Midwestern cities require forecasts of surface nitrate loads to bring additional treatment processes online or activate alternative water supplies. Concurrently, networks of nitrate monitoring ...stations are being deployed in river basins, co‐locating water quality observations with established stream gauges. However, tools to evaluate the future value of expanded networks to improve water quality forecasts remains challenging. Here, we construct a synthetic data set of stream discharge and nitrate for the Wabash River Basin—one of the United States’ most nutrient polluted basins—using the established Agro‐IBIS and THMB models. Synthetic data enables rapid, unbiased and low‐cost assessment of potential sensor placements to support management objectives, such as near‐term forecasting. Using the synthetic data, we established baseline 1‐day forecasts for surface water nitrate at 12 cities in the basin using support vector machine regression (SVMR; RMSE 0.48–3.3 ppm). Next, we used the SVMRs to evaluate the improvement in forecast performance associated with deployment of additional nitrate sensors. We identified the optimal sensor placement to improve forecasts at each city, and the relative value of sensors at each candidate location. Finally, we assessed the co‐benefit realized by other cities when a sensor is deployed to optimize a forecast at one city, finding significant positive externalities in all cases. Ultimately, our study explores the potential for machine learning to make near‐term predictions and critically evaluate the improvement realized by expanding a monitoring network. While we use nitrate pollution in the Wabash River Basin as a case study, this approach could be readily applied to any problem where the future value of sensors and network design are being evaluated.
This study applies machine learning to: (1) produce near‐term water quality forecasts based on an existing monitoring network; and (2) evaluation of future network configurations to increase predictive power. Using the synthetic data, we established 1‐day forecasts for surface water nitrate at 12 cities using support vector machine regression (SVMR; RMSE 0.48–3.3 mg/L). We then showed how those cities could improve their forecast with new data (5%–82% reduction in RMSE).
Farmers' conservation decisions are central to addressing regional environmental challenges, such as biodiversity loss, water quality impairment, or climate change. However, three decades of ...substantial investment in agri-environmental programs has not yielded widespread adoption or improved environmental outcomes. It remains difficult to explain why farmers adopt despite an extensive body of research on the topic. One possible reason for this is that researchers are limiting the types of metrics they are analyzing to explain farmer decisions. We systematically and critically evaluated the social science adoption literature to address three important gaps: (1) How are adoption studies measuring adoption effectiveness? (2) How do studies integrate individual farmer perspectives into broader institutional (i.e., social and governance) contexts? (3) What are the most prevalent metrics that adoption research uses to characterize the human-natural system? We coded 174 studies and found that only 10% connect adoption decisions to conservation outcomes or undertake longitudinal research, while the dominant approach in adoption research excludes the institutional contexts in which farmers are situated. The most prevalent metrics focus on farmer demographics, financial and technical capacity to adopt, and economic motivations. The lack of attention to both conservation outcomes and longitudinal studies limits researchers' ability to analyze the effectiveness of CP adoption. To advance our understanding of adoption, we recommend that future research measure conservation outcomes and track how knowledge about adoption effectiveness feeds back into farmer perceptions and social norms towards adoption. Research should also consistently measure how agri-environmental programs mediate the social acceptability of adoption. Lastly, institutional metrics that can be widely incorporated into coupled human-natural systems research will advance synthesis efforts to better explain why farmers adoption conservation practices.
•Only 10% of studies measure the effectiveness of adopted conservation practices.•Few studies situate farmer decisions in their broader institutional context.•The diversity of metrics characterizing adoption limits synthesis opportunities.•Future research should measure outcomes to identify system feedbacks.•Future research should address individual and institutional dynamics jointly.
Access to and extensive use of fluorometric analyses is limited, despite its extensive utility in environmental transport and fate. Wide-spread application of fluorescent tracers has been limited by ...the prohibitive costs of research-grade equipment and logistical constraints of sampling, due to the need for high spatial resolutions and access to remote locations over long timescales. Recently, low-cost alternatives to research-grade equipment have been found to produce comparable data at a small fraction of the price for commercial equipment. Here, we prototyped and benchmarked performance of a variety of fluorometer components against commercial units, including performance as a function of tracer concentration, turbidity, and temperature, all of which are known to impact fluorometer performance. While component performance was found to be comparable to the commercial units tested, the best configuration tested obtained a functional resolution of 0.1 ppb, a working concentration range of 0.1 to >300 ppb, and a cost of USD 59.13.
•Implementation of a mechanistic, dynamic model of network expansion and contraction.•Importance of geologic setting and hydrologic forcing change through a water year.•Network expansion is ...insensitive to hydrologic forcing under wet conditions.•Geologic setting matters most under low and moderate discharge conditions.•Prediction of channel network dynamics may inform management of river corridors.
Headwater stream networks expand and contract in response to changes in stream discharge. The changes in the extent of the stream network are also controlled by geologic or geomorphic setting – some reaches go dry even under relatively wet conditions, other reaches remain flowing under relatively dry conditions. While such patterns are well recognized, we currently lack tools to predict the extent of the stream network and the times and locations where the network is dry within large river networks. Here, we develop a perceptual model of the river corridor in a headwater mountainous catchment, translate this into a reduced-complexity mechanistic model, and implement the model to examine connectivity and network extent over an entire water year. Our model agreed reasonably well with our observations, showing that the extent and connectivity of the river network was most sensitive to hydrologic forcing under the lowest discharges (Qgauge < 1 L s−1), that at intermediate discharges (1 L s−1 < Qgauge < 10 L s−1) the extent of the network changed dramatically with changes in discharge, and that under wet conditions (Qgauge > 10 L s−1) the extent of the network was relatively insensitive to hydrologic forcing and was instead determined by the network topology. We do not expect that the specific thresholds observed in this study would be transferable to other catchments with different geology, topology, or hydrologic forcing. However, we expect that the general pattern should be robust: the dominant controls will shift from hydrologic forcing to geologic setting as discharge increases. Furthermore, our method is readily transferable as the model can be applied with minimal data requirements (a single stream gauge, a digital terrain model, and estimates of hydrogeologic properties) to estimate flow duration or connectivity along the river corridor in unstudied catchments. As the available information increases, the model could be better calibrated to match site-specific observations of network extent, locations of dry reaches, or solute break through curves as demonstrated in this study. Based on the low initial data requirements and ability to later tune the model to a specific site, we suggest example applications of this parsimonious model that may prove useful to both researchers and managers.
Guidelines advocate changes in fatty acid consumption to promote cardiovascular health.
To summarize evidence about associations between fatty acids and coronary disease.
MEDLINE, Science Citation ...Index, and Cochrane Central Register of Controlled Trials through July 2013.
Prospective, observational studies and randomized, controlled trials.
Investigators extracted data about study characteristics and assessed study biases.
There were 32 observational studies (530,525 participants) of fatty acids from dietary intake; 17 observational studies (25,721 participants) of fatty acid biomarkers; and 27 randomized, controlled trials (103,052 participants) of fatty acid supplementation. In observational studies, relative risks for coronary disease were 1.02 (95% CI, 0.97 to 1.07) for saturated, 0.99 (CI, 0.89 to 1.09) for monounsaturated, 0.93 (CI, 0.84 to 1.02) for long-chain ω-3 polyunsaturated, 1.01 (CI, 0.96 to 1.07) for ω-6 polyunsaturated, and 1.16 (CI, 1.06 to 1.27) for trans fatty acids when the top and bottom thirds of baseline dietary fatty acid intake were compared. Corresponding estimates for circulating fatty acids were 1.06 (CI, 0.86 to 1.30), 1.06 (CI, 0.97 to 1.17), 0.84 (CI, 0.63 to 1.11), 0.94 (CI, 0.84 to 1.06), and 1.05 (CI, 0.76 to 1.44), respectively. There was heterogeneity of the associations among individual circulating fatty acids and coronary disease. In randomized, controlled trials, relative risks for coronary disease were 0.97 (CI, 0.69 to 1.36) for α-linolenic, 0.94 (CI, 0.86 to 1.03) for long-chain ω-3 polyunsaturated, and 0.89 (CI, 0.71 to 1.12) for ω-6 polyunsaturated fatty acid supplementations.
Potential biases from preferential publication and selective reporting.
Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.
British Heart Foundation, Medical Research Council, Cambridge National Institute for Health Research Biomedical Research Centre, and Gates Cambridge.
Clarify jurisdiction of US Clean Water Act Ward, Adam S; Wade, Jeffrey; Kelleher, Christa ...
Science (American Association for the Advancement of Science),
01/2023, Volume:
379, Issue:
6628
Journal Article
Catchment hydrologists have long puzzled over the question: How can catchments rapidly generate storm flows and pulses of solutes in response to storm events? Conceptual models viewing catchments as ...composed of discrete source areas generating flow at unique time scales and with unique chemical characteristics have been used to explain the observed changes in flow and water chemistry. Surprisingly, those conceptual models usually do not treat the stream channel as one of the potential source areas. Here, we propose the channel‐source hypothesis in which the stream itself should be considered as a potential source with the same rigour as other contributing areas. We pose this in the spirit of the scientific use of the word: a hypothesis is not a proven idea but rather a provisional supposition serving as the basis for further study. We suggest that the channel should be considered as a potential source for dissolved organic carbon (DOC). Channels store substantial amounts of organic matter, and stream ecologists have long studied stream carbon cycling. From those studies, we know that leaching and decomposition can generate DOC from particulate organic carbon (POC). Further, POC is stored in channel ‘dead‐zones’—regions of low flow velocity ‐ that can be activated as flow velocity increases, thus releasing accumulated DOC during storms. All catchments are different; there is no reason to assume that channel sources are always important, in every catchment, in every storm. Thus, the channel‐source hypothesis does not replace existing conceptual models. Instead, it adds another potential mechanism that may explain DOC dynamics observed in streams. The channel‐source hypothesis has substantial implications for catchment studies examining sources of DOC in stream water or using DOC as a tracer to determine the locations of, and proportional contributions of, different source areas for streamflow generation.
Organic matter from litter fall or autochthonous production is stored in dead zones within the wetted stream channel under low‐flow conditions. Leaching and microbial processes generate DOC within the organic matter. As water depth and flow velocity increase during the rising leg of the storm hydrograph, organic matter can be scoured out of dead zones, releasing the accumulated DOC into the active stream channel.
Threshold changes in rainfall‐runoff generation commonly represent shifts in runoff mechanisms and hydrologic connectivity controlling water and solute transport and transformation. In watersheds ...with limited human influence, threshold runoff responses reflect interaction between precipitation event and antecedent soil moisture. Similar analyses are lacking in intensively managed landscapes where installation of subsurface drainage tiles has altered connectivity between the land surface, groundwater, and streams, and where application of fertilizer has created significant stores of subsurface nitrogen. In this study, we identify threshold patterns of tile‐runoff generation for a drained agricultural field in Illinois and evaluate how antecedent conditions—including shallow soil moisture, groundwater table depth, and the presence or absence of crops—control tile response. We relate tile‐runoff thresholds to patterns of event nitrate load observed across multiple storm events and evaluate how antecedent conditions control within‐event nitrate concentration‐discharge relationships. Our results demonstrate that an event tile‐runoff threshold emerges relative to the sum of gross precipitation and indices of antecedent shallow soil moisture and antecedent below‐tile groundwater moisture deficit, indicating that both shallow soil and below‐tile storages must be filled to generate significant runoff. In turn, event nitrate load shows a linear dependence on runoff for most time periods, suggesting that subsurface nitrate export and storage can be estimated using runoff threshold relationships and long‐term average nitrate concentrations. Finally, within‐event nitrate concentration‐discharge relationships are controlled by event size and the antecedent tile flow state because these factors dictate the sequence of flow path activation and tile connectivity over a storm event.
Plain Language Summary
Improving nutrient management in intensively managed landscapes requires understanding of how human alterations for agriculture have influenced nutrient transport from and storage within the landscape. In addition to creating large subsurface stores of nitrogen through fertilizer application, humans have altered the drainage structure of intensively managed landscapes by installing subsurface drainage (commonly “tiles”) to maintain optimal moisture conditions for crops. Although highly engineered systems, it is unclear how tiles influence the timing and magnitude of water and nutrient export from these landscapes. Here, we identify how prestorm wetness conditions control rapid, nonlinear changes in tile flow (thresholds). We find that a tile flow initiation threshold results from the sequential filling of first a depleted shallow soil storage and then deeper below‐tile groundwater storage. Further, nitrate export reflects tile‐runoff thresholds, indicating that the factors controlling tile‐runoff are also primary controls on tile nitrate export.
Key Points
A tile‐runoff threshold emerges as a function of both above‐tile and below‐tile antecedent storage
Total storm event nitrate load is primarily controlled by the same factors that dictate event tile‐runoff
Within‐event nitrate concentration‐discharge relationships reflect a threshold of soil water mobilization
Recent revisions to the definition of the ‘waters of the United States’ (WOTUS) have considerably altered how wetlands are federally regulated under the Clean Water Act. The two most recent ...modifications to WOTUS, the Clean Water Rule (CWR) and the Navigable Waters Protection Rule (NWPR), represent two opposing approaches to the federal wetland policy. The impacts of these two rules on the regulation of wetlands have as of yet been poorly characterized at broad spatial scales. Using New York State (NYS) as a case study, we evaluated the jurisdictional statuses of more than 253 000 wetlands under the CWR and the NWPR to assess the landscape‐scale effects of WOTUS re‐definitions. We found that statewide and within each of NYS's hydrologic regions, the NWPR protects fewer wetlands and less total wetland area than the CWR. The efficacy of the two regulations varied considerably in space across NYS, highlighting the need for comprehensive, nationwide assessments of wetland policy outcomes. We also observed that both rules produced non‐uniform patterns in jurisdiction across a range of landscape positions and wetland sizes, preferentially protecting large wetlands close to the stream network. This effect was particularly pronounced under the NWPR, which excludes all geographically isolated wetlands from protection. Our findings in NYS emphasize the existence of unique patterns in protected wetlands across spatial scales, highlighting the value in applying geospatial analyses to evaluate environmental policy.
Abstract
Non-perennial streams are widespread, critical to ecosystems and society, and the subject of ongoing policy debate. Prior large-scale research on stream intermittency has been based on ...long-term averages, generally using annually aggregated data to characterize a highly variable process. As a result, it is not well understood if, how, or why the hydrology of non-perennial streams is changing. Here, we investigate trends and drivers of three intermittency signatures that describe the duration, timing, and dry-down period of stream intermittency across the continental United States (CONUS). Half of gages exhibited a significant trend through time in at least one of the three intermittency signatures, and changes in no-flow duration were most pervasive (41% of gages). Changes in intermittency were substantial for many streams, and 7% of gages exhibited changes in annual no-flow duration exceeding 100 days during the study period. Distinct regional patterns of change were evident, with widespread drying in southern CONUS and wetting in northern CONUS. These patterns are correlated with changes in aridity, though drivers of spatiotemporal variability were diverse across the three intermittency signatures. While the no-flow timing and duration were strongly related to climate, dry-down period was most strongly related to watershed land use and physiography. Our results indicate that non-perennial conditions are increasing in prevalence over much of CONUS and binary classifications of ‘perennial’ and ‘non-perennial’ are not an accurate reflection of this change. Water management and policy should reflect the changing nature and diverse drivers of changing intermittency both today and in the future.
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