Transitional Flow Between Orifice and Non-Orifice Regimes at a Rectangular Canal Gate

The main objective of this research was to analyze the hydraulic transition between non-orifice and orifice flow regimes at a rectangular sluice gate through the calibration of various discharge equations, and determining the value of a coefficient, which defines the transition between orifice and non-orifice flow conditions. The second objective was to determine whether a single equation could be used to represent the stage-discharge relationship for both free and submerged non-orifice flow through a rectangular sluice gate. Several hundred data sets were collected in a hydraulic laboratory, each including the measurement of water upstream depth and downstream for five different gate openings, and 17 different steady-state discharges, from 0.02 to 0.166 m3/s. Three approaches were used to define the limits of the non-orifice-to-orifice regime transition: (1) using an empirical equation; (2) using the traditional submerged non-orifice equation; and (3) using the specific-energy equation for open-channel flow. Based on the results of this research, the latter approach was ultimately chosen to define the boundaries of the transition between orifice and non-orifice flow regimes. Once the transition limits were defined, the estimation of the non-orifice-to-orifice transition coefficient, Co , was made. The transition coefficient was defined as the ratio of gate opening to upstream water depth. The experimental results indicate that orifice flow always exists when Co is less than 0.83, and non-orifice flow always exists when Co is greater than 1.00. To identify the flow regime (orifice or non-orifice) within the range 0.83 \u3c Co \u3c 1.00, it is necessary to consider the submergence, S, which is the ratio of downstream to upstream water depth. With respect to the second objective, laboratory data for non-orifice flow regimes were used to test several different empirical equation forms that could potentially represent both free and submerged flow conditions. The strategy was to find a relationship among flow rate, upstream depth, downstream depth, and submergence. As a result of the analysis, one particular equation form was found to have a relatively high coefficient of determination and low standard error of the estimate. This equation fits the laboratory data for submergences up to 0.87 with a discharge error not exceeding +-10%

Systems Optimization Models to Improve Water Management and Environmental Decision Making

System models have been used to improve water management and environmental decision making. In spite of the many existing mathematical models and tools that attempt to improve environmental decision making, few efforts have been made to identify how scarce resources (e.g., water, budget) can be more efficiently allocated to improve the environmental and ecological performance of different ecosystems (e.g., wetland habitat). This dissertation presents a set of management tools to improve the environmental and ecological performance. These tools are described in three studies. First, a simple optimization model is developed to help regulators and watershed managers determine cost-effective best management practices (BMPs) to reduce phosphorus load at the Echo Reservoir Watershed, Utah. The model minimizes the costs of BMP implementation to achieve a specified phosphorus load reduction target. Second, a novel approach is developed to quantify wetland habitat performance. This performance metric is embedded in a new optimization model to recommend water allocations and invasive vegetation control in wetlands. Model recommendations are subject to constraints such as water availability, spatial connectivity of wetland, hydraulic infrastructure capacities, vegetation growth and responses to management, plus financial and time resources available to allocate water and invasive vegetation control. Third, an agent-based model is developed to simulate the spread of the invasive Phragmites australis (common reed), one of the most successful invasive plant species in wetlands. Results of the agent-based model are embedded into an optimization model (developed in the second study) to recommend invasive vegetation control actions. The second and third studies were applied at the Bear River Migratory Bird Refuge, which is the largest wetland complex on the Great Salt Lake, Utah. These three studies provide a set of decision-support tools that recommend: (1) BMPs to reduce phosphorus loading in a watershed, (2) management strategies to improve wetland bird habitat, and (3) control strategies to minimize invasive Phragmites spread. Together, these models provide important insights and recommendations for managers to make informed decisions to manage excess nutrients in water bodies as well as to improve wetland management

Simple Optimization Method to Determine Best Management Practices to Reduce Phosphorus Loading in Echo Reservoir, Utah

This study develops and applies a simple linear optimization program to identify cost effective Best Management Practices (BMPs) to reduce phosphorus loading to Echo Reservoir, Utah. The optimization program tests the feasibility of proposed Total Maximum Daily Load (TMDL) allocations based on potential BMP options and provides information regarding the spatial redistribution of loads among sub-watersheds. The current version of the TMDL for Echo reservoir allocates phosphorus loads to existing non-point phosphorus sources in different sub-watersheds to meet a specified total load. Optimization results show that it is feasible to implement BMPs for non-point sources in each sub-watershed to meet reduction targets at a cost of $1.0 million. However, relaxing these targets can achieve the overall target at lower cost. The optimization program and results provide a simple tool to test the feasibility of proposed TMDL allocations based on potential BMP options and can also recommend spatial redistributions of loads among sub-watersheds to lower costs

Systems Modeling to Improve the Hydro-Ecological Performance of Diked Wetlands

Water scarcity and invasive vegetation threaten arid-region wetlands and wetland managers seek ways to enhance wetland ecosystem services with limited water, labor, and financial resources. While prior systems modeling efforts have focused on water management to improve flow-based ecosystem and habitat objectives, here we consider water allocation and invasive vegetation management that jointly target the concurrent hydrologic and vegetation habitat needs of priority wetland bird species. We formulate a composite weighted usable area for wetlands (WU) objective function that represents the wetland surface area that provides suitable water level and vegetation cover conditions for priority bird species. Maximizing the WU is subject to constraints such as water balance, hydraulic infrastructure capacity, invasive vegetation growth and control, and a limited financial budget to control vegetation. We apply the model at the Bear River Migratory Bird Refuge on the Great Salt Lake, Utah, compare model-recommended management actions to past Refuge water and vegetation control activities, and find that managers can almost double the area of suitable habitat by more dynamically managing water levels and managing invasive vegetation in August at the beginning of the window for control operations. Scenario and sensitivity analyses show the importance to jointly consider hydrology and vegetation system components rather than only the hydrological component

Transitional Flow Between Orifice and Non-Orifice Regimes at a Rectangular Canal Gate

The main objective of this research was to analyze the hydraulic transition between nonorifice and orifice flow regimes at a rectangular sluice gate, and to determine the value of a coefficient (Co) used to define the transition between orifice and non-orifice flow conditions. Several dozen data sets were collected in a hydraulic laboratory, each including the measurement of upstream and downstream water depth for five different gate openings, and 17 different steady-state discharges from 0.02 to 0.166 m3/s. Various approaches were tested to define the limits of the non-orifice-to-orifice regime transition; one of these uses the specific-energy equation for open-channel flow. Once the transition limits were defined, an estimation of the non-orifice-to-orifice transition coefficient, Co, was made. The transition coefficient was defined as the ratio of gate opening to upstream water depth. The experimental results indicate that orifice flow always exists when Co is less than 0.83, and non-orifice flow always exists when Co is greater than 1.00. To determine the flow regime (orifice or non-orifice) within the range 0.83 \u3c Co \u3c 1.00, it is necessary to consider the submergence, S, which is the ratio of downstream to upstream water depth

Systems Modeling to Improve the Hydro-Ecological Performance of Diked Wetlands

We developed a systems model to recommend water allocations and invasive plant management to improve hydro-ecological performance of diked wetlands. Model recommendations are subject to constraints like water availability, spatial connectivity of wetland units, hydraulic infrastructure capacities, vegetation growth and responses to management, plus financial and time resources available to manage invasive vegetation and water. We developed a hydro-ecological performance metric which we call the weighted usable area for wetlands that represent the available surface area that provides suitable hydrological and ecological conditions for priority bird species. The metric combines habitat suitability indices, water depth, vegetation cover, weights by priority species and the wetted surface. We applied the model at the Bear River Migratory Bird Refuge, which is the largest wetland complex on the Great Salt Lake, Utah. Stakeholders participated by helping to identify the problem through interpreting results. We ran the model for a base case representing hydrologic conditions in 2008 and seven scenarios that independently consider changes in water availability, financial budget, vegetation responses, and gate operation. We compared model-recommended management actions to past management activities and found that more dynamically managing water levels can increase by almost two-fold wetland hydro-ecological performance. Model results also show that wetland performance is more sensitive to changes in vegetation response, gate operation, and water availability than to changes in the financial budget. This participatory modeling effort demonstrates a framework to develop and apply hydro-ecological performance metrics for wetlands and embed those metrics in models that recommend management to improve wetland performance

System Analysis to Improve Wetland Water Allocation at the Bear River Migratory Bird Refuge, Utah

This study presents a systems modeling methodology to determine the quantity of water to supply among wetland units to increase ecological performance. Ecological performance is measured by a parameter defined as weighted usable area for wetlands (WUAW). The WUAW represents the surface area available that provides suitable condition to reach specific wetland management goals and is measured in square meters. The systems model considers water depth, flow duration, and vegetation coverage as decisions variables to improve wetland performance. Input data include water depth/area relationships in individual wetland units, wetland water distribution network of canals and remote sensing images. Hydrological and ecological decisions are limited by water availability, spatial connectivity, and hydraulic infrastructure. These decision variables, performance indicators, and constraints were identified through participatory meetings and discussions with wetland managers at the Bear River Migratory Bird Refuge (BRMBR). The BRMBR is located on the northeast side of Great Salt Lake, Utah and constitutes one of the most important habitats for migratory birds for the Pacific and Central Flyway of North America. The study showcases a methodology to allocate water to improve ecological benefits in wetlands

Wetlands without Water? A systematic review of drought effects on wetland plant communities

Wetlands in arid regions, like the western United States, regularly experience water shortages which likely will be exacerbated by climate change and increased human impacts on water supplies. Unfortunately, little consensus exists on the effects of drought on wetlands. Nor is it clear how wetland research can best inform management of wetlands in the face of declining water supplies. To address these limitations, we conducted a systematic literature review of the impacts of drought on wetland vegetation. We approached this analysis with four broad questions. First, where and why are studies about wetlands and drought being conducted? Second, how is drought defined and evaluated in the literature? Third, what are the known effects of drought on wetland plant communities, and have threshold effects been identified? Finally, how can we best manage wetlands in the face of drought and climate change? The results of the systematic review of 157 peer-reviewed studies show that most research is conducted in temperate-humid biomes, particularly in North America, primarily by academic researchers. The vast majority of studies are conducted in palustrine (non-tidal, emergent marshes) and freshwater systems. Most research analyzed one short-term drought event and the definitions of drought and measurements of its impact varied greatly. Drought was not defined at all in 30% of the studies; terms like drawdown and drought are often used interchangeably. Thresholds for drought impacts are rarely mentioned, but when they are, the focus is on thresholds with regard to the depth of a drought, the speed of a drought, or the life stage of vegetation experiencing drought. Very few studies sought to improve wetland management strategies; instead most wetland research tested general ecological theories. These findings suggest the need for more consistent research methods and definitions that cross ecology, hydrology, engineering, science policy, and other disciplines to make comparing or aggregating results of wetland studies possible and useful. There is also a need for more collaboration between researchers and managers who may have long-term data sets and insights into wetland response to various on-going management manipulations. In this way, research efforts can be made more relevant to management needs and to the types of drought that naturally occur, which are generally longer-term or more severe than what are evaluated in the literature. Finally, more research is needed to identify the impacts of drought on many different wetland types, particularly in regions that are not as well studied but are likely to experience water scarcity