Average Outflow Research Articles

Quantifying the impact of bathymetric changes on the hydrological regimes in a large floodplain lake: Poyang Lake

The hydrological regime of a lake is largely dependent on its bathymetry. A dramatic water level reduction has occurred in Poyang Lake in recent years, coinciding with significant bed erosion. Few studies have focused on the influence of bathymetric changes on the hydrological regime in such a complex river-lake floodplain system. This study combined hydrological data and a physically based hydrodynamic model to quantify the influence of the bathymetric changes (1998–2010) on the water level spatiotemporal distribution in Poyang Lake, based on a dry year (2006), a wet year (2010) and an average year (2000–2010). The following conclusions can be drawn from the results of this study: (1) The bed erosion of the northern outlet channel averaged 3 m, resulting in a decrease in the water level by 1.2–2 m in the northern channels (the most significantly influenced areas) and approximately 0.3 m in the central lake areas during low-level periods. The water levels below 16 m and 14 m were significantly affected during the rising period and recession period, respectively. The water level reduction was enhanced due to lower water levels. (2) The water surface profiles adjusted, and the rising and recession rates of the water level increased by 0.5–3.1 cm/d at the lake outlet. The bathymetric influence extended across the entire lake due to the emptying effect, resulting in a change in the water level distribution. The average annual outflow increased by 6.8%. (3) The bathymetric changes contributed approximately 14.4% to the extreme low water level in autumn 2006 and enhanced the drought in the dry season. This study quantified the impact of the bathymetric changes on the lake water levels, thereby providing a better understanding of the potential effects of continued sand mining operations and providing scientific explanations for the considerable variations in the hydrological regimes of Poyang Lake. Moreover, this study attempts to provide a reference for the assessment of similarly dramatic bathymetric changes in complex floodplain lakes.

Hubble Space Telescope Observations of Extended [O iii]λ 5007 Emission in Nearby QSO2s: New Constraints on AGN Host Galaxy Interaction

Abstract We present a Hubble Space Telescope survey of extended [O iii] λ5007 emission for a sample of 12 nearby (z < 0.12), luminous Type 2 quasars (QSO2s), which we use to measure the extent and kinematics of their AGN-ionized gas. We find that the size of the observed [O iii] regions scale with luminosity in comparison to nearby, less luminous Seyfert galaxies and radially outflowing kinematics to exist in all targets. We report an average maximum outflow radius of ∼600 pc, with gas continuing to be kinematically influenced by the central active galactic nucleus (AGN) out to an average radius of ∼1130 pc. These findings question the effectiveness of AGNs being capable of clearing material from their host bulge in the nearby universe and suggest that disruption of gas by AGN activity may prevent star formation without requiring evacuation. Additionally, we find a dichotomy in our targets when comparing [O iii] radial extent and nuclear FWHM, where QSO2s with compact [O iii] morphologies typically possess broader nuclear emission lines.

Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. I. Spatially Resolved Mass Outflow Rates for the Seyfert 2 Galaxy Markarian 573∗ †

Abstract We present the first spatially resolved mass outflow rate measurements ( ) of the optical emission line gas in the narrow line region (NLR) of a Seyfert 2 galaxy, Markarian 573. Using long slit spectra and [O iii] imaging from the Hubble Space Telescope and Apache Point Observatory in conjunction with emission line diagnostics and Cloudy photoionization models, we find a peak outflow rate of at a distance of 210 pc from the central supermassive black hole (SMBH). The outflow extends to distances of 600 pc from the nucleus with a total mass and kinetic energy of M ≈ 2.2 × 106 M ⊙ and E ≈ 5.1 × 1054 erg, revealing the outflows to be more energetic than those in the lower luminosity Seyfert 1 galaxy NGC 4151. The peak outflow rate is an order of magnitude larger than the mass accretion and nuclear outflow rates, indicating local in situ acceleration of the circumnuclear NLR gas. We compare these results to global techniques that quantify an average outflow rate across the NLR, and find the latter are subject to larger uncertainties. These results indicate that spatially resolved observations are critical for probing AGN feedback on scales where circumnuclear star formation occurs.

A case series of favorable vessel dilatation using a nitinol scoring element-equipped helical balloon catheter (AngioSculpt®).

Although percutaneous transluminal angioplasty is an effective therapy against vascular access failure in hemodialysis patients, recurrent stenosis imposes enormous burden for hemodialysis patients. A nitinol scoring element-equipped helical balloon catheter (AngioSculpt®) has been altered the landscape for treating several vascular diseases. It is not, however, fully elucidated whether AngioSculpt for advanced vascular access stenosis, difficult to expand by conventional balloons, successfully provides bailout angioplasty. Here, we report our cases whose intradialytic venous pressure significantly improved after percutaneous transluminal angioplasty without any serious adverse complications using AngioSculpt. Among patients undergoing hemodialysis in Masuko Memorial Hospital, 16 cases with resistant and recurrent vascular access stenosis underwent AngioSculpt (diameter 6 mm, total length 4 cm) angioplasty. We simultaneously measured the average venous pressures during hemodialysis before and after percutaneous transluminal angioplasty. The average outflow vessel stenosis rate was 73.0 ± 11.3% before AngioSculpt intervention. Fully enlarged vessels were observed by expanding vessels at maximum pressure of 14 atm in all cases without any complications including vascular ruptures. Their intradialytic venous pressures decreased from 181.8 ± 39.2 mmHg to 150.5 ± 39.3 mmHg ( p < 0.0001). AngioSculpt may provide a promising option for treating hemodialysis patients with severely advanced vascular access stenosis, who would otherwise need repeated vascular access surgeries and/or conventional percutaneous transluminal angioplasties.

Hydrologic performance of bioretention in an expressway service area.

Bioretention can be an effective measure for stormwater treatment. However, there is a lack of systematic analysis of the impact of bioretention design parameters on hydrologic performance. Herein, SWMM and RECARGA models were applied to generate the typical annual rainfall runoff and simulate the water balance of the bioretention system in an expressway service area. The purpose of the investigation was to identify key design parameters for the bioretention system and delineate the priorities in developing the design. Results showed that the average groundwater recharge ratios for bioretention basins with and without an underdrain were 58.29% and 92.27%, respectively, the average overflow ratios were 4.13% and 4.19%, the average evapotranspiration ratios were 4.48% and 4.47%, and the average outflow ratio for bioretention with an underdrain was 33.94%. The ratio of the bioretention area to drainage area, and the saturated infiltration rates of planting soil and native soil were the main factors influencing water balance, while the underdrain diameter and gravel layer depth exerted little effect. Based on the impact analysis, multivariate nonlinear regression models of runoff reduction rate for two types of bioretention basin were established, which both exhibited high determination coefficients and acceptable Nash-Sutcliffe coefficients.

Factors influencing the sediment delivery ratio of the Three Gorges Reservoir

In recent years, the sediment delivery ratio (SDR) of the Three Gorges reservoir (TGR) has noticeably decreased as a result of the increase in water levels at the dam site and the decrease in inflow of fine particles, thereby resulting in increased reservoir siltation. Therefore, it is vital to research the factors that influence the SDR of the TGR. Factors that could have impact on the SDR were studied using TGR monitoring data. The study indicated that the water level at the dam site and inflow and outflow rates could have contributed to the change in the SDR. A sensitivity analysis of the influencing factors was then carried out using a mathematical model to simulate numerous sediment movement scenarios in the TGR. By changing the input conditions of the model, sufficient results were obtained to enable a sensitivity analysis of each factor. The results showed the flood retention time (FRT)—the ratio of reservoir capacity to average outflow discharge—was the principal factor influencing the SDR. The other factors (inflow sediment concentration, inflow sediment coefficient, inflow sediment gradations, and the shape coefficient of the inflow flood shape coefficient), also had an influence on the SDR. However, under different levels of FRT, their degrees of influence on the SDR were not the same..

Estimating outflow facility through pressure dependent pathways of the human eye.

We develop and test a new theory for pressure dependent outflow from the eye. The theory comprises three main parameters: (i) a constant hydraulic conductivity, (ii) an exponential decay constant and (iii) a no-flow intraocular pressure, from which the total pressure dependent outflow, average outflow facilities and local outflow facilities for the whole eye may be evaluated. We use a new notation to specify precisely the meaning of model parameters and so model outputs. Drawing on a range of published data, we apply the theory to animal eyes, enucleated eyes and in vivo human eyes, and demonstrate how to evaluate model parameters. It is shown that the theory can fit high quality experimental data remarkably well. The new theory predicts that outflow facilities and total pressure dependent outflow for the whole eye are more than twice as large as estimates based on the Goldman equation and fluorometric analysis of anterior aqueous outflow. It appears likely that this discrepancy can be largely explained by pseudofacility and aqueous flow through the retinal pigmented epithelium, while any residual discrepancy may be due to pathological processes in aged eyes. The model predicts that if the hydraulic conductivity is too small, or the exponential decay constant is too large, then intraocular eye pressure may become unstable when subjected to normal circadian changes in aqueous production. The model also predicts relationships between variables that may be helpful when planning future experiments, and the model generates many novel testable hypotheses. With additional research, the analysis described here may find application in the differential diagnosis, prognosis and monitoring of glaucoma.

The change of quantity and quality outflow of water in Ochożanka River basin

AbstractThe aim of this research work is to evaluate changes in the quantities of water and chemical parameters of outflow water from the forest catchment. Research was carried over a hydrological five-year period in the Ochożanka River basin (Western Polesie). The structure of the catchment area of 33.1 km2 is dominated by forestland constituting 81% of the area. During this period the precipitation amounted to 627 mm, which was 100 mm higher than the multi-year average. Precipitation of the summer half-year was almost three times higher than in the winter half-year. Data analysis shows that the average unit outflow from the catchment unit was 3.0 dm3·s−1·km−2. Outflow in the winter half-year was 52% higher than in the summer half-year. The waters of the river are used, they are usually characterized by good chemical status. In case 30% samples concentration of Kjeldahl nitrogen (&gt;2 mg N·dm−3), total phosphorus (&gt;0.4 mg P·dm−3) exceed the limit values for second class quality water. Indicators of oxygen conditions reach medium and high values. In spring, it happens that the limits are exceeded for second class water quality. These values are respectively COD &gt; 20 mg O2·dm−3 and oxygen &lt;5 mg O2·dm−3. An important issue related to the value parameters is the seasonal variability of their concentration in water outflow from the catchment. The maximum value chemical parameters are recorded in March, when the occurred largest outflows water.

ALMA suggests outflows in z ∼ 5.5 galaxies

We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of 9 star-forming ($\rm SFR=31\pm 20~M_{\odot}~yr^{-1}$) $z\sim 5.5$ galaxies for which the [CII]158$\mu$m line has been previously obtained with ALMA. We first fit each line with a Gaussian function and compute the residuals by subtracting the best fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterised by a flux excess of $\sim 0.5$ mJy extended over $\sim 1000$ km~s$^{-1}$. Although we cannot exclude that part of this signal is due to emission from faint satellite galaxies, we show that the most probable explanation for the detected flux excess is the presence of broad wings in the [CII] lines, signatures of starburst-driven outflows. We infer an average outflow rate of $\rm \dot{M}=54\pm23~ M_{\odot}~yr^{-1}$, providing a loading factor $\eta=\rm \dot{M}/SFR=1.7\pm1.3$ in agreement with observed local starbursts. Our interpretation is consistent with outcomes from zoomed hydro-simulations of {\it Dahlia}, a $z\sim 6$ galaxy ($\rm SFR\sim 100~\rm M_{\odot}~yr^{-1}$) whose feedback-regulated star formation results into an outflow rate $\rm \dot{M}\sim 30~ M_{\odot}~yr^{-1}$. The quality of the ALMA data is not sufficient for a detailed analysis of the [CII] line profile in individual galaxies. Nevertheless, our results suggest that starburst-driven outflows are in place in the EoR and provide useful indications for future ALMA campaigns. Deeper observations of the [CII] line in this sample are required to better characterise feedback at high-$z$ and to understand the role of outflows in shaping early galaxy formation.

Removal of selected risk elements from wastewater in a horizontal subsurface flow constructed wetland

AbstractRemoval of Pb, Cd, Cr, Mo, V, Be and Ba from municipal wastewater using a horizontal subsurface flow constructed wetland was studied. The removal efficiencies attained for these elements were 50, 86, 71, 59, −53, 37 and 40%, respectively. The average inflow and outflow Pb concentrations were 1.5 and 0.7 µg/L. Similarly, the inflow and outflow concentrations of 0.14 and 0.02 µg/L were obtained for Cd. Cr inflow and outflow concentrations were 3.7 and 1.1 µg/L, respectively. Concentrations of 0.78 and 0.32 µg/L were measured for Mo. V was washed out from the system. Its average inflow and outflow concentrations were 4.8 and 7.4 µg/L, respectively. Be inflow and outflow concentrations were rather low (1.03 and 0.65 µg/L), however, the concentrations of Ba were significantly higher (189 and 113 µg/L). The main perspective of the constructed wetland is the removal of toxic elements forming insoluble compounds (e.g. CdS) depositing in the wetland bed.

Evaluating sedimentation effect on reservoirs water quality: a case study, Shahriyar reservoir

In this research, total dissolved solids (TDS) was simulated by CE-QUAL-W2 software in two scenarios of with and without sedimentation in normal, dry, and wet periods of inflow for Shahriyar reservoir, an under-construction dam located in Iran. Shahriyar reservoir is a dam with a total capacity of 700 million cubic meters (MCM) and a dead volume of 360 MCM. In case of with sedimentation compared with without sedimentation, results showed an annual average increase of 4, 4.3, and 8.7% in TDS of outflow for normal, wet, and dry periods, respectively. There is no significant change in TDS profile of the reservoir in both conditions. According to the average outflow TDS of 1448, 1301, and 1555 mg/L compared with the average inflow TDS of 1714, 1520, and 1835 in normal, wet, and dry conditions, respectively, the effect of dam on inflow TDS adjustment can be also observed. With the mentioned outflow TDS, there is no limitation to use of reservoir water for agricultural purposes based on FAO irrigation guidelines for both scenarios.

The Role of Impeller Outflow Conditions on the Performance of Vaned Diffusers

Highly loaded impellers, typically used in turbocharger and gas turbine applications, exhaust an unsteady, transonic flow that is nonuniform across the span and pitch and swirling at angles approaching tangential. With the exception of the flow angle, conflicting data exist regarding whether these attributes have substantial influence on the performance of the downstream diffuser. This paper quantifies the relative importance of the flow angle, Mach number, nonuniformity, and unsteadiness on diffuser performance, through diffuser experiments in a compressor stage and in a rotating swirling flow test rig. This is combined with steady and unsteady Reynolds-averaged Navier–Stokes (RANS) computations. The test article is a pressure ratio 5 turbocharger compressor with an airfoil vaned diffuser. The swirling flow rig is able to generate rotor outflow conditions representative of the compressor except for the periodic pitchwise unsteadiness and fits a 0.86 scale diffuser and volute. In both rigs, the time-mean impeller outflow is mapped across a diffuser pitch using miniaturized traversing probes developed for the purpose. Across approximately two-thirds of the stage operating range, diffuser performance is well correlated to the average impeller outflow angle when the metric used is effectiveness, which describes the pressure recovery obtained relative to the maximum possible given the average inflow angle and Mach number and the vane exit metal angle. Utilizing effectiveness captures density changes through the diffuser at higher Mach numbers; a 10% increase in pressure recovery is observed as the inlet Mach number is increased from 0.5 to 1. Further, effectiveness is shown to be largely independent of the time-averaged spanwise and unsteady pitchwise nonuniformity from the rotor; this independence is reflective of the strong mixing processes that occur in the diffuser inlet region. The observed exception is for operating points with high time-averaged vane incidence. Here, it is hypothesized that temporary excursions into high-loss flow regimes cause a nonlinear increase in loss as large unsteady angle variations pass by from the rotor. Given that straight-channel diffuser design charts typically used in preliminary radial vaned diffuser design capture neither streamtube area changes from impeller exit to the diffuser throat nor vane incidence effects, their utility is limited. An alternative approach, utilizing effectiveness and vane leading edge incidence, is proposed.

Intensity contrast of the average supergranule

While the velocity fluctuations of supergranulation dominate the spectrum of solar convection at the solar surface, very little is known about the fluctuations in other physical quantities like temperature or density at supergranulation scale. Using SDO/HMI observations, we characterize the intensity contrast of solar supergranulation at the solar surface. We identify the positions of ${\sim}10^4$ outflow and inflow regions at supergranulation scales, from which we construct average flow maps and co-aligned intensity and magnetic field maps. In the average outflow center, the maximum intensity contrast is $(7.8\pm0.6)\times10^{-4}$ (there is no corresponding feature in the line-of-sight magnetic field). This corresponds to a temperature perturbation of about $1.1\pm0.1$ K, in agreement with previous studies. We discover an east-west anisotropy, with a slightly deeper intensity minimum east of the outflow center. The evolution is asymmetric in time: the intensity excess is larger 8 hours before the reference time (the time of maximum outflow), while it has almost disappeared 8 hours after the reference time. In the average inflow region, the intensity contrast mostly follows the magnetic field distribution, except for an east-west anisotropic component that dominates 8 hours before the reference time. We suggest that the east-west anisotropy in the intensity is related to the wave-like properties of supergranulation.

Diagnosing cross‐shelf transport along an ocean front: An observational case study in the Gulf of Lion

AbstractExchanges between coastal regions and the open ocean are often associated with intermittent and localized processes such as eddies, fronts, and filaments. Since these features are difficult to observe, their impact has been predominantly investigated using numerical models and remote sensing. In this study, satellite sea surface temperature maps, Lagrangian surface drifter trajectories, and ship‐based surveys of currents and hydrography from the Latex10 campaign are used to quantify cross‐shelf exchanges associated with a temperature front in the western Gulf of Lion. Satellite imagery and thermosalinograph sections provide the characterization of the various water masses associated with the front. Lagrangian drifter trajectories are used to identify the main transport structures and to quantify the velocity components associated with near‐inertial oscillations. These are removed from the instantaneous ADCP observations with which the cross‐shelf exchanges are then computed. The results indicate an average outflow of 0.074 ± 0.013 Sv and an inflow of 0.021 ± 0.006 Sv. Integrated over the 2 week lifetime of the front, such outflow induced a total export of ∼90 ± 14 km3 of water, indicating that three to four of such events are sufficient to completely renew the surface waters of the Gulf of Lion. The total import was ∼25 ± 7 km3, suggesting larger inflows at depth or in the eastern part of the gulf to maintain its volume balance. These in situ estimates represent a key term of comparison for the further development of numerical model‐based and satellite‐based studies of cross‐shelf exchanges associated with this type of processes.

Hydrochemical balance of Itkul–Shira lake system (Khakassia, Russian Federation)

The water and hydrochemical balance of Shira and Itkul lakes, located in the arid (steppe) zone in the Republic of Khakassia (Russian Federation), has been calculated. It is shown that Lake Itkul can be considered a drained lake, which significantly determines the basic differences of the hydrochemical balance in the two water bodies. The outflow of water from Itkul to Shira is, on average, 6791000 m3/year, and the average outflow of dissolved salts is 35697 t/year. Lake Shira can be considered a drainless water body with an evaporation mechanism of formation of the chemical composition of its waters, and Lake Itkul is considered a flowing water reservoir. The salt concentration in Itkul is not as high as that in Shira due to the lower influence of evaporation on the formation of the chemical composition of waters and time of their interaction. It has been assumed that this phenomenon is regular, rather than exceptional, for the arid zone of Northern and Central Asia.

Zróżnicowanie przestrzenne i zmienność odpływu w zlewniach fliszowych na obszarze Masywu Babiej Góry

&lt;p&gt;The paper refers to spatial diversity and lability of outflow from Flysh type drainage basins. It also shows dynamics of mean and high discharge by defining the trend, the variability index and the periodicity of the hydrological parameters mentioned. The research has been taken in the partial drainage basins located in the upper drainage basin of Skawica (the streams of Czatożanka, Marków Potok, Rybny Potok, Jaworzyna) and in the upper drainage basin of Czarna Orawa (Kiczorka) at the Babia Góra slopes. The analyzed two-year period (2012–2013) has been characterized comparing to the multiannual period of 1973–2014. The hydrological and meteorological data have been obtained due to monitoring of the hydrological environment of Babiogórski National Park. The database includes the data gained from The Institute of Meteorology and Water Management research. Poland is the one of the less water-rich European countries. The unit outflow is only 5.5 dm3·s-1·km-2 (Fall 1997). The water outflow is very space and time varied through the whole country. The outflow from drainage basins of Babia Góra area is one of the biggest in Poland (about 30 dm3·s-1·km-2). The outflow index (rate of outflow?) from Babia Góra area is 88% per annum, which distinguishes this area from the Beskidy Mountains. During the winter semester the outflow index is 12.7% and during the summer semester it is 70% (Łajczak).&lt;/p&gt;&lt;p&gt;The outflow index and the seasonal lability of the outflow from the particular Babia Góra drainage basins are very varied which is the most noticeable between the northern and southern slopes located drainage basins, however the variety is also very clear to observe from the east to the west direction. The analyzed cycle were a general low-flow period including one thaw flood within this period (2012s) and several minor floods caused by severe rainfalls (2013s). The maximum unit outflow during the flood has been noticed in Czatożanka drainage basin and the minimum unit outflow has been noticed in Kiczorka drainage basin. The highest annual average unit outflow occurred within Marków Potok, and the lowest annual average unit outflow occurred within Czatożanka. The drainage basins located at the northern slopes of Babia Góra were characterized by big seasonal outflow fluctuation between winter and summer semesters. Only at the southern slopes in the Kiczorka drainage basin the outflow was not much varied comparing the particular semesters.&lt;/p&gt;

Screening for Outflow Cannula Malfunction of Left Ventricular Assist Devices (LVADs) With the Use of Doppler Echocardiography: New LVAD-Specific Reference Values for Contemporary Devices

BackgroundEchocardiographic assessment of left ventricular assist devices (LVADs) is used as a screening tool to evaluate the integrity and mechanics of the pump and circuit. We aimed to 1) establish the normal range and upper reference limit of peak velocity of the outflow cannula for the modern era of LVADs and 2) assess the clinical performance of the currently cited and newly proposed reference limits in patients with continuous-flow LVADs as a screening tool for cannula malfunction. MethodsLVAD outflow peak CW velocities were measured with the use of Doppler transthoracic echocardiography (TTE) in 57 patients with LVADs (44 with Heartmate II (HM2), 13 with Heartware (HW)). The average velocity and the upper and lower normal reference limits (defined as ±2 standard deviations from the mean) for each LVAD type was calculated. The upper reference limit was then used as a screening threshold for cannula malfunction. ResultsThe average outflow cannula peak velocity for the normal HM2 cohort was 1.86 ± 0.44 m/s with upper and lower reference limits of 2.73 m/s and 0.98 m/s, respectively. The average outflow cannula peak velocity for the normal HW cohort was 2.36 ± 0.53 m/s with upper and lower reference limits of 3.42 m/s and 1.3 m/s, respectively, which was significantly higher than the HM2 cohort (P = .004). ConclusionsIn both HM2 and HW LVADs, the average peak outflow velocity and reference limit for the normal population, as measured by Doppler TTE, was markedly higher than the currently used LVAD reference limits of 2 m/s and are significantly different between devices. Patients with peak outflow velocities above our upper reference limits should be evaluated for LVAD outflow cannula malfunction.

Supplemental irrigation potential and impact on downstream flow of Karkheh River basin in Iran

Abstract. Supplemental irrigation of rainfed winter crops improves and stabilises crop yield and water productivity. Although yield increases by supplemental irrigation are well established at the field level, its potential extent and impact on water resources at the basin level are less researched. This work presents a Geographic Information Systems (GIS)-based methodology for identifying areas that are potentially suitable for supplemental irrigation and a computer routine for allocating streamflow for supplemental irrigation in different sub-basins. A case study is presented for the 42 908 km2 upper Karkheh River basin (KRB) in Iran, which has 15 840 km2 of rainfed crop areas. Rainfed crop areas within 1 km from the streams, with slope classes 0–5, 0–8, 0–12, and 0–20 %, were assumed to be suitable for supplemental irrigation. Four streamflow conditions (normal, normal with environmental flow requirements, drought and drought with environmental flow) were considered for the allocation of water resources. Thirty-seven percent (5801 km2) of the rainfed croplands had slopes less than 5 %; 61 % (3559 km2) of this land was suitable for supplemental irrigation, but only 22 % (1278 km2) could be served with irrigation in both autumn (75 mm) and spring (100 mm), under normal flow conditions. If irrigation would be allocated to all suitable land with slopes up to 20 %, 2057 km2 could be irrigated. This would reduce the average annual outflow of the upper KRB by 9 %. If environmental flow requirements are considered, a maximum (0–20 % slopes) of 1444 km2 could receive supplemental irrigation. Under drought conditions a maximum of 1013 km2 could be irrigated, while the outflow would again be reduced by 9 %. Thus, the withdrawal of streamflow for supplemental irrigation has relatively little effect on the outflow of the upper KRB. However, if the main policy goal would be to improve rainfed areas throughout the upper KRB, options for storing surface water need to be developed.

Highly variable nutrient concentrations in the Northern Gulf of Mexico

The distribution of surface nutrients along the salinity gradient in the Mississippi-Atchafalaya River outflow region was examined during four cruises, including two simultaneous cruises, conducted in the northern Gulf during the summer of 2010 and 2011, and in late spring of 2012. The new, extensive data set covers the salinity gradient from 11 to 37psu (practical salinity unit) in a year of extraordinarily high river discharge (2011), with few samples from a year of average (2010) and below average (2012) river outflow. The overall surface concentrations of nitrate+nitrite, orthophosphate and silicate are compared to those recorded in cruises spanning the 1985 – 2009 interval. Using Monte Carlo simulations to test the statistical significance, we found that surface orthophosphate and nitrate+nitrite concentrations are approximately three and two fold smaller, respectively, in the 2010–2012 period compared to the previous years. Changes in silicate concentrations were, in most cases, not significant, and their assessment complicated by different measurement techniques and potential preservation artifacts. The weighted river loading of these nutrients was, on the other hand, very high in the latest period when samples mostly covered 2011. The well-known negative correlation between nutrient concentrations and salinity at the ocean surface is confirmed in the most recent data. The area surrounding the Mississippi River mouth is characterized by inorganic N:P ratios greater than 30:1 that decrease to values typically less than 10:1 at about 100km from of the mouth. Overall our analysis suggests that surface nutrient concentrations in the northern Gulf of Mexico cannot be described with any good accuracy by a linear model based on river discharge alone.

Abstract 16514: Screening for Outflow Cannula Malfunction of Left Ventricular Assist Devices Using Doppler Echocardiography: Establishing New Reference Values

Background: Echocardiographic assessment of left ventricular assist devices (LVAD) is used as a screening tool to evaluate the integrity and mechanics of the pump and circuit. We aimed to 1) establish the normal range and upper reference limit of peak velocity of the outflow cannula for the modern era of LVADs and 2) assess the performance of the current reference limit and our new reference limit in patients with continuous flow LVADs as a screening tool for cannula malfunction. Methods: LVAD outflow peak velocities were measured with Doppler echocardiography (TTE) in 57 patients with LVADs (HeartMate II (HMII) = 44, HeartWare (HW) = 13). The average velocity and the upper and lower normal reference limits (defined as +/- two standard deviations from the mean) for each LVAD type was then calculated. The upper reference limit was then used as a screening threshold for cannula malfunction. Results: The average outflow cannula peak velocity for the HMII cohort was 1.94 m/sec +/- 0.42 with an upper and lower reference limit of 2.78 m/sec and 1.10 m/sec, respectively. The average outflow cannula peak velocity for the HW cohort was 2.36 +/- 0.53 with an upper and lower reference limit of 3.42 m/sec and 1.3 m/sec, respectively, which was significantly higher than the HMII cohort (p=0.004). Velocities from both cohorts were dramatically higher than the commonly citied upper reference limit velocities of 2 m/sec. Use of the previously cited reference limit poorly discriminated between normal and malfunctioning LVAD cannulas whereas our new reference limit identified all four patients with outlet cannula malfunction (Figure1). Conclusions: In both HeartMate II and HeartWare LVADs, the average peak outflow velocity and reference limit for the normal population as measured by Doppler-TTE was markedly higher than currently cited LVAD reference limits. Patients with peak outflow velocities above our upper reference limit should be evaluated for LVAD outflow cannula malfunction.