Before revision: The discharge calculation can be summarised as where Q is the volumetric flow rate of fluid (the discharge), C is the flow coefficient for the structure (on average a figure of 3.33), L is the width of the crest, H is the height of head of water over the crest, n varies with structure (e.g., 3/2 for horizontal weir, 5/2 for v-notch weir).
After revision: The discharge calculation can be summarised as where is the volumetric flow rate of fluid (the discharge), is the flow coefficient for the structure (on average a figure of 3.33), is the width of the crest, is the height of head of water over the crest, varies with structure (e.g., for horizontal weir, for v-notch weir).