Nitrogen interception in floodwater of rice field in Taihu region of China

A field experiment located in Taihu Lake Basin of China was conducted, by application of urea or a mixture of urea with manure, to elucidate the interception of nitrogen （N） export in a typical rice field through ＂zero-drainage water management＂ combined with sound irrigation, rainfall forecasting and field drying. N concentrations in floodwater rapidly declined before the first event of field drying after three split fertilizations, and subsequently tended to rearm to the background level. Before the first field drying, total particulate nitrogen （TPN） was the predominant N form in floodwater of plots with no N input, dissolved inorganic nitrogen （DIN） on plots that received urea only, and dissolved organic nitrogen （DON） on plots treated with the mixture of urea and manure. Thereafter TPN became the major form. No N export was found from the rice field, but total nitrogen （TN） of 15.8 kg/hm^2 was remained, mainly due to soil N sorption. The results recommended the zero-drainage water management for full-scale areas for minimizing N export.

Study of Dynamics of Floodwater Nitrogen and Regulation of Its Runoff Loss in Paddy Field-Based Two-Cropping Rice with Urea and Controlled Release Nitrogen Fertilizer Application

The article deals with the effects of urea and controlled release nitrogen fertilizer （CRNF） on dynamics of pH, electronic conductivity （EC）, total nitrogen （TN）, NH4^＋-N and NO3 -N in floodwater, and the regulation of runoff TN loss from paddy field-based two-cropping rice in Dongting Lake, China, and probes the best fertilization management for controlling N loss. Studies were conducted through modeling alluvial sandy loamy paddy soil （ASP） and purple calcareous clayey paddy soil （PCP） using lysimeter, following the sequence of the soil profiles identified by investigating soil profile. After application of urea in paddy field-based two-cropping rice, TN and NHa＋-N concentrations in floodwater reached peak on the 1st and the 3rd day, respectively, and then decreased rapidly over time; all the floodwater NO3--N concentrations were very low; the pH of floodwater gradually rose in case of early rice within 15 d （late rice within 3 d） after application of urea, and EC remained consistent with the dynamics of NH4^＋-N. The applied CRNF, especially 70% CRNF, led to significantly lower floodwater TN and NH4^＋ concentrations, pH, and EC values compared with urea within 15 d after application. The monitoring result for N loss due to natural rainfall runoff indicated that the amount of TN lost in runoff from paddy field- based two-cropping rice with urea application in Dongting Lake area was 7.47 kg ha^-1, which accounted for 2.49% of urea- N applied, and that with CRNF and 70% CRNF application decreased 24.5 and 27.2% compared with urea application, respectively. The two runoff events, which occurred within 20 d after application, contributed significantly to TN loss from paddy field. TN loss due to the two runoffs in urea, CRNF, and 70% CRNF treatments accounted for 72, 70, and 58% of the total TN loss due to runoff over the whole rice growth season, respectively. And the TN loss in these two CRNF treatments due to the first run-off event at the 10th day after application to early rice decreased 44.9 and 44.2% compared with urea, respectively. In conclusion, the 15-d period after application of urea was the critical time during which N loss occurred due to high floodwater N concentrations. But CRNF decreased N concentrations greatly in floodwater and runoff water during this period. As a result, it obviously reduced TN loss in runoff over the whole rice growth season.

An experimental study on embankment failure induced by prolonged immersion in floodwater

Prolonged immersion in floodwater is one of the main causes of embankment failure or dam breaks, although failure mechanisms have not been extensively studied. In this study, an embankment model was constructed to investigate the influence of prolonged immersion in floodwater on the failure of an embankment. The results indicate that： （1） the phreatic surface gradually rises and negative pore pressures gradually dissipate with the time of prolonged immersion in floodwater, and, finally, a stable and fully saturated state is reached; （2） observable cracks and a heave phenomenon are found near the downstream toe and in the top stratum of the foundation, which are attributed to the large uplift pressure on the interface between the top stratum and the pervious substratum, the tremendous impact effect induced by the rapid rise in water level, and the reduction of shear strength of heavy silt loam. The present study enhances our in-depth knowledge of the mechanisms of embankment failure induced by floodwater, and provides experimental data for validation of mathematical models of the embankment seepage failure.

Floodwater utilization of the Three Gorges Project

Floods are both risks and resources. Floodwater utilization is an important part of flood management. Considering the rising shortage of water resources, serious water pollution, and undersupply of electric power, it’s imperative to strengthen flood management. In light of the hydrological characteristics of the Three Gorges Project (TGP) on the Yangtze River in P. R. China, we investigated the necessity and feasibility of TGP floodwater utilization, proprosed dynamic control of limited water level during flood season of the reservoir and basin-wide integrated floodwater management as strategies, and identified problems that might occur in practice.

沿海中小河流域地表-地下水库联合调控洪水资源利用研究:Ⅱ.实例应用

以山东半岛乳山河流域为例,构建了时、日、月多时间尺度嵌套的乳山河流域地表-地下水库联合调控模型,通过对地表水库泄流、河道闸坝控制水位、地表-地下水库供水等调控规则的优化,提出了地表-地下水库联合调控洪水资源利用方案。研究结果表明:在洪水来临之前通过地表-地下水库联合调控抬升河道控制水位、加大地下水库供水比例、增加河道入渗量,可将地表水库多余水量适时转移到地下水库,腾空地表水库拦洪库容,有效增加流域洪水资源利用量;联合调控方案下,乳山河流域洪水资源的丰(2007年)、平(1994年)、枯(1967年)年,洪水资源利用量分别增加了846.96万、728.77万、106.35万m^(3),验证了地表-地下水库联合调控模型的实际应用效果。

巢湖流域防洪新格局方案构建研究

2020年巢湖发生流域性大洪水,同期遭遇长江高水位,长时间不能自排,导致流域大面积破圩。鉴于巢湖流域现状防洪体系已不能满足经济发展的要求,本文通过典型年洪水分析,按2020年巢湖最恶劣典型年排洪条件,构建巢湖流域“蓄洪、自排、抽排”相结合的综合防洪新格局方案,以保障流域防洪安全。

新型储水储能模式在引沅补资方案中的初步探索

跨流域调水需要水源工程和能量驱动,而汛期超额洪水及电力系统弃能需要寻找出路。文章以引沅补资方案为例,提出了一种新的储水储能模式,实现了调水蓄洪储能。在为调水工程找到能量来源、促进清洁能源消纳的同时,实现了洪水的资源化利用,使生态调水工程得以良性运行。方案的提出,为跨流域水资源配置和电网储能建设提供了新思路。

从黄河“96.8”洪水看黄河小北干流河段面临的防洪形势

当前,黄河龙门站发生中常洪水的可能性很大。1996年8月,黄河龙门站发生了11 200 m3/s的较大洪水,对该次洪水进行探讨,有助于正确认识防汛形势,为防汛工作提供借鉴。本文通过调查该次洪水的特点、造成的危害,分析了暴露出来的问题和当前黄河小北干流河段面临的防汛形势。

邢台市“96.8”洪灾与防洪减灾措施

分析了邢台市“96.8”洪水造成的洪灾损失情况,并进行了反思。指出了水利工程的防洪减灾作用,提出了加大防洪宣传力度,实施分格防洪,重视滞洪区排水工作的防灾减灾措施与对策。

从“96.8”大洪水看人水和谐的重要性

"96.8"洪水使我们进一步认清了暴雨洪水的突发性,洪水灾害的严重性和防汛抗洪的长期性、艰巨性复杂性。自人类文明诞生以来,人类社会与水就是一对发展着的矛盾体,然而,面对人类社会的飞速发展和大自然的发难,人类必须在人水关系上作出新的选择——人水和谐。

众志成城抗大洪——临汾地区大战“96.8”洪水纪实

8月,大地铺满希望的季节。 当辛勤劳作的人们正喷夸赞着多年少见的秋作物长势,沉浸在丰收的希冀中时,苍天似乎有意要与人们作对,大雨、暴雨一场接一场,汹涌的洪水集中流向汾河。 7月31日以来,由于汾河流域连降暴雨我区汾河干流出理了30年来最大洪峰: 8月5日凌晨3时,汾河水位开始上涨; 8月8日零时,洪洞赵城水文站达到9】0—1200立方米/秒洪峰; 8月8日12时,临汾市马务桥发生880立方米/秒洪峰; 8月8日20时。

从“96.8”洪水看我省黄河防洪存在的突出问题

1996年8月5日、13日,黄河下游花园口站出现了7600立方米每秒和5520立方米每秒两次洪峰(简称“96.8”洪水),这是1985年以来黄河下游的最大洪水,这次洪水对黄河下游防洪工程和滩区人民群众生产生活所造成的灾害是多年来少见的。

用“96.8”暴雨洪水复核引江交叉河道设计洪水的认识

引江总干渠穿越河北省太行山山前丘陵坡水区，与众多大小河流交叉，而多数河流无实测流量资料，设计洪水由暴雨途径推求。“96．8”洪水为复核暴雨法设计洪水的合理性、提高成果的精度提供了一个良好的契机。运用一次特大暴雨资料复核暴雨途径推求的设计洪水，在国内水文计算方面还不多见。通过邯、邢两市段交叉河流暴雨法设计成果的复核验证得出几点认识。

施用猪粪和化肥对稻田土壤表面水氮磷动态的影响

2005年在利用渗漏池模拟长江中游双季稻地区两种主要水稻土壤的基础上,进行了施用化肥和配施等P2O5猪粪对稻田氮、磷等养分动态特征影响的研究。结果表明,表面水电导率(EC)、总氮(TN)、总磷(TP)浓度和NH+4-N浓度在施肥后1～3d达到最高,然后均随着时间的延长迅速下降,至7～15d逐渐接近CK。7～15d内表面水pH逐渐升高,至30d后逐渐趋于平缓。与施用化肥相比,峰值时猪粪处理的表面水TN浓度降低了28.9%～62.9%;NH4+-N浓度降低了43.7%～48.8%,但NO-3-N却远高于施用化肥,且晚稻较早稻平均升高56.5%;晚稻表面水TP浓度提高51.2%。而且早、晚稻在7～50d期间维持TP浓度均高于化肥。河沙泥的表面水TN、TP浓度高于红黄泥,但两种土壤的表面水铵氮、硝氮差异不显著。

土壤脲酶活性对稻田田面水氮素转化的影响

以浙江省嘉兴市双桥农场的青紫泥水稻田为研究对象，采用大田小区的研究方法，对不同供肥水平下水稻追施尿素后田面水中氮素主要形态的浓度变化进行了动态监测，并从土壤酶学的角度探讨了其氮素转化的深层机制。研究发现．土壤脲酶在稻田田面水氮素转化中起着关键作用，施尿素后3天内田面水中总氮、氨氮的浓度及氨氮／总氮比值达到峰值．且第二次追肥较第一次追肥后峰值低．随后急剧下降。5天后维持在较低的水平，说明施肥后前5天是氮素大量且快速流失的关键时期，其流失以氨氮为主；土壤脲酶活性在第一次追肥后3～5天也出现了明显的增长趋势，第二次追肥后脲酶活性增强幅度远小于第一次追肥．N270处理初期甚至出现了负增长；线性相关分析表明田面水中氨氮／总氮的比值与土壤脲酶活性之间存在显著的正相关关系．说明土壤脲酶在水土界面氮素迁移转化过程中发挥着关键作用，因此，抑制脲酶活性可能是降低稻田氮素流失的主要途径之一。

江汉平原洪水沉积物的粒度特征及环境意义——以2005年汉江大洪水为例

2005年10月初汉江发生了自1983年以来最大的一次洪水。通过对江汉下游仙桃河段不同地貌单元洪水沉积物的系统取样和分析,发现2005年汉江洪水沉积的粒度特征具有以下特点:1)不同河道地貌单元的沉积物粒级组分有所不同,高河漫滩的粒径相对偏细,主要以粉砂级组分为主(49.56%),粘土含量相对较高(约为4.871%)。低河漫滩和平水位边滩沉积物的粒径相对偏粗,主要以砂级组分为主(低河漫滩为82.96%,边滩为69.72%),低河漫滩沉积物中粘土含量较少,只有1.058%;2)平水位边滩沉积物的粒径的统计平均值比高河漫滩沉积物值偏大,而标准差值的统计平均值却比高河漫滩和低河漫滩沉积物的偏小;3)3种地貌单元中,高河漫滩的偏度平均值最大,低河漫滩的偏度平均值最小,但低河漫滩偏度平均值的分布范围却较大;4)低河漫滩沉积的粒度参数值曲线的空间波动起伏最为明显,而高河漫滩粒度参数值的空间变化不大;5)3种地貌单元的峰态系数的统计平均值均大于1.15(为窄态),频率曲线表现为单峰,概率累积曲线都较平缓且均为2段式,反映了一般河流高水位沉积的基本特征。分析认为,粒度特征与河道不同地貌单元的微地貌形态和沉积结构是一致的,均是由洪水时不同地貌单元的水动力特征决定的。