Drainage Discharge Research Articles

Vulnerability Assessment for Sea Level Rise Impacts on Coastal Systems of Gamasa Ras El Bar Area, Nile Delta, Egypt

The objective of the current study was to assess the vulnerability of coastal systems to sea level rise (SLR) impacts in the Gamasa Ras El Bar area, which is one of the most vulnerable coastal areas in the Nile delta, Egypt. To achieve the study objective, a field campaign was carried out to investigate, measure and collect data. These data, as well as historical data, were analyzed to identify projected inundation areas, erosion and accretion rates, shoreline changes, wave climate and saltwater intrusion, as well as drainage infrastructure efficiency. The results of a 73-cm SLR, projected up to the end of current century in the study area, indicate the following. Inundation areas will be about 2.16% of the study area. Although the significant wave height increased by 3.1 cm per year from 1999 to 2010, the results are indicative and might be taken into consideration in future coastal management plans. The expected variation in groundwater heads due to sea level rise will lead to an increase in groundwater heads ranging from 0 to 0.5 m above the current level. The change expected in groundwater will lead to saltwater intrusion by 1 km landward. The analysis of our results showed that about 271 km2 (60%) of the area under study will be negatively affected by rising groundwater. This area is occupied by about 70% of the localities in the study area. The analysis of the projected groundwater level rise showed that it will increase the discharges of the sub-drainage system by about 10% of the current rates and less than 1.2% for the open system. It is concluded that the drainage system has the sub-capacity to host the expected increase in drainage discharges without any modifications of the cross-sectional area of most of the drains. In addition, the coastal groundwater aquifer was found to be the most vulnerable system in the study area.

The importance of the hydrological pathways in exporting nitrogen from grazed artificially drained land

When considering hydrological export pathways from drained pastoral fields, the shallow groundwater underlying the artificial drainage system may fulfil an as important role as the artificial drainage system itself. However, the important split between artificial drainage and groundwater flows at a field site is usually unknown. Consequently, the effects that the groundwater system’s redox status may have on the forms and total amounts of nitrogen (N) exported from the site cannot be confidently assessed. We addressed these deficiencies by investigating the export of various forms of N in the artificial drainage and the shallow groundwater beneath two dairy farming sites (Tatuanui, Waharoa) within the Piako River catchment in New Zealand.Due to the very low hydraulic conductivity of the degraded peat in the saturated zone perched on a clay aquiclude, no significant water or contaminants were exported at Tatuanui via the unconfined shallow groundwater. Accordingly, artificial drainage discharge into the receiving surface collector drain was the only export pathway for N at this site. The sealed nature of the groundwater zone resulted in the accumulation of organic-N and ammonium-N in the peaty shallow saturated zone underlying the mineral soil. In contrast, the Waharoa site featured a more mobile shallow groundwater system, which on average conveyed approximately equal volumes of water offsite as the artificial drainage system.Nitrate (NO3-N) was at both sites the predominant form of N (76%) leached from the aerobic soil profile and discharged through the artificial drainage. As the shallow groundwater was at both sites in a reduced redox state, any NO3-N leached from the rootzone into the saturated zone was consumed. Accordingly, even the mobile shallow groundwater at Waharoa did not convey significant NO3-N. The NO3-N consumption in the reduced groundwater presumably occurred due to dissimilatory NO3-N reduction (concomitant increases in ammonium-N concentrations, with no organic material available for mineralisation in the saturated zone) and microbial denitrification (producing gaseous forms of N). The NO3-N reductions in the groundwater resulted in the average total N exports via the shallow groundwater pathway at the Waharoa site being substantially lower (31% of the exported N) than in the artificial drainage (69%). This is despite both pathways exporting similar water volumes. Because of the NO3-N consumption in the reduced shallow groundwater at Waharoa, over 98% of the N exported through this pathway was either as ammonium-N or organic-N.

Development of fuzzy analytic hierarchy process based water quality model of Upper Ganga river basin, India

The ecological sustainability of rivers is in question due to severe pollution and lack of stringent regulations. Long term (1990–2016) water quality data of five stations namely Haridwar, Bareilly, Kanpur, Prayagraj and Varanasi of Upper Ganga river, India was considered for analysis using fuzzy analytical process (FAHP) based water quality index (WQI) to assess surface water quality. The value of water physical, biological and chemical parameters of temporal resolution (monthly, seasonal and yearly) indicate that value of electrical conductivity (EC), total dissolved solids (TDS), biological oxygen demand (BOD), chemical oxygen demand (COD), total alkalinity (Mg CaCO3), total hardness (Mg CaCO3), calcium (Ca), magnesium (Mg), sodium (Na), chlorine (Cl) and bicarbonate (HCO3) were observed very high compared to recommended value of Bureau of Indian Standards (BIS) and World Health Organization (WHO) at Kanpur, Prayagraj and Varanasi stations. However, low value of parameters is observed at Haridwar and Bareilly stations. Also, the high deviation was observed in water quality parameters during 1990–2010 whereas the deviation of parameters is decreased in 2011–2016. It is observed from the piper diagram that magnesium and bicarbonate at Haridwar, sodium, potassium and bicarbonate in Bareilly, Kanpur, Prayagraj and Varanasi stations are dominant during monthly and seasonal periods. The fuzzy based WQI value indicate that water quality is excellent to poor at Haridwar, while poor to unsuitable in Bareilly, Kanpur, Prayagraj and Varanasi during monthly and seasonal periods. The water quality ranges from poor to unsuitable during the 1990–2010 period and good to very poor during the 2011–2016 period at Bareilly, Kanpur, Prayagraj and Varanasi stations. Whereas very good to good during 1990–2010 and excellent to good during 2011–2016 at Haridwar. It was also determined that water quality parameters (Ca, Na+K, SO4, Hardness, Cl and Mg) and WQI values were increased with length of the stream. It indicates that drain discharge, urban growth, urban functions, ecological footprints and crop area increment were key sources of pollution.

Limited carbon sources prevent sulfate remediation in circumneutral abandoned mine drainage.

Passive remediation systems (PRS) use both biotic and abiotic processes to precipitate contaminants from abandoned mine drainage (AMD) so that the contaminants do not spread into local watersheds. PRS are efficient at removing heavy metals but sulfate remediation frequently does not occur. To understand the reasons for the lack of sulfate remediation, we studied four PRS that treat circumneutral AMD and one raw mine drainage discharge. Using 16S sequencing analysis, microbial community composition revealed a high relative abundance of bacterial families with sulfur cycling genera. Anaerobic abiotic studies showed that sulfide was quickly geochemically oxidized in the presence of iron hydroxides, leading to a buildup of sulfur intermediates. Supplementation of laboratory grown microbes from the PRS with lactate demonstrated the ability of actively growing microbes to overcome this abiotic sulfide oxidation by increasing the rate of sulfate reduction. Thus, the lack of carbon sources in the PRS contributes to the lack of sulfate remediation. Bacterial community analysis of 16S rRNA gene revealed that while the microbial communities in different parts of the PRS were phylogenetically distinct, the contaminated environments selected for communities that shared similar metabolic capabilities.

An Empirical V-notch Weir Equation and Standard Procedure to Accurately Estimate Drainage Discharge

HighlightsAn empirical flow equation was developed for a metal-edge sharp-crest V-notch weir.A top-down approach was used to determine the height of the V-notch apex.A combination of the weighing method and a flow meter was used to develop the stage-discharge equation.A standard procedure was presented to accurately estimate the flow rate.Abstract. A reliable empirical flow equation for V-notch weirs will provide flow estimates that can be used to calculate nutrient loads leaving fields with subsurface drainage. The objective of this study was to develop such an equation for an AgriDrain metal-edge sharp-crest 45° V-notch weir. In this undertaking, we measured flow rate with a combination of the weighing method for low flow and a turbine flow meter for high flow. The head of water (H) was measured inside a 25-cm AgriDrain control structure with a three-step method. First, we measured the water level (a) and height of the control structure (b). Second, we measured the height of the V-notch apex (c). Third, we calculated head using this equation: H= (b-a) – (b-c). Based on the flow meter readings (Q) and H measurements, we developed the following stage-discharge equation: Q = 0.749H 2.25, with Q in liters per minute and H in centimeters. This equation is valid for an H less than the height of the V-notch (i.e., flow through the V-notch) with unsubmerged flow. Based on field experience, we provide a standard procedure for accurate estimation of drainage discharge. In conclusion, the stage-discharge equation developed in this study can provide reliable flow estimates for subsurface drainage studies. Keywords: Flow rate, Metal-edge weir, Sharp-crest weir, Subsurface drainage, Tile drainage, Weir placement.

Effectiveness of Nutrient Management on Water Quality Improvement: A Synthesis on Nitrate-Nitrogen Loss from Subsurface Drainage.

Nutrient management, as described in NRCS Code 590, has been intensively investigated, with research largely focused on crop yields and water quality. Yet, due to complex processes and mechanisms in nutrient cycling (especially the nitrogen (N) cycle), there are many challenges in evaluating the effectiveness of nutrient management practices across site conditions. We therefore synthesized data from peer-reviewed publications on subsurface-drained agricultural fields in the Midwest U.S. with corn yield and drainage nitrate-N (NO3-N) export data published from 1980 to 2019. Through literature screening and data extraction from 43 publications, we obtained 577 site-years of data with detailed information on fertilization, corn yields, precipitation, drainage volume, and drainage NO3-N load/concentration or both. In addition, we estimated flow-weighted NO3-N concentrations ([NO3-N]) in drainage for those site-years where only load and volume were reported. Furthermore, we conducted a cost analysis using synthesized and surveyed corn yield data to evaluate the cost-effectiveness of different nutrient management plans. Results from the synthesis showed that N fertilizer rate was strongly positively correlated with corn yields, NO3-N loads, and flow-weighted [NO3-N]. Reducing N fertilizer rates can effectively mitigate NO3-N losses from agricultural fields; however, our cost analysis showed negative economic returns for continuous corn production at lower N rates. In addition, organic fertilizers significantly boosted corn yields and NO3-N losses compared to inorganic fertilizers at comparable rates; however, accurate quantification of plant-available N in organic fertilizers is necessary to guide appropriate nutrient management plans because the nutrient content may be highly variable. In terms of fertilizer application methods, we did not find significant differences in NO3-N export in drainage discharge. Lastly, impact of fertilization timing on NO3-N export varied depending on other factors such as fertilizer rate, source, and weather. According to these results, we suggest that further efforts are still required to produce effective local nutrient management plans. Furthermore, government agencies such as USDA-NRCS need to work with other agencies such as USEPA to address the potential economic losses due to implementation of lower fertilizer rates for water quality improvement.

DRAINMOD-P: A Model for Simulating Phosphorus Dynamics and Transport in Drained Agricultural Lands: II. Model Testing

HighlightsDRAINMOD-P was tested using a dataset from a drained field with desiccation cracks.Surface and subsurface phosphorus losses were mainly in the particulate form.Surface runoff was a major pathway for phosphorus loss in this field.The model performance in predicting edge-of-field phosphorus loss is promising.Abstract. The recently developed phosphorus (P) model DRAINMOD-P was tested using a four-year dataset from a subsurface-drained field in northwest Ohio with significant potential for desiccation cracking or preferential flow. The model satisfactorily predicted subsurface drainage discharge, with a monthly Nash-Sutcliffe efficiency (NSE) of 0.59 and index of agreement (IOA) of 0.89. Lack of annual water budget closure was reported and was likely caused by uncertainty in measured surface runoff and/or modeling approaches representing macropore flow. More than 80% of predicted surface and subsurface P losses were in the particulate form. Surface runoff was the major pathway for P loss, contributing 78% of predicted total P (TP) load. On average, predicted macropore flow represented about 15% of drainage discharge and contributed 21% of DRP loss via subsurface drains. The performance of DRAINMOD-P in predicting monthly dissolved reactive P and TP losses through subsurface drains can be rated as poor (NSE = 0.33 and IOA = 0.60) and very good (NSE = 0.81 and IOA = 0.95), respectively. DRAINMOD-P demonstrated potential for simulating P fate and transport in drained cropland. More testing is needed to further examine newly incorporated hydrological and biogeochemical components of the model. Keywords: Agricultural drainage, Edge-of-field phosphorus load, Macropore flow, Phosphorus model, Sediment yield, Water quality modeling.

Outcome of Post Cholecystectomy Bile Duct Injury Management in a High Volume Referral Center in Iran

Introduction: However more than a century pass from first cholecystectomy and iatrogenic bile duct injury, still this is a big problem, here we report our experience in a high volume referral center in Iran about handling of this complication. Methods: We collect data of 59 patient who referred us , suspected to post-cholecystectomy bile duct injury for 3 years since may 2016 both retrospectively through review of charts and calling them and prospectively by regular out-patient visit. Results: In this period 59 patients with age range of 20 to 74y/o referred our center, 15 male and 44 female. 21 patients underwent definite repair in 2 weeks from injury,17 patient after 2 weeks and before 6 weeks and 21 patients after 6 weeks. The most common presenting feature was bilious drain discharge, MRCP and ERCP was falsely negateive in 23.07% and 11.53% repsctively and the most reliable point was primary surgeon think of “something is wrong during surgery”.17% of patients had failed repair in original hospital and 33.9% had exploration ,irrigation and drainage.laboratory abnormality just in 66% of patients detected, most injuries was in Bismuth classII(18%),III(16%)and IV(16%),and Rt hepatic artery injury detected in 27(45.8%)patients.hepatectomy did in two patients and two patients died. No significant deference found when interval from injury to definite surgery compared between groups. Conclusion: Best decision for patients suspected to bile duct injury is referring to a high volume center at any time before exploration and with any interval from injury, HPB surgeon can go for repair.

Surgical Advantage of Ultrasonically Activated Devices During Axillary Lymph Node Dissection for Breast Cancer

Purposes Axillary dissection is the gold standard for axillary lymph node metastasis in breast cancer patients. We compared surgical outcomes between ultrasonically activated devices (USADs) and thermal scalpel (TS) during axillary lymph node dissection in breast cancer patients. Methods We conducted a retrospective analysis for 73 patients using TS between June 2012 to May 2016 and 63 patients using USADs between June 2016 to January 2019 in the breast cancer patients who received axillary dissection. Surgical outcomes were compared among the groups statistically. Results Median operative time in the USAD group was significantly shorter than in the TS group (136 versus 182 minutes, P < 0.001). Intraoperative blood loss in the USAD group was also significantly lower than in the TS group (35 versus 120 mL, P < 0.001). Furthermore, the total drainage discharge in the USAD group was also significantly lower than in the TS group (570 versus 700 mL, P = 0.016). The lymphedema frequency in the USAD group was significantly less than in the TS groups (1 of 63 versus 7 of 73, P = 0.0296). Conclusion The USADs could improve surgical outcomes, such as lymphedema, for axillary dissection of the breast cancer surgery compared with TS.

Effectiveness of Conservation Crop Rotation for Water Pollutant Reduction from Agricultural Areas.

Legumes included in corn-based crop rotation systems provide a variety of benefits to the subsequent crops and potentially to the environment. This review aims to synthesize available data from the literature on legume N credits and the effects of crop rotations on water quality, as well as to analyze the cost benefits associated with different legume-corn rotation systems. We found that there was much variation in reported values for legume N credits to subsequent corn crops, from both empirical results and recommendations made by U.S. land grant universities. But despite inherent complexity, accounting for this contribution is critical when estimating optimal N fertilizer application rates as part of nutrient management. Results from research on the influence of crop rotations on water quality show that including legumes in corn-based rotation systems generally decreases nitrate-N concentrations in subsurface drainage discharge. Our cost analysis showed that incorporating legumes in cropping systems reduced N fertilizer and pesticide costs compared to conventional cropping systems, i.e., continuous corn and corn-soybean rotations, but extended rotations, such as corn-soybean-alfalfa-alfalfa-alfalfa, are not as profitable as conventional systems in the U.S. Midwest. In comparing continuous corn and corn-soybean rotations, although their impacts on water quality are not significantly different when using overall means from the literature data, corn-soybean rotations are more profitable than continuous corn. When using data from papers that directly compared the two, we found that switching from continuous corn to corn-soybean can provide a benefit of $5 per kg N loss reduction. The cost analysis methods used could be tailored to any location or management scenario with appropriate inputs and serve as a useful tool for assessing cost benefits for other agricultural conservation practices. Legume-corn crop rotations have the potential to be an effective conservation practice with the ultimate goal of improving water quality, and, with further research, these rotations could be made even more effective by integrating them into a multi-practice system.

Influence of different controlled drainage strategies on the water and salt environment of ditch wetland: A model-based study

Ditch wetlands reduce agricultural nonpoint source pollution and protect the water environment in drainage areas. One effective management option is controlled drainage. However, for ditch wetlands receiving salt-laden drainage water in arid or semi-arid irrigation areas, controlled drainage may lead to eventual build up of salinity to critical levels that are detrimental to the ecological services and agricultural production of wetland systems. In order to evaluate the positive and negative impacts of agricultural practice of using controlled drainage to manage ditch wetlands water quality in arid or semi-arid irrigation area, based on the principle of water-salt balance we constructed an analysis model. A ditch wetland as a case example in semi-arid irrigation area was then used to display model predictions of salinity variations over time under different watertable control depths. The ditch wetland area to farmland area ratio is 0.091, and the input sources of water and salt are not unique. The results showed that the model established by considering various inflows and outflows has higher simulation accuracy. The water stored in the wetland is key to affecting the salt concentration of the wetland, and the amount of water can be regulated by controlled drainage. Controlled drainage changes the hydrological process of farmland and ditch wetlands, reduces drainage output and damage by high concentrations of salt. But this management measure also increases the risk of medium salt concentrations that may cause an increase in salt output. Considering agricultural production and environmental protection of ditch wetlands, the drainage water table controlled at 1.2 m is a suitable drainage management measure in this irrigation area. The results provide the underlying insights needed to guide the design of drainage management practices in ditch wetlands that receive drainage discharge in semi-arid regions that can be sustained to the maximum benefit of the agricultural system and the environment.

A New Approach to Analyse the Consolidation of Soft Soils Improved by Vertical Drains and Submitted to Progressive Loading

Prefabricated vertical drains combined with preloading and staged construction is a frequently used technique to accelerate consolidation in soft soils. Nevertheless, an installed vertical drain discharge capacity rapidly reduces over consolidation. Most reasons are the lateral confining pressure, the drain deformation and filter clogging. This greatly affects the rate of consolidation by increasing well resistance. This article presents an exact solution under equal-strain consolidation case of progressive loading. Total vertical stress increase caused by loading is principally modelled as a linear curve depending on time and depth. The discharge capacity of the drain is supposed to lower linearly with depth and inversely with time. The smear effect is also considered by assuming constant permeabilities of the soil in both smear zone and undisturbed zone. Excess pore-water pressure at any arbitrary point in soil is assessed, and the global average degree of consolidation is found. Comparisons are made with an available solution from the literature. The suggested solution is then applied to three pre-loading embankments of the Moroccan high-speed railway project. A good agreement is found between the solution and measured data from field monitoring.

Improvement of the Water Erosion Prediction Project (WEPP) model for quantifying field scale subsurface drainage discharge

In the poorly drained regions of the world, subsurface drainage systems are required to remove excess water for crop growth. Plastic drains alter a field’s hydrology by lowering the water table, reducing surface ponding, and reducing surface runoff. One significant concern with the use of subsurface drainage systems is adverse environmental effects because of the modification of the soil water dynamics. Some effects include the reduction of ecological services since wetlands change to croplands, water quality concerns, particularly sediment, nitrogen, and phosphorus losses in agricultural subsurface discharge water, as well as changes in the volume and timing of off-site discharges. Hydrological simulation models predict surface and artificial subsurface flow at different scales. Often in these models, Hooghoudt-based expressions are adapted in their internal algorithms. In this study, the Water Erosion Prediction Project (WEPP) model, developed by the United States Department of Agriculture - Agricultural Research Service (USDA-ARS) for soil and water conservation planning activities, was tested and improved to simulate surface and subsurface discharges. The modified WEPP model was tested and validated on an extensive dataset collected at four experimental sites managed by USDA-ARS within the Lake Erie Watershed. Predicted drainage discharges show Nash-Sutcliffe Efficiency (NSE) values ranging from 0.50 to 0.70, and Percent Bias ranging from −30% to +15% at daily and monthly resolutions. Evidence suggests that the WEPP model can be used to produce reliable estimates of subsurface flow with minimum calibration. Future work includes the extension of the model for quantifying subsurface drainage under controlled water table and watershed-scale simulations.

Adsorption Media for the Removal of Soluble Phosphorus from Subsurface Drainage Water.

Phosphorus (P) is a valuable, nonrenewable resource in agriculture promoting crop growth. P losses through surface runoff and subsurface drainage discharge beneath the root zone is a loss of investment. P entering surface water contributes to eutrophication of freshwater environments, impacting tourism, human health, environmental safety, and property values. Soluble P (SP) from subsurface drainage is nearly all bioavailable and is a significant contributor to freshwater eutrophication. The research objective was to select phosphorus sorbing media (PSM) best suited for removing SP from subsurface drainage discharge. From the preliminary research and literature, PSM with this potential were steel furnace slag (SFS) and a nano-engineered media (NEM). The PSM were evaluated using typical subsurface drainage P concentrations in column experiments, then with an economic analysis for a study site in Michigan. Both the SFS and generalized NEM (GNEM) removed soluble reactive phosphorus from 0.50 to below 0.05 mg/L in laboratory column experiments. The most cost-effective option from the study site was the use of the SFS, then disposing it each year, costing $906/hectare/year for the case study. GNEM that was regenerated onsite had a very similar cost. The most expensive option was the use of GNEM to remove P, including regeneration at the manufacturer, costing $1641/hectare/year. This study suggests that both SFS and NEM are both suited for treating drainage discharge. The use of SFS was more economical for the study site, but each site needs to be individually considered.

Using bioanalytical tools to detect and track organic micropollutants in the Ganga River near two major cities

Major rivers in India are subject to ongoing impacts from urban drain discharges, most of which contain high levels of domestic and industrial wastewater and stormwater. The aim of the present study was to determine the levels of bioactive organic micropollutants at the discharge points of major urban drains in comparison to upstream and downstream sites. To achieve this, we employed a panel of in vitro bioanalytical tools to quantify estrogenic, androgenic, progestogenic, glucocorticoid and peroxisome proliferator-like activity in water extracts collected from two Indian cities in the Ganga Basin. Cytotoxicity of the water extracts in a human-derived cell line and the potential to cause oxidative stress in a fish cell line were also investigated. We found high levels of activity for all endpoints in samples directly receiving urban drain discharge and low levels at sites upstream from drain discharges. Estrogenicity was detected at levels equivalent to 10 ng/L 17β-estradiol, representing a high likelihood of biomarker effects in fish. Sites located downstream from drain discharges exhibited low to intermediate activity in all assays. This study demonstrates the importance of managing urban drain discharges and the utility of applying bioanalytical tools to assess water quality.

Analysis of risk factors for anastomotic leakage after lower rectal Cancer resection, including drain type: a retrospective single-center study

BackgroundWe investigated the correlations between surgery-related factors and the incidence of anastomotic leakage after low anterior resection (LAR) for lower rectal cancer.MethodsA total of 630 patients underwent colorectal surgery between 2011 and 2014 in our department. Of these, 97 patients (15%) underwent LAR and were enrolled in this retrospective study. Temporary ileostomy was performed in each patient.ResultsAnastomotic leakage occurred in 21 patients (21.7%). Univariate analysis showed a significant association between operative duration (p = 0.005), transanal hand-sewn anastomosis (p = 0.014), and operation procedure (p = 0.019) and the occurrence of leakage. Multivariate regression reanalysis showed that underlying disease (p = 0.044), transanal hand-sewn anastomosis (p = 0.019) and drain type (p = 0.025) were significantly associated with the occurrence of leakage. The propensity-score analysis showed that closed drainage were 6.3 times more likely to have anastomotic leakage than open drainage in relation to the amount of postoperative drainage (ml), according to the inverse probability of treatment-weighted analysis.ConclusionsOur results indicate that underlying disease, transanal hand-sewn anastomosis, and closed drain may be a risk and predictive factors for anastomotic leakage after LAR for lower rectal cancer. The notable finding was that closed drainage was related to the occurrence of anastomotic leakage and closed drainage was correlated with less volume of postoperative drain discharge than open drain.

Active Gate Drive With Gate–Drain Discharge Compensation for Voltage Balancing in Series-Connected SiC MOSFETs

Imbalanced voltage sharing during the turn-off transient is a challenge for series-connected silicon carbide (SiC) MOSFET application. This article first discusses the influence of the gate-drain discharge deviation on the voltage imbalance ratio, and its primary causes are also presented and verified by LTspice simulation. Accordingly, a novel active gate drive, which aims to compensate the discharge difference between devices connected in series, is proposed and analyzed. By only using the original output of the driving IC, the proposed gate drive is realized by implementing an auxiliary circuit on the existing commercial gate drive. Therefore, unlike other active gate drives for balancing control, no extra isolations for power/signal are needed, and the number of the devices in series is unlimited. The auxiliary circuit includes three subcircuits as a high-bandwidth current sink for regulating switching performance, a relative low-frequency but reliable sampling and control circuit for closed-loop control, and a trigger combining the former and the latter. The operational principle and the design guideline for each part are presented in detail. Experimental results validate the performance of the proposed gate drive and its voltage balancing control algorithm.

Exploring the effectiveness of drainage water management on water budgets and nitrate loss using three evaluation approaches

Subsurface (tile) drainage is a necessary practice for economic crop production in humid, poorly drained regions of the world. Drainage water management (DWM), also known as controlled drainage, is among the suite of practices designed to mitigate water quality issues associated with subsurface drainage. Studies evaluating DWM generally include field experiments or simulation models to estimate water quality impacts. Combining field studies with model simulations can provide a more comprehensive assessment. Furthermore, using multiple approaches can provide a range of effectiveness rather than a single estimate, which can help define the uncertainty associated with DWM effectiveness. The goal of this study was to demonstrate the variability in estimated DWM effectiveness using 10 years of measured data and a calibrated hydrologic model. The study field, located in central Ohio, was under a free drainage (FD) mode from 2005 through 2008, and under DWM from 2009 through 2014. We used three approaches to compare discharge and nitrate concentrations and loads: before-and-after, paired-field, and DRAINMOD-NII simulated scenarios. Based on the three evaluation approaches, DWM increased surface runoff by 50% (∼13 mm), reduced annual drainage discharge between 8 and 23% (∼19 to 69 mm), annual mean NO3-N concentrations between −1 and 2.5%, and NO3-N loads between 9 and 25% (∼2.8 to 10.3 kg ha−1 yr−1). DWM also reduced the frequency of drainage discharge, and increased magnitudes of surface runoff, evapotranspiration, and seepage losses. The true magnitude of DWM effectiveness remains somewhat uncertain, especially in fields prone to seepage and runoff losses. However, using a combined assessment approach can help address the uncertainty associated with estimated DWM effectiveness at watershed and regional scales.

Experimental Investigation on Mechanical Characteristics of Waterproof System for Near-Sea Tunnel: A Case Study of the Gongbei Tunnel

The water around thenear-sea tunnels is supplied infinitely, and mechanical characteristics of the lining and movement joint are inevitably affected by waterproof methods. The research on the mechanical characteristics of the waterproof system is immature. As a case study of the Gongbei tunnel, a scale model was established in this study, and the stratum, pipe curtain, grouting circle, lining, waterproof board, and movement joint were simulated based on the similarity theories. By changing the externally applied water pressure and drainage discharge, the variation and distribution of the water pressure and strain on the lining with the fully wrapped waterproof (FWW) method, the lining with the partially wrapped waterproof (PWW) method, and the movement joint were investigated. Furthermore, several suggestions on the selection of the waterproof method were presented. The results indicate that the PWW method can reduce the water pressure and strain on the lining under the drained state. Under the state of free drainage, the strain on the lining with the PWW method may get a discount of about 30%. More attention could be paid to the waterproof of the movement joints in the construction process, especially the invert. The research results may offer some valuable insights into the waterproof design of similar near-sea tunnels.

Investigation and Assessment of Polycyclic Aromatic Hydrocarbons Concentrations in Sediments at Drainage Discharge Points into the Mangrove Stretch of New Calabar River, Port Harcourt, Nigeria

Sediment samples were collected from surface of sediments from parts of the mangrove wetlands of the New Calabar River at points of effluents discharge. The samples were treated according to standard procedures and analyzed for the concentrations of polycyclic aromatic hydrocarbons (PAHs). The results showed the presence of ten PAHs at Iwofe Jetty and Police Post stations and eleven PAHs at the Minipiti station. The summation of the total PAHs in the stations showed 23.440, 33.694 and 51.094 mg/Kg in sediments from Iwofe Jetty, Minipiti and Police Post stations respectively. Pyrene was the most abundant PAH in sediment from Iwofe station, Dibenzo (a,h) anthracene was the most abundant PAH at the Minipiti Station and acenaphthylene was the most abundant PAH at the Police Post Station. The categorization of the PAHs classes showed that the high molecular weight PAHs (HMW PAHS) were more abundant than the low molecular weight (PAHs) in all the stations examined, although, at the Police Post station, the values were very close. The 4-membered rings were more abundant in sediments from Iwofe Jetty station. The 4 and 5-membered rings were more abundant at the Minipiti station and the 2-3 membered rings were dominant at the police Post station. The 6-membered rings were the least abundant or undetected in all the stations. Source and origin diagnosis showed that LMW/ HMW PAHs as pyrogenic in all the stations, An/(An+Phe) ratio revealed pyrogenic sources of PAHs, Fl/(Fl+Pyr) analysis in all the stations indicated petrogenic origin of PAHs, BaA/ (BaA+Chr) evaluation in all the stations revealed pyrogenic sources of PAHs. The mixed sources of PAHs in the wetlands drainage discharge points calls for concern and therefore, efforts should be geared to identify the points at which they were introduced into the effluents and be adequately controlled to prevent harm to the environment.