Experimental study on water-saving and emission-reduction effects of controlled drainage technology

Field experiments and laboratory analysis were carried out to determine the effects of controlled drainage（CTD） and conventional drainage（CVD） technologies on drainage volume, concentrations of NH4^＋ -N, NO3^-N, and total phosphorus（TP）, nitrogen and phosphorus losses, rice yield,and water utilization efficiency. Results show that CTD technology can effectively reduce drainage times and volume; NH4^＋ -N, NO3^-N, and TP concentrations, from the first to the fourth day after four rainstorms decreased by 28.7%e46.7%, 37.5%e47.5%, and 22.7e31.2%, respectively,with CTD. These are significantly higher rates of decrease than those observed with CVD. CTD can significantly reduce nitrogen and phosphorus losses in field drainage, compared with CVD; the reduction rates observed in this study were, respectively, 66.72%, 55.56%, and 42.81% for NH4^＋ -N, NO3^-N, and TP. Furthermore, in the CTD mode, the rice yield was cut slightly. In the CVD mode, the water production efficiencies in unit irrigation water quantity, unit field water consumption, and unit evapotranspiration were, respectively, 0.85, 0.48, and 1.22 kg/m^3, while in the CTD mode they were 2.91, 0.84, and 1.61 kg/m^3 din other words, 3.42, 1.75, and 1.32 times those of CVD. Furthermore, the results of analysis of variance（ANOVA） show that the indicators in both the CVD and CTD modes, including the concentrations of NH4^＋ -N, NO3^-N, and TP, the losses of NH4^＋ -N, NO3^-N, and TP, irrigation water quantity, and water consumption, showed extremely significant differences between the modes, but the rice yield showed no significant difference.

Experimental Study on the Distribution of Soil Nitrate and Ammonium Nitrogen under Controlled Drainage

A field experimental project was set up to assess the effects of controlled drainage on the distribution and concentration of nitrogen in the soil at the Irrigation and Drainage Experimental Station under Four-Lake Engineering Administration of Jingzhou City, Hubei Province. Two plots drain runoff by controlled drainage system, with an area of 0.1 hm^2 （20 m×50 m） each. The third one with an area of 0.04 hm^2 （8 m×50 m） has a conventional subsurface drainage system. Under this experimental condition, the study draws the following conclusions： ① The controlled drainage system has a remarkable effect on the diminishing ratios of nitrate nitrogen between neighboring layers. It is presented that the diminishing ratio increases with the raising height of drain outlet. Controlled drainage system also reduces the transference of nitrate nitrogen in topsoil.② Different from nitrate nitrogen, the concentration of ammonium nitrogen is stable along the longitudinal section of soil, which is little affected by the controlled drainage system. It indicates that the concentration of ammonium nitrogen decreases according to the lowering of controlling height of the drain outlet.

Comparative Analysis of Tunnel Seepage Field under Different Waterproof and Drainage System Using Analytical Methods

Tunnel seepage is an important factor affecting the progress and safety of tunnel construction. In this paper, the mining method tunnel construction in the water-rich weathered granite stratum is taken as the research object. Through the analytical calculation method, the distribution law of tunnel seepage field under different waterproof and drainage types is studied, and the comparative analysis is carried out. According to the analytical solution, the influencing factors of grouting parameters are proposed. The sensitivity of the tunnel seepage field to the variation of grouting parameters is analyzed. A novel waterproof and drainage system, and construction technology suitable for subway tunnels with large buried depth below groundwater level were proposed.

Utilisation of transparent synthetic soil surrogates in geotechnical physical models: A review

Coal extraction in Huainan area is basically characterized by one of typical multi-seam mining conditions observed in China, where coal is mined in soft seams characterized by high gas content, high stress, low permeability and difficult geological conditions. The average mining depth in Huainan area is 875 m and continues to increase by 15-25 m annually. The rise in mining depth increases the risk of coal and gas outbursts and makes it more difficult to control outburst risk in Huainan coalmines. This paper reviews the main achievements（e.g. theories, technologies and equipment） in outburst control in Huainan, and tries to analyze some key challenging issues, and to present associated strategies to address these issues.It suggests that the outburst control in Huainan must take a combination approach of both regional and localized control in which the former plays a dominant role. Other outburst prevention principles include（1） non-outburst seams protecting outburst seams,（2） less outburst-prone seams protecting strong outburst-prone seams,（3） stress-releasing mining, and（4） the combination of ground and underground gas drainage（the model is dubbed as ＂walking on two legs＂）. The paper concludes that we should conduct fundamental researches on outburst mechanism, and develop outburst control technologies and equipment to ensure safe and efficient coal mining of deep coal resources in Huainan area.

Design and evaluation of control strategies in urban drainage systems in Kunming city

Real time control （RTC） of urban drainage systems （UDSs） is an important measure to reduce combined sewer overflow （CSO） and urban flooding, helping achieve the aims of ＂Sponge City＇. Application of RTC requires three main steps： strategy design, simulation-based evaluation and field test. But many of published RTC studies are system-specific, lacking discussions on how to design a strategy step by step. In addition, the existing studies are prone to use hydrologic model to evaluated strategics, but a more precise and dynamic insight into strategy performance is needed. To fill these knowledge gaps, based on a case UDS in Kunming city, a studio on RTC strategy design and Management Model （SWMM） - uncier four typical rainfall events characterized by different return periods （1-year or 0.5 year） and different spatial distributions （uniform or uneven）. The equal filling strategy outperformss other two strategies and it can achieve 10% more CSO reduction and 5% more flooding reduction relative to the no-tank case.

Optimizing water-saving irrigation schemes for rice(Oryza sativa L.)using DSSAT-CERES-Rice model

Rice is one of the major crops in China,and enhancing the rice yield and water use efficiency is critical to ensuring food security in China.Determining how to optimize a scientific and efficient irrigation and drainage scheme by combining existing technology is currently a hot topic.Crop growth models can be used to assess actual or proposed water management regimes intended to increase water use efficiency and mitigate water shortages.In this study,a CERES-Rice model was calibrated and validated using a two-year field experiment.Four irrigation and drainage treatments were designed for the experiment:alternate wetting and drying(AWD),controlled drainage(CD),controlled irrigation and drainage for a low water level(CID1),and controlled irrigation and drainage for a high water level(CID2).According to the indicators normalized root mean square error(NRMSE)and index of agreement(d),the calibrated CERES-Rice model accurately predicted grain yield(NRMSE=6.67%,d=0.77),,shoot biomass(NRMSE=3.37%,d=0.77),actual evapotranspiration(ETa)(NRMSE=3.83%,d=0.74),irrigation volume(NRMSE=15.56%,d=0.94),and leaf area index(NRMSE=9.69%,d=0.98)over 2 a.The calibrated model was subsequently used to evaluate rice production in response to the four treatments(AWD,CD,CID1,and CID2)under 60 meteorological scenarios which were divided into wet years(22 a),normal years(16 a),and dry years(22 a).Results showed that the yield of AWD was the largest among four treatments in different hydrological years.Relative to that of AWD,the yield of CD,CID1,and CID2 were respectively reduced by 5.7%,2.6%,8.7%in wet years,9.2%,2.3%,8.6% in normal years,and 9.2%,3.8%,3.9% in dry years.However,rainwater use efficiency and irrigation water use efficiency were the greatest for CID2 in different hydrological years.The entropy-weighting TOPSIS model was used to optimize the four water-saving irrigation schemes in terms of water-saving,labor-saving and high-yield,based on the simulation results of the CERES-Rice model in the past 60 a.These results showed that CID1 and AWD were optimal in the wet years,CID1 and CID2 were optimal in the normal and dry years.These results may provide a strong scientific basis for the optimization of water-saving irrigation technology for rice.

Mechanism of water savings and pollution reduction in paddy fields of three typical areas in southern China

Field irrigation and drainage regulation and fertilization application could affect water utilization and pollution transportation in a paddy field.In this study,representative rice-producing areas of Zhejiang Province in southern China were selected to study the effects of different field water level control(conventional irrigation and drainage W0,controlled irrigation and drainage W1 and W2)and different fertilization methods(2 times of fertilization F2 and three times of fertilization F3)on water irrigation quantity and consumption of rice,rice growth,water utilization,and pollution reduction.Results showed that field water level control had a great effect on irrigation quota in growing period rather than that in soaking period,and irrigation quota for W0 was 37.0%-71.7%higher than that for W1 and W2 in the whole growth period of rice.Although the upper limit of rain storage was greatly increased by W1 and W2,on the contrary,the yield under W1 and W2 was 0.4%-2.1%higher than that under W0.Water consumption,water leakage,and evapotranspiration were 16.63%-34.4%,39.97%-60.8%,and 9.40%-31.53%lower under W1 and W2 than those under W0,respectively,while it showed no significant changes under W1 and W2.Rainfall use rate and WUEI(water use efficiency of irrigation)under W1 and W2 had been significantly improved by 8.20%-129.58%and 31.58%-201.61%compared to W0.The contribution of nitrogen and phosphorus loss from surface water accounted for 90%and the total pollution load of total nitrogen(TN),NO_(3)^(-)-N,NH_(4)^(+)-N and chemical oxygen demand(COD)were 20.0%-63.4%,21.8%-66.3%,21.5%-63.8%,and 21.4%-46.5%lower for W1 and W2 than that for W0,respectively.Meanwhile,compared to F2,dispersed fertilization(F3)was beneficial to increase the yield and decrease pollutant load.Additionally,the path of IRA→NH_(4)^(+)-N→COD and IRA→WCA→WUE_(I) presented partial remediation effect,and the effect size was 23.6%and 38.1%,respectively,the path of IRA→WUE_(I)→WUE_(ET) presented a full remediation effect,and the path of IRA→WCA→WUE_(ET) presented suppression effect.