Thesis (Ph. D.)--University of Washington, 1982. / Vita. Bibliography: leaves [398]-451.

Thesis (M.S.)--Oregon State University, 1971. / Partially funded by Oregon Agricultural Experiment Station. Includes bibliographical references (leaves 39-41). Also available on the World Wide Web.

Graduation date: 2006 / Dam removal is increasingly viewed as a river restoration tool because dams affect so many aspects of river hydrology, geomorphology, and ecology; but removal also has impacts. When a dam is removed, sediment accumulated over a dam’s lifetime may be transported downstream; and the timing, fate and consequences of this sediment remain some of the greatest unknowns associated with dam removal. In this thesis, I develop a conceptual model for erosion and deposition following removal of sediment-filled dams in mountain streams, and use field studies to document actual change. The data show that reservoir erosion in mountain rivers is likely to occur by knickpoint migration, with 85% of stored sediment being released during a single storm event in two field studies, at shear stresses less than that required for mobilization of the median surface particle size. Coarse sediment is predicted to deposit close to the dam with channel aggradation decreasing exponentially with increasing distance downstream, although some channel features are shown to have a greater propensity for aggradation than others. Field studies show that turbidity associated with dam removal and reservoir erosion may decrease hyporheic exchange, but gravel deposition (e.g., 470 m3 of gravel from Dinner Creek Dam) has the potential to more than offset that decrease, and increased hyporheic exchange is shown to reduce diurnal temperature change. Macroinvertebrate density and taxa richness did not respond to dam removal itself, but rather with time-lagged reservoir erosion. Following reservoir erosion, macroinvertebrate density recovered quickly, although longterm taxa community composition appears to be altered. On the Sandy River, field measurements of shear stress and patterns of sediment deposition following cold lahars were used as an analog to predict the fate of fine sediment, which is likely to deposit far from the dam. Results show that the Sandy River has little capacity for fine sediment storage in pools above RK 6.4 (~ 42 kilometers below Marmot Dam) at discharges associated with reservoir sediment releases. Taken as a whole, this paper illustrates a complex suite of process that may accompany removal of sediment-filled dams in mountain rivers.

Increasing salinity has been a growing concern for users of waters from the Pecos River and the reservoirs it feeds in the Texas portion of the River's watershed. Irrigation water diverted from the river in the northern reach of this watershed is often only suitable for a limited number of crops, reducing harvesting options for local farmers. In the south, the Pecos feeds into the International Amistad Reservoir along the border with Mexico. During the 1990s, total dissolved solids concentrations in the reservoir rose as much as 10 mg/L per year and often approached the drinking water standard for potable water (1000 mg/L). Since this time, control efforts have focused on reducing the river's salinity, requiring the identification of salt sources. Hydrologic trend analysis and geochemical identification methods were used to determine these sources for the reach of the river between Red Bluff Reservoir and Brotherton Ranch. Between Red Bluff Reservoir and Coyanosa, flow diversions remove much of the flow that carries the salts, resulting in decreased salt loads, but also making the river more sensitive to evapotranspirative concentration. This sensitivity is evident in the river between Coyanosa and Girvin, where salinity begins to increase to the highest levels within the study area. However, salt loads increase here as well, indicating external salt sources as a contributor. The most substantial increase in bromide ions and the Br-/Cl- ratio appears between Grandfalls and Imperial, although no conclusion could be drawn regarding the identity of the source. The ratio continues to increase up to Girvin, where it appears that evapotranspirative concentration again has a significant effect. Here, several points drifted to the right of the groundwater mixing zones, plotting at values that were uncharacteristic of these sources.

Several studies indicates China is experiencing a water crisis, were several regions are suffering of severe water scarcity and rivers are heavily polluted. On the other hand, water is used inefficiently and wastefully: water use efficiency in the agriculture sector is only 40% and within industry, only 40% of the industrial wastewater is recycled. However, based on statistical data, China’s total water resources is ranked sixth in the world, based on its water resources and yet, Yellow River and Hai River dries up in its estuary every year. In some regions, the water situation is exacerbated by the fact that rivers’ water is heavily polluted with a large amount of untreated wastewater, discharged into the rivers and deteriorating the water quality. Several regions’ groundwater is overexploited due to human activities demand, which is not met by local. Some provinces have over withdrawn groundwater, which has caused ground subsidence and increased soil salinity. So what is the situation in China? Is there a water crisis, and if so, what are the causes?This report is a review of several global water scarcity assessment methods and summarizes the findings of the results of China’s water resources to get a better understanding about the water situation. All of the methods indicated that water scarcity is mainly concentrated to north China due to rapid growth, overexploitation from rivers and reduced precipitation. Whereas, South China is indicated as abundant in water resources, however, parts of the region are experiencing water scarcity due to massive dam constructions for water storage and power production. Too many dam constructions in a river disrupts flow of the river water and pollutants are then accumulated within floodgates.Many Chinese officials and scholars believe that with economic growth comes improved environmental quality when the economy has reached to a certain of per-capita level. However, with the present water situation it is not sustainable or possible for China to keep consuming and polluting its water resources. Improvement of environmental quality does not come automatically with increased income, and policies, laws and regulations are needed in order to stop further deterioration of the environment.China’s water situation is not any news and the key factor is human activities, but the question is how to solve it. China’s water crisis is much more complex than over exploitation of groundwater and surface water. There are three water issues in China: “too much water – floods, too little water – droughts, and too dirty water – water pollution” (Jun & Chen, 2001). Thus, solving China’s water crisis is a huge challenge to solve without negatively affecting the economic growth.

This dissertation investigates the dynamics of the tidally modulated outflow from the Columbia River mouth using high resolution measurements of velocity, density and turbulent microstructure. At high tide, flow through the river mouth reverses from flood (onshore) to ebb (offshore). During ebb, buoyant fluid issues from the river mouth and spreads offshore across the ocean surface. This is the Columbia River tidal plume. The fluid velocity of the tidal plume is super-critical (greater than the wavespeed of coastal stratification), which creates a zone of sharp surface velocity convergence at its leading edge, causing a front to form. From early ebb to peak ebb, constant front propagation speed and plume expansion rate are controlled by a linearly increasing volume-flux through the river mouth. Within the plume, turbulence at the plume base is strongly related to the difference between the shear-squared, S², and four times the buoyancy frequency squared, 4N². A parameterization based on the excess shear-squared, S² - 4N², represents Reynolds stress well, indicating that it is driven by Kelvin-Helmholtz instability. During peak ebb of large tides, high volume-flux through the mouth drives high S² - 4N², causing high plume-base stress, which forces significant deceleration of the plume. During smaller tides the volume-flux is smaller, S² - 4N² lower, and the stress too weak to significantly decelerate the plume. During mid-ebb of both small and large ebbs, increasing buoyancy flux from the river mouth raises plume stratification, which suppresses S² - 4N² and stress. As ebb ends, decreasing volume flux and deflection by the Coriolis effect limit plume expansion. This weakens surface velocity convergence, causing the front to diffuse. On longer timescales, plume N² is modulated by changes in river flow; higher river flow causes higher N². During peak ebb of large tides this increase in N² supports higher S², resulting in higher S² - 4N², which causes larger internal stress. These results describe the primary dynamics of the Columbia River tidal plume from front formation to late-ebb, and relate variability in those dynamics to tidal and river-flow forcing. / Graduation date: 2011 / Access restricted to the OSU Community at author's request from Jan. 26, 2011 - Jan. 26, 2013

Maximum equilibrium scour depths, equilibrium scour volumes, and induced equilibrium movements at isolated obstacles on river beds were investigated in clear-water scour. The research was achieved by a systematic flume study based on the results of dimensional analysis of local scour. The main tested obstacles for local scour were cubes. Local scour at a circular cylinder of aspect ratio 1 and a sphere were also examined for comparison with scour at cubes. Each obstacle was placed on a flat movable bed and oriented normal to the incident flow. Non-cohesive uniform medium sand and very fine gravel were used as movable beds. The tested flow conditions were controlled to give many combinations of the relevant dimensionless parameters for local scour: the flow Froude Number, relative obstacle size, and relative roughness of bed material. Water surface profiles and longitudinal velocity profiles along the plane of symmetry, as well as the horizontal velocities near the bed around isolated obstacles on a fixed bed were examined in several runs. For a slightly submerged cube, the path of maximum velocity downstream of the cube moves from the water surface into the lower part of the flow. At a greater distance downstream, the path of maximum velocity tends to move upward toward the water surface. An increase of flow Froude Number leads to a hydraulic jump behind the cube. The relative longitudinal velocity near the bed is increased in this region. The decrease of relative water depth or the increase of flow Froude Number can lead to increased average relative horizontal velocity (V/u) near a cube. The cube has the highest average V/u value, as compared to flow near a circular cylinder and a sphere. The local scour processes and equilibrium scour patterns at isolated cubes on movable beds were also examined. There is not a unique equilibrium scour pattern for clear-water scour at a cube on a movable bed. Equations were developed to predict the maximum equilibrium scour depth and scour volume and the critical condition for incipient motion of bed material at a cube in clear-water scour. As the water becomes relatively deep, the shape effect of the circular cylinder and the sphere become negligible. The major equilibrium movement of a cube on a movable bed due to scour involves longitudinal displacement, vertical settlement, and longitudinal inclination. Equations were developed to predict the equilibrium movement and the critical condition for incipient upstream movement of a cube in clear-water scour. / Graduation date: 1991

This thesis investigates the potential application of a two-dimensional depth-averaged sediment transport and morphological model on a large braided river system and examines its capability to build a computational gravel budget and predict the morphological changes. The Lower Fraser River gravel reach is characterized by an irregularly sinuous single-thread channel split around large gravel bars and vegetated islands, and riverbed aggradation because of gradual gravel deposition over the years, bank hardening and channel confinement. Gravel removal from selected locations is considered as one of the viable management options to maintain the safety and integrity of the existing flood protection system along the reach. Therefore, any gravel removal plan in this reach requires a reliable sediment budget estimation and identification of deposition zones. It is also required to examine the possible future morphological changes with and without gravel removal and to assess its impact on design flood level. The main objective of this study is to build a computational sediment (gravel) budget for the 33 km long gravel reach that extends from Agassiz-Rosedale Bridge to Sumas Mountain near Chilliwack. In this study, a two-dimensional depth-averaged curvilinear mathematical model MIKE 21C was modified and applied to predict the gravel bedload transport and detect the change of morphology for the next 10 years period. A gravel transport formula was coded and added into the MIKE 21C model. Sediment transport code modification and application has been done side by side in a trial and error fashion. This is the first use of a conventional two-dimensional depth-averaged model for the entire gravel reach of the Lower Fraser River within affordable computational effort. The model application was successful in term of gravel budgeting, aggradation and degradation zones identification and long-term morphological change prediction, with some limitations and drawbacks. Further modification and model testing with recent bedload data is recommended.

This thesis combines detailed analyses of living plant communities with paleolimnological methods to develop the use of plant macrofossils as an effective tool to track hydroecological changes in ponds of the Slave River Delta (SRD), N.W.T. Several approaches were used to develop an understanding of the relationships between hydrolimnological conditions, living plant communities, and the composition of sedimentary macrofossil remains across spatial and temporal scales. A spatial survey approach was used to assess the relationships between the composition of plant macrofossil assemblages contained in the surface sediments and the hydrological and limnological conditions of 40 SRD basins that span a broad range of hydrological settings in the delta. Results show that there are strong relationships between the prevailing hydrolimnological conditions in the SRD and the composition of sedimentary macrofossil remains, and subsequently indicator macrofossil taxa were identified to distinguish between sites with high river influence (flood-dominated sites: ostracode shells, Daphnia ephippia, Chara oospores; exchange-dominated sites: Myriophyllum winter-bud scales, Daphnia ephippia) and sites with low river influence (evaporation-dominated: Ceratophyllum leaves, Lemna leaves, Drepanocladus leaves). In light of the strong connection between spring flood events and the hydrolimnological conditions of SRD ponds, and growing concerns that the frequency of spring floods have declined in recent decades, paleolimnological investigations were initiated at a pond (SD2) adjacent to the Slave River to construct a record of flood events in the SRD. Prior to analysis of macrofossil assemblages from sediment cores, a detailed study of the living plant community was conducted at SD2, and results were compared to the distributions of surficial sedimentary plant macrofossil assemblages to assess how representative surficial sediment assemblages are of the living plant community. This study indicates distinct patch-scale (or quadrat-scale)similarity between the living vegetation and sedimentary remains in the central basin, as well as distinct similarity between the living aquatic macrophytes and sedimentary remains at a pond-scale, suggesting there is excellent potential to track changes in the composition and percent cover of aquatic macrophytes in pond sediment cores using plant macrofossil assemblages. Additionally, this study indicates that influence of long-distance transport of macrofossils during the 2005 flood event was minor at this pond, and may not be an important factor affecting paleolimnological reconstructions of plant communities. With contemporary studies as a framework, an ~90-year record of ice-jam flood frequency was reconstructed from a sediment core collected from pond SD2. Multi-proxy analyses indicated decadal-scale oscillations in flood frequency at this site, with at least three multi-year periods of low river influence. Beginning in ~1943, an 18-year period of particularly low river influence and greatly reduced water levels was indicated by abundant macrofossils of Sagittaria cuneata and represents the driest period over the past ~90-years. Similarities between the flood history of SD2 and upstream sites in the Peace-Athabasca Delta suggest that spring discharge generated from headwaters and major contributing rivers plays a key role in the frequency and magnitude of spring flood events of both deltas.

The purpose of the study was to investigate possible environmental impacts of a reduced catchment area (~25 %) for Kaunisjärvi lake and Patojoki river due to establishment of a iron ore mine in Kaunisvaara, Pajala municipality. To accomplish this, two methods were used; first a literary study was inducted to establish impacts of reduced inflow to lakes and reduced flow in rivers. Secondly, the state of the waters was determined by collecting background data from the mining company (Northland Resources SA) which included chemical- and biological parameters. The result showed that a reduced inflow can affect a lake by either eutrophication or oligotrophication, depending on the lakes condition and the character of the inflow, which in turn has impacts on the entire food-web. Reduced flow in rivers also has impacts on the entire food-web by increased water temperature, decreased dissolved oxygen levels, decreased inundation (witch effects nutrient and organic material exchange), decreased biodiversity in phytoplankton, benthos and fish and inhibiting migration, studies differed in effects on pH and alkalinity. The result also showed that both Kaunisjärvi and Patojoki are affected by nutrient load and organic matter, which impacts the entire ecosystem of the waters. Possible consequences for Kaunisjärvi and Patojoki of reduced inflow and reduced flow are discussed. The report concluded that the reduced catchment area will have impacts on environmental goals set by EU and also on national level, but that the interest of exploitation weighs higher.