Naturalized flow distribution component of a water availability modeling system

Abstract

Under Senate Bill 1, Article VII of the 751 Texas Legislature the State of Texas will develop a Water Availability Modeling (WAM) system to support water rights, regulatory functions and water management in this state. The goal is assurance of a supply of water in the future. In order to determine the reliability of water resources, it is important to be able to assess current water supply and to use this data to project water supply in the future. This process includes the ability to estimate the amount of water at a location where there is not a record of flow. This research focused on the transfer of naturalized flow from gaged to ungaged locations for incorporation into the WAM system. The following general approaches for estimating naturalized flows at ungaged sites are addressed in various degrees of detail in this report: * distribution of flows in proportion to drainage area * flow distribution equation with ratios for various watershed parameters * adaptation of the NRCS CN method * use of stream gage records to develop regression equations relating flows to watershed characteristics * use of recorded data at gaging stations to develop precipitation-runoff relationships. These approaches were tested and some conclusions were drawn on the different methods of transferring flow from gaged to ungaged locations. The conclusion reached is that it is difficult to reproduce flow for any specific month, but that long term averages are reproduced with a greater degree of accuracy than monthly values. The alternative flow distribution methods provide about the same level of accuracy, and for this reason the decision of method used should be based on the judgment of the people studying the watershed. It is important that further research be done on this subject with the goal being increased accuracy of prediction of flow from gaged to engaged locations.