- This paper addresses the methodology for developing monthly naturalized flow of the Texas Water Availability Model (WAM) system datasets by developing and applying Water Rights Analysis Package (WRAP)-based methods. The methodology is based on converting gaged stream flows adjusted to remove human impacts to naturalized flows using a current use WRAP model input dataset from the WAM System modified to represent actual use. An actual use scenario dataset is developed by modifying the current use scenario dataset to better represent actual water resources development, allocation, management, and use. The simulation iterations continue until the regulated flows very closely match the actual gaged flows. The regulated flow computed using the new naturalized flow shows the close match to gaged flow. The methodology developed in this study could potentially be used to update the other river basin datasets in the statewide WAM System. 2011 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.