for design and calibration of the long-throated flume has been developed as a Windows 98/2000 application using the Visual Basic programming language. The new program has several function modules such as flume dimension design, adjustment and calculation for throat section geometry, rating equation fitting, and graphical output.