Lower Peak Discharge Research Articles

Application of GIS and remote sensing in morphometric analysis of river basin at the south-western part of great Ganges delta, Bangladesh

Abstract Analysing the morphometric parameters is the most expedient and parsimonious way of representing the hydrologic and physiographic attributes of river basins. The present study attempts to measure the morphometric parameters for assessing the understanding of morphological, hydrological, and physiographic properties of the south-western part of the Ganges delta. Parameters were analysed from Shuttle Radar Topography Mission's (SRTM) maps and total of eight linear, six areal, eight relief, and five drainage texture parameters have taken with hypsometric analysis for the four major rivers and two tributary river basins. The values of linear parameter denote that most of the streams (82%) fall in first order, and other orders have homogeneous underline materials. The aerial parameters represent low peak discharge and the upper region is less vulnerable to flood. The relief parameter values show that the entire basin has low surface runoff and they are less erosional (slope < 3.97°). The drainage density indicates the coarser nature and circularity ratio (0.08) represents the elongated shape. The southern portion of the basin has a greater flood potential and hypsometric index (0.49) shows the entire basin is in mature stage of formation. These results would be helpful for reckoning the watersheds for drainage management and environmental planning for ecological management and sustainable development.

Forecasting of Flash Floods Peak Flow for Environmental Hazards and Water Harvesting in Desert Area of El-Qaa Plain, Sinai.

Water resources in arid and semi-arid regions are limited where the demands of agriculture, drinking and industry are increasing, especially in drought areas. These regions are subjected to climate changes (CC) that affect the watershed duration and water supplies. Estimations of flash flooding (FF) volume and discharge are required for future development to meet the water demands in these water scarcity regions. Moreover, FF in hot deserts is characterized by low duration, high velocity and peak discharge with a large volume of sediment. Today, the trends of flash flooding due to CC have become very dangerous and affect water harvesting volume and human life due to flooding hazards. The current study forecasts the peak discharges and volumes in the desert of El-Qaa plain in Southwestern Sinai, Egypt, for drought and wet seasons by studying the influence of recurrence intervals for 2, 5, 10, 25, 50 and 100 years. Watershed modeling system software (WMS) is used and applied for the current study area delineation. The results show that the predictions of peak discharges reached 0, 0.44, 45.72, 195.45, 365.91 and 575.30 cubic meters per s (m3 s−1) while the volumes reached 0, 23, 149.80, 2,896,241.40, 12,664,963.80 and 36,681,492.60 cubic meters (m3) for 2, 5, 10, 25, 50 and 100 years, respectively, which are precipitation depths of 15.20, 35.30, 50.60, 70.70, 85.90 and 101 mm, respectively. Additionally, the average annual precipitation reached 13.37 mm, with peak flow and volume reaching 0 m3 s−1 where all of water harvesting returned losses. Moreover, future charts and equations were developed to estimate the peak flow and volume, which are useful for future rainwater harvesting and the design of protection against flooding hazards in drought regions due to CC for dry and wet seasons. This study provides relevant information for hazard and risk assessment for FF in hot desert regions. The study recommends investigating the impact of recurrence intervals on sediment transport in these regions.

Sedimentology of the modern seasonal lower Ganges River with low inter-annual peak discharge variance, Bangladesh

The Ganges River, one of the largest rivers on Earth, is a typical monsoonal and flood-controlled system but has low inter-annual peak discharge variability. The seasonal discharge can reach 70 000 m 3 s −1 during the wet season but maintains a low base flow of 500–3000 m 3 s −1 during the dry season. However, the constancy in peak discharge every year categorizes the lower Ganges River as a river with low inter-annual peak discharge variability. This paper examines the modern lower Ganges River by conducting a detailed process-oriented investigation of the main channel, channel margin and overbank deposits, supplemented by satellite image observation and comparison with other modern fluvial systems. The channel and braid bar deposits show a dominance of small-scale to medium-scale cross-sets, with a variety of accretion processes constructing braid bars. The braid bar and channel deposits are typical of facies models of rivers with low inter-annual peak discharge variance. In contrast, the channel flank deposits are dominated by planar lamination, massive sand and mud couplets, and some ripple cross-lamination, with very little cross-bedding. Characteristic channel margin deposits represent sediments that accumulated by high-speed flows, multiple-surge and rapidly depositing flows, rapid or regular waning flows and hyperconcentrated flows. The overbank deposits predominantly comprise current ripples with long, thin bedforms and soft sediment deformation structures, which record flow transformation on the muddy flat topography and the processes of an unstable river bank. Our study shows that the channel margin and floodplain deposits are entirely different from those of the braid bar and channel. The bedform distribution of the fluvial deposits here (main channel, channel margin and overbank) may be an important tool in the identification of similar seasonal rivers with low inter-annual peak discharge variance and in the interpretation of fluvial processes. Supplementary material : The sediment texture and the depositional age is available at: https://doi.org/10.6084/m9.figshare.c.5144403

Sustained fluvial deposition recorded in Mars\u2019 Noachian stratigraphic record

Orbital observation has revealed a rich record of fluvial landforms on Mars, with much of this record dating 3.6–3.0 Ga. Despite widespread geomorphic evidence, few analyses of Mars’ alluvial sedimentary-stratigraphic record exist, with detailed studies of alluvium largely limited to smaller sand-bodies amenable to study in-situ by rovers. These typically metre-scale outcrop dimensions have prevented interpretation of larger scale channel-morphology and long-term basin evolution, vital for understanding the past Martian climate. Here we give an interpretation of a large sedimentary succession at Izola mensa within the NW Hellas Basin rim. The succession comprises channel and barform packages which together demonstrate that river deposition was already well established >3.7 Ga. The deposits mirror terrestrial analogues subject to low-peak discharge variation, implying that river deposition at Izola was subject to sustained, potentially perennial, fluvial flow. Such conditions would require an environment capable of maintaining large volumes of water for extensive time-periods, necessitating a precipitation-driven hydrological cycle.

Overview of modern atmospheric patterns controlling rainfall and floods into the Dead Sea: Implications for the lake's sedimentology and paleohydrology

The Dead Sea sedimentary fill is the basis for interpreting limnological conditions and regional paleohydrology. Such interpretations require an understanding of present-day hydroclimatology to reveal the relative impact of different atmospheric circulation patterns on water and sediment delivery to the Dead Sea. Here we address the most important meteorological conditions governing regional and local rainstorm occurrences, with different discharge characteristics. These meteorological controls over the Dead Sea watershed offer insights into past hydrometeorological processes that could have governed the Dead Sea water budget, seasonal and annual flows, floods, and the resultant sedimentology. Rainfall is typically associated with synoptic-scale circulation patterns forced by an upper-level trough that include Mediterranean cyclones (MCs), active Red Sea troughs (ARSTs), and active subtropical jets (STJs), although other rainstorms and sub-synoptic processes also affect the region. We point to their relative importance in inflow volume, peak discharges, and delivery of sediments from the various environments of the basin. MCs control the annual water amount discharging into the Dead Sea. A change in their frequency, intensity, or latitude can substantially alter the lake water balance. A change in frequency or intensity of ARSTs and STJs affects extreme flood and sediment discharge. Floods reach the lake through (a) the Mediterranean-climate-controlled Lower Jordan River, (b) desert-climate-controlled Nahal HaArava, and (c) the arid wadies draining directly into the Dead Sea, some with wetter headwaters. Floods in the wetter parts of the watershed are mainly controlled by MCs, and characterized by larger frequency, volume, and duration, but lower peak discharges and possibly sediment delivery, than floods in the desert parts, which can be produced by the three synoptic types. ARSTs contribute to heavy rainfall, typically of a spotty nature, in the desert parts of the watershed. STJs are currently rare, but their rainfall accumulation may be greater than the annual mean over a broad area in the southern dry Dead Sea watershed. This article presents a review of recent studies, which is extended with new analyses of meteorological, rainfall and flood data, underlining the importance of the Lower Jordan River in supplying water volume to the Dead Sea, as compared to the high-discharge, low-volume floods of the arid part of the watershed. Our analyses will help interpret paleoenvironmental conditions in the Dead Sea sedimentary record, and cope with the region's changing climate.

Upper-bar deposits in large Amazon rivers: Occurrence, morphology and internal structure

Although large anabranching rivers are a very common element in the greatest modern drainage basins, the recognition of such systems in the rock record is hampered by insufficient sedimentological information from active rivers. That is particularly the case of bar-top depositional environments in large anabranching rivers, motivating the survey of six selected areas of seasonally emergent bars in the Solimões and Japurá rivers (western Brazilian Amazonia) using Ground Penetrating Radar, Sub Bottom Profiler and Multibeam Echosounder, as well as direct observation sediment sampling. GPR surveys and field observations indicate these bars are dominated by 0.5 to 4 m tall subaqueous dunes with the local presence of metric angle-of-repose bar-side surfaces. Downstream accretion components are characterized by radar facies indicating horizontal to low-angle downstream-dipping cosets of dm-scale to cm-scale cross-strata. Lateral accretion components are characterized by radar facies indicating m-scale high-angle cross-strata sets passing laterally to low-angle and inclined cosets composed of dm-scale cross-strata sets. Upstream accretion components are characterized by radar facies indicating upstream-inclined cosets of m- and dm-scale cross-strata sets with local mud drapes. Preservation of accretionary bar forms in these periodically exposed areas is supported by calculation of the coefficient of variation of peak discharge, which indicates low interannual peak discharge variability over the bar tops.

The influence of aquatic buffer characteristic of Ciliwung River from the Katulampa Weir to Manggarai Water Gate on hydrograph characteristics of design flood

Increasing population in Jakarta leads to increased needs of settlements and their supporting facilities. To compensate, various methods are being undertaken, from utilization of open area to the riparian, especially in the Ciliwung River. This utilization results in the loss of riparian natural ability, which changes the river’s hydraulic condition. These riparian changes will significantly affect the roughness coefficient. The roughness coefficient is a value that is affected by channel irregularity, variation of cross-section, effects of obstructions, vegetation, and degree of meandering. Changes of the roughness coefficient will influence the velocity of the stream. The purpose of this research is to determine the effect of riparian characteristics to the roughness coefficient that affects the stream velocity, which has impact on the peak time of the hydrograph. The peak time shift can be seen in the flood hydrograph characteristics of the Ciliwung River from the Katulampa Weir to the Manggarai sluice gate. Identification of Ciliwung riparian conditions at that segment is conducted by river routing. HEC-RAS 4.1.0 [1] application is used to obtain a design flood hydrograph at Manggarai Water Gate. To know the influence of riparian characteristics to roughness coefficient, HEC-RAS 4.1.0 simulation is done using existing and natural condition to compare the hydrographs between those two conditions. It obtains a lower peak discharge and extended duration of the hydrograph.

Effects of Urban Stormwater Control Measures on Denitrification in Receiving Streams

Urban areas are increasingly adopting the use of ecologically-based technologies for stormwater management to mitigate the effects of impervious surface runoff on receiving water bodies. While stormwater control measures (SCMs) reduce runoff, their ability to influence ecosystem function in receiving streams is not well known. To understand the effect of SCMs on net ecosystem function in stream networks, we measured sediment denitrification in four streams across a gradient of urban and suburban residential development in Charlotte, NC. We evaluated the influence of SCM inputs on actual (DNF) and potential (DEA) denitrification activity in stream sediments at the SCM-stream confluence to quantify microbial processes and the environmental factors that control them. DNF was variable across sites, ranging from 0–6.60 mg-N·m−2·h−1 and highly correlated with in-stream nitrate (NO3-N) concentrations. Sites with a greater impervious area showed a pattern of significantly higher DEA rates upstream of the SCM compared to downstream, while sites with less imperviousness showed the opposite trend. We hypothesize that this is because of elevated concentrations of carbon and nitrogen provided by pond and wetland outflows, and stabilization of the benthic habitat by lower peak discharge. These results suggest that SCMs integrated into the watershed have the potential to create cascading positive effects on in-stream nutrient processing and thereby improve water quality; however, at higher levels of imperviousness, the capacity for SCMs to match the scale of the impacts of urbanization likely diminishes.

Late Holocene channel pattern change from laterally stable to meandering – a palaeohydrological reconstruction

Abstract. River channel patterns may alter due to changes in hydrological regime related to changes in climate and/or land cover. Such changes are well documented for transitions between meandering and braiding rivers, whereas channel pattern changes between laterally stable and meandering rivers are poorly documented and understood. We hypothesize that many low-energy meandering rivers had relatively low peak discharges and were laterally stable during most of the Holocene, when climate was relatively stable and human impact was limited. Our objectives in this work are to identify a Late Holocene channel pattern change for the low-energy Overijsselse Vecht river, to develop and apply a novel methodology to reconstruct discharge as a function of time following a stochastic approach, and to relate this channel pattern change to reconstructed hydrological changes. We established that the Overijsselse Vecht was laterally virtually stable throughout the Holocene until the Late Middle Ages, after which large meanders formed at lateral migration rates of about 2 m yr−1. The lateral stability before the Late Middle Ages was constrained using a combination of coring information, ground-penetrating radar (GPR), radiocarbon (14C) dating, and optically stimulated luminescence (OSL) dating. We quantified bankfull palaeodischarge as a function of time based on channel dimensions that were reconstructed from the scroll bar sequence and channel cut-offs using coring information and GPR data, combined with chronological constraints from historical maps and OSL dating. We found that the bankfull discharge was significantly greater during the meandering phase compared to the laterally stable phase. Empirical channel and bar pattern models showed that this increase can explain the channel pattern change. The bankfull discharge increase likely reflects climate changes related to the Little Ice Age and/or land use changes in the catchment, in particular as a result of peat reclamation and exploitation.

Geo-hydrological analysis and sub watershed prioritization for flash flood risk using weighted sum model and Snyder’s synthetic unit hydrograph

The present study demonstrates the usefulness of remote sensing data for analyzing the flash flood risk in Uhl River watershed situated in the western Lesser Himalayan region. This is one of the most vulnerable flash flood watersheds in Himachal Pradesh which, suffers heavy damages to man-made features almost every year. In this study different morphometric properties that direct the hydrological response and pertinent to flash flood risk of the watershed have been used to prioritize the sub-watersheds using weighted sum analysis (WSA) model. The result indicates that 12.83 and 16.94 percent of the total area come under very high and high flash flood risk respectively. In addition, the Snyder’s synthetic unit hydrograph method was employed to assess the hydrological behavior and prioritization of sub-basins which shows that sub-basins falling under very high and high-risk group have low lag time and high peak discharge per unit of watershed area. This study concludes Watershed 7 and 8 of Uhl River basin in Himachal Pradesh comes under high priority class and is vulnerable to flash floods.

Stream hydrology and geochemistry along a rural to urban land use gradient

High frequency monitoring of water quality and stable isotopes quantify large hydrological and geochemical differences across a rural to urban land use gradient that includes three watersheds and two of their subbasins. Following precipitation events, floods on a rural stream feature hydrographs with low peak discharges and long lag times, high baseflow contributions, and small geochemical variations. In contrast, the flows of an urban stream and its tributary respond in a flashy manner, with average lag times decreasing by at least 55% compared to the rural stream. We also observed that baseflow contributions during floods decreased by an average of 40% in the urban streams. Importantly, we find that reduced baseflow as a function of increasing impervious surface area is not a linear trend among the streams, and suburban streams are less impacted than would be predicted by impervious surface area alone. The urban streams also exhibit large variations in water quality parameters during flooding events, often with five times the variability of the rural end-member. These differences are observed among all physical and geochemical characteristics that were monitored, including flow magnitude, stable isotope ratios, temperature, dissolved oxygen (DO), pH, turbidity, specific conductivity, concentrations of Cl− and nutrients, and bacterial loads. The great variability of urban streams following storms is paralleled by their larger diurnal and seasonal oscillations. Collectively, the extreme variations in the physical and geochemical character of urban streams have negative consequences to environmental quality and aquatic life.

Dynamics of Mediterranean late Quaternary fluvial activity: An example from the River Ebro (north Iberian Peninsula)

Late Pleistocene and Holocene fluvial evolution of the upper River Ebro (Miranda basin, north Spain) is analysed using geomorphological, sedimentological, and optical dating techniques. Maximum regional crustal uplift of 0.98m/ka approximately helped preserve a suite of terraces in the Miranda basin: 5 river terraces (T1–5) were identified and their formation attributed to MIS 6 (T1), MIS 5d (T2), MIS 4 (T3), MIS 2 (T4), MIS 1 (T5). Alluvium deposited in terraces T1, T2, T3, and T4 is well-sorted, clast-supported gravels; whereas the T5 deposit is exclusively composed of silt. Gravels were deposited during cold and dry periods when reduced vegetation cover on hillslopes increased sediment supply to the trunk river. Silt was deposited in overbank settings under warmer and wetter climate conditions when vegetation cover stabilised hillslopes and restricted sediment supply. It also resulted in lower peak discharge and reduced flow velocities over vegetated floodplains. The chronological sequence of terraces indicates that incision occurred during climatic transitions. We conclude that the upper River Ebro responded to fluctuations in sediment supply and discharge controlled by late Quaternary climate cycles.

Some Characteristics of Peak Flow in the Richelieu River, Quebec

This paper presents a statistics analysis of 1938-2012 data of daily discharge and water level collected from a gauging station on the Richelieu River in Southern Quebec, Canada. Using the most recent data, this paper aims to update flood characteristics from previous decades old analyses. Such update is important to the flood-prone region. The present analysis covers peak flow magnitude, duration, timing and, more importantly, their changes. The main findings are: There are no significant changes over time in average magnitude of floods, but there are increasing fluctuations between low and high peak discharges. The distribution of annual peak discharges shows a signifcaint shift of skewness from left to right; if this condition persists, future floods are expected to have a larger magnitude than historic flood events. The timing of peak discharges has not shown any significant trend of changes. A new flow rating curve has been obtained for discharge estimates.

Modelling the impacts of land-cover change on streamflow dynamics of a tropical rainforest headwater catchment

A modelling experiment is used to examine different land-use scenarios ranging from extreme deforestation (31% forest cover) to pristine (95% forest cover) conditions and related Payment for Ecosystem Services (PES) schemes to assess whether a change in streamflow dynamics, discharge extremes and mean annual water balance of a 73.4-km2 tropical headwater catchment in Costa Rica could be detected. A semi-distributed, conceptual rainfall–runoff model was adapted to conceptualize the empirically-based, dominant hydrological processes of the study area and was multi-criteria calibrated using different objective functions and empirical constraints on model simulations in a Monte Carlo framework to account for parameter uncertainty. The results suggest that land-use change had relatively little effect on the overall mean annual water yield (<3%). However, streamflow dynamics proved to be sensitive in terms of frequency, timing and magnitude of discharge extremes. For low flows and peak discharges of return periods greater than one year, land use had a minor influence on the runoff response. Below these thresholds (<1-year return period), forest cover potentially decreased runoff peaks and low flows by as much as 10%, and non-forest cover increased runoff peaks and low flows by up to 15%. The study demonstrated the potential for using hydrological modelling to help identify the impact of protection and reforestation efforts on ecosystem services. Editor Z.W. Kundzewicz Citation Birkel, C., Soulsby, C., and Tetzlaff, D., 2012. Modelling the impacts of land-cover change on streamflow dynamics of a tropical rainforest headwater catchment. Hydrological Sciences Journal, 57 (8), 1543–1561.

Late Holocene alluvial history of the Cuyama River, California, USA

Dryland river deposits are archives of past changes in fluvial-system form and process. Chronostratigraphic reconstruction of the late Holocene alluvial history of the Cuyama River in west-central California reveals past spatial and temporal variation in dryland channel form and process. The modern Cuyama River consists of a wide braided reach in the upper drainage basin, a narrower arroyo reach in the middle of the drainage basin, and a bedrock canyon reach in the lower drainage basin that drains to the Santa Maria coastal plain. Along the arroyo reach, late Holocene stratigraphy is well exposed and is the focus of this study. Between ca. 1700 and 350 yr B.P., two widespread deposits of tabular-bedded clay, silt, and fine sand were deposited, separated by a buried soil formed between 950 and 700 yr B.P. Channel incision occurred between 550 and 350 yr B.P. Next, deposition of massive to bedded sands occurred in a pattern alternating between poorly confined deposition on top of older deposits onto the broad valley floor, and channelized deposition along the valley axis inset into older deposits. The superposed deposits now underlie the main valley terrace, and the valley-axis deposits are preserved as inset fill terraces. Historical arroyo cutting then formed a 65-km-long arroyo ca. 150 yr B.P. Based on correlation to regional paleoclimate records, channel aggradation occurred during periods of relative aridity and low peak discharge events, while wet periods, possibly floods after drought, led to fluvial incision. These cycles are superimposed on a transition from a wide, silt- and fine-sand-dominated fluvial system to a modern, narrow, sand– and gravel-dominated arroyo channel. The relationship between times of fluvial process change and climate change in Cuyama Valley bears considerable similarity to other well-studied dryland rivers in the southwestern United States; however, the complex sedimentology and geometry of preserved fluvial deposits suggest that a wider range of fluvial modes occurred along the Cuyama River than has been reported in simpler cut-and-fill–dominated channels elsewhere. These spatial and sedimentological complexities underscore the need to link fluvial deposits and their bounding unconformities along a channel in order to fully understand the spatial and temporal evolution of ancient fluvial systems.

A critical perspective on 1‐D modeling of river processes: Gravel load and aggradation in lower Fraser River

We investigate how well a width‐averaged morphodynamic model can simulate gravel transport and aggradation along a highly irregular 38‐km reach of lower Fraser River and discuss critical issues in this type of modeling. Bed load equations with plausible parameter values predict a gravel input consistent with direct measurements and a sediment budget. Simulations using spatially varying channel width, and forced by dominant discharge or a 20‐year hydrograph, match the observed downstream fining well. They reproduce major qualitative features of a 47 year sediment budget and match maximum local rates of aggradation and degradation to well within a factor of 2. Locations and rates of aggradation and degradation are influenced by channel constrictions. Runs for single years of unusually high or low peak discharge suggest that the main transfers of gravel occur in different parts of the reach in different years. One‐dimensional morphodynamic modeling of highly nonuniform rivers has serious conceptual limitations but may be a valuable complement to empirical approaches.

Hydroclimatic controls on the occurrence of break-up and ice-jam flooding in the Mackenzie Delta, NWT, Canada

Concern has been expressed regarding the impacts of climate change on freshwater aquatic ecosystems in arctic regions. Populated with lakes controlled by flooding from spring break-up ice jams, arctic deltas such as the Mackenzie Delta in northern Canada are particularly sensitive to changing ice break-up conditions and the hydroclimatic controls on break-up and ice-jam flooding. An understanding of these controls is necessary for assessing future climate change effects. This paper presents an assessment of hydroclimatic conditions controlling break-up over the period 1974–2006, with a focus on extreme flood events. Both the upstream driving force, capturing elements of the spring discharge hydrograph, and the downstream resistance force, describing the competence of the downstream ice cover, were quantified with reference to the Mackenzie River at Arctic Red River hydrometric station such that the contribution of each to the severity and timing of break-up could be explored. Results show that the severity of peak break-up stage is most influenced by upstream discharge and the balance between upstream and downstream melt, while timing is related to delta ice conditions and the rise of the spring hydrograph. The highest peak stage events require a rapid rise in discharge and high peak discharge. Minimal downstream melting degree-days and greater ice thickness are also important, although no relationship of these appears to control the level of backwater produced from broken ice and ice jamming effects. The pattern of rapid (protracted) upstream melt and lower (higher) intensity melt in the delta characterizes the highest (lowest) break-up events. For the most severe events, upstream forces are important in controlling discharge-driven events, while an altered hydrologic response occurring for ice-driven events was noted, meriting future examination. Finally, trends toward a longer prebreak-up melt interval, lower peak discharge, rate of rise in discharge, and ice thickness, and higher freeze-up stage were observed, with greater variability of these controls and break-up severity in the most recent decade.

Central Neuroplasticity and Decreased Heart Rate Variability after Particulate Matter Exposure in Mice

BackgroundEpidemiologic studies show that exposure to fine particulate matter [aerodynamic diameter ≤ 2.5 μm (PM2.5)] increases the total daily cardiovascular mortality. Impaired cardiac autonomic function, which manifests as reduced heart rate variability (HRV), may be one of the underlying causes. However, the cellular mechanism(s) by which PM2.5 exposure induces decreased HRV is not known.ObjectivesWe tested the hypothesis that exposure to PM2.5 impairs HRV by decreasing the excitability of the cardiac vagal neurons in the nucleus ambiguus. We also detemined the effect of iron on PM-exposure–induced decrease in HRV.MethodsWe measured 24-hr HRV in time domains from electrocardiogram telemetry recordings obtained in conscious, freely moving mice after 3 days of exposure to PM2.5 in the form of soot only or iron-soot. In parallel studies, we determined the intrinsic properties of identified cardiac vagal neurons, retrogradely labeled with a fluorescent dye applied to the sinoatrial node.ResultsSoot-only exposure decreased short-term HRV (root mean square of successive difference). With the addition of iron, all HRV parameters were significantly reduced. In nonexposed mice, vagal blockade significantly reduced all HRV parameters, suggesting that HRV is, in part, under vagal regulation in mice. Iron-soot exposure had no significant effect on resting membrane potential but decreased spiking responses of the identified cardiac vagal neurons to depolarizations (p < 0.05). The decreased spiking response was accompanied with a higher minimal depolarizing current required to evoke spikes and a lower peak discharge frequency.ConclusionsThe data suggest that PM-induced neuroplasticity of cardiac vagal neurons may be one mechanism contributing to the cardiovascular consequences associated with PM2.5 exposure seen in humans.

Simulation of water quality in a flood detention area using models of different spatial discretization

Detention areas provide a means to lower peak discharges in rivers by temporarily storing excess water. In the case of extreme flood events, the storage effect reduces the risk of dike failures or extensive inundations for downstream reaches and near the site of abstraction. Due to the large amount of organic matter contained in the river water and the inundation of terrestrial vegetation in the detention area, a deterioration of water quality may occur. In particular, decay processes can cause a severe depletion of dissolved oxygen (DO) in the temporary water body. In this paper, we studied the potential of a water quality model to simulate the DO dynamics in a large but shallow detention area to be built at the Elbe River (Germany). Our focus was on examining the impact of spatial discretization on the model’s performance and usability. Therefore, we used a zero-dimensional (0D) and a two-dimensional (2D) modeling approach in parallel. The two approaches solely differ in their spatial discretization, while conversion processes, parameters, and boundary conditions were kept identical. The dynamics of DO simulated by the two models are similar in the initial flooding period but diverge when the system starts to drain. The deviation can be attributed to the different spatial discretization of the two models, leading to different estimates of flow velocities and water depths. Only the 2D model can account for the impact of spatial variability on the evolution of state variables. However, its application requires high efforts for pre- and post-processing and significantly longer computation times. The 2D model is, therefore, not suitable for investigating various flood scenarios or for analyzing the impact of parameter uncertainty. For practical applications, we recommend to firstly set up a fast-running model of reduced spatial discretization, e.g. a 0D model. Using this tool, the reliability of the simulation results should be checked by analyzing the parameter uncertainty of the water quality model. A particular focus may be on those parameters that are spatially variable and, therefore, believed to be better represented in a 2D approach. The benefit from the application of the more costly 2D model should be assessed, based on the analyses carried out with the 0D model. A 2D model appears to be preferable only if the simulated detention area has a complex topography, flow velocities are highly variable in space, and the parameters of the water quality model are well known.

Utilization of Remote Sensing Techniques for Monitoring and Evaluation of Solo Watershed Management

This research is an application of remote sensing technology for monitoring and evaluation of watershed management, which was conducted is Solo Watershed, Central and East Java. The research objectives were 1) to investigate the capability of photomorphic analysis of Landsat Thematic Mapper (TM) and Enhanced Themmatic Mapper (ETM +) imagery as the basic for analyzes of landforms, landuse, and morphometry of the land surface; 2) to calculate the overland flow – peak discharge and erosion – sediment yield as indicators of land degradation of the area; 3) to use the indicators as set of instrument for monitoring and evaluation of watershed management. In this study, visual interpretation by means of on-screen digilization of the digital imagery was carried out in order to identify and to delineate land parameters using photomorphic approach. Based on the photomorphic analysis, several image – based parameters such as relief topography, physical soil characteristic, litho – stratigraphy, and vegetation cover were integrated with other themati maps in a geographic information system (GIS) environment. Estimation of overland flow (C) based on Cook methods (1942) and calculation of peak disccharge (Qmax) based on rational method (Qmax = C. I. A) were applied. Meanwhile, estimation of surface erosion was carried out using Universal Soil Loss Equation (USLE, A = R. K. L. S. CP). The sediment yield (Sy) was estimated using seddiment delivery ratio ( SDR) based on the following formula: Sy = [A + (25% x A)] x SDR. Both pairs of C – Qmax and A – Sy, were utilized as the basis for monitoring and evaluation of the watershed. The combination of C – Qmax and A – Sy were also used as the basis for selection of stream gauge setting / AWLR within particular sub – catchment. It was found that the photomorphic analysis is only color/tone, slope aspects, pattern, and texture, unit boundaries between volcanic – origin landscape (Wilis volcanic complex) and folded – hills landforms (Kendeng ridges) can be delineated. Within the volcanic features, coarse – textured units indicating pyroclastic materials with high drainage density (western part of Lawu volcano). In terms of calculated overland flow and peak discharge of 100 sub – catchment within the Solo Watershed, it was found that there are four sub – catchment with relatively high values (&gt; 0.60 and &gt; 1200 m3s1 for overland flow and peak discharge repectively), namely Samin (Karanganyar), Keduang (Wonogiri), Dengkeng (Klaten), and Sungkur (Ponorogo). Five sub-catchment might be categorized as having moderate peak discharge (Qmax ranges from 1000 – 1200 m3s1), namely Ketonggo (Ngawi), Keyang (Ponorogo), Gandong – Semawur (Magetan), Pepe (Boyolali), and Soko (Bojonegoro), while the remaining 91 sub-catchments are categorized as having low peak discharge. Based on the calculation of erosion and sediment yield, there was no sub-catchment with moderate category (60 – 180 ton ha1yr1), i.e. Samin (Karanganyar), Gonggong (Magetan), Ngisip and Kedung Cilik (Tuban), and Pepe (Boyolali). The other 95 sub-catchment might be categorized as gentle to good. In terms of values representing overland flow – flood and erosion – sediment yield, there are several sub-catchments require first priority in monitoring and evaluation, and are recommended as suitable sites for stream gauge setting, i.e. Samin (Karanganyar), Gonggong (Magetan), Ngisip and Kedung Cilik (Tuban).