Local Watershed Research Articles

Spatial and temporal controls on the solute behavior of rivers in arid watersheds: The Okavango River, NW Botswana

Solute cycling models for rivers in arid watersheds must identify solute sources and their spatial and temporal connectivity to rivers to assess the processes that control the solute behavior in these rivers. In this study, we collected hourly time series of total dissolved ions (TDI) concentrations, water levels, water temperatures and air temperatures at select stations distributed longitudinally in a river in an arid watershed. Our objectives were to: (1) document the spatial and temporal variations in solute concentrations and (2) determine the processes controlling the spatial and temporal variations in solute concentrations. We conducted this investigation over a two-year period at four stations along the Okavango River flowing through the Okavango Delta (Delta) in the middle Kalahari Desert, Botswana. At the spatial scale, we observed progressive downriver enrichment in TDI concentrations associated with evapotranspiration of river water because of the 5 months river transit across the hot Delta. At a temporal scale, the TDI concentrations increased seasonally from evapoconcentration and sub-seasonally from solute transfer from the watershed to the river. We analyzed sub-seasonal TDI concentration perturbations using the slope (β) of the relationship between TDI concentrations and normalized water level (C-NWL) relationships. We find that at low discharge during flow recession and at the beginning of rising discharge from flooding, the solute enrichment anomalies with β > 0 are related to hydrologic connectivity between the river and solute stores in the river floodplains, hundreds of thousands of salt islands and isolated evapoconcentrated wetland pools. Our findings indicate that hydrologically-driven river connectivity to solute stores in the local watershed and evapotranspiration jointly control the solute behavior at variable spatial and temporal scales in rivers in arid watersheds. We anticipate that our findings will inform solute transport and solute cycling models for rivers in arid watersheds.

An Approach for Prioritizing Natural Infrastructure Practices to Mitigate Flood and Nitrate Risks in the Mississippi-Atchafalaya River Basin

Risks from flooding and poor water quality are evident at a range of spatial scales and climate change will exacerbate these risks in the future. Natural infrastructure (NI), consisting of structural or perennial vegetation, measures that provide multiple ecosystem benefits have the potential to reduce flood and water quality risks. In this study, we intersected watershed-scale risks to flooding and nitrate export in the Mississippi-Atchafalaya River Basin (MARB) of the central U.S. with potential locations of seven NI practices (row crop conversion, water, and sediment control basins, depressional wetlands, nitrate-removal wetlands, riparian buffers, and floodplain levees and row crop change) to prioritize where NI can be most effective for combined risk reduction at watershed scales. Spatial data from a variety of publicly-available databases were analyzed at a 10 m grid cell to locate NI practices using a geographic information system (GIS). NI practices were presented at the regional basin scale and local Iowa-Cedar watershed in eastern Iowa to show individual practice locations. A prioritization scheme was developed to show the optimal watersheds for deploying NI practices to minimize flooding and water quality risks in the MARB. Among the 84 HUC4 basins in the MARB, 28 are located in the Upper Mississippi and Ohio Rivers basins. The Wabash and Iowa-Cedar basins (HUCs 0512 and 0708, respectively) within these basins were found to rank among the uppermost quintile for nearly all practices evaluated, indicating widespread opportunities for NI implementation. Study results are a launching point from which to improve the connections between watershed scale risks and the potential use of NI practices to reduce these risks.

Incorporating Evidence into Collaborative Ecosystem Restoration: A Content Analysis of Bibliographic References and their Use in Salmon Recovery Plans.

Collaborative environmental management draws on a wide range of information, from a variety of stakeholders, to inform policy. Scientific information is particularly relevant for ecosystem restoration plans, such as those created for recovering species on the brink of extinction. This study examines use of evidence in salmon recovery plans in Puget Sound, USA. Across 12 plans, coders characterized 1104 references to identify their source, recency, domain, and context. Subsequently, 11 plans were analyzed in-depth to identify how each reference was used to support particular kinds of claims. Results indicate the most frequent source of information cited in salmon recovery plans is government agencies, especially from national and state governments, followed by peer reviewed journal articles and scientific books. Journal articles come predominantly from high impact (top quartile) journals, although these articles are on average 15 years old. Sources are almost exclusively from the domain of natural sciences (97%), with just 1% social sciences and 2% non-scientific. More references come from beyond than within the local watershed. Different reference sources are used to support different kinds of claims, with government agency sources positively associated with claims about species status/trends, and peer reviewed journal articles positively associated with claims about causes of species decline. Overall, the lack of social science references, and lack of references to support claims about levels of community support, reduce managers' abilities to incorporate features of social systems into species recovery planning.

Effects of a place-based digital gameful learning experience on middle school students’ watershed literacy and attitudes about desktop virtual reality gameplay

ABSTRACT Digital game-based and gamified technologies hold much promise to promote the development of learners’ conceptual knowledge. This efficacy study used desktop virtual reality (dVR) to investigate how the place-based digital gameful learning experience (DGLE) “Watershed Explorers”, implemented as a curriculum enhancement activity, impacted students’ watershed literacy as well as their attitudes towards playing and learning during dVR gameplay. Thirty-five middle school students completed a pretest-posttest content assessment measuring watershed literacy, a motivation to play with a dVR game survey, and a perception of learning with dVR games survey. Results showed that using “Watershed Explorers” as a curriculum enhancement activity can positively impact learning, especially middle school students’ ability to identify their own local watershed and its connections to the ocean. Most participants perceived this DGLE as a helpful and engaging type of learning technology that can promote stimulating ways of presenting content materials and make school learning more interesting. Implications for the design of future iterations of “Watershed Explorers” to enhance learning are also discussed.

Linking Climate-Change Impacts on Hydrological Processes and Water Quality to Local Watersheds

Estimation of hydrological processes and water quality is central to water resource management, clean water supply, environmental protection, and ecological services [...]

Applying a Coupled Hydrologic-Economic Modeling Framework: Evaluating Alternative Options for Reducing Impacts for Downstream Locations in Response to Upstream Development

Economic input-output and watershed models provide useful results, but these kinds of models do not use the same spatial units, which typically limits their integration. A modular hydrologic-economic modeling framework is designed to couple the Rectangular Choice-of-Technology (RCOT) model, a physically constrained, input-output (I-O) model, with the Hydrological Simulation Program-Fortran (HSPF). Integrating these two models can address questions relevant to both economists and hydrologists, beyond addressing only administrative or watershed concerns. This framework is utilized to evaluate alternative future development prospects within Fauquier County, northern Virginia, specifically residential build-up, and agricultural intensification in the upstream location of the local watershed. Scenarios are designed to evaluate the downstream impacts on watershed health caused by upstream development and changes made within the economic sectors in response to these impacts. In the first case, an alternative residential water technology is more efficient than the standard for ensuring adequate water supply downstream. For scenarios involving upstream agricultural intensification, a crop shift from grains to fruits and vegetables is the most efficient of the alternatives considered. This framework captures two-way feedback between watershed and economic systems that expands the types of questions one can address beyond those that can be analyzed using these models individually.

Infrared small target detection based on gray intensity descent and local gradient watershed

Robust infrared (IR) small target detection is an essential part of infrared search and tracking systems. Existing IR target detection methods based on human visual system usually use statistical features of rectangular region to measure the difference between target and background. In the case that the dim target size is smaller than the rectangular window cell size, since the window cell contains both the target and the background pixels, the statistical features cannot well represent the target contrast. The use of a rectangular window structure for calculation reduces the statistical difference between the target and the background, that is, reduces the saliency of the target, resulting in a slow rise in the ROC curve of the HVS method. This paper proposes a novel non-window structure filter for small target detection. Firstly, we obtain candidate target points by combining the high-frequency information of the image with the local maximum points, and at the same time, calculate the Sobel gradient map to prepare for subsequent processing. Then, a filter is designed based on gray intensity descent and local gradient watershed (GID-LGW) characteristics of the target, and it is used to calculate the contrast of each candidate target point. Finally, an adaptive threshold operation is applied to extract the target. Experiments show that compared with several baseline methods, the proposed method has a better detection rate, lower false alarm, and high speed, especially for small and weak targets with a size smaller than 3 × 2.

Major point and nonpoint sources of nutrient pollution to surface water have declined throughout the Chesapeake Bay watershed

Understanding drivers of water quality in local watersheds is the first step for implementing targeted restoration practices. Nutrient inventories can inform water quality management decisions by identifying shifts in nitrogen (N) and phosphorus (P) balances over space and time while also keeping track of the likely urban and agricultural point and nonpoint sources of pollution. The Chesapeake Bay Program’s Chesapeake Assessment Scenario Tool (CAST) provides N and P balance data for counties throughout the Chesapeake Bay watershed, and these data were leveraged to create a detailed nutrient inventory for all the counties in the watershed from 1985–2019. This study focuses on three primary watershed nutrient balance components—agricultural surplus, atmospheric deposition, and point source loads—which are thought to be the leading anthropogenic drivers of nutrient loading trends across the watershed. All inputs, outputs, and derived metrics (n=53) like agricultural surplus and nutrient use efficiency, were subjected to short- and long-term trend analyses to discern how sources of pollution to surface water have changed over time. Across the watershed from 1985–2019, downward trends in atmospheric deposition were ubiquitous. Though there are varying effects, long-term declines in agricultural surplus were observed, likely because nutrients are being managed more efficiently. Multiple counties’ point source loads declined, primarily associated with upgrades at major cities that discharge treated wastewater directly to tidal waters. Despite all of these positive developments, recent increases in agricultural surpluses from 2009–2019 highlight that water quality gains may soon be reversed in many agricultural areas of the basin. Besides tracking progress and jurisdictional influence on pollution sources, the nutrient inventory can be used for retrospective water quality analysis to highlight drivers of past improvement/degradation of water quality trends and for decision makers to develop and track their near- and long-term watershed restoration strategies.

Efficacy of Morphine Combined with Mechanical Ventilation in the Treatment of Heart Failure with Cardiac Magnetic Resonance Imaging under Artificial Intelligence Algorithms.

This study was aimed at exploring the efficacy of morphine combined with mechanical ventilation in the treatment of heart failure with artificial intelligence algorithms. The cardiac magnetic resonance imaging (MRI) under the watershed segmentation algorithm was proposed, and the local grayscale clustering watershed (LGCW) model was designed in this study. A total of 136 patients with acute left heart failure were taken as the research objects and randomly divided into the control group (conventional treatment) and the experimental group (morphine combined with mechanical ventilation), with 68 cases in each group. The left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), left ventricular ejection fraction (LVEF), N-terminal pro-brain natriuretic peptide (NT-proBNP), arterial partial pressure of oxygen (PaO2), and arterial partial pressure of carbon dioxide (PaCO2) were observed. The results showed that the mean absolute deviation (MAD) and maximum mean absolute deviation (max-MAD) of the LGCW model were lower than those of the fuzzy k-nearest neighbor (FKNN) algorithm and local gray-scale clustering model (LGSCm). The Dice metric was also significantly higher than that of other algorithms with statistically significant differences (P < 0.05). After treatment, LVEDD, LVESD, and NT-proBNP of patients in the experimental group were significantly lower than those in the control group, and LVEF in the experimental group was higher than that in the control group (P < 0.05). PaO2 of patients in the experimental group was also significantly higher than that in the control group (P < 0.05). It suggested that the LGCW model had a better segmentation effect, and morphine combined with mechanical ventilation gave a better clinical efficacy in the treatment of acute left heart failure, improving the patients' cardiac function and arterial blood gas effectively.

Effectiveness of a Constructed Wetland with Carbon Filtration in Reducing Pesticides Associated with Agricultural Runoff

The Salinas Valley in Monterey County, California, USA, is a highly productive agricultural region. Irrigation runoff containing pesticides at concentrations toxic to aquatic organisms poses a threat to aquatic ecosystems within local watersheds. This study monitored the effectiveness of a constructed wetland treatment system with a granulated activated carbon (GAC) filter installation at reducing pesticide concentrations and associated toxicity to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus. The wetland was supplied with water pumped from an impaired agricultural and urban drainage. Across five monitoring trials, the integrated system’s average pesticide concentration reduction was 52%. The wetland channel and GAC filtration components individually provided significant treatment, and within each, pesticide solubility had a significant effect on changes in pesticide concentrations. The integrated treatment system also reduced nitrate by 61%, phosphate by 73%, and turbidity by 90%. Input water was significantly toxic to C. dubia and H. azteca in the first trial. Toxicity to C. dubia persisted throughout the system, whereas toxicity to H. azteca was removed by the channel, but there was residual toxicity post-GAC. The final trial had significant input toxicity to H. azteca and C. dilutus. The channel reduced toxicity to H. azteca and removed toxicity to C. dilutus. GAC filtration reduced H. azteca toxicity to an insignificant level. There was no input toxicity in the other three trials. The results demonstrate that a wetland treatment system coupled with GAC filtration can reduce pesticide concentrations, nutrients, suspended particles, and aquatic toxicity associated with agricultural runoff.

Relationship between fish assemblage structure and predictors related to estuarine productivity in shallow habitats of a Neotropical estuary

Abstract The variability of fish assemblage structure with respect to seasonality in salinity and productivity remains to be elucidate to many Neotropical estuaries. In this study, we hypothesized that salinity gradient and a set of variables related to ecosystem productivity drive community parameters in the shallow-water fish assemblage of the north-south axis of the Paranaguá Estuarine Complex (Southern Brazilian coast). Samples were taken with beach seine monthly from May 2000 to April 2001. Supporting our hypothesis, richness and abundance increased with turbidity, warmer waters of the rainier summer seasons, which are more productive. This environmental setting favors reproduction, as well as juvenile recruitment and growth, whose intensities are highest in this period. Highest abundance was found in inner areas, which may be explained by greater food and habitat availability. Richness was higher in more saline waters, due to the proximity of the rich pool of marine fish species. We suggest that local human interventions (e.g., dredging) should be avoided during the rainy seasons that are critical for species life cycles. Salinization, low estuarine productivity, and warmer waters, which are expected with climate change and human impacts in the local watershed, could affect the integrity of the local fish assemblage.

Using targeted messages to improve farmer engagement in conservation programs

In this time of information overload, successfully engaging farmers with compelling outreach materials is a major challenge for conservation programs and related research projects. One potential approach is targeting information to the recipient, e.g., local rather than regional soil and water conditions, when sending messages to farmers. Targeted information may increase engagement by making materials stand out as more relevant and useful; conversely, it may decrease engagement by making farmers wary of the program and how it is using the information. We tested the effect of targeted information on farmer engagement using a large, randomized controlled trial in Iowa. In partnership with Iowa State University, we sent 2,996 farmers a single mailing with information about erosion at the local watershed (targeted) or state (control) level and measured their responses to a two-minute survey. We found that targeted information increased relative response rates by 20%, from 13.8% to 16.4%. This level of increase is meaningful for practitioners, as well as statistically significant. Our findings show that targeted information can be an important tool for practitioners and researchers seeking to better connect with farmers who are inundated with marketing mail.

Estimates of soil erosion rates in a principal watershed in Gozo, Malta under current and future climatic conditions

The aim of the study was to estimate the current and future annual soil erosion rate in the Ramla watershed situated in Gozo, Malta. The RUSLE-GIS was applied using innovative approaches, such as the inclusion of the highest possible DEM data as well as reflecting climatic changes to the R Factor based on the latest climate projections for Gozo derived from a total of eight CMIP6 climate change models. A climate change impact analysis was carried to estimate the likely future risk of soil erosion in this local watershed for the first time. The estimated annual soil loss, as a percentage of the total area of study varies from low (85.1%), to moderate (13.3%) and high (1.6%). Within a climate change context, a reduction in the annual soil erosion rate has been estimated for the period 2080–2100, ranging from −5 ton ha−1 yr−1 under SSP126 to −6 ton ha−1 hr-1 under SSP585. The estimated decrease of annual soil loss within the high soil erosion risk category is attributed to an increased aridity of the local climate as projected by eight CMIP6 climate models. Specific hydrological sub-watersheds were identified within the study area that warrant urgent considerations. The outcomes of this study are based on the inclusion of micro-topographical information derived from high resolution 1 m LiDAR DEM. This modelling work is seen as the first study which can be used to provide some objective guidance on the minimization of potential soil losses within the Ramla watershed. Our estimated soil loss and its spatial distribution can assist in a fuller management plan for the sustainability of this watershed. These results should not be interpreted in absolute terms but as an understanding of the underlying controlling processes, the relative spatial and temporal variations, and of possible future scenarios.

Comparison of potential drinking water source contamination across one hundred U.S. cities

Drinking water supplies of cities are exposed to potential contamination arising from land use and other anthropogenic activities in local and distal source watersheds. Because water quality sampling surveys are often piecemeal, regionally inconsistent, and incomplete with respect to unregulated contaminants, the United States lacks a detailed comparison of potential source water contamination across all of its large cities. Here we combine national-scale geospatial datasets with hydrologic simulations to compute two metrics representing potential contamination of water supplies from point and nonpoint sources for over a hundred U.S. cities. We reveal enormous diversity in anthropogenic activities across watersheds with corresponding disparities in the potential contamination of drinking water supplies to cities. Approximately 5% of large cities rely on water that is composed primarily of runoff from non-pristine lands (e.g., agriculture, residential, industrial), while four-fifths of all large cities that withdraw surface water are exposed to treated wastewater in their supplies.

Identifying factors that affect mountain lake sensitivity to atmospheric nitrogen deposition across multiple scales

Increased nitrogen (N) deposition rates over the past century have affected both North American and European mountain lake ecosystems. Ecological sensitivity of mountain lakes to N deposition varies, however, because chemical and biological responses are modulated by local watershed and lake properties. We evaluated predictors of mountain lake sensitivity to atmospheric N deposition across North American and European mountain ranges and included as response variables dissolved inorganic N (DIN = NNH4+ + NNO3–) concentrations and phytoplankton biomass. Predictors of these responses were evaluated at three different spatial scales (hemispheric, regional, subregional) using regression tree, random forest, and generalized additive model (GAM) analysis. Analyses agreed that Northern Hemisphere mountain lake DIN was related to N deposition rates and smaller scale spatial variability (e.g., regional variability between North American and European lakes, and subregional variability between mountain ranges). Analyses suggested that DIN, N deposition, and subregional variability were important for Northern Hemisphere mountain lake phytoplankton biomass. Together, these findings highlight the need for finer-scale, subregional analyses (by mountain range) of lake sensitivity to N deposition. Subregional analyses revealed differences in predictor variables of lake sensitivity. In addition to N deposition rates, lake and watershed features such as land cover, bedrock geology, maximum lake depth (Zmax), and elevation were common modulators of lake DIN. Subregional phytoplankton biomass was consistently positively related with total phosphorus (TP) in Europe, while North American locations showed variable relationships with N or P. This study reveals scale-dependent watershed and lake characteristics modulate mountain lake ecological responses to atmospheric N deposition and provides important context to inform empirically based management strategies.

Hydrologic connectivity and land cover affect floodplain lake water quality, fish abundance, and fish diversity in floodplain lakes of the Wabash‐White River basin

AbstractFloodplain lakes are important aquatic resources for supporting ecosystem services, such as organismal habitat, biodiversity, and the retention of nutrients and sediment. Due to geomorphic alteration of river channels and land‐cover change, degradation to floodplain lakes in the Ohio River basin is occurring at a rate that will escalate as climate change causes increased flood intensity and the seasonal redistribution of rainfall. A better understanding of the local drivers that affect oxbow lakes is needed for targeted floodplain restoration efforts designed to slow degradation. We examined the effects of land cover, topography, and hydrologic connectivity on water quality and fish diversity and abundance in nine floodplain lakes with potentially high remnant ecological function in the Wabash‐White watershed (Indiana, Ohio, and Illinois). Data collection included water‐quality parameters; stable water isotopes; total phosphorus, total nitrogen, and chlorophyll‐a; and fish community diversity and abundance. Results indicate that hay/pasture land cover and decreased topographic relief in the local oxbow watersheds, along with reduced river hydrologic connectivity, were related to an increase in total phosphorus, total nitrogen, and chlorophyll‐a. Greater biodiversity and abundance in fish assemblages were evident in oxbow lakes that were more disconnected from the main channel. The results of this study suggest that hydrologic connectivity of oxbow lakes with the contributing drainage area and the main channel influence nutrients and fish communities. Knowing the influencing factors can help ecosystem managers better protect these valuable floodplain lake ecosystems and prioritize restoration efforts amidst increasing stressors due to climate and land‐use changes.

Model my watershed: an investigation into the role of big data, technology, and models in promoting student interest in watershed action

The Meaningful Watershed Educational Experience (MWEE) is a curriculum framework designed to support students’ Environmental Literacy (E-Lit) by promoting critical thinking about watersheds, but there is a paucity of empirical evidence in the literature to demonstrate its effectiveness in increasing E-Lit and a lack of understanding of what MWEE instructional activities best support E-Lit. The Teaching Environmental Sustainability—Model My Watershed (TES-MMW) middle school curriculum is a data-rich MWEE that promotes student analysis of local watersheds. This large-scale study was conducted in eight states across the United States of America from 2016 to 2018, with data from 38 teachers and 1,263 students ages 11–18. The data shows a positive impact on students’ E-Lit in watershed content and action. The study further suggests that four of the project’s curricular elements were most influential in promoting environmental action for students. These curricular elements follow the MWEE framework, and as such, the MWEE essential elements are valuable guides in curricular design to support students’ E-Lit development.

SOIL THICKNESS SPATIAL DISTRIBUTION INFLUENCE ON FACTOR OF SAFETY EQUATION

Mass movements occurrences are well studied, however there are still possible improvements regarding their factor of safety simulation. This paper focus on the influence of spatialized pedological data and geotechnical data, two of the major limitations for this type of modeling. Numerous mass movements were triggered by an extreme precipitation event in southern Brazil, when the rainwaters reached 300mm in just 24 hours. A local watershed was chosen for field campaigns to supply a safety factor model and show the direct influence of field data on the result efficiency. For this, four different scenarios were created using combination of field data and spatialized soil thickness throughout the watershed area. The results showed an improve of 12% on the simulation efficiency when compared to a homogeneus soil thickness and average geotechnical values scenario, showing the importance of field studies for factor of safety simulations.

Land-based sediment sources and transport to southwest Puerto Rico coral reefs after Hurricane Maria, May 2017 to June 2018

The effects of runoff from land on nearshore ecosystems, including coral reef communities, are influenced by both sediment supply and removal by coastal processes. Integrated studies across the land-sea interface describing sources and transport of terrestrial sediment and its nearshore fate allow reef protection initiatives to target key onshore and offshore areas. Geochemical signatures in the fine fraction of terrestrial sediment from watersheds in southwest Puerto Rico were determined by multivariate principal component analysis and used to identify terrestrial sources of sediment runoff to nearshore coral reefs. Sediment settling out of suspension at reefs was collected at approximately 2 month-long intervals in bottom-mounted sediment traps from May 2017 to June 2018, a period that included Hurricanes Irma and Maria. Bulk sediment accumulation rates in traps exceeded a 10 mg/cm2/d threshold found to stress corals at 5 of 7 reef sites throughout the 13 month-long study. Geochemical signatures showed that watersheds 10s km to the east were a predominant, year-round source of fine sediment to reefs offshore of Guánica Bay and could have introduced sediment-bound contaminants due to a higher degree of industrialization and urbanization than the local watershed. Sediment runoff from the local watershed appeared to be constrained to a narrow band close to shore. During the 2.5 months after Hurricanes Irma and Maria, bulk sediment accumulation rates increased substantially and fine sediment geochemical signatures were indicative of predominantly distal sources, except outside of the mouth of Guánica Bay, which was strongly impacted by local runoff. Mass wasting, sediment runoff, and coastal turbidity persisted for months after Hurricane Maria and could account for the appearance of a small fraction of geochemical variance from a distal sediment source that appeared in reef traps 4 months post-hurricane and persisted through the end of the study 9 months post-hurricane. Sediment geochemical sourcing in temporally resolved records from sediment traps showed how landscape-scale changes after a major hurricane affected both near-term and long-term sediment delivery to reef communities. In addition, the importance of fine sediment advection from distal sources indicates that successful reduction of land-based pressures on nearshore ecosystems will require cross-jurisdictional strategies.

Piloting During a Pandemic

Key TakeawaysFour pilot teams shared experiences with piloting during the COVID‐19 pandemic, emphasizing that thoughtful planning streamlines the piloting process while mitigating the risk of transmitting illness.Remote access to and control of pilot equipment, along with the use of virtual communication platforms, enabled teams to successfully perform pilot‐scale studies.Operating pilot systems through the pandemic allowed teams to respond to drastic changes on a small scale to mitigate risks around full‐scale processes at the treatment plant.