Zhonglong Zhang

Development of a Distributed Watershed Contaminant Transport, Transformation, and Fate (CTT&F) Sub-model

CTT&F is a physically based, spatially distributed watershed contaminant transport, transformation, and fate sub-model designed for use within existing hydrological modeling systems. To describe the fate of contaminants through landscape media as well as spatial variations of contaminant distributions, physical transport and transformation processes in CTT&F are simulated for each cell in the model and routed to the watershed outlet. CTT&F simulates contaminant erosion from soil and transport across the land surface by overland flow. The model also simulates contaminant erosion from stream bed sediment and transport through channels in addition to transport of contaminants inputs by overland flow. CTT&F can simulate solid (granular) contaminant transport and transformation, including partitioning between freely dissolved, dissolved organic carbon (DOC) bound, and particle-sorbed phases. To demonstrate model capabilities, CTT&F was coupled with an existing distributed hydrologic model and was tested and validated to simulate RDX and TNT transport using two experimental plots. These experiments examined dissolution of solid contaminants into the dissolved phase and their subsequent transport to the plot outlet. Model results were in close agreement with measured data. Such a model provides information for decision makers to make rational decisions relevant to the fate of toxic compounds.

Watershed Scale Physically Based Water Flow, Sediment and Nutrient Dynamic Modeling System

Non-point source (NPS) runoff of pollutants is viewed as one of the most important factors causing impaired water quality in freshwater and estuarine ecosystems and has been addressed as a national priority since the passage of the Clean Water Act. To control NPS pollution, state and federal agencies developed a variety of programs that rely heavily on the use of watershed management in minimizing riverine and receiving water pollution. Watershed models have become critical tools in support of watershed management. Lumped, empirical models such as HSPF do not account for spatial heterogeneity within subwatersheds and the simulations of the actual processes are greatly simplified. This chapter describes a distributed water flow, sediment and nutrient dynamic modeling system developed at U.S. Army Engineer Research and Development Center. The model simulates detailed water flow, soil erosion, nitrogen (N) and phosphorus (P) cycling at the watershed scale and computes sediment transport across the landscape, nutrient kinetic fluxes for N and P species. The model consists of three distinct parts: (1) watershed hydrology, (2) soil erosion and sediment transport, and (3) nitrogen and phosphorus transport and cycling. The integrated watershed model was tested and validated on two watersheds in Wisconsin (French Run and Upper Eau Galle Watersheds). The model performed well in predicting runoff, sediment, nitrogen and phosphorus. This chapter presents the model development and validation studies currently underway in Wisconsin.

The Demonstration and Validation of a Linked Watershed Riverine Modeling System for DOD Installations-Calleguas, California : Resource Conservation and Climate Change Projects, RC-201302, Version 2.00

The objective of this project is to demonstrate and validate a linked watershed and riverine modeling system for the Calleguas Creek Watershed. The system helps land managers assess outcomes resulting from military activities; the system also supports installation sustainability through informed watershed management of water, water quality, contaminants, and land-use impacts. The modeling system was developed and enhanced from existing watershed and riverine models. Hydrological Simulation Program-Fortran (HSPF) was used to compute water flow, soil erosion/sedimentation, nutrients, and contaminant loadings, whereas the Hydrologic Engineering Centers-River Analysis System (HEC-RAS) was used to evaluate instream water quality and aquatic ecosystem responses from watersheds both within and outside an installation. HSPF simulates, for extended periods of time, the hydrologic and associated water quality processes on pervious and impervious land surfaces and in streams and well-mixed impoundments. Benefits can be derived from the ability of the linked modeling system to determine contaminant loads entering and leaving the installation. In certain locations, this information can be used to identify to what extent the installation is responsible for the impaired waters. In cases where mitigation is necessary, the system will help land managers better assess which scenarios will provide the most environmental benefits for the least financial cost. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

Hydrologic Engineering Center River Analysis System (HEC-RAS) Water Temperature Models Developed for the Missouri River Recovery Management Plan and Environmental Impact Statement

Abstract : This report describes the Hydrologic Engineering Center-River Analysis System (HEC-RAS) water temperature models for five Missouri river reaches (e.g., Fort Peck Dam to Garrison Dam; Garrison Dam to Oahe; Fort Randall Dam to Gavins Point Dam; Gavins Point Dam to Rulo, NE; and Rulo, NE to the mouth of the Missouri River). These models were developed based on calibrated HEC-RAS flow models that the Omaha and Kansas City Districts of U.S. Army Corps of Engineers (USACE) provided. Of five HEC-RAS water temperature models, three models were run for an 18-year period (1995-2012) for six alternatives in support of developing the Missouri River recovery program (MRRP) management plan (ManPlan) and environmental impact statement (EIS). The HEC-RAS water temperature model results that were used to establish a baseline and management alternative scenarios are presented in this report. Likewise, the sources of model uncertainty are discussed in this report as well.

Development of Nutrient Sub-Modules (NSM) for Integration with USACE Hydraulic and Hydrologic Modeling Systems

The control of nutrients arising form Non-Point Source Pollution (NPSP) is difficult because the source areas can be hard to identify and typical treatment methods are infeasible due to the distributed nature. While restoration attempts may provide significant returns, they can be costly to implement and often are met with resistance. In order to quantify potential benefits, detailed hydrologic/water quality modeling of watersheds and the effects of Best Management Practices (BMP) is required. Extending model results beyond the range of calibration to model future conditions requires the use of physically based models that include the important processes that generate stream flow, material transport, uptake, loss, transformation, and recycling. In addition, given the complex nature of surface water and groundwater interaction, as well as the spatial nature of nutrient distribution, a distributed source transport model is needed to accurately account for the movement of water and nutrients through the various landscape media where more simplistic models are not applicable, or are homogeneous which is not appropriate for the heterogeneous nature of distributed sources. This paper will discuss the current research efforts and demonstrations taking place at the Engineer Research and Development Center (ERDC) as it relates to the nutrient sub-modules.