Several studies in high-latitude catchments have demonstrated the importance of near-stream riparian zones as hydrogeochemical hotspots with a substantial influence on stream chemistry. An adequate representation of the spatial variability of riparian-zone processes and characteristics is the key for modeling spatio-temporal variations of stream-water quality. This thesis contributes to current knowledge by refining landscape-analysis techniques to describe riparian zones and by introducing a conceptual framework to quantify solute exports from riparian zones. The utility of the suggested concepts is evaluated based on an extensive set of hydrometric and chemical data comprising measurements of streamflow, groundwater levels, soil-water chemistry and stream chemistry. Standard routines to analyze digital elevation models that are offered by current geographical information systems have been of very limited use for deriving hydrologically meaningful terrain indices for riparian zones. A model-based approach for hydrological landscape analysis is outlined, which, by explicitly simulating groundwater levels, allows better predictions of saturated areas compared to standard routines. Moreover, a novel algorithm is presented for distinguishing between left and right stream sides, which is a fundamental prerequisite for characterizing riparian zones through landscape analysis. The new algorithm was used to derive terrain indices from a high-resolution LiDAR digital elevation model. By combining these terrain indices with detailed hydrogeochemical measurements from a riparian observatory, it was possible to upscale the measured attributes and to subsequently characterize the variation of total organic-carbon exports from riparian zones in a boreal catchment in Northern Sweden. Riparian zones were recognized as highly heterogeneous landscape elements. Organic-rich riparian zones were found to be hotspots influencing temporal trends in stream-water organic carbon while spatial variations of organic carbon in streams were attributed to the arrangement of organic-poor and organic-rich riparian zones along the streams. These insights were integrated into a parsimonious modeling approach. An analytical solution of the model equations is presented, which provides a physical basis for commonly used power-law streamflow-load relations. / At the time of doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press; Paper 4: Manuscript. / Swedish Research Council (VR, grant no. 2005-4289)

Stormwater runoff from urban areas is a major source of pollution to surface water bodies. The discharge of nutrients such as nitrogen and phosphorus is particularly damaging as it results in harmful algal blooms which can limit the beneficial use of a water body. Stormwater best management practices (BMPs) have been developed over the years to help address this issue. While BMPs have been investigated for years, their use has been somewhat limited due to the fact that much of the data collected is for specific applications, in specific regions, and it is unknown how these systems will perform in other regions and for other applications. Additionally, the research was spread across the literature and performance data was not easily accessible or organized in a convenient way. Recently, local governments and the USEPA have begun to collect this data in BMP manuals to help designers implement this technology. That being said, many times a single BMP is insufficient to meet water quality and flood control needs in urban areas. A treatment train approach is required in these regions. In this dissertation, the development of methodologies to evaluate the performance of two BMPs, namely green roofs and pervious pavements is presented. Additionally, based on an extensive review of the literature, a model was developed to assist in the evaluation of site stormwater plans using a treatment train approach for the removal of nutrients due to the use of BMPs. This model is called the Best Management Practices Treatment for Removal on an Annual basis Involving Nutrients in Stormwater (BMPTRAINS) model. The first part of this research examined a previously developed method for designing green roofs for hydrologic efficiency. The model had not been tested for different designs and assumed that evapotranspiration was readily available for all regions. This work tested this methodology against different designs, both lab scale and full scale. Additionally, the use of the Blaney-Criddle equation was examined as a simple way to determine the ET for regions where data was not readily available. It was shown that the methods developed for determination of green roof efficiency had good agreement with collected data. Additionally, the use of the Blaney-Criddle equation for estimation of ET had good agreement with collected and measured data. The next part of this research examined a method to design pervious pavements. The water storage potential is essential to the successful design of these BMPs. This work examined the total and effective porosities under clean, sediment clogged, and rejuvenated conditions. Additionally, a new type of porosity was defined called operating porosity. This new porosity was defined as the average of the clean effective porosity and the sediment clogged effective porosity. This porosity term was created due to the fact that these systems exist in the exposed environment and subject to sediment loading due to site erosion, vehicle tracking, and spills. Due to this, using the clean effective porosity for design purposes would result in system failure for design type storm events towards the end of its service life. While rejuvenation techniques were found to be somewhat effective, it was also observed that often sediment would travel deep into the pavement system past the effective reach of vacuum sweeping. This was highly dependent on the pore structure of the pavement surface layer. Based on this examination, suggested values for operating porosity were presented which could be used to calculate the storage potential of these systems and subsequent curve number for design purposes. The final part of this work was the development of a site evaluation model using treatment train techniques. The BMPTRAINS model relied on an extensive literature review to gather data on performance of 15 different BMPs, including the two examined as part of this work. This model has 29 different land uses programmed into it and a user defined option, allowing for wide applicability. Additionally, this model allows a watershed to be split into up to four different catchments, each able to have their own distinct pre- and post-development conditions. Based on the pre- and post-development conditions specified by the user, event mean concentrations (EMCs) are assigned. These EMCs can also be overridden by the user. Each catchment can also contain up to three BMPs in series. If BMPs are to be in parallel, they must be in a separate catchment. The catchments can be configured in up to 15 different configurations, including series, parallel, and mixed. Again, this allows for wide applicability of site designs. The evaluation of cost is also available in this model, either in terms of capital cost or net present worth. The model allows for up to 25 different scenarios to be run comparing cost, presenting results in overall capital cost, overall net present worth, or cost per kg of nitrogen and phosphorus. The wide array of BMPs provided and the flexibility provided to the user makes this model a powerful tool for designers and regulators to help protect surface waters.

This dissertation presents the design of an integrated watershed model, WASH123D version 3.0, a first principle, physics-based watershed-scale model of integrated hydrology/hydraulics and water quality transport. This numerical model is comprised of three modules: (1) a one-dimensional (1-D) simulation module that is capable of simulating separated and coupled fluid flow, sediment transport and reaction-based water quality transport in river/stream/canal networks and through control structures; (2) a two-dimensional (2-D) simulation module, capable of simulating separated and coupled fluid flow, sediment transport, and reactive biogeochemical transport and transformation in two-dimensional overland flow systems; and (3) a three-dimensional (3-D) simulation module, capable of simulating separated and coupled fluid flow and reactive geochemical transport and transformation in three-dimensional variably saturated subsurface systems. The Saint Venant equation and its simplified versions, diffusion wave and kinematic wave forms, are employed for surface fluid flow simulations and the modified Richards equation is applied for subsurface flow simulation. The reaction-based advection-dispersion equation is used as the governing equation for water quality transport. Several physically and mathematically based numerical options are provided to solve these governing equations for different application purposes. The surface-subsurface water interactions are considered in the flow module and simulated on the basis of continuity of interface. In the transport simulations, fast/equilibrium reactions are decoupled from slow/kinetic reactions by the decomposition of reaction networks; this enables robust numerical integrations of the governing equation. Kinetic variables are adopted as primary dependent variables rather than biogeochemical species to reduce the number of transport equations and simplify the reaction terms. In each time step, hydrologic/hydraulic variables are solved in the flow module; kinetic variables are then solved in the transport module. This is followed by solving the reactive chemical system node by node to yield concentrations of all species. Application examples are presented to demonstrate the design capability of the model. This model may be of interest to environmental scientists, engineers and decision makers as a comprehensive assessment tool to reliably predict the fluid flow as well as sediment and contaminant transport on watershed scales so as to evaluate the efficacy and impact of alternative watershed management and remediation techniques prior to incurring expense in the field.

Nutrient enrichment, which can be detrimental to the health of aquatic systems, is one of the leading causes of impairment of our Nations? waters. Development and initial calibration of a hydrologic, hydrodynamic, and water quality model of dissolved oxygen and nutrient concentration for the St. Louis Bay watershed in coastal Mississippi is documented herein. The model was developed using the USEPA BASINS 3.0 analysis system and WinHSPF, a comprehensive watershed loading and transport modeling software. The resulting model simulates significant watershed and instream physical, chemical and biological processes including rainfall runoff and associated water quality from a variety of land use categories. Extensive data describing the study area, land use practices, hydrology and water quality are presented, analyzed and discussed relative to model development and adequacy to support future modeling projects. Integration of this data into a valuable water quality assessment model and preliminary model calibration is also presented.

Many communities are currently seeking to balance urban water needs with preservation of sensitive fish habitat. As part of that effort, CE-QUAL-W2, a hydrodynamic and temperature model, was developed for Chester Morse Lake and the lower Cedar River, WA. Chester Morse Lake is approximately 10 km long with a maximum depth at full pool of 40 m. The Cedar River model started immediately downstream of the Chester Morse dam and ended 21 km downstream at Landsburg, where drinking water is diverted for the City of Seattle. This water quality model was coupled with a fish habitat and bioenergetics model for bull trout and was calibrated to temperature data between 2005 and 2008. Bull trout fish bioenergetics parameters were provided by the USGS. The CE-QUAL-W2 model was found to be highly accurate in modeling temperature variation in the lake - at most locations having an average absolute mean error of between 0.5 and 0.8 oC. The Cedar River model had an average absolute mean error of 0.7oC. This tool is designed to allow managers and operators to estimate the impact to fish habitat and growth potential from various management decisions including extent of drawdown, timing/volume of flows, and various pumping operations. Future studies could include incorporating further water quality parameters such as nutrients, algae, and zooplankton as they relate to fish productivity.