Beginning in April, the flow gradually decreases to the low summer-fall waters that occur from July to October. The average monthly flow decreases to a consistent flow of about in September. The fluctuations are more pronounced over short periods or between years. At low water level, the 3 consecutive-day minimum flow can drop to during a five-year dry period, which is far from severe. Floods are moderately important, given the small size of its watershed. They are proportionally more or less half as large as those of its neighbor, the Orne. The 2-year and 5-year peak instantaneous flows are and . The 10-year peak flow is , the 20-year peak flow is and the 50-year peak flow is . The highest instantaneous flow recorded at Florange was on 12 April 1983, with an average flow of that day. This flood was of a two-year order, and therefore not at all exceptional. Overall, the Fensch is a very abundant river, more than most rivers of the Moselle basin, particularly those of the Moselle department. Annual rainfall in its basin is , which is more than twice that of France as a whole and well above the average of the French part of the Moselle basin, which is per year. The river's flow reaches per of the basin. The Fensch Valley is known for its iron and steel industry. Part of the course of the river is even covered where it crosses the town of Hayange and by facilities of the ArcelorMittal ironworks of Florange. The foundation stone for the Sollac mill was laid on 23 December 1949 in the small village of Serémange on the banks of Fensch river. U.S. Ambassador David K. E. Bruce said at the groundbreaking ceremony, which was attended by the French Foreign Minister Robert Schuman and Minister of Industry Robert Lacoste, that he hoped the French iron-steel industry would soon be the first in Europe". The region inspired Bernard Lavilliers's "Fensch Vallée", the title song of his fourth album, "Les Barbares" (1976).