Abstract: The prediction of a pollutant spill on downstream water quality is dependent on the water velocity, longitudinal mixing, and seasonal effects on water inflows, where velocity is the most important, but most difficult, aspect. This paper provides a study on the calculation of travel-time from one bank discharge to another by using a one dimension Lagrangian river model. A one dimension Lagrangian river model was developed and applied to the 210 plus miles for the lower Rio Grande River Basin from the Falcon Dam to the head water of Brownsville that pours onto the Gulf of Mexico. The lower reach includes two dams, seven inflows into the river, various wastewater treatment plants, and five main diversions (either stems or city extracts). A set of time-series flow hydrographs was obtained as an input to the model that was simulated to give an output of velocities, stage, and flow hydrographs in order to obtain the travel time. The numerical treatment of series of dams and spillway (that included uncontrolled overflow spillway, gate-controlled ogee spillway; and underflow gates) were created to give a realism to the modeling. Special attention was focused on the high spatial and temporal variation of flows in the river basin, a result of the large variation in inflows, and channel geometry due to dams and reservoirs along the river. For the reach there were slopes greater than about 0.0002, travel times could be predicted by computing the active flow area using the average Manning equation with n = 0.032 and assuming a constant inactive area for each reach. Predicted and measured spatial and seasonal variation of flow profiles along the river show good agreement. The simulated travel time of the modeled output was compared against gauge data for both water elevation and flow data provided by the IBWC from the dates of 2006-2010. Being that this is a Lagrangian model, this is computationally efficient model that has the potential to become a tool that could be used for long term simulation for water resource planning, management and operation decision making in a large and complex river basin system.
Keywords: Travel time, numerical model, stormwater drainage, water flow rate.
Title: Travel Time Estimation of the Lower Rio Grande Water Transportation Model
Author: Jose Gonzalez, Jungseok Ho
International Journal of Civil and Structural Engineering Research
ISSN 2348-7607 (Online)
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