Procedures are presented for casting 50-ft3/sec trapezoidal water measurement flumes in 2-foot bottom width lined and unlined ditches. Drawings and construction details for the concrete forms used are also presented. Flumes installed in concrete-lined ditches require about 13 man-hours and cost about $230. Flow can be determined for both free and submerged flow conditions from rating tables with depth measured in a stilling well or with a sloping gage on the flume sidewall.