ABSTRACTAdvance knowledge of flow rate variations in the water supply to a spring‐fed trout farm is of great value to the farm manager since the weight of stock that can be sustained at any one time is dependent on the discharge rate of the spring. Annual variations of flow rate in groundwater dominated streams and rivers follow a fairly regular pattern with a recession occurring from the highest flows in the spring to the lowest flows in the late summer and autumn. This paper describes a simple technique for predicting discharge rates during periods of recession. Use of the technique which is illustrated by data from Belleau springs in Lincolnshire would enable fish farm managers to obtain a conservative estimate of the flows during summer and autumn and give adequate forewarning of impending low flow