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Poor water resource management is a major cause of water loss and exacerbates water shortages. In order to avoid some misconceptions and misunderstandings associated with irrigation efficiency, the term real water savings (RWS) has been introduced in contrast to apparent water savings (AWS). In this study, irrigation technology interventions were evaluated in terms of return flow and water saving in the Qazvin Plain irrigation network in Iran. This was accomplished using the REWAS tool developed by FAO to evaluate the effects of technological and management interventions on the RWS at the macro level (network, basin, etc.). According to the results, switching the irrigation system from furrow to center pivot with height-regulated sprinklers (Scenario A), center pivot with height-fixed sprinklers (Scenario B), linear-move irrigation system (Scenario C), and solid-set sprinkler irrigation (Scenario D), results in RWS of 390, 383, 326, and 331 mm, respectively. In turn, as a result of applying scenarios A, B, C, and D, the AWSs at the field scale were determined to be 90%, 88%, 75%, and 76%, respectively, while the RWS at the irrigation network scale was determined to be 19%, 19%, 17%, and 18%, respectively. Due to the influence of nonrecoverable return flows, the RWS is much lower than expected. In conclusion, the RWS can only be increased by preventing nonrecoverable return flows. The assessment of RWS can assist decision-makers in choosing sustainable interventions to improve agricultural water productivity by providing insight into field flows, irrigation networks, and basin scales. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Naturalium Universitatis Pekinensis is the property of Editorial Office of Acta Scientiarum Naturalium Universitatis Pekinensis and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In response to the incident of tourists falling into the sea due to waves on the seawall berm at Macau Road, Qingdao, during the passage of Typhoon "Songda" in 2022, a combination of numerical simulations and physical model experiments was performed to investigate the mechanics of the event, with emphasis on the wave flow characteristics and the flow evolution process on the seawall berm as well as the force exerted on a human body-equivalent cylinder model. The study found that the thickness of the return flow was significantly greater than that of the overtopping flow on the landward part of the berm. The recoil forces applied to the model on the berm were larger than the impact forces, and the ratio tended towards 1 as the wave height increased. In addition, the stability of pedestrians on the seawall berm was analyzed. The instability conditions for pedestrians in cross-wave flows differed slightly from those in floods. [ABSTRACT FROM AUTHOR]

The term "sea effect" generally refers to the process of air mass modification after cold air flows above a warm sea surface. Affected by the sea effect, small-scale and sudden fogs have occasionally been observed on the western coast of the Bohai Sea. A more in-depth study of this type of fog is crucial for ensuring the safety of maritime and aerial traffic routes in this region. This study investigated the formation mechanism of this specific type of fog on the morning of 17 October 2007, utilizing both meteorological stations and 255 m tower observations, combined with the results of the Weather Research and Forecasting model (WRF). It is demonstrated that Bohai Sea evaporation and the associated water vapor advection played crucial roles in the formation of fog along the west coast of the Bohai Sea. The cold return flow became more moist as it passed over the warm Bohai Sea, which was the primary contributor to triggering regional fog on the western coast. A moisture budget analysis revealed that water vapor from the Bohai Sea intruded into its western coast along an eastward trajectory, dominating the oscillations in the net moisture flux. The eastern water vapor flux significantly increased at 17:00 on the 16th (Local time, LST), reaching its peak at 21:00. Correspondingly, the fog water growth rate began to increase at 23:00 on the 16th, reaching its maximum at 03:00 on the 17th. A sensitivity experiment on evaporation further indicated that the Bohai sea effect played a decisive role in fog formation. With a tenfold reduction in evaporation from the Bohai Sea and subsequent significant weakening of water vapor advection, the simulated fog along the western coast of the Bohai Sea completely disappeared. Understanding the formation mechanism of this type of fog is beneficial for refining forecasting focal points, thereby enhancing forecast accuracy in a targeted manner. [ABSTRACT FROM AUTHOR]

Various program codes for the investigation of a viscous turbulent compressible gas flow around complicated configurations are described. A series of test calculations for a tandem of 3D back-forcing and forward-forcing steps are performed. The purpose of the calculations is to analyze the resolution accuracy of the separation zones using classical and modern methods. To achieve the goal, the physical features of the flow are described and the results obtained using different codes in the back-forcing and forward-forcing steps tandem test case are compared. [ABSTRACT FROM AUTHOR]

Inventorying nutrient and trace element sources in the Sacramento-San Joaquin Delta (the Delta) is critical to understanding how changes—including alterations to point source inputs such as upgrades to the Sacramento Regional Wastewater Treatment Plant (SRWTP) and landscape-scale changes related to wetland restoration—may alter the Delta’s water quality. While island drains are a ubiquitous feature of the Delta, limited data exist to evaluate island drainage mass fluxes in this system. To better constrain inputs from island drains, we measured monthly discharge along with nutrient and trace element concentrations in island drainage on three Delta islands and surrounding rivers from June 2017 to September 2018. These data were used to calculate island-level fluxes and then upscaled to estimate Delta-wide contributions from island drains. Based on these results, we present (1) new estimates of gross and net nutrient and trace element fluxes from Delta island drains, and (2) concomitant N stable isotope data to improve our understanding of island N cycling. Over 60% of nearly all island drainage gross nutrient and trace element loads occurred in winter and spring. Upscaled island drainage net annual total nitrogen (TN), total dissolved nitrogen (TDN), and NH4+ loads comprised an estimated 9%, 7%, and 4%, respectively, of annual inputs to this system in 2018, before the SRWTP upgrade. Under a post-upgrade scenario, we estimated net annual island drainage TDN contributions to increase to 11% and NH4+ contributions to 45% of total Delta inputs as the SRWTP NH4+ load diminished to near zero. Our results suggest that island drainage is a measurable N source that has likely become increasingly important now that the SRWTP upgrade is complete. With over 200 potential active outfalls, these inputs may affect aquatic biogeochemical cycling in many regions of the Delta, especially in areas with long residence times.

We propose a method for distinguishing return flow from streamflow time series in rivers located in urban and industrial watersheds. The trend analysis is conducted using the Mann–Kendall method, while streamflow time series are divided into pre- and post-change sets using the Mann–Whitney change point method. The Two-Parameter Filtering (TPF) is utilized to separate baseflow before determining the return flow. By employing modified Local Minimum Flow (LMF) method, the TPF results are decomposed into groundwater baseflow and return flow. The LMF method was adjusted by modifying the time interval based on low flow during the dry season. To validate the calculated subsurface flow and runoff, the physical method is verified using the Soil and Water Assessment Tool (SWAT). After calibrating the model for the pre-change period, modeling is conducted for the entire streamflow time series. This method is applied to industrial land that has proliferated over the past two decades upstream of the Ergene River Basin in the European part of Türkiye. The proposed method estimates return flows with satisfactory accuracy and reliability, representing more than half of the baseflow. Since 1990, the return flow has increased from 5 to 38 percent of river streamflow. The research demonstrates that conventional filtering methods could not reliably separate the baseflow of human-induced rivers. A reanalysis is necessary to determine the actual groundwater baseflow and return flow based on the results obtained from these methods. [ABSTRACT FROM AUTHOR]

Abstract The article critically reviews the methodology adopted by the Central Ground Water Board (CGWB) for the assessment of groundwater resources in India. The authors developed a water balance equation that simulates the changes in annual and seasonal groundwater storages of an agricultural region, using a water accounting framework; they solved the developed equation using the data of annual and seasonal water level fluctuations for a wet year for Ludhiana district of Punjab to estimate different components of the water balance. The estimated values are used to test the robustness of the CGWB methodology for monsoon recharge. The annual groundwater storage change obtained from solving the water balance equation was compared with the observed change in annual groundwater storage and was found to closely tally. As per the water balance equation, the CGWB estimates of rainfall recharge conform to the annual water level fluctuations recorded by the agency and therefore are not reliable. Hence, we could infer that our methodology is superior to that of CGWB for estimating monsoon recharge. The validated equation was also used to estimate the recharge from rainfall during a dry year. Using these outputs in a simple groundwater balance equation, irrigation return flows were estimated for the wet and dry years. The equation was then extended to the Ahmednagar district of Maharashtra, a hard rock area, for estimating the surface water import during a wet year, the key unknown in the region's water balance. Hence, our methodology can be employed to estimate rainfall recharge for dry years using annual changes in groundwater storage and estimated consumptive uses of water, when the “WLF approach,” used by CGWB, fails, owing to the presence of an additional variable, that is, monsoon draft. For wet years, it can be used to arrive at the consumptive use of water for various purposes.

Using recently collected high‐resolution seismic data along a dense linear transect across Ohio, West Virginia, and Virginia (called Mid‐Atlantic Geophysical Integrative Collaboration (MAGIC) profile), we analyze P‐to‐S receiver functions to investigate the undulations of the mantle transition zone (MTZ) discontinuities (410‐ and 660‐km) beneath the central Appalachian region. Our results incorporating the effects of local crustal and mantle structures suggest shallowing of both the 410‐ and the 660‐km discontinuities from the northwest (inland) to the southeast (coast) along MAGIC profile. Hydro‐thermal upwelling beneath the eastern U.S. coastal plain due to a hydrated MTZ and hot upwelling return flow associated with the descending lower mantle Farallon slab is consistent with our observations of MTZ structure considering 3D velocity heterogeneity. The inferred hydrous hot upwelling rising into the upper mantle may trigger dehydration melting atop the 410‐km discontinuity, which may help to explain the presence of a low velocity upper mantle anomaly beneath the region today. Plain Language Summary: The dynamic and tectonic processes of passive continental margins that do not lie on plate boundaries are poorly understood compared with active continental margins. The mantle flow patterns beneath the eastern North America, a long‐lived passive continental margin, are debated, due to limited local high‐resolution seismic studies. Using a dense seismic array through Ohio, West Virginia, and Virginia (called MAGIC profile) with unprecedented resolution, we investigate the undulations of 410‐ and 660‐km discontinuities (boundaries of the mantle transition zone) beneath the eastern U.S. by analyzing seismic waves that have been converted at these discontinuities. After correcting for local crustal and mantle structures, we identify positively correlated shallowing of the 410‐ and 660‐km discontinuities from the inland to the coast, which are hard to explain by thermal heterogeneity alone. Our findings suggest the existence of hot upwelling return flow associated with the neighboring descending Farallon slab in the lower mantle beneath the eastern U.S. When this passive hot return flow rises through the hydrated transition zone into the upper mantle, dehydration melting atop 410‐km discontinuity may be triggered. The buoyant melt may further rise through the upper mantle, providing a potential explanation for upper mantle velocity anomalies beneath the region. Key Points: Seismic receiver functions image mantle transition zone discontinuities from a regional high‐resolution transect across the eastern U.SThe results are difficult to reconcile with either thermal or hydration variations alone in the transition zoneLocal hydro‐thermal upwelling due to hydrated transition zone and hot return flow associated with the descending Farallon slab may exist [ABSTRACT FROM AUTHOR]

In North China, the return flow (RF) refers to the airflow at the rear of an inshore high pressure, bringing southerly wind to the Beijing–Tianjin–Hebei (BTH) region when the high pressure pushes deeper from coast into the mainland. Many studies have pointed out the significant contribution of southerly anomalies to the transport and accumulation of pollutants in the BTH region. However, the relationship between RF and heavy pollution episodes (HPEs) in the BTH region requires more in-depth analysis, and this study will focus on this topic. By objectively identifying RFs and HPEs based on the ERA5 reanalysis data and observed hourly PM2.5 concentration data during 9 winters of 2012–2020, it is found that almost two-thirds of the HPEs in the BTH region coincide with the occurrence of RFs. The northward transport of warm and humid air is stronger in the HPEs under RF conditions, whereas the sinking motion and the decrease in boundary layer height dominate the HPEs without any RF. We then classify the RFs into north and south types by a demarcation line of 32°N. Both types of RFs are featured with a zonal circulation pattern, stable atmosphere, and southerly airflow favoring the development of HPEs, but the south type RFs bring warmer and wetter air masses to the BTH region, forming a more stable and thicker inversion layer and causing more severe HPEs. With occurrences of the RF, low-level winds are observed to accelerate, and the ageostrophic wind components contribute mainly to this acceleration. During the presence of RFs, the kinetic energy generation at the high level decreases, and the weakened downward transport results in weak low-level northerly winds, weak turbulence, and a shallow boundary layer, thus hindering the diffusion of atmospheric pollutants in the BTH region. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Agricultural irrigation practices have changed through time as technology has enabled more efficient conveyance and application. In some agricultural regions, irrigation can contribute to incidental aquifer recharge important for groundwater return flows to streams. The Henrys Fork Snake River, Idaho (United States) overlies a portion of the Eastern Snake Plain Aquifer, where irrigated agriculture has occurred for over a century. Using irrigator interviews, aerial and satellite imagery, and statistical streamflow analysis, we document the impact of farm-scale decisions on basin-scale hydrology. Motivated to improve economic efficiency, irrigators began converting from surface to center-pivot sprinkler irrigation in the 1950s, with rapid adoption of center-pivot sprinklers through 2000. Between 1978–2000 and 2001–2022, annual surface-water diversion decreased by 311 Mm3 (23%) and annual return flow to the river decreased by 299 Mm3 over the same period. Some reaches that gained water during 1978–2000 lost water to the aquifer during the later period. We use an interdisciplinary approach to demonstrate how individual farm-scale improvements in irrigation efficiency can cumulatively affect hydrology at the landscape scale and alter groundwater-surface water relationships. Return flows are an important part of basin hydrology in irrigated landscapes and we discuss how managed and incidental aquifer recharge can be implemented to recover return flows to rivers.

The term “sea effect” generally refers to the process of air mass modification after cold air flows above a warm sea surface. Affected by the sea effect, small-scale and sudden fogs have occasionally been observed on the western coast of the Bohai Sea. A more in-depth study of this type of fog is crucial for ensuring the safety of maritime and aerial traffic routes in this region. This study investigated the formation mechanism of this specific type of fog on the morning of 17 October 2007, utilizing both meteorological stations and 255 m tower observations, combined with the results of the Weather Research and Forecasting model (WRF). It is demonstrated that Bohai Sea evaporation and the associated water vapor advection played crucial roles in the formation of fog along the west coast of the Bohai Sea. The cold return flow became more moist as it passed over the warm Bohai Sea, which was the primary contributor to triggering regional fog on the western coast. A moisture budget analysis revealed that water vapor from the Bohai Sea intruded into its western coast along an eastward trajectory, dominating the oscillations in the net moisture flux. The eastern water vapor flux significantly increased at 17:00 on the 16th (Local time, LST), reaching its peak at 21:00. Correspondingly, the fog water growth rate began to increase at 23:00 on the 16th, reaching its maximum at 03:00 on the 17th. A sensitivity experiment on evaporation further indicated that the Bohai sea effect played a decisive role in fog formation. With a tenfold reduction in evaporation from the Bohai Sea and subsequent significant weakening of water vapor advection, the simulated fog along the western coast of the Bohai Sea completely disappeared. Understanding the formation mechanism of this type of fog is beneficial for refining forecasting focal points, thereby enhancing forecast accuracy in a targeted manner.

Abstract Using recently collected high‐resolution seismic data along a dense linear transect across Ohio, West Virginia, and Virginia (called Mid‐Atlantic Geophysical Integrative Collaboration (MAGIC) profile), we analyze P‐to‐S receiver functions to investigate the undulations of the mantle transition zone (MTZ) discontinuities (410‐ and 660‐km) beneath the central Appalachian region. Our results incorporating the effects of local crustal and mantle structures suggest shallowing of both the 410‐ and the 660‐km discontinuities from the northwest (inland) to the southeast (coast) along MAGIC profile. Hydro‐thermal upwelling beneath the eastern U.S. coastal plain due to a hydrated MTZ and hot upwelling return flow associated with the descending lower mantle Farallon slab is consistent with our observations of MTZ structure considering 3D velocity heterogeneity. The inferred hydrous hot upwelling rising into the upper mantle may trigger dehydration melting atop the 410‐km discontinuity, which may help to explain the presence of a low velocity upper mantle anomaly beneath the region today.

Exhumed high‐pressure/low‐temperature (HP/LT) metamorphic rocks provide insights into deep (∼20–70 km) subduction interface dynamics. On Syros Island (Cyclades, Greece), the Cycladic Blueschist Unit preserves blueschist‐to‐eclogite facies oceanic‐ and continental‐affinity rocks that record the structural and thermal evolution linked to Eocene subduction. Despite decades of research, the metamorphic and deformation history (P‐T‐D) and timing of subduction and exhumation are matters of ongoing discussion. We suggest that Syros comprises three coherent tectonic slices and that each slice underwent subduction, underplating, and syn‐subduction return flow along similar P‐T trajectories, but at progressively younger times. Subduction and exhumation are distinguished by lineations and ductile fold axis orientations, and are kinematically consistent with previous studies that document top‐to‐the‐S‐SW shear (prograde‐to‐peak subduction), top‐to‐the‐NE shear (blueschist facies exhumation), and then E‐W coaxial stretching (greenschist facies exhumation). Amphibole zonations record cooling during decompression, indicating return flow above a cold slab. Multi‐mineral Rb‐Sr isochrons and compiled metamorphic geochronology show that the three slices record distinct stages of peak subduction (53–52, ∼50, and 45 Ma) that young with structural depth. Retrograde blueschist and greenschist facies fabrics span ∼50–40 and ∼43–20 Ma, respectively, and also young with structural depth. Synthesized data sets support a revised tectonic framework for Syros, involving subduction of structurally distinct coherent slices and simultaneous return flow of previously accreted tectonic slices in the subduction channel shear zone. Distributed, ductile, dominantly coaxial return flow in an Eocene‐Oligocene subduction channel proceeded at rates of ∼1.5–5 mm/yr and accommodated ∼80% of the total exhumation of this HP/LT complex. Key Points: Syros is a tectonic stack composed of three slices constructed by subduction and underplating; peak subduction ages young with structural depthThe subduction‐to‐exhumation transition is marked by kinematic rotation and cooling during decompressionMetamorphic geochronology indicates syn‐subduction exhumation occurred continuously in an Eocene‐Oligocene subduction channel [ABSTRACT FROM AUTHOR]

Irrigation can be a significant source of groundwater recharge in many agricultural regions, particularly in arid and semi-arid climates. Once infiltrated, irrigation recharge can travel via subsurface flowpaths that return to the river system in a lagged manner, supplementing natural streamflow weeks, months, or even years from when the irrigation was applied. In regions that experience low flows during summer and early fall, return flows can be a significant source of supplementary streamflow. Many water planning and operations models either ignore return flows or roughly approximate them with analytical solutions. Thus, return flows represent an important but often overlooked component of the hydrological exchange and overall water balance in agricultural regions. This study uses groundwater models to explore a wide range of factors that control irrigation return flow timing in irrigated alluvial valleys. A sensitivity analysis approach is used to assess how factors such as the extent of irrigated land adjacent to a stream, irrigation recharge rate, aquifer hydraulic conductivity, aquifer thickness, water table configuration, and seasonal fluctuations in stream stage control the timing of subsurface return flows. Modeling is conducted using MODFLOW models representing an irrigated alluvial valley adjacent to a stream. While a simplification of the full complexity in real systems, the models are a significant advancement from the analytical solution and provide new insight into the timescales of return flows over a broad range of possible conditions. To contextualize our modeling results, they are compared to an analytical solution commonly used for approximating return flows to evaluate its performance. Our findings show what factors and conditions influence return flow timing and control whether they contribute to streamflow over short term (months) or longer term (seasonal) time scales.

Phase changes in the precipitation processes of early winter and late spring in midlatitude regions represent challenges when forecasting the timing and magnitude of snowfall. On 4 April 2018, a heavy snow process occurred in Beijing and northwestern Hebei Province, becoming the most delayed occurrence of heavy spring snow ever recorded over Beijing in the last 30 years. This paper uses observational and numerical simulation data to investigate the causes for the rapid rain-to-snow (RRTS) phase transition during this process. The following results are obtained. (1) Return flows (RFs), an interesting type of easterly wind, including those at 1000, 925, and 800 hPa, played an important role in this heavy snow process and presented a characteristic "sandwich" structure. The RFs, complex topography, and snow particles that dominated the clouds, were the three key factors for the RRTS transition. (2) The RRTS transition in the plains was directly related to the RF at 925 hPa, which brought about advective cooling initiated approximately 4–6 h before the onset of precipitation. Then, the RF played a role of diabatic cooling when snow particles began to fall at the onset of precipitation. (3) The RRTS transition in the northern part of the Taihang Mountains was closely related to the relatively high altitude that led to a lower surface temperature owing to the vertical temperature lapse rate. Both immediately before and after the onset of precipitation, the snow particles in clouds entrained the middle-level cold air downward, causing the melting layer (from surface to the 0°C-isotherm level) to become very thin; and thus the snow particles did not have adequate time to melt before falling to the ground. (4) The rapid RRTS over the Yanqing mountainous area in the northwest of Beijing could have involved all the three concurrent mechanisms: the advective cooling of RF, the melting cooling of cloud snow particles, and the high-altitude effect. Compared with that in the plain area with less urbanization, the duration of the RRTS in the plain area with significant urbanization was extended by approximately 2 h. [ABSTRACT FROM AUTHOR]

Irrigation is vital for the sustainability of water‐limited agricultural areas. However, higher irrigation efficiency (IE) rarely reduces irrigation water consumption, a paradox well noted in the real world. Resolving this paradox requires rigorous assessment of basin‐scale IE, which remains rare. This study holistically analyzed basin‐scale IE using the Zhangye Basin (ZB), a typical agricultural area in arid northwestern China, as the testbed. A new basin‐scale IE index was proposed that factors in irrigation return flow and groundwater's direct contributions to crop evapotranspiration. A novel approach was also developed to calculate this new index based on integrated ecohydrological modeling. The major study findings for the ZB include the following. First, return flow accounts for approximately 13% of irrigation water, which creates a difference of 0.1 between the new basin‐scale IE index and a traditional field‐scale index. Second, although basin‐scale IE has notable interannual fluctuation, its multiyear average shows stability, which may be dependent on the basin's physical characteristics. Third, basin‐scale IE reflects large spatial heterogeneity and is influenced by the intensity of surface water‐groundwater interaction. Finally, under the projected future climate, return flow in the ZB will be enhanced by 3.2% per decade, and basin‐scale IE shows an increasing trend. Overall, rigorous evaluation of basin‐scale IE is critical to making heterogeneous policies and developing adaptive management strategies under the changing climate. The integrated modeling approach developed in this study provides a methodological foundation for overcoming misunderstandings about the IE paradox and benefits the reform of the current IE policy agenda. Key Points: A basin‐scale irrigation efficiency index was proposed to consider irrigation return flow and crop ET directly from groundwaterA novel approach was developed to assess basin‐scale irrigation efficiency based on integrated ecohydrological modelingThis study provides a methodological foundation for overcoming misunderstandings about the paradox of irrigation efficiency [ABSTRACT FROM AUTHOR]

The Nile River is the main route for inland navigation in Egypt. The vessels navigating through inland waterways generate complex physical forces that need to be studied extensively. Quantifying the effects of vessels sailing along a waterway is a complex problem because the river flow is unsteady and the river bathymetry is irregular. This paper aims to investigate the hydrodynamic effects resulting from the movement of vessels such as return currents around the vessel, the draw down of the water surface, under keel clearance, and the shear stress induced by vessels operating in the Nile River. Modeling such effects has been performed by applied the two-dimensional ADH (adaptive hydraulics) model to a river reach for different navigation channel operation scenarios. The obtained results show that the draw down heights, the water fluctuation, and the shear stress magnitude are larger when the river cross sectionals are narrow and the shallow water depths. These river sections are considered more disposed to bed erosion and it is morphologically unsafe. The section having the narrowest width and the lowest depth was associated with the largest drawdown percentages of 98.3% and 87.3% in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least drawdown percentages of 48.5% and 51.9% in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was associated with the largest fluctuations of 22.0 cm and 41.9 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least fluctuations of 0.6 cm and 1.8 cm in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was the worst section for under keel clearance of 5.0 cm and 33.3 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was the best section, where its clearance values were 183.2 cm and 155.0 cm in one-way and two-way scenarios. It is concluded that a numerical model is a valuable tool for predicting and quantifying the hydrodynamic effects of vessels moving through a two-dimensional flow field and can be used to evaluate different scenarios that are difficult to measure in the field or a physical model. Also, it provides visualization products that help us understand the complicated forces produced by vessels moving in a navigation channel. [ABSTRACT FROM AUTHOR]

In Kushiro River basin, inundation is likely to occur due to heavy rain, since the river-bed slope is very gentle in the downstream portion, which has natural levees. Consequently, in past floods, river discharge was observed to increase slowly and a delay of a few days in peak river discharge was observed compared to the peak precipitation. Therefore, we applied a distributed hydrological model, Geophysical fluid CIRCulation model (GeoCIRC), to reproduce such flood discharge in Kushiro River. GeoCIRC is based on object-oriented programming and various hydrological processes, such as infiltration flow, underground water flow, surface flow, and river flow can be implemented easily. We proposed a model that can incorporate the effect of return flow using storage function by introducing new parameters, such as storage time and time lag. This was done to consider not only the flood inundation in Kushiro River but also the return flow from flood inundation to the river flow. As a result, we obtained high Nash-Sutcliffe coefficients for river discharge for two large flood events. [ABSTRACT FROM AUTHOR]

Agriculture and food security have always faced challenges related to water scarcity, so agricultural water conservation is the most important strategy for overcoming this challenge. In this study, the REWAS tool developed by FAO and Future Water was used to evaluate the effects of technological and management strategies on real water savings (RWS) in the Zarrineh River sub-basin, Iran. Nine farms were investigated (wheat, corn, tomato, sugar beet), including control and treatment farms. According to changes in water consumption and return flows, RWS was calculated for various scenarios of field interventions. To assess the water consumption in Basin scale, REWAS was simplified the accounting framework for water consumption (consumed and unconsumed). In the Zarrineh River sub-basin, the use of the techniques applied in the treatment farm, compared to the control farm (according to farmer customary practices), resulted in a significant reduction of non-beneficial consumption. For example, according to the REWAS evaluation in West s17 farn, the treatment farm consumed the most useful water compared to the control farm (331 mm and 267 mm, respectively), which led to the most useful water consumption at basin scale (to the order of 3920 mm and 3166 mm). According to the results on the scale of the basin , the highest amount of recoverable discharge was also obtained in the control farm with an increase of 3774 MCM over the treatment farm. Using strategies to reduce water consumption resulted in apparent water saving (AWS) at the farm scale, but these AWS were very different from their RWS at the basin scale and the RWS at the basin scale (13%) was much lower than the AWS at the farm scale (38%). According to the results, apparent water savings (AWS) at the farm scale do not reduce water consumption, and may actually increase it when viewed in a basin scale. REWAS concepts indicate that significant amounts of "lost" water are actually recoverable return flows that can be used by downstream users or contribute to wetlands. According to REWAS concepts, real water savings can only be achieved by preventing non-recyclable backflows. Assessing RWS can help decision makers select sustainable interventions that will improve agricultural water productivity by providing information on farm flows, irrigation networks, and basin scales. [ABSTRACT FROM AUTHOR]

Nowadays, Companies need to collect and to deliver goods from and to their depots and their customers. Reusable containers are considered as a greener choice and a cost saving strategy. This paper addresses a dynamic management of reusable containers (e.g gases bottles, wood pallets, maritime containers, etc.) in a Closed-loop supply chain. The aim of the study is to find an optimal lot sizing and assignment strategy that minimizes the cost of reusable containers management under environmental constraint. In this contribution, a new integer-linear-programming model and two hybrid approaches based on the genetic algorithm are proposed to solve the problem. The second hybrid method is enhanced with a local search based on the VNS (variable neighborhood search). The numerical results show the performance of the two hybrid approaches in terms of solution quality and response time.

Flood irrigation is globally one of the most used irrigation methods. Typically, not all water that is applied during flood irrigation is consumed by plants or lost to evaporation. Return flow, the portion of applied water from flood irrigation that returns back to streams either via surface or subsurface flow, can constitute a large part of the water balance. Few studies have addressed the connection between vertical and lateral subsurface flows and its potential role in determining return flow pathways due to the difficulty in observing and quantifying these processes at plot or field scale. We employed a novel approach, combining induced polarization, time‐lapse electrical resistivity tomography, and time‐lapse borehole nuclear magnetic resonance, to identify flow paths and quantify changes in soil hydrological conditions under nonuniform application of flood irrigation water. We developed and tested a new method to track the wetting front in the subsurface using the full range of inverted resistivity values. Antecedent soil moisture conditions did not play an important role in preferential flow path activation. More importantly, boundaries between lithological zones in the soil profile were observed to control preferential flow pathways with subsurface run‐off occurring at these boundaries when saturation occurred. Using the new method to analyse time‐lapse resistivity measurements, we were able to track the wetting front and identify subsurface flow paths. Both uniform infiltration and preferential lateral flows were observed. Combining three geophysical methods, we documented the influence of lithology on subsurface flow processes. This study highlights the importance of characterizing the subsurface when the objective is to identify and quantify subsurface return flow pathways under flood irrigation. [ABSTRACT FROM AUTHOR]

This study aims to investigate a possibility of quantitative assessment of the relationship between return flow from paddy fields and river regime by using hydrogen- and oxygen-isotopic ratios of water (i.e., δD and δ18O). In the Saba River Basin and three caldera lakes (Tamblingan, Buyan, and Bratan) locating near the basin in the north of Bali Island, Indonesia, the δD and δ18O in fresh rainwater, river water, spring water, the surface water of several paddy plots with ponding, and lake surface water were measured from 2012 to 2014. In the middle and the lower areas of this basin, paddy fields are predominant land use. In contrast, in the upper area, plantation and forest are major, while paddy fields are very limited. All the δD–δ18O regression relationships in the upper river water, the spring water, and the fresh rainwater reasonably agreed with the Bali rainwater line (BRL), which is the "meteorological water line" specified for Bali (Kayane in water cycle and water use in Bali Island. Dissertation, Institute of Geoscience, University of Tsukuba, 1992). The regression lines for the paddy surface water [Paddy Line (PL)] and for the caldera lakes water (Lake Line), both of which had high correlation, could be significantly differentiated each other and also from the BRL. Almost all the plotted points of δ18O vs. δD in the middle and the lower river waters containing discharge from paddy fields were located in a range between the BRL and the PL on a δ-diagram. Although further investigations are still needed, we concluded that it is possible to quantitatively assess the relationship between return flow from paddy fields and river regime, algebraically. In addition, according to the same logic, it was assumed with high possibility that the water in Lake Tamblingan adjacent to the Saba River Basin is flowing into the Panas River, which is a branch river of the Saba, beyond the basin boundary. [ABSTRACT FROM AUTHOR]

A new method is proposed to correct shallow-water model resistance tests for the effect of the tank side walls, i.e. to correct the resistance curve towards shallow water of infinite width. From computed flow fields along ships in shallow water and channels, the tank or channel walls are found to increase the overspeed along the ship (return flow) by an amount that is roughly constant over the channel section. An algebraic equation is derived from which this amount can be solved, using a volume flux derived from a single potential-flow computation. The effect of the tank walls on the resistance curve is represented by a speed shift corresponding with this overspeed. The assumptions made are checked against computed flow fields and resistances. The overspeed increment is very well predicted; its effect on the resistance is fairly well estimated as long as it is not too strong. The method, in routine use for shallow-water tests at MARIN, is most practical; and in view of the large tank wall effects in shallow water, it is essential for good predictions. [ABSTRACT FROM AUTHOR]

We develop an idealised one dimensional (cross-shore) morphodynamic model that couples wave, tide and sediment dynamics to study the effect and evolution of a shoreface nourishment. Sediment fluxes driven by wave skewness, wave asymmetry (both onshore) and return flow (offshore) are considered. With the aid of new analytical expressions for the skewness and standard deviation of wave velocity and acceleration, sediment fluxes are calculated. Nourishment is viewed as a perturbation to the system in equilibrium that is subject to the divergence of the perturbed sediment flux and a gravity driven diffusion term. Depending on the location, a nourishment may provide a feeder or lee effect. In moderate and mild wave conditions, the evolution of a nourishment primarily depends on the relative location of nourishment and break point. Placed well offshore of the break point, the nourishment induces an overall positive perturbation in sediment flux, resulting in onshore migration (feeder effect). Located closer to the break point, the nourishment induces an earlier wave breaking, which dissipates part of the wave energy (lee effect), leading to a negative sediment flux perturbation around this break point and a positive sediment flux perturbation around the break point of the un-nourished beach. Depending on the intensity of the earlier breaking, the nourishment either migrates onshore (weak break) or splits into onshore and offshore moving parts (strong break). The relative importance of the diffusion term and the divergence of perturbed sediment flux may lead to a primarily migrating or decaying evolution of nourishment. In storm wave conditions, the nourishment tends to move offshore due to the predominance of return flow driven sediment flux. The sensitivity to wave period and tide are also studied. Model results are consistent with observations, as well as prevailing theory on cross-shore sediment transport. • An idealised one dimensional (cross-shore) morphodynamic model that couples wave, tide and sediment dynamics is developed to study the e_ect and evolution of a shoreface nourishment. • In moderate and mild wave conditions, a nourishment placed well o_shore from the break point induces an overall positive perturbation in sediment ux, resulting in onshore migration (feeder e_ect). Located closer to the break point, the nourishment induces an earlier wave breaking, which dissipates part of the wave energy (lee e_ect), resulting in onshore migration (weak break) or splitting into onshore and o_shore moving parts (strong break). In storm wave conditions, nourishment moves o_shore due to the predominance of return-ow-driven sediment ux. • Tide a_ects nourishment evolution through shifting the relative location of the nourishment and break point. The sediment dynamics at low tide dominate the evolution of the nourishment. [ABSTRACT FROM AUTHOR]

The objective of present work is to find out the sources of fluid-borne noise in vertical inline pump for various flow rates. The three-dimensional unsteady Reynolds Average Navier Stokes equation was solved using computational fluid dynamics code to predict the acoustic distribution. The pump chosen for study was of low specific speed and the experimental performance characteristic was very well matched with computational head developed. PROUDMAN sound power contour analysis showed the critical zone of noise in inlet pipe,impeller,and volute. Based on this,the variations of acoustic power were depicted over the cross section of inlet pipe,along the mean streamline of inlet pipe,as well along the volute circumference. The result concludes that the predominant flow noise is at tongue region and followed by noise generated due to turbulence in inlet pipe which occurs by the sudden variation in flow passage as well it depends on the operating condition of pump. The frequency analysis gives a glimpse of understanding about the broadband noise distribution due to flow phenomenon over a frequency range. [ABSTRACT FROM AUTHOR]

Highlights • We examined the influence of irrigation methods on potential groundwater recharge (PGR). • We combined experimental & modelling approaches to study PGR in semi-arid regions of Iran. • Water-saving irrigation methods almost disconnected root zone water cycle from that of unsaturated zone. • Furrow irrigation assured the groundwater sustainability over sprinkler and drip. Abstract Water saving irrigation systems (e.g. drip and sprinkler) conserve water but they can reduce potential groundwater recharge (PGR) over traditional systems (e.g. furrow) and may impair sustainability, particularly in arid and semi-arid regions. This study used a hybrid (experimental and numerical) approach to determine the effects of different irrigation systems on the dynamics of PGR in a semi-arid region. A 210-cm tall, 300-cm long and 150-cm wide soil column was prepared to simulate the soil environment of the Karaj region in Iran. A range of soil and environmental properties were monitored during a winter wheat cropping season (∼140 days) under different irrigation systems (treatments). Soil water content and drainage were measured under each irrigation system and these were used to a) calculate different components of water balance and b) model long-term soil water flow dynamics using HYDRUS-1D. About 14.83, 0.14 and 0.80% of the applied water (as irrigation and precipitation) under furrow, drip and sprinkler systems, respectively, were drained below 200 cm and this was estimated as the PGR. Annual PGR under furrow irrigation was estimated in the range of 19–228 mm, with an average of 111.3 mm. However, mean annual PGR under the sprinkler (4.1 mm) and drip (0.7 mm) was an order of magnitude lower than furrow irrigation. Deep drainage leading to PGR under the water saving methods was observed only after a very large rainfall event. The absence of large rainfall events between irrigations reduced PGR under water-saving irrigation systems in the arid and semi-arid region. The simulated model was further used to estimate the total amount of PGR over a 20-year period of wheat cultivation. Furrow irrigation estimated much higher amounts of PGR (222.7 cm) over drip and sprinkler systems; this raised questions about the sustainability of water-saving irrigation methods in the study area. As groundwater is the main source of irrigation in these areas, the recharge capacity of the adopted methods is critical to ensure the future availability and use of groundwater in the Karaj region of Iran as well as similar arid and semi-arid regions elsewhere. [ABSTRACT FROM AUTHOR]

Stepwise hydrochemical and isotope-based methodology was adopted to identify mineralization processes, assess the impact of resources overexploitation and flood irrigation, and conceptualize groundwater hydrodynamics in the Djérid aquifer system, Tunisia. The study demonstrates that the main processes controlling groundwater geochemistry are dissolution of evaporates and phosphate-bearing rocks, cation exchange, mixing between high and low TDS end-members, and irrigation return flow. Interpretation of isotope data demonstrates that the deep aquifer was mostly recharged by late Pleistocene palaeowater, while the shallow aquifer is entirely recharged by return flow. The intermediate aquifer groundwater is actually a mixing of early to middle Holocene palaeowater, late Pleistocene deep aquifer palaeowater and return flow waters. The established conceptual model shows that deep and shallow groundwater leakages into the intermediate aquifer are enhanced by the presence of deep faults, the high hydraulic head of the deep aquifer, the overexploitation of the intermediate aquifer, and the long-term flood irrigation. [ABSTRACT FROM AUTHOR]