Mark C. Stone

Water yield responses to high and low spatial resolution climate change scenarios in the Missouri River Basin

River Basin in Colorado. However, differences in water yields calculated from GCM and regional climate model scenarios have not been compared for a major river basin. [3] The uncertainty in hydrologic impacts due to the spatial scale of climate scenarios needs further exploration. Given the computer and human resources needed to generate higher resolution scenarios, it is important to determine the added value and/or further uncertainty in impacts assessment that result from their use. Moreover, the differences in hydrological impact could have implications for water resource planning in the long-term future. [4] In this project, two climate change scenarios were developed for the Missouri River Basin: one from a coarse grid GCM and one from a fine scale Regional Climate Model (RCM). The GCM provided the initial and lateral boundary conditions for driving the RCM. Impacts of these scenarios on water yields were analyzed using the Soil and Water Assessment Tool (SWAT) hydrologic model.

Evaluating velocity measurement techniques in shallow streams

Accurate flow field measurements in shallow rivers are necessary for many applications including biological investigations and numerical model development. Unfortunately, river velocity data is difficult to obtain due to the limitations of traditional velocity meters. Acoustic Doppler Current Profilers (ADCP) provide a potential alternative to traditional point-velocity measurements. However, these instruments have not been thoroughly tested against accepted techniques in natural streams. The objectives of this research were to evaluate the adequacy of ADCP instruments for conducting velocity measurements in quasi-wadeable streams and to provide instrument selection guidance for similar flow environments. These objectives were met by conducting ADCP, Acoustic Doppler Velocimeter (ADV), and Price current meter measurements at nine coinciding verticals in two rivers. The performance of each instrument was evaluated with regards to data accuracy, desired parameters, and required sampling time. ADCP measurements compared favorably with ADV and Price meter data for velocity profiles and depth-averaged velocities. The ADCP also showed a significant improvement in estimates of local bed shear stress when compared to global estimates determined from the water surface profile. However, excessive noise reduced the effectiveness of ADCP measurements of velocity standard deviation and velocity components. The results are discussed in the context of instrument selection for parameterization of models

Modeling water ages and thermal structure of Lake Mead under changing water levels

Abstract Water age and thermal structure of Lake Mead were modeled using the 3-dimensional hydrodynamic Environmental Fluid Dynamics Code (EFDC). The model was calibrated using observed data from 2005 and then applied to simulate 2 scenarios: high-stage with an initial water level of 370.0 m and low-stage with a projected initial water level of 320.0 m. The high-stage simulation described predrought lake hydrodynamics, while the low-stage simulation projected how lake circulation could respond under significant lake drawdown, should drought conditions persist. The results indicate that water level drawdown plays an important role in thermal stratification and water movement of Lake Mead during receding water levels. The impact of the dropping water level on lake thermal stratification is more significant in shallow regions such as Las Vegas Bay. Depth-averaged (the mean value of 30 vertical layers) water temperature in the low-stage was estimated to increase by 4–7 C and 2–4 C for shallow (<20 m) and deep (>70 m) regions, respectively. Further, depth-averaged water age decreased about 70–90 d for shallow regions and 90–120 d for deep regions under the simulated drought scenario. Such changes in temperature and water age due to continuous drought will have a strong influence on the hydrodynamic processes of Lake Mead. This study provides a numerical tool to support adaptive management of regional water resources by lake managers.

Sensitivity Analysis of Nonequilibrium Adaptation Parameters for Modeling Mining-Pit Migration

The nonequilibrium adaptation parameters of a depth-averaged two-dimensional hydrodynamic and sediment transport model were examined in the study. Calculated results were compared to data measured in two sets of published laboratory experiments that investigated mining-pit migration under well-controlled boundary conditions including steady flow and uniform rectangular cross sections along the flume except in the vicinity of the experimental mining area. The two sets of experiments were chosen as representatives of bed-load-dominated and suspended-load-dominated cases, respectively. A sensitivity analysis was conducted to estimate the influence of the nonequilibrium adaptation parameters on mining-pit migration simulation. Calculated results indicate that appropriate selection of the adaptation parameters is critical in order to close the nonequilibrium sediment transport formulas when modeling mining-pit migration.

Spatiotemporal patterns in nutrient loads, nutrient concentrations, and algal biomass in Lake Taihu, China

Abstract Lake Taihu, Chinas third largest freshwater lake, exemplifies the severity of eutrophication problems in rapidly developing regions. We used long term land use, water quality, and hydrologic data from 26 in-lake and 32 tributary locations to describe the spatiotemporal patterns in nutrient loads, nutrient concentration, algal biomass, measured as chlorophyll a (Chl-a), in Lake Taihu. Point and nonpoint sources, as determined by chemical oxygen demand, contributed approximately 75 and 25% of the total nutrient loads to the lake, respectively. Spatial patterns in total phosphorus (TP) and total nitrogen (TN) concentrations in Lake Taihu strongly corresponded with observed loads from adjoining rivers with high concentrations proximate to densely populated areas. Chl-a concentrations exhibited spatial patterns similar to TP and TN concentrations. Generally, nutrient and Chl-a concentrations were highest in the northwestern region of the lake and lowest in the southeastern region of the lake. Seasonally, the largest nutrient loads occurred during summer. The annual net retention rate of TP and TN in Lake Taihu was approximately 30% of the total load. This study identifies regions of the lake and the watershed that are producing more nutrients to develop targeted management strategies. Reducing external P and N input from both point and nonpoint sources is obviously critical to address water quality issues in the lake. In addition, atmospheric deposition and resuspension of existing lake sediments also likely play a role in eutrophication processes and harmful algal blooms occurrence.

Mechanical analysis for emergent vegetation in flowing fluids

Vegetation plays an important role in stream processes and management efforts. However, the description of mechanical behaviours of vegetation–fluid interaction requires an improved understanding of the underlying physics and of the methods used for investigating this interaction. The objective of this research was to develop a method for describing vegetation mechanics in flowing fluids. This was accomplished by outlining methods for describing vegetation responses to flow under rigid and bending conditions for simple vegetation elements. The results of the theoretical analyses provide insight into influences of vegetation biomechanical properties to force distributions, bending behaviour, and potential vegetation rupture locations and conditions. The approach can be used to estimate hydraulic conditions for vegetation failure and flow resistance caused by vegetation, especially for flexible species. Although the techniques developed here are based on simplifying assumptions, the present analysis provides a foundation for future development for submerged vegetation and complex vegetation clusters.

Regime shifts and panarchies in regional scale social-ecological water systems

In this article we summarize histories of nonlinear, complex interactions among societal, legal, and ecosystem dynamics in six North American water basins, as they respond to changing climate. These case studies were chosen to explore the conditions for emergence of adaptive governance in heavily regulated and developed social-ecological systems nested within a hierarchical governmental system. We summarize resilience assessments conducted in each system to provide a synthesis and reference by the other articles in this special feature. We also present a general framework used to evaluate the interactions between society and ecosystem regimes and the governance regimes chosen to mediate those interactions. The case studies show different ways that adaptive governance may be triggered, facilitated, or constrained by ecological and/or legal processes. The resilience assessments indicate that complex interactions among the governance and ecosystem components of these systems can produce different trajectories, which include patterns of (a) development and stabilization, (b) cycles of crisis and recovery, which includes lurches in adaptation and learning, and (3) periods of innovation, novelty, and transformation. Exploration of cross scale (Panarchy) interactions among levels and sectors of government and society illustrate that they may constrain development trajectories, but may also provide stability during crisis or innovation at smaller scales; create crises, but may also facilitate recovery; and constrain system transformation, but may also provide windows of opportunity in which transformation, and the resources to accomplish it, may occur. The framework is the starting point for our exploration of how law might play a role in enhancing the capacity of social-ecological systems to adapt to climate change.

Spatially implemented Bayesian network model to assess environmental impacts of water management

Bayesian networks (BNs) have become a popular method of assessing environmental impacts of water management. However, spatial attributes that influence ecological processes are rarely included in BN models. We demonstrate the benefits of combining two-dimensional hydrodynamic and BN modeling frameworks to explicitly incorporate the spatial variability within a system. The impacts of two diversion scenarios on riparian vegetation recruitment at the Gila River, New Mexico, USA, were evaluated using a coupled modeling framework. We focused on five individual sites in the Upper Gila basin. Our BN model incorporated key ecological drivers based on the “recruitment box” conceptual model, including the timing of seed availability, floodplain inundation, river recession rate, and groundwater depths. Results indicated that recruitment potential decreased by >20% at some locations within each study site, relative to existing conditions. The largest impacts occurring along dynamic fluvial landforms, such as side channels and sand bars. Reductions in recruitment potential varied depending on the diversion scenario. Our unique approach allowed us to evaluate recruitment consequences of water management scenarios at a fine spatial scale, which not only helped differentiate impacts at distinct channel locations but also was useful for informing stakeholders of possible ecological impacts. Our findings also demonstrate that minor changes to river flow may have large ecological implications.

Evaluating the impacts of hydrologic and geomorphic alterations on floodplain connectivity

Ecohydrology. 2017;10;e1833. https://doi.org/10.1002/eco.1833 Abstract The dynamic interaction between a river and its floodplain is important for a variety of hydrologic, ecological, and geomorphic processes. However, water management activities have widely disrupted the natural flow regime and in many cases reduced floodplain connectivity. Recent environmental flow research has called for techniques that incorporate hydrogeomorphic processes, which are important for ecological and riverscape health. The objective of this study was to evaluate the impacts of hydrologic alterations on floodplain dynamics and connectivity. Changes in floodplain inundation dynamics and interface dynamics were investigated for 2 hydrologic scenarios on 2 distinct rivers—the Gila River and the Rio Grande, both in New Mexico, USA. The objective was achieved using a combination of 2‐D hydrodynamic models and analysis techniques to evaluate large spatial and temporal datasets. The results improved understanding of inundation patterns and water flux between the channel and floodplain under baseline and altered hydrologic scenarios. Due to the distinct qualities of the study sites, unique insights were gleaned. In the Gila River, discernible changes in floodplain dynamics were observed in spite of the relatively minor alterations from the baseline hydrologic conditions. In contrast, the Rio Grande results revealed the importance of not only hydrologic alterations but also channel incision on reduced floodplain connectivity. The proposed techniques can be adapted to a wide range of river systems depending on the nature of hydrologic or geomorphic alterations under consideration. As a result, the degree of alteration of floodplain connectivity can be better understood, leading to improved river management.

Five ways to support interdisciplinary work before tenure

Academic institutions often claim to promote interdisciplinary teaching and research. Prescriptions for successfully engaging in interdisciplinary efforts, however, are usually directed at the individuals doing the work rather than the institutions evaluating them for the purpose of tenure and promotion. Where institutional recommendations do exist, they are often general in nature and lacking concrete guidance. Here, we draw on our experiences as students and faculty participating in three interdisciplinary water resource management programs in the USA to propose five practices that academic institutions can adopt to effectively support interdisciplinary work. We focus on reforms that will support pre-tenure faculty because we believe that an investment in interdisciplinary work early in one’s career is both particularly challenging and seldom rewarded. Recommended reforms include (1) creating metrics that reward interdisciplinary scholarship, (2) allowing faculty to “count” teaching and advising loads in interdisciplinary programs, (3) creating a “safe fail” for interdisciplinary research proposals and projects, (4) creating appropriate academic homes for interdisciplinary programs, and (5) rethinking “advancement of the discipline” as a basis for promotion and tenure.