Damming Weakens the Groundwater and Surface Water Exchange and Its Nitrate Removal in Semi-arid Prairie Rivers

Surface water (SW)-Groundwater (GW) exchange plays a vital role in a prairie aquatic system and the biogeochemical cycling in such a system. Considering the inadequate understanding of damming on SW-GW exchange, a damming prairie river in Southeast Eurasian steppe was chosen to investigate variations of the SW-GW exchange and its influences on the fate of nitrate (NO3-). Both hydraulic and hydrochemical methods were applied to precisely depict the daily and seasonal exchange processes. The upstream and downstream reaches of the dam were observed to be upwelling and downwelling conditions respectively within a hydrologic year. Results obtained from multiple tracer methods and hydraulic method indicate that damming contributed to transfer the stream from the upwelling to the downwelling condition and weaken the SW-GW exchange in the downstream. The patterns of SW-GW exchange modulated the NO3- uptake or production between the SW and the GW. NO3- was mainly removed in the SW-GW exchange zone (SW-GW EZ) of the upwelling segment, while produced in the downwelling segment. Both the removal and production of NO3- were enhanced during snowmelt period, which might be an active period for the SW-GW exchange and NO3- fate. This study underscores the negative effect of damming on the SW-GW exchange and accompanied NO3- removal in prairie river systems.

Automated stand for the study of injectors made of polymer materials for hydraulic weed destruction

The work describes a new technological process for weed destruction and tillage in the near-stem zones of fruit trees and covers the prospects for studying the hydraulic method of weed destruction. The quality of hydraulic tillage and weed destruction has been determined to be conditioned by the shape and the required pressure of the jet. The results of theoretical calculations and initial tests show that an automated stand is needed for nozzles’ testing and optimizing the operating modes of the hydraulic device. A working body and an automated stand have been designed to study the parameters of nozzles made of polymer materials and the impact of the working body on various weeds and soil surfaces.

Embolism resistance of different aged stems of a California oak species (Quercus douglasii): optical and microCT methods differ from the benchtop-dehydration standard

Vulnerability of xylem to embolism is an important trait related to drought resistance of plants. Methods continue to be developed and debated for measuring embolism. We tested three methods (benchtop dehydration/hydraulic, micro-computed tomography (microCT) and optical) for assessing the vulnerability to embolism of a native California oak species (Quercus douglasii Hook. & Arn.), including an analysis of three different stem ages. All three methods were found to significantly differ in their estimates, with a greater resistance to embolism as follows: microCT > optical > hydraulic. Careful testing was conducted for the hydraulic method to evaluate multiple known potential artifacts, and none was found. One-year-old stems were more resistant than older stems using microCT and optical methods, but not hydraulic methods. Divergence between the microCT and optical methods from the standard hydraulic method was consistent with predictions based on known errors when estimating theoretical losses in hydraulic function in both microCT and optical methods. When the goal of a study is to describe or predict losses in hydraulic conductivity, neither the microCT nor optical methods are reliable for accurately constructing vulnerability curves of stems; nevertheless, these methods may be useful if the goal of a study is to identify embolism events irrespective of hydraulic conductivity or hydraulic function.

Influence of reservoir shape upon the choice of Hydraulic vs. Hydrologic reservoir routing method

The objective of the paper is to compare the hydrologic and hydraulic reservoir routing methods in term of assumptions, equations, numerical computation procedures, necessary data and advantages-disadvantages of their use. To test the results provided by the two methods, a set of two reservoirs from Romania was chosen: one long and narrow and the other one roundly shaped. Corresponding inflow hydrographs were chosen, and similar conditions were imposed for the outflow dam control structures, namely the initial water level in the reservoir to be at the Spillway Crest Level (SCL) and no outflow control. For the hydrologic method the Puls procedure was used and a program was written in Scilab to solve the continuity equation in finite differences. For the hydraulic method HEC-RAS software was used to solve the 1D Saint-Venant equations. Outflow and stage hydrographs at the dam were compared together with the stage hydrograph at the reservoir tail for the hydraulic method. Results show that the hydraulic method should be used for the long and narrow reservoirs, as it considers the backwater effect, whereas the hydrologic method can be efficiently used for all other reservoirs where this effect is negligible.

Substantiation of the parameters of the tailings storage core during the storing of the cleaning rejects by hydraulic method

The paper analyzes the current state of artificial tailings storages. These unique anthropogenic facilities may be considered both as the sources of environmental hazard and as promising anthropogenic deposits. The relevance of their development is shown. Taking into account the existing technologies of tailings storing, it is substantiated that the future anthropogenic deposit is formed by hydraulicking layers of the same thickness, displaced relative to each other in the horizontal plane by the same amount. As a result of research dependences were obtained that allow estimation of the probable volumes of stored mineral processing products and available storage volume when building up dams, as well as justification of the location of the inner boundary between the core of the artificial storage and the body of the retaining prism.

Numerical Simulation of Safety Rod and its Drive Mechanism in Sodium-Cooled Fast Reactor During Scram Action

Safety rod and its drive mechanism is one of the shutdown systems in sodium-cooled fast reactor, which must be quickly inserted into the core to achieve emergency shutdown in the event of an accident. Therefore, it is necessary to study the falling process of safety rod. In this paper, the numerical simulation method is used to analyze the falling process of safety rod and its drive mechanism in China Experimental Fast Reactor. According to the flow path of the safety rod and its drive mechanism, the pipe system hydraulic method is used to model the safety rod and its drive mechanism and calculate the hydraulic force of the safety rod and its drive mechanism during the falling process. The relationship between time, displacement, velocity and acceleration is presented. The drop time of safety rod is calculated, which is compared with the experimental results. The factors that affect the drop process are analyzed and a sensitivity analysis is presented.

Hydraulic method to determine the ecological flow for fish

Social and economic development will influence the nature environment and lead to ecological problems, among which the ecological flow concerns the food chain and fish populations. Although there are many computation formulas for counting ecological flow, it is very difficult to unite and get reasonable values. According to the existing research of ecological flow, the concept and calculation method of ecological flow are analyzed, which shows that in a complex ecological system, ecological water requirement is difficult to meet the requirements of all the protection object of water requirement at the same time. Therefore, we should focus on the specific fish with reference value to build ecological protection object and determine the ecological flow. Furthermore, the ecological flow should be the regulation of water quality and water quantity in time and space. Using hydraulic method, the fish living space under different water flow environments can be determined, and specific time and space regulation schemes can be obtained.