Estimation of streamflow characteristics and assessment of trends in the Niobrara River at Mariaville, Nebraska

A computer model was used to synthesize a long-term streamflow record for the Niobrara River at Mariaville, Nebraska. The record was developed on the basis of 30-plus years of streamflow data from 3 upstream sites, and the U. S. Geological Survey 's CONROUT model was calibrated using 294 days of measured flow at Mariaville; for the calibration period, 87% of the synthesized daily discharges were within 15% of the measured values. The synthesized record was analyzed for trends in streamflow characteristics. A marked decrease in the average consecutive-day, low-flow discharges was detected after 1964, ranging between 162 cu ft/sec less for the 1-day low flow and 200 cu ft/sec less for the 14-day low flow. The decrease probably was caused by the start-up of operations at Merritt Reservoir. (Author 's abstract)