Influences of drip and flood irrigation on soil carbon dioxide emission and soil carbon sequestration of maize cropland in the North China Plain

The need is pressing to investigate soil CO2 （carbon dioxide） emissions and soil organic carbon dynamics under water-saving irrigation practices in agricultural systems for exploring the potentials of soil carbon sequestration. A field experiment was conducted to compare the influences of drip irrigation （DI） and flood irrigation （FI） on soil organic carbon dynamics and the spatial and temporal variations in CO2 emissions during the summer maize growing season in the North China Plain using the static closed chamber method. The mean CO2 efflux over the growing season was larger under DI than that under FI. The cumulative CO2 emissions at the field scale were 1959.10 and 1759.12 g/m2 under DI and FI, respectively. The cumulative CO2 emission on plant rows （OR） was larger than that between plant rows （BR） under FI, and the cumulative CO2 emission on the irrigation pipes （OP） was larger than that between irrigation pipes （BP） under DI. The cumulative CO2 emissions of OP, BP and bare area （BA） under DI were larger than those of OR, BR and BA under FI, respectively. Additionally, DI promoted root respiration more effectively than FI did. The average proportion of root respiration contributing to the soil CO2 emissions of OP under DI was larger than that of OR under FI. A general conclusion drawn from this study is that soil CO2 emission was significantly influenced by the soil water content, soil temperature and air temperature under both DI and FI. Larger concentrations of dissolved organic carbon （DOC）, microbial biomass carbon （MBC） and total organic carbon （TOC） were observed under FI than those under DI. The observed high concentrations （DOC, MBC, and TOC） under FI might be resulted from the irrigation-associated soil saturation that in turn inhibited microbial activity and lowered decomposition rate of soil organic matter. However, DI increased the soil organic matter quality （the ratio of MBC to TOC） at the depth of 10-20 cm compared with FI. Our results suggest that the transformation from conventional FI to integrated DI can increase the CO2 emissions and DI needs to be combined with other management practices to reduce the CO2 emissions from summer maize fields in the North China Plain.

Community-Based Approach in the Prevention and Management of Flood Disasters in Babessi Sub-Division (Ndop Plain, North West Cameroon)

Flood is a recurrent natural disaster that has caused enormous human and material damage in many places and continues to hit local committees at an alarming rate. The need to setup permanent committees to prevent and manage flood disasters by local communities is therefore indispensable. In rural areas, the creation of such a structure is always a welcome relief to flood victims but it is often marred by numerous management problems. This study aimed to analyze the community-based approach in the prevention and management of flood disasters in Babessi Subdivision (North West Cameroon), to identify the causes of flood disasters and the preventive strategies used by this local community. A total number of 300 questionnaires as well as structured interviews were used to collect data in the field and the data were analyzed by simple descriptive statistics. The main results revealed that the main cause of flood disasters is heavy and consistent rainfall. Also, poor refuse disposal and drainage system management contribute to floods. The identification of areas likely to be affected by floods and preventing the riparian population from constructing houses along these areas especially beside the main rivers are the flood preventive measures adopted by the local flood management committee. The flood victims are reluctant to relocate to the settlement site earmarked by the Government, meanwhile, the local flood committee do not have the legal tools to forcefully relocate them. The population of Babessi needs to be sensitized on the impending dangers of flood hazard and be encouraged to participate in implementing the adopted strategies to prevent and manage subsequent flood disasters.

Assessing Biogeomorphological State of the Teesta River Flood Plain: A Study on Gangachara Upazila, Rangpur, Bangladesh

Teesta river flood plain is one of the most significant landscapes in Bangladesh. The main theme of this research was to assess the present biogeomorphological state (biomass, herbaceous vegetation species, density of all vegetation species, flood plain extension mapping) of Teesta river flood plain under Gangachara upazila. The research work was conducted based on the objectives to prepare a map of Teesta river flood plain extension area, to estimate herbaceous vegetation (biomass, species types), and to find out the vegetation density to assess the present biogeomorphological state of study area. To present the flood plain area of Teesta river in the Gangachara upazila, base map has been used;herbaceous vegetation samples have been collected through quadrat method to estimate biomass (both in dry and before dry condition) using digital weight machine;vegetation density has been shown through NDVI of satellite image (Landsat-8) using red and NIR band in ArcGIS 10.1 software. From the results of this research, river flood plain area is found 68.5 sq. km;total 31 types of herbaceous species have been identified where Pouzolzia indica is the most dominated species covering 11.59% of the total area;maximum DNs value of NDVI is found +0.475242 which represents the highest vegetation density covering an area of 78 sq. km of the total area. The research may assist for the further study of river flood plain biogeomorphology throughout the country as well as in the world.

Current Situation and Evolution of Drought and Flood in Fen-wei Plain

Based on the latest results and data of drought and flood in Fen-wei Plain, current situation and evolution of drought and flood in Fen-wei Plain were analyzed. The results show that in Fen-wei Plain drought and flood are natural disasters bringing about the most serious damage, and drought risk in east central Weihe Plain is serious. In Fen-wei Plain, precipitation tended to decrease, and temperature, drought days and intensity increased over the past 50 years. There were obvious differences between two decades in drought and flood. Drought was the severest in the 1990s, and flood was the most serious in Fenhe Plain in the 1960s and in Weihe Plain from the late 1970s to the early 1980s. Over the past ten years, precipitation and flood frequency increased, and temperature, drought days and intensity decreased. In Fen-wei Plain, temperature will rise and precipitation will increase slightly in next 20 -40 years. Monitoring and early warning capability of drought and flood in Fen-wei Plain have im- proved gradually, but some issues need to be paid more attention to and solved.

Flood disaster monitoring based on Sentinel-1 data:A case study of Sihu Basin and Huaibei Plain,China

Summer floods occur frequently in many regions of China,affecting economic development and social stability.Remote sensing is a new technique in disaster monitoring.In this study,the Sihu Basin in Hubei Province of China and the Huaibei Plain in Anhui Province of China were selected as the study areas.Thresholds of backscattering coefficients in the decision tree method were calculated with the histogram analysis method,and flood disaster monitoring in the two study areas was conducted with the threshold method using Sentinel-1 satellite images.Through satellite-based flood disaster monitoring,the flooded maps and the areas of expanded water bodies and flooded crops were derived.The satellite-based monitoring maps were derived by comparing the expanded area of images during a flood disaster with that before the disaster.The difference in spatiotemporal distribution of flood disasters in these two regions was analyzed.The results showed that flood disasters in the Sihu Basin occurred frequently in June and July,and flood disasters in the Huaibei Plain mostly occurred in August,with a high interannual vari-ability.Flood disasters in the Sihu Basin were usually widespread,and the affected area was between Changhu and Honghu lakes.The Huaibei Plain was affected by scattered disasters.The annual mean percentages of flooded crop area were 14.91%and 3.74% in the Sihu Basin and Huaibei Plain,respectively.The accuracies of the extracted flooded area in the Sihu Basin in 2016 and 2017 were 96.20% and 95.19%,respectively.

Frequency of Floodplain Spills in the Tisza River Valley at Vylok (Transcarpathia, Ukraine)

Record-breaking floods occurred in the autumn of 1998 and the spring of 2001 in the lowlands of Transcarpathia,as well as in the areas of Hungary and Romania bordering Ukraine,which caused severe damage.Our research was to determine the frequency of floods.The fluctuation of precipitation values brings about the increased frequency of the rivers’inundation as well.The research is based on the data of the Tisza River’s inundation onto the flood plain near Vylok,as well as the precipitation data of the Rakhiv meteorological station.Both data series include the data of the latest 46 years(1970-2015),highlighting the pre-flood period of 1970-2001.To evaluate the data,we used linear trend analysis,which was edited using the Microsoft Excel spreadsheet program.The results of the study showed that no particular changes in precipitation were observed,but the frequency of flood waves and the coverage of the floodplain with water showed a gradually increasing trend.The results of studying the amount of precipitation and the Tisza River’s inundation:in recent decades the frequency of flood wave formation and the coverage of the flood plain with water show a gradually increasing tendency.

A differential wide field electromagnetic method and its application in alkaline-surfactant-polymer(ASP) flooding monitoring

To improve effectiveness of ASP flooding, it is necessary to establish a reliable parameter design and tracking adjustment method to monitor the process of oil displacement. A differential wide field electromagnetic method was proposed and applied to the ASP displacement monitoring test in a block of the Daqing Oilfield. In the process of ASP flooding, the electromagnetic field was measured many times. The data acquired before the ASP flooding were set as the background field, and the resistivity model was obtained by inversion. Then, the resistivity data were calibrated by logging data and the resistivity model was established. Finally, the range and front of ASP flooding were deduced with the residual gradient from the spatial domain first-order difference of the resistivity model. Production data of well groups in this block have proved that this method can work out the range and front of ASP flooding accurately, providing support for optimization of ASP flooding parameters.

Inundation Calculation of the Coastal Narrow Plain Strip Impacted by Upstream Reservoir Flood Discharge in Rainy and Extreme Flood Conditions

In the context of current climate change, an abnormality of flooding is a common form of disaster in Vietnam. Hanh Stream reservoir has occurred great flood in 1986, 2010. In the future, the risk of flooding is possible to happen again. In view of management of the risk of natural disasters： large flooding situation downstream is one of the most dangerous risks for the reservoir. Due to downstream of Hanh Stream reservoir is a narrow coastal plains, quick infrastructure development, especially interwoven road and railway systems, so that flood drainage ability will be affected greatly. The consciousness of risks that may be occurred in the future in order to propose preventive measures and proactive response to minimize damages always is the requirement for all projects. The hydrodynamic calculation, flooding maps, emergency plan to prevent flooding downstream of Hanh Stream reservoir is also needed. The article is raised the issue of requirements to calculate coastal narrow delta strip flooding in the Central of Vietnam when impacted by the upstream reservoir of flood discharge in terms of extreme heavy rain and flooding and presented computational methods of Mike software package for case flooded plain of Cam Ranh Bay in downstream reservoirs of Hanh Stream, Khanh Hoa Province, Vietnam.

Soft Sediment Deformation Structures in the Sediment Deposits of Ganga River and Its Oxbow Lakes in Parts of Indo-Gangetic Plain: Implications for Quake Proxies and Paleoseismicity Tracking

The Late Quaternary thick sedimentary fills of the Ganga basin predominantly consist of unconsolidated fluvial sandy deposits which are often intercalated with mud. These deposits at various places record the evidence of earthquakes, which occurred in the recent geological past. The evidence is contained and manifested in the form of Soft Sediment Deformation Structures (SSDSs). Saturated sediments/muds/soils are liquefied by earthquake tremors which either generate SSDS or produce structural discordance in the pre-existing sedimentary structures. The present study reports the occurrence of SSDS, e.g. load and associated flame structures, clastic dikes and sill structures, slump structures and sedimentary breccias, etc. from the Ganga River and adjacent oxbow lake sediment deposits. An attempt has been made to establish the origin of soft sediment structures of this region in accordance with its neotectonic history and in turn, identification of seismic structural proxies to delineate paleoseismic events in this region with futuristic implications. The preservation of soft sediment deformation structures in large numbers with multiple geomorphology and scale, in the river and adjoining lake sediments, is indicative of frequent earthquakes of high magnitude consequent to tectonic activism in the Himalayan region.

不同泥沙含量下受淹胁迫对鄱阳湖平原双季稻生长与产量的影响

为探究鄱阳湖平原区洪涝时期不同泥沙含量下受淹胁迫对双季稻生长及产量的影响,采用大田试验与室内分析相结合的方法,设置淹2/3株高和全淹2种受淹深度,S1(0 kg/m^(3))、S2(0.5 kg/m^(3))、S3(1.0 kg/m^(3))3种泥沙含量,对淹水后6、9 d早稻和中稻的生长指标和水稻产量进行了观测研究。结果表明:适度受淹刺激水稻伸长,节间不断分化,叶片伸长、增宽。早稻抽穗开花期受淹株高、节间长增加9.35%、12.75%,2/3淹下叶面积增加11.00%。但胁迫过大抑制水稻生长,中稻全淹下株高和分蘖数减小33.49%、29.28%,叶面积减小30.94%,此时中稻难以伸出水面,导致功能叶片附沙严重,泥沙含量增大进一步抑制了水稻生长。受淹导致早稻和中稻穗干物质量平均减小32.35%、58.72%(P<0.05)。结实率和千粒质量减小是早稻抽穗开花期受淹后产量下降的主要原因,此时泥沙含量和淹水时间的影响并不明显。中稻全淹下泥沙导致减产加剧,S2、S3下减产率比S1下显著增加31.63%、52.20%(P<0.05),此时产量下降是穗长、有效穗数、穗粒数、结实率、千粒质量综合作用的结果。研究结果可为鄱阳湖平原区洪涝灾害治理和粮食安全保障提供理论和技术支撑。

海河“23·7”流域性特大洪水复盘模拟

为支撑海河流域特大洪水的决策及预报预警工作,基于实测降水与流量资料,采用新安江-海河模型对海河流域2023年7月发生特大洪水的大清河2个典型小流域——紫荆关流域和漫水河流域进行了洪水模拟,并选取紫荆关流域1996—2020年5场洪水、漫水河流域1953—2016年8场洪水进行了参数率定,选取海河“23·7”流域性特大洪水进行了验证。结果表明:新安江-海河模型对“23·7”流域性特大洪水的模拟精度较高,可反映实际洪水过程,两个小流域洪峰、洪量模拟的相对误差均在20%以内,峰现时间误差均为0 h;相较于受人类活动影响小的紫荆关流域,在受人类活动影响更大的漫水河流域,新安江-海河模型的模拟效果较新安江模型的模拟效果提升更为明显。

治涝导向的平原河网地区海绵城市实施路径探索——以宿迁市国家海绵城市示范系统化实施方案为例

针对平原河网地区的排涝特征与问题,在梳理构建治涝片区排水格局的基础上分类提出了针对性的治涝策略。对于具有一定坡度。在多数时期可以实现自排的治涝片区,采用“上蓄+中分+下排”模式,分段缓解排涝压力,提高城区排涝标准对于整体地势低洼,在多数时期很难自排的治涝片区,采用“建闸营圩,蓄排并举”模式,将雨水排口分散建设小型雨水泵站的模式调整为片区排涝主干河道末端建设大型排涝泵站的模式,充分利用片区内部河网的输送和调蓄能力,增强城区应对暴雨的韧性。

三峡水库运用后长江中游河漫滩演变趋势分析

长江中游历来是防洪重点,河漫滩的演变速率虽然相对缓慢,但新水沙条件下河漫滩的长期累积性变化值得关注。以三峡水库175 m运行期长江中游多处典型河漫滩淹没特征流量的统计分析作为基础,量化分析了三峡水库蓄水前后径流过程在河漫滩淹没特性方面的变化,结合滩面植物对季节性水文波动淹没耐受能力的分析,指出三峡水库蓄水前后径流过程变化造成的季节性淹没不足以阻断滩面植物的生长发育。由于一系列涉水工程的控制作用,长江中游河漫滩的横向变形受到了极大的抑制,但在滩面植被缓流滞沙效应下,长江中游河漫滩总体仍呈现缓慢淤高的长期趋势。

“23·7”特大暴雨对河北平原玉米产量的影响研究

洪涝是一种破坏力巨大的自然灾害,对粮食生产构成严重威胁。受台风“杜苏芮”和“卡奴”的影响,2023年7月29日至8月1日京津冀地区出现百年一遇的特大暴雨洪水灾害,给京津冀地区造成了重大损失,导致部分农田几乎绝收。为评估极端暴雨事件对当地粮食产量的影响,本研究使用MODIS MOD09GQ数据分析了暴雨前后的归一化植被指数(NDVI)变化,据此划定了本次暴雨造成的受灾农田区域(主要在河北平原)及其受灾程度,同时结合2016—2020年玉米种植空间分布、农业统计数据和NDVI数据,估算了受灾农田区域未发生暴雨和发生暴雨后两种情景下的玉米产量,进而评估了本次暴雨造成的玉米产量损失。主要得到以下结果:1)暴雨发生后,河北平原受灾农田区域的NDVI普遍减少0~0.35,相比之下,未受灾农田区域的NDVI均有所增加。2)本次强降雨导致河北平原约24万hm^(2)农田受到影响,绝产面积约13万hm^(2),减产面积约11万hm^(2)。3)蓄滞洪区周边的22个县(市、区)是本次暴雨的主要受灾区域,据回归分析结果,本次暴雨可能造成的玉米产量损失多达22万t,且92%的产量损失是由作物绝产所致。本研究为遥感手段估算极端降雨导致的粮食减产提供了一个快速且可靠的计算框架,同时强调了极端降雨对粮食安全的巨大威胁。

基于循环神经网络的山前平原型城市河道洪水预报研究

山前平原型城市拥有复杂的下垫面条件,其洪水兼具了山洪和城市洪水的特征,为水文模拟和洪水预报增加了难度。以小清河济南市黄台桥水文站以上流域为研究对象,构建了基于循环神经网络变体的洪水预报模型,并评估了模型的预测性能。研究结果表明,所构建的洪水预报模型既适用于对场次洪水的预报,又适用于对长系列洪水过程的连续预测,且能够灵活地输出流量、水位过程,在一定预测步长内拥有较高的预测精度,其中基于双向门控循环单元(Bidirectional Gate Recurrent Unit,BiGRU)网络构建的模型预测性能最佳,且随预测步长的延长,其性能衰减最弱,能够作为山前平原型城市河道洪水预报的新方法新手段。

滨海平原区可能最大洪水计算研究

平原河网区受城市区域空间交错、河湖蓄滞洪区联通、水利工程密布等因素的影响,瞬时单位线、经验公式等传统方法推及可能最大洪水(PMF)存在很大的局限性。为弥补传统方法在平原河网地区的适用性问题,尝试使用水动力洪水演进模型法,并综合考虑水库溃坝、可能最大降雨(PMP)、海洋风暴潮等不同叠加因素的影响,选取典型区域(江苏省连云港市西陬山地区某厂址附近区域)研究多种组合条件下平原河网区域的洪水演进过程,及在特定区域内产生的可能最大洪水,以期为平原河网地区可能最大洪水位的推求及工程设计提供参考。

海河“23·7”流域性特大洪水北京市拒马河洪水调查分析与河道治理建议

受2305号台风“杜苏芮”北上影响,2023年7月29日至8月2日京津冀地区连续降雨,海河流域发生“23·7”流域性特大洪水,造成严重的人员伤亡和财产损失。对北京市境内拒马河进行洪水调查,在深入分析拒马河治理现状的基础上,采用天然河道恒定流水面线计算和均匀流计算方法推求洪痕对应的流量,并以此复盘分析洪水频率。根据洪水分析成果及水毁情况,从拒马河水域空间划定、河道治理及建筑物设计等方面提出规划治理建议,以期为后续河道整治提供参考。

MIKE FLOOD耦合模型在杭嘉湖流域嘉兴地区洪水风险图编制工作中的应用

中国是世界上受洪涝灾害影响最为严重的国家之一,随着社会经济的快速发展,洪灾损失也越来越严重。我国正将防洪策略从洪水控制向洪水管理进行转变。洪水管理需要进行洪水风险分析,数值模拟则是洪水风险分析的一个重要手段。依托全国洪水风险图编制试点项目(二期)工作,以浙江嘉兴地区为研究对象,运用MIKE11软件建立该区域一维河网模型,模拟河道水位变化情况。再运用MIKE 21软件建立该区域二维模型,模拟暴雨情况下的洪水演进过程。最后运用MIKE FLOOD耦合模型,模拟河道溃堤洪水在区域内的演进情况,分析洪水风险,为嘉兴地区洪水风险图编制工作提供技术支撑。

海河“23·7”流域性特大洪水北京市永定河洪水调查分析及对设计洪水的建议

受2305号台风“杜苏芮”影响,海河流域发生“23·7”流域性特大洪水,造成严重人员伤亡和财产损失。通过对北京市境内永定河全面开展降雨分析和洪水调查计算,并与设计雨量、历史洪水、实测洪水和设计洪水进行对比分析,确定永定河不同历时雨量、流量、洪量及重现期标准,结合本次暴雨洪水特点重点分析了永定河三家店至卢沟桥段洪水规律的变化情况。针对永定河防洪工程设计洪水工作中存在问题和“23·7”特大洪水实际,提出防洪工程设计洪水工作思路和建议,以期为防洪工程规划设计提供参考。