# WRSM-Pitman: Calculating alpha in the wetland surface area equation for estimating wetland evaporation

I am estimating the wetland water balance variables for the comprehensive wetland module. For evaporation, it is calculated based on the net rainfall and average wetland storage area for the month. In the WRSM 2000 manual (Bailey and Pitman, 2015 page 136 of 186), alpha, a shape constant, is defined by relating the wetland volume to surface area as follows: a = Anom / Snomb Is this equation a typo?