Modeling of Solute Transport and Retention in Upper Amite River
Streams play an important role in a solute transport through a stream network. Transient storage is one of the important processes that control mass exchange between a main stream and transient storage zones because of increase in the residence time of solute. In order to take account of the effect of transient storage on solute transport in streams, a variable residence time (VART) model was developed. The model is characterized by several features: (1) actual varying residence time was used, (2) no-user specified residence time distributions (RTD) were required, (3) less calibration parameters were involved as compared to existing models, and (4) production of various types of RTDs such as power-law, lognormal, and exponential distributions for an instantaneous release of solute. Comparisons between the VART model and some existing solute transport models using tracer concentration data measured in 33 streams show that the VART model is capable of reproducing exponential, power-law, and lognormal RTDs observed in streams with the accuracy higher than or at least comparable to existing solute transport models. In addition, the results show that stream channel size affects the type of breakthrough curves (BTCs). The BTCs switch from the upwardly curving VART - +U and VART - 0U to a straight line (VART - -P) and further to the downwardly curving VART - -L distributions with increasing flow depth. Large rivers generally exhibit VART - -L distributions. Small streams commonly display either the upwardly curving (VART - +U and VART - 0U) distributions or VART - -P distributions. Moderate rivers may exhibit any types of VART series distributions. The application of VART model to the Upper Amite River shows that the VART model provides a simple yet effective tool for predicting solute dispersion and transport in natural streams and rivers. The VART model also provides a potential tool for estimating nutrient retention in the Amite River and other natural streams.
Advisor:Deng, Zhi-Qiang; Malone, Ronald; Chen, Jim
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Keywords:civil environmental engineering
Date of Publication:10/01/2008