Installation Of Buffers Research Articles

Ultrasonic Guided Wave Health Monitoring of High-Temperature Aircraft Structures Based on Variational Mode Decomposition and Fuzzy Entropy

This paper presents an innovative approach to high-temperature health monitoring of aircraft structures utilizing an ultrasonic guided wave transmission and reception system integrated with a zirconia heat buffer layer. Aiming to address the challenges posed by environmental thermal noise and the installation of heat buffers, which can introduce structural nonlinearities into guided wave signals, a composite guided wave consisting of longitudinal and Lamb waves was proposed for online damage detection within thermal protection systems. To effectively analyze these complex signals, a hybrid damage monitoring technique combining variational mode decomposition (VMD) and fuzzy entropy (FEN) was introduced. The VMD was employed to isolate the principal components of the guided wave signals, while the fuzzy entropy of these components served as a quantitative damage factor, characterizing the extent of the structural damage. Furthermore, this study validated the feasibility of piezoelectric probes equipped with heat buffer layers for both exciting and receiving ultrasonic guided wave signals in a dual heat buffer layer, a one-transmit-one-receive configuration. The experimental results demonstrated the efficacy of the proposed VMD-FEN damage factor for real-time monitoring of damage in aircraft thermal protection systems, both at ambient and elevated temperatures (up to 150 °C), showcasing its potential for enhancing the safety and reliability of aerospace structures operating under extreme thermal conditions.

Measuring environmental and cost benefits of riparian buffers for drinking water production in a Midwest watershed

AbstractThis study focuses on the economic value and carbon benefits of riparian buffers in urban drinking water production. The impact of riparian buffers on the waterworks operation in the Raccoon River watershed was quantified using the following metrics: nitrate concentration, days of nitrate removal operation, material and energy cost (based on 17 years of historical records with a watershed model), regression, and cost analysis. The findings indicate that the presence of riparian buffers in agricultural land can substantially decrease nitrate concentration in the water intake of the waterworks during the crop‐growing season: 19% in April, 9% in May, and 11% in June. These reductions mean less nitrate treatment of the plant intake flow: 23% in April, 12% in May, and 3% in June. These changes lead to significant resource savings: 425 metric tons of sodium chloride (NaCl), 147 810 kWh of electricity, 253 metric tons of powdered activated carbon, and 20.8 million liters of fresh water. The buffers would also reduce greenhouse gas emissions by 86.9 metric tons (CO2 equivalent) in 17 years. The total cost saving was estimated at $327 326, with the highest potential savings in May ($215 100), followed by April ($65 465), and June ($46 761). When factoring in buffer installation, cropland loss, nitrate removal, and cost associated with buffer harvest for biofuel in an established biomass market, the benefit to the entire watershed community would be $2.63 million annually. The results underscore the significant cost benefits and environmental benefits associated with cropland riparian buffers in a watershed community. The approach employed in this study holds promise for assessing riparian buffer benefits in other watersheds, contributes to an understanding of sustainable water management practices, and provides a basis for decision making in a wide range of agricultural regions.

Probabilistic modelling of the inherent field-level pesticide pollution risk in a small drinking water catchment using spatial Bayesian belief networks

Abstract. Pesticides are contaminants of priority concern that continue to present a significant risk to drinking water quality. While pollution mitigation in catchment systems is considered a cost-effective alternative to costly drinking water treatment, the effectiveness of pollution mitigation measures is uncertain and needs to be able to consider local biophysical, agronomic, and social aspects. We developed a probabilistic decision support tool (DST) based on spatial Bayesian belief networks (BBNs) that simulates inherent pesticide leaching risk to ground- and surface water quality to inform field-level pesticide mitigation strategies in a small (3.1 km2) drinking water catchment with limited observational data. The DST accounts for the spatial heterogeneity in soil properties, topographic connectivity, and agronomic practices; the temporal variability of climatic and hydrological processes; and uncertainties related to pesticide properties and the effectiveness of management interventions. The rate of pesticide loss via overland flow and leaching to groundwater and the resulting risk of exceeding a regulatory threshold for drinking water was simulated for five active ingredients. Risk factors included climate and hydrology (e.g. temperature, rainfall, evapotranspiration, and overland and subsurface flow), soil properties (e.g. texture, organic matter content, and hydrological properties), topography (e.g. slope and distance to surface water/depth to groundwater), land cover and agronomic practices, and pesticide properties and usage. The effectiveness of mitigation measures such as the delayed timing of pesticide application; a 10 %, 25 %, or 50 % reduction in the application rate; field buffers; and the presence/absence of soil pan on risk reduction were evaluated. Sensitivity analysis identified the month of application, the land use, the presence of buffers, the field slope, and the distance as the most important risk factors, alongside several additional influential variables. The pesticide pollution risk from surface water runoff showed clear spatial variability across the study catchment, whereas the groundwater leaching risk was uniformly low, with the exception of prosulfocarb. Combined interventions of a 50 % reduced pesticide application rate, management of the plough pan, delayed application timing, and field buffer installation notably reduced the probability of a high risk of overland runoff and groundwater leaching, with individual measures having a smaller impact. The graphical nature of BBNs facilitated interactive model development and evaluation with stakeholders to build model credibility, while the ability to integrate diverse data sources allowed a dynamic field-scale assessment of “critical source areas” of pesticide pollution in time and space in a data-scarce catchment, with explicit representation of uncertainties.

Can interactive data visualizations promote waterfront best management practices?

Ward NK, Sorice MG, Reynolds MS, Weathers KC, Weng W, Carey CC. 2022. Can interactive data visualizations promote waterfront best management practices? Lake Reserv Manage. XX:XX–XX. Lake water quality management often requires private property owner engagement since land-use change generally occurs on private property. Educational components of lake management outreach must connect current property owner behaviors with future water quality. However, it may be challenging for property owners to associate their current behaviors with water quality outcomes due to the time lag between a behavior (e.g., fertilizer application) and a water quality outcome (e.g., decreased water clarity). Interactive data visualizations, characterized by user-determined selections that change visualization output, may be well suited to help property owners connect current behavior to future water quality. We tested the effectiveness of an online, interactive visualization as an educational intervention to alter property owners’ perspectives related to applying lawn fertilizer and installing waterfront buffers. We used cognitive psychology measures to quantify intervention effectiveness. Since property owners’ decision making may be driven by connections to their property, we also explored relationships between seasonal and permanent residents and intentions to apply fertilizer or install waterfront buffers and intervention effectiveness. Despite no significant difference in effectiveness between the interactive and noninteractive versions, the combined responses demonstrated a positive shift in behavioral beliefs and intentions related to lawn fertilizer application and waterfront buffer installation. Seasonal residents were less likely than permanent residents to apply lawn fertilizer before the intervention and more likely to shift their intentions after the intervention. This study provides evidence that brief educational interventions—regardless of their interactivity—can shift private property owner beliefs and intentions regarding lakefront property management.

Quantifying the effectiveness of a saturated buffer to reduce tile NO3-N concentrations in eastern Iowa.

Agricultural drainage tiles are primary contributors to NO3-N export from Iowa croplands. Saturated buffers are a relatively new conservation practice that diverts tile water into a distribution tile installed in a riparian buffer parallel to a stream with the intent of enhancing NO3-N processing within the buffer. In this study, tile NO3-N concentration reductions were characterized through two different saturated buffers at a working farm site in eastern Iowa. Study objectives were to (1) evaluate the hydrogeology and water quality patterns in the saturated buffer and (2) quantify the reduction in tile NO3-N concentration from the saturated buffer installation. Results showed that the two saturated buffers are reducing NO3-N concentrations in tile drainage water from input concentrations of approximately 15 mg/l to levels < 1.5 mg/l at the streamside well locations. The reduction occurs rapidly in the fine-textured and organic-rich alluvial soils with most of the reduction occurring within 1.5 m of the distribution line. Denitrification is hypothesized as being primarily responsible for the concentration reductions based on soil and water chemistry conditions, completion of a geophysical survey (quantifying low potential for N loss to deeper aquifers), and comparisons to other similar Iowa sites. The study provides more assurance to new adopters that this practice can be installed in many areas throughout the Midwestern Cornbelt region.Supplementary informationThe online version contains supplementary material available at 10.1007/s10661-021-09297-3.

Farmer-centered ecological intensification: Using innovation characteristics to identify barriers and opportunities for a transition of agroecosystems towards sustainability

CONTEXTEcological intensification (EI) describes farming practices that aim to use ecological processes for producing agricultural yields. While evidence for the ecological benefits of EI is plentiful, the question of how it can be more widely adopted by farmers, and why it has not been so far, remains pertinent, since only approximately 9% of the globally farmed land is currently managed with EI practices. We suggest that considering farmers as central while attending to farm and system level factors can help to identify barriers and facilitators to EI adoption. To do this, we look to diverse, overlapping bodies of literature encompassing EI practice details, systems thinking, and farmer adoption. Innovation characteristics is one framework that has been used to study farmer adoption of new farm management tools and practices. OBJECTIVEOur objective is to use innovation characteristics for identifying farmer, farm, and system level barriers and potential solutions to EI adoption. We then aim to synthesize broader lessons for a sustainability transition in agriculture. METHODSWe treat EI as a suite of innovations, including practices, technologies, and knowledge. We explore how the innovation characteristics of EI - i.e. their relative advantage, compatibility, complexity, trialability and observability – manifest at each of three levels: farmer, farm, and system. We apply our approach to three case studies of EI adoption from different world regions: 1) managing landscape complexity in Germany, 2) installation of riparian buffers in the USA and 3) organic farming in India. RESULTS AND CONCLUSIONSAn analysis of our case studies using innovation characteristics helped identify barriers to EI adoption and at what level these barriers should be addressed. Barriers included: uncoupled financial and farm-level ecological relative advantages of EI (system level), framing that is not in line with farm values and needs (farmer level), insufficient training for managing complex systems (farmer level), and time constraints for experimentation with and observation of EI effects (farm level). System level solutions could support training and experimentation with EI, empowering farmers by providing them with autonomy to adapt and apply EI as they see fitting. SIGNIFICANCEUsing innovation characteristics and diverse bodies of knowledge allowed us to identify barriers, but also opportunities at farmer, farm, and system level. Abundant work focuses on convincing farmers of what science says is right, so showing farmers that barriers are not explicit to them is a helpful step forward in the transition towards sustainability.

Evaluation of selected watershed characteristics to identify best management practices to reduce Nebraskan nitrate loads from Nebraska to the Mississippi/Atchafalaya River basin

Nebraskan streams contribute excess nitrogen to the Mississippi/Atchafalaya River Basin and Gulf of Mexico, which results in major water-quality impairments. Reducing the amount of nitrogen (N) exported in these streams requires the use of best management practices (BMPs) within the landscape. However, proper BMP utilization has rarely been statistically connected to potential controls of N export within watersheds, particularly precipitation and soil characteristics. In this study, 19 watershed variables were evaluated in five categories (hydrological, physiographic, point sources, land use, and soil properties) to determine the characteristics that influenced variable nitrate nitrogen (NO3-N) concentrations in 17 Nebraska watersheds with known high NO3-N export rates. Each characteristic was derived from publicly-available datasets in an effort to develop a multiregional method. Of the 19 variables evaluated, 10 variables (developed, cropland, herbaceous, forest, excessively-drained soils, precipitation, base-flow index, slope, organic matter and point sources) were identified to statistically influence stream NO3-N concentrations. The 17 watersheds were divided into five subset groups using principal component analysis. Distributions of the 10 watershed variables were then used to determine the most applicable BMPs for NO3-N reductions for each stream subset: excessively drained with high baseflow index (Groups 1 and 2), dominantely row crop land usage with well-drained soils, higher precipitation, and an increased tendency for surface runoff concerns (Group 3), highly developed watersheds (Group 4), and single river dominated by wastewater treatment plant discharge (Group 5). Based on the most influential variables a variety of BMPs were recommended, including N fertilizer application management and accounting for N credit from mineralization and NO3-N in irrigation water (Groups 1 and 2), installation of riparian buffers and wetlands (Group 3), urban BMPs such as bioretention cells and permeable pavement (Group 4), and upgrades to the wastewater treatment plant (Group 5). This study provides an improved technique for facilitating watershed management by linking BMPs directly to the characteristics of each watershed to reduce current nitrate export.

Adaptations to extreme storm events by conservation organizations

Extreme precipitation events are associated with increased runoff of sediment and nutrients into surface waters, exacerbating water quality problems and creating challenges for soil and water managers. This change in the hydrologic cycle is expected to intensify under future climate change. Soil and water conservation professionals responsible for advising farmers and other land managers are on the front lines of adaptation to these climate change impacts. This study uses a survey of Soil and Water Conservation District staff (n = 260) in the United States Upper Midwest to better understand adaptation planning and implementation and the factors influencing adaptations by public organizations. In contrast to a typical planning-implementation gap finding, our respondents report a greater emphasis on some kinds of adaptation actions over planning. We find that the concerns of individual government employees about climate change have a greater association with adaptation planning strategies (e.g., planning document updates) compared to implemented adaptations on-the-ground (e.g., stream buffer installation). Also, weather projections were being used in conjunction with both adaptation planning and implementation. This study contributes to efforts to open up the black box of adaptation decision-making in the public sector, revealing the important role of individual concerns and information use.

Nutrient Reduction in Agricultural Green Infrastructure: An Analysis of the Raccoon River Watershed

Agricultural intensification has had the undesirable effect of degrading water quality throughout the United States. Nitrate pollution presents a difficult problem for rural and urban communities, and it contributes to the immense Gulf of Mexico Hypoxia Zone. Current U.S. policy prohibits regulation of agricultural runoff because it is a nonpoint source. The Raccoon River Watershed upstream of Des Moines, Iowa, USA has some of the highest nitrate levels in the nation, and the drinking water utility in Des Moines unsuccessfully pursued litigation against drainage districts in the watershed. We propose a cooperative solution between urban residents and upstream rural residents—namely, the installation of agricultural green infrastructure in the form of riparian buffers throughout the watershed enabled by the principles of water quality trading. We compare this distributed, green approach with a centralized, gray approach (i.e., building a new nitrate removal facility at the drinking water utility). Using terrain analysis, we determined that first-order streams are the most fitting location for riparian buffers. We estimate the buffer installation to cost between $155–$185 million; maintenance of the current nitrate removal facility will cost $72 million, while a new facility could cost up to $184 million. Riparian buffer installation offers more indirect, non-quantified benefits than maintaining or building new centralized, gray treatment (e.g., living-wage jobs and in-stream water quality improvement). Our analysis could act as a model for water quality trading and distributed agricultural green infrastructure in other communities facing similar water quality challenges.

Redundant configuration of robotic assembly lines with stochastic failures

One of the main challenges in the operation of robotic assembly lines is the occurrence of failures. Due to the connection of the stations via a material handling system, failures at one station often result in throughput losses. To some extent, these throughput losses can be reduced by installing buffers between the stations. However, the installation of buffers requires considerable investments and scarce factory space. Due to the advances of manufacturing technologies that form the foundation of ‘Industry 4.0’, new solutions to reduce failure-related throughput losses open up. One solution is a redundant configuration, in which downstream (backup) stations automatically take over the operations of failed stations during repair time. The throughput loss in these situations depends on the allocation of operations and the assignment of backup stations. Existing approaches in the literature that consider redundancies in the configuration of automated lines neglect the resulting production rate. Instead, the lines’ level of redundancy is used as a surrogate measure for optimisation. We present a genetic algorithm for the redundant configuration of robotic assembly lines with stochastic failures to maximise the production rate of the line. In a numerical analysis, it is demonstrated that this approach allows for productivity improvements.

Redundant configuration of automated flow lines based on “Industry 4.0”-technologies

Over the past decades, robots have been heavily used for flow lines to increase productivity and product quality and to relieve workers of repetitive and dangerous tasks. However, despite continuous improvement of robots, the occurrence of failures remains a significant challenge in the operation of automated flow lines. Due to the connection of the stations in a flow line via a material handling system, failures at one station can quickly lead to throughput losses due to blocking and starving of upstream and downstream stations, respectively. To some extent, these throughput losses can be reduced by installing buffers between the stations. However, the installation of buffers requires considerable investments and scarce factory space. Therefore, the minimization of the total number of buffers is one of the primary objectives in flow line planning. Due to the advances of manufacturing technologies that form the foundation of “Industry 4.0”, new solutions to reduce throughput losses caused by equipment failures open up. One solution is a redundant configuration, in which downstream stations automatically take over the operations of failed stations in the event of failure. The throughput loss in these situations mainly depends on the level of redundancy designed into the system. Based on existing methods for the design of automated flow lines, we present two line balancing formulations for the configuration of automated flow lines under consideration of redundancies. The first formulation aims at maximizing the lines’ level of redundancy. The second formulation aims at a balanced allocation of redundancies along the line. To evaluate the presented formulations, we compare the performance with an existing line balancing approach for automated lines. With respect to this approach, improvements of the throughput rate between 3 % and 7 % are achieved.

Redundant Configuration of Automated Flow Lines

Robot failures are a significant challenge in the operation of automated flow lines since they result in throughput losses due to blocking and starvation of upstream and downstream stations, respectively. To some extent, these throughput losses can be reduced by installing buffers between the stations. However, the installation of buffers requires considerable investments and scarce factory space. With the emergence of advanced robotics and autonomous transportation units flow lines become increasingly flexible. This opens up new solutions to reduce throughput losses caused by failures. One solution is a redundant configuration, in which downstream stations automatically take over the tasks of failed stations and therefore make the line more robust against failures. The throughput loss in these situations mainly depends on the level of redundancy designed into the system. The focus of this contribution is set on a mathematical formulation to balance flow lines under consideration of redundancies. The developed approach maximizes the lines’ level of redundancy for a given number stations. In a numerical analysis we demonstrate the effectiveness of the approach and show that redundant configurations lead to an increase of average throughput rates.

State-of-the-art and proof-of-concept installations for repository concepts based in crystalline rock

AbstractOver the last five decades private and national energy programmes worldwide have been producing a variety of radioactive wastes. One of the safest ways of disposing of this waste is to bury it deep underground in purpose-built geological disposal facilities. Currently, there is no operating geological repository in Europe for high-level waste but the goal of the IGD-TP is that the first repository shall be fully operational before the year 2025. Several studies and experiments are ongoing at various potential repository sites in Europe with the goal to establish general approaches that can be adapted for any country in need of a geological repository.The Swedish Nuclear Fuel and Waste Management Co (SKB) in Sweden and Posiva Oy in Finland are developing a method for geological disposal of high-level long-lived nuclear waste in crystalline rock, the KBS-3 method. KBS-3V (vertical) is both organizations reference design, but KBS-3H (horizontal) emplacement is also being researched as a potential alternative. Of high importance in the development is demonstrating the technical feasibilityin situof safe and reliable construction, manufacturing, disposal and sealing of such geological disposal facilities. Parts of these demonstrations are carried out under the framework of EurAtom/FP7 and one of these projects is the LUCOEX project where SKB is demonstrating horizontal emplacement, the Multi Purpose Test (MPT), and Posiva is demonstrating vertical buffer installation processes.The MPT includes the key components of the horizontal design and comprises all essential steps; manufacturing of the full-scale components, their assembly, installation in the drift and monitoring of the early buffer evolution. The MPT installation was successfully performed in late 2013. By combining the components, an initial verification of the design implementation has been achieved. At the same time, integrating the components has meant the recognition of some design weaknesses and the design will be updated accordingly.Posiva's KBS-3V buffer installation equipment that places buffer blocks with high precision in vertical deposition holes is currently being developed and will be tested during 2014 and 2015 in real underground conditions. The machine uses vacuum lifting tools for moving the buffer blocks and laser scanning technology to position both the machine and blocks. Functionality of the concept and equipment selected will be confirmed by the tests and the installation tests will provide important information about the suitability of the selected buffer dimensions and tolerances.

Dairy farm impacts of fencing riparian land: An analysis of farmers' perceptions of the costs and benefits

U ncontrolled stock access to streams contributes excessive nutrient and pathogen inputs from urine and dung, causes trampling and pugging or poaching of banks, and leads to overgrazing of riparian vegetation (Trimble and Mendel 1995; Hooda et al. 2000; Agouridis et al. 2005). In addition, in Victoria, Australia, all of the processes that potentially threaten riparian biodiversity are influenced by grazing management of riparian areas (NRE 1997; Lowe et al. 2000). The grazing-based dairy industry in the Gippsland region accounted for 35.3% of Victoria's dairy production in 2009 and 2010 (DA 2011) and half of the agricultural production in Gippsland (WGCMA 2004). GippsDairy, the regional dairy board, highlighted water and biodiversity management for community and on-farm benefits as major challenges currently facing the industry (GippsDairy 2006), with the desired outcomes including (1) a reduction in nutrient contamination of waterways and groundwater while maintaining dairy farm productivity and (2) the protection and enhancement of native vegetation, wildlife habitat, stream banks, and wetlands on dairy farms to increase biodiversity assets. Riparian Interventions. Improvement in riparian management and water quality on dairy farms includes the installation of buffers (Dabney et al. 2006), exclusion of stock (Line et al. 2000), and rotational grazing (RMS 2009).

Agri-Environmental Program Compliance in a Heterogeneous Landscape

Heterogeneity of agricultural landscapes may necessitate the use of spatially targeted instruments. But costly enforcement may be needed to ensure compliance with these policies. This paper examines the design of agri-environmental policies designed to achieve reductions in fertilizer application rates and installation of riparian buffers through the use of incentive-based instruments. We derive monitoring strategies capable of ensuring perfect compliance from risk neutral farmers given realistic limits on penalties for non-compliance. We then apply that framework empirically using a parametric model reflecting Finnish agricultural and environmental conditions. The results of our simulations indicate that subsidies for installing and maintaining buffer strips, used alone, are the most cost effective means of reducing nitrogen runoff from crop production. This policy is also the most attractive politically, in that it reduces farm income less than the alternatives considered.

Runoff and dissolved organic carbon loss from a paired-watershed study of three adjacent agricultural Watersheds

Organic matter plays several important roles in the biogeochemistry of terrestrial and aquatic ecosystems including the mobilization and transport of nutrients and pollutants. Cropping, tillage practices and vegetative buffer strip installation affect losses of dissolved organic carbon (DOC). While many studies show reductions in pollutant export from agroecosystems where vegetative buffers have been implemented, buffer strips may be a source of DOC and contribute to surface water pollution. Using a paired-watershed approach, the objectives of this study were to determine the effect of grass and agroforestry buffers on runoff and DOC loss, compare runoff and DOC losses between the growing and fallow seasons, and investigate crop effects on runoff and DOC losses. The study design consisted of three small agricultural Watersheds in a no-till, maize-soybean rotation located in the claypan region of northeast Missouri, USA; one watershed was planted with grass buffer strips, one with agroforestry buffer strips, and one unaltered watershed served as the control. Runoff and DOC loss were measured during a six-year calibration period (1991–1997) prior to buffer installation and for a nine-year treatment period (1997–2006). The grass buffer strips significantly decreased runoff by 8.4% ( p = 0.015) during the treatment period while the agroforestry buffer system exhibited no significant change in runoff ( p = 0.207). Loss of DOC was not significantly affected by grass or agroforestry buffer installation ( p = 0.535 and p = 0.246, respectively). Additionally, no significant difference in runoff or DOC loss was found between crops (maize and soybean) or between seasons (growing and fallow). Overall, this study indicates that grass buffer systems are effective at reducing runoff and that DOC contamination of surface waters is not exacerbated by either type of vegetative buffer strip.

Farmlink: promoting conservation buffers farmer-to-farmer

Farmer-to-farmer outreach was used within a targeted watershed to promote the installation of conservation buffers. In this program called “FarmLink”, four farmers/landowners were employed part-time as “advisors” and trained by University of Nebraska-Lincoln Extension, Natural Resources Conservation Service, and Natural Resources District personnel. Topics included basic buffer design and benefits, availability of incentive programs, and sales techniques. These individuals then contacted their neighbors to explain the need for and benefits of buffers and other conservation practices. In early 2003, 42 landowners were contacted, leading to contracts for the establishment of 16 separate conservation practices on 24.8 ha (61.3 acres) of farmland. These included just over 8 ha (20 acres) of grassed waterways or similar plantings and 14 ha (35 acres) of streamside buffers. In addition, because of information received in the training sessions, one of the advisors installed 1.7 ha (4.3 acres) of streamside buffers, 0.45 ha (1.1 acres) of grassed waterways, and 2.0 ha (5.0 acres) of grasses and forbs on his own land. During these contacts, it became apparent that: (1) many farmers and landowners were not familiar with the multitude of programs available to assist with the installation and maintenance of conservation practices; and (2) landowners generally appreciated the personal touch of someone coming out to talk directly to them, pointing out specific areas on their land where conservation practices could best be implemented, discussing available compensation programs, and describing management needed to help ensure practice success. Although one-to-one contacts cannot be used in all cases, it was demonstrated to be effective in this watershed.

Responses to Riparian Restoration in the Spring Creek Watershed, Central Pennsylvania

Abstract Riparian treatments, consisting of 3‐ to 4‐m buffer strips, stream bank stabilization, and rock‐lined stream crossings, were installed in two streams with livestock grazing to reduce sediment loading and stream bank erosion. Cedar Run and Slab Cabin Run, the treatment streams, and Spring Creek, an adjacent reference stream without riparian grazing, were monitored prior to (1991–1992) and 3–5 years after (2001–2003) riparian buffer installation to assess channel morphology, stream substrate composition, suspended sediments, and macroinvertebrate communities. Few changes were found in channel widths and depths, but channel‐structuring flow events were rare in the drought period after restoration. Stream bank vegetation increased from 50% or less to 100% in nearly all formerly grazed riparian buffers. The proportion of fine sediments in stream substrates decreased in Cedar Run but not in Slab Cabin Run. After riparian treatments, suspended sediments during base flow and storm flow decreased 47–87% in both streams. Macroinvertebrate diversity did not improve after restoration in either treated stream. Relative to Spring Creek, macroinvertebrate densities increased in both treated streams by the end of the posttreatment sampling period. Despite drought conditions that may have altered physical and biological effects of riparian treatments, goals of the riparian restoration to minimize erosion and sedimentation were met. A relatively narrow grass buffer along 2.4 km of each stream was effective in improving water quality, stream substrates, and some biological metrics.

Setting priorities for research on pollution reduction functions of agricultural buffers.

The success of buffer installation initiatives and programs to reduce nonpoint source pollution of streams on agricultural lands will depend the ability of local planners to locate and design buffers for specific circumstances with substantial and predictable results. Current predictive capabilities are inadequate, and major sources of uncertainty remain. An assessment of these uncertainties cautions that there is greater risk of overestimating buffer impact than underestimating it. Priorities for future research are proposed that will lead more quickly to major advances in predictive capabilities. Highest priority is given for work on the surface runoff filtration function, which is almost universally important to the amount of pollution reduction expected from buffer installation and for which there remain major sources of uncertainty for predicting level of impact. Foremost uncertainties surround the extent and consequences of runoff flow concentration and pollutant accumulation. Other buffer functions, including filtration of groundwater nitrate and stabilization of channel erosion sources of sediments, may be important in some regions. However, uncertainty surrounds our ability to identify and quantify the extent of site conditions where buffer installation can substantially reduce stream pollution in these ways. Deficiencies in predictive models reflect gaps in experimental information as well as technology to account for spatial heterogeneity of pollutant sources, pathways, and buffer capabilities across watersheds. Since completion of a comprehensive watershed-scale buffer model is probably far off, immediate needs call for simpler techniques to gage the probable impacts of buffer installation at local scales.

A Genetic Algorithm for the Allocation of Buffer Storage Capacities in a Production Line with Unreliable Machines

In this paper, we consider a flow-line manufacturing system organized as a series of workstations separated by finite buffers. The failure and repair times of machines are supposed to be exponentially distributed. The production rate of each machine is deterministic, and different machines may have different production rates. The buffer allocation problem consists in determining the buffer capacities with respect to a given optimality criterion, which depends on the average production rate of the line, the buffer acquisition and installation cost, and the inventory cost. For this problem we propose a genetic algorithm where the tentative solutions are evaluated with an approximate method based on the Markov-model aggregation approach.