Application of a unit hydrograph based on subwatershed division and comparison with Nash's instantaneous unit hydrograph

The Unit Hydrograph (UH) technique is widely used for runoff estimation, especially for determining peak discharges. In this paper, a geomorphologically based UH has been applied. Its most remarkable characteristic is that it includes the watershed structure in its formulation. This is defined from the drainage network, each subwatershed being considered as a linear reservoir. In this method, the fact of considering this reservoir sequence according to the drainage network leads to the formulation of the model only depending on a single parameter. The Geomorphological Unit Hydrograph of Reservoirs (GUHR), proposed in this paper, is compared with Nash's Instantaneous Unit Hydrograph (Nash's IUH), by applying the two methods to the Aixola watershed. This 4.7-km² watershed is located in Gipuzkoa (Northern Spain). It is characteristic of the headwaters watersheds of the area. Most of them are forested and have steep slopes. Annual rainfall is over 1500 mm and many intense rainfall events are observed, among which 18 were selected for this study. Both UH techniques were applied to the rainstorms. The resulting hydrographs were plotted against registered data and the best fits were determined. According to these results, the GUHR model behaved similarly to Nash's IUH. However, the GUHR method seemed able to reproduce a wider range of rainstorms than Nash's IUH. While analyzing the UHs calculated, seasonal behavior was observed in runoff generation, and different average UHs were proposed for two different periods. This variability was also observed in values adopted by the GUHR model parameter, providing some information about the watershed time response. The dynamic character of the only uncertain parameter, and the model formulation, in which the watershed morphology is reflected, together with the model's simplicity, leads us to consider GUHR as being a promising UH model.     

Spatial variation in drainage characteristics and geomorphic instantaneous unit hydrograph (GIUH); implications for watershed management—A case study of the Varada River basin,Northern Karnataka

Geomorphological characteristics can be treated as signatures of hydrological responses. Geomorphologic instantaneous unit hydrograph (GIUH) is of utmost use in planning watershed management programs on a broad scale in absence of hydrologic data. Fifth order basins from different agroclimatic zones in the Varada River basin were selected to understand the spatial variation in drainage characteristics. These sub-basins show significant differences in their morphometric properties such as basin area, drainage density, bifurcation ratio, circularity ratio, constant of channel maintenance etc. These differences reflect variation in the hydrological process and geomorphologic instantaneous unit hydrograph (GIUH) of different sub-basins and can be used to understand watershed management aspects. Fifth order sub-basin in the Southern Transition agroclimatic zone is potential for artificial recharge programs. Sub-basins in the Hilly non-forest zone on the north are ideal for surface water storage like tank development program while Forested Hilly zone on the north are environmentally sensitive and prone to erosion.     

基于能量转换的地貌单位线计算方法及应用

该研究基于能量转换原理构建汇流模型,针对中小河流汇流参数确定困难、汇流计算准确度低的问题,分析流域内水质点能量的空间分布,采用将重力势能转化为动能的方式估计地表水流速度,计算空间流速场并提取地貌单位线。采用分辨率30 m×30 m的数字高程模型（Digital Elevation Model,DEM）数据,将湖南省竹溪坡流域划分为57个计算单元,分别采用能量转换法和坡度雨强法提取了地貌单位线。构建了研究区的分布式模型,其中产流计算采用新安江模型,坡面汇流采用地貌单位线模型,河网汇流采用马斯京根法,对竹溪坡流域36场降雨径流过程进行模拟。采用统计方法分析汇流参数,对参数的取值范围进行了评估。结果表明,与坡度雨强法相比,基于能量转换方式的洪水模拟结果中,峰现时间误差不超过1 h的场次比例由30.5%提高到83.3%,确定性系数不低于0.9的场次由9场提升至17场,平均确定性系数达到0.89,显著提高了模拟精度。通过对断面流速进行统计分析,评估竹溪坡流域汇流参数取值范围为[0.008, 0.014],当参数在此区间浮动时,确定性系数不低于0.9的场次比例为44%～50%,与率定得到的结果接近。该方法物理意义明确,参数可以通过率定或者测量方式确定,为无资料地区汇流规律研究提供了一种可靠思路。     

太行山区坡地暂时饱和区形成机理及渗流补给特性

为了研究岩土特性对坡地雨水转化及再分配的影响,采用时域反射仪(TDR)对太行山区坡地岩土水分进行了长期连续监测,分析了岩土水分特性的时空变异。结果表明：太行山区坡地岩土水分变化存在时空变异性,坡地0～100 cm岩土层内岩土水分含量在垂直空间上与季节上均呈“低-高-低”的变化趋势,同时土壤层与岩体层的结合部位在8月份前后存在暂时饱和区;坡地岩土介质的空间变异性,特别是岩土二元结构的地质结构特性为暂时饱和区的形成提供了地质条件,而强降雨过程为暂时饱和区的形成提供了水文条件,暂时饱和区的水分状态达到或超过饱和状态的时间与前期岩土水分含量及降雨特性有关;该暂时饱和区的存在为坡地渗流中“侧向优先流”及“垂向优先流”的产生创造了有利条件,两个方向上的“优先流”相互作用,促进了岩土水分的快速下渗,提高了地下水的转化效率。     

罗玉沟流域典型暴雨洪水及其产沙特性

以罗玉沟流域实测水文泥沙数据和洪水调查资料为基础,分析几场造成极强烈侵蚀的典型特大暴雨的雨、洪、沙特性。结果表明：典型暴雨面雨量离差系数为0．15—0．74,不均匀系数为0．37—0．90,极端降雨比值系数为1．3-188．8,暴雨中心最大10min、最大30min和最大60min降雨量分别占次降雨总量的19％-29％、35％-73％和60％-100％;次暴雨洪量超过年径流量的30％,径流系数0．20—0．49,洪峰流量模数为4．07—9．34m^3／（s·km^2）,洪水总历时6—96h,上涨历时15—80min;次洪输沙量超过年输沙量的60％,次洪输沙模数为0．71-1．40万m^3／km^2,最大含沙量高达774kg／m^3,且沙峰多超前于洪峰10—20min,沙量过程线的消退明显滞后于流量过程线,最大含沙量出现时的流量较最大流量偏小40％-50％;历次暴雨的雨、洪、沙特性差异主要受暴雨时空分布特征和下垫面条件控制,水土保持措施具有明显的滞洪减沙效应。     

Responses of flood peaks to land use and landscape patterns under extreme rainstorms in small catchments - A case study of the rainstorm of Typhoon Lekima in Shandong,China

Investigations of the formation mechanisms of flood peaks in small catchments facilitate flood prediction and disaster prevention under extreme rainstorms. However, there have been few studies on the responses of flood peaks to land use landscape patterns using field surveys during extreme rainstorm events. Based on field data from 17 small catchments near the rainstorm center of Typhoon Lekima, 7 landscape indices were chosen. The flood peak and its sensitivity to the land use landscape were investigated by combining remote sensing interpretation and related analysis. The conclusions are as follows: (1) The peak discharge of the small catchment was 2.36–56.50 m³/s, the peak modulus was 8.00–48.89 m³/(s·km²), and the flood index K ranged from 3.61 to 4.55. (2) Under similar rainfall conditions, the flood peak modulus, K and the proportion of sloping cropland had significantly positive correlations (p < 0.05). The flood peak modulus was significantly negatively correlated with the proportion of forest-grassland and terrace (p < 0.05), and K and the proportion of forest-grassland and terraced land exhibited a negative correlation. (3) The flood peak modulus and K were positively correlated with the landscape fragmentation. (4) The sensitivities of small catchments to floods were evaluated to be moderate compared to K values from other studies. The ability of small catchments to cope with extreme rainstorms can be improved by increasing the areas of forest-grassland, and terraces and reducing landscape fragmentation. Our results could be applied to provide a basis for land use planning and support for the response against disasters caused by extreme floods.     

Geochemical traces of flood layers in the fluvial sedimentary archive; implications for contamination history analyses

We studied three cores from a well-dated sediment archive from an oxbow lake of the River Morava, Czech Republic, using a high-resolution (1 cm) multiproxy stratigraphic analysis and a concentration of selected heavy metals. The objective was to investigate how the vertical distribution of pollutants could be affected by episodic flood sedimentation in archives with high sedimentation rates. Stratigraphic proxies (magnetic susceptibility/MS/, X-ray densitometry and visible-light diffuse reflectance spectrometry), supported by grain-size analyses, enabled us to identify relatively coarse-grained flood layers and correlate them in the proximal-to-distal direction in the oxbow-lake delta. A correlation of the flood layers with the time series of the river discharge was used to improve the age model based primarily on ¹³⁷Cs dating. The refined age model is nonlinear and shows periods of lower and higher sediment accumulation rates, which coincided with periods of lower and higher frequency of floods in the river, respectively. Concentrations of most heavy metals, normalized to lithogenic aluminium, revealed vigorous short-term variation related to floods, whose magnitude exceeds that of long-term trends. There is a substantial risk that temporal contamination trends, even if normalized to lithogenic elements, can be strongly influenced by facies, which may lead to potential misinterpretations. Element normalizing to MS, which proved to be a good proxy of grain size, provided smoother long-term trends whose interpretation was less affected by short-term variations. The long-term trends exhibit decreasing concentrations of most heavy metals for the last ~ 25 years, most notably between ~ 1987 and ~ 1992. These historical patterns correspond well to the significant improvement in environmental pollution reported elsewhere in Central Europe. In contrast, concentrations of Na have systematically increased up until the present, partly being driven by the widespread use of de-icing salt for winter road treatment.     

播种单体对地下压力测量方法和数学模型

对播种下压力实时测量是精准控制的基础,为了提高现有测量方法的通用性、准确性和稳定性,该研究在对播种下压力和播种深度关系模型分析基础上,采用轴销传感器播种下压力测量方法,进行了传感器力学分析和设计选型方法研究,并针对不同播深设定下单一测量模型误差大的问题,建立了融合播种深度因素的播种下压力测量修正模型,模型决定系数(R²)为0.991 6,均方根误差(root mean square error,RMSE)为28.88 N,验证试验表明,不同播深设定下,模型预测误差绝对值最大为44.13 N,最大相对预测误差为3.28%,提高了播种下压力测量模型通用性和准确性。播种下压力田间动态变化分析试验结果表明,在4～8km/h车速下,播种下压力振荡主频幅值随车速增加而减小,且免耕处理下主频幅值和功率谱密度(powerspectraldensity,PSD)峰值均大于旋耕处理。不同车速和耕作方式下,播种下压力振荡主频变化较小,主要集中在0～1 Hz,为后续信号稳定输出的滤波处理提供依据。该研究结果可为播种下压力的精准控制奠定基础。     

朱溪流域水土流失治理序列芒萁叶片叶绿素的变化分析

芒萁是南方红壤区水土流失治理的先锋植物,但其叶片叶绿素含量的作用尚未明晰。以南方红壤区典型流域朱溪流域为研究区,选择4个不同水土流失治理年限样地和2个对照样地以形成水土流失治理序列。通过调查、测定芒萁生长环境和叶片叶绿素含量,分析叶片叶绿素含量在水土流失不同治理年限的变化,揭示其在芒萁抵抗环境胁迫时的表现方式。结果表明:沿治理序列,土壤全碳、全氮和全磷含量均趋于增加且总体上未治理对照地最低,植被郁闭度增加且总体上治理36年样地和风水林对照地相对较高,而芒萁叶片叶绿素a含量、叶绿素b含量、叶绿素a/b和总叶绿素含量均呈上升趋势,总体上上述数值在未治理对照地与治理6年样地和治理12年样地均无显著差异,治理36年样地和风水林对照地相对较高。综上,水土流失治理初期土壤养分未对芒萁产生严重胁迫,提高叶绿素含量和改善叶绿素比例结构是芒萁抵御水土流失治理后期遮阴胁迫的重要方式之一。     

基于GIS的东北黑土区土壤侵蚀模数计算

为了监测及评估我国东北黑土区土壤侵蚀现状,在地理信息系统技术的支持下,应用CSLE模型,结合0.5 m分辨率的World View遥感影像,定量估算黑龙江省克山县古城小流域的土壤侵蚀量。结果表明:1)研究区的土壤侵蚀强度为轻度侵蚀,侵蚀区主要集中在该区的西北、东北和中南部地区;2)当坡度<20°时,土壤侵蚀程度较低,当坡度>20°时,土壤侵蚀较严重,此外坡度还能通过影响耕作措施的方式对土壤侵蚀强度产生间接作用,而水土保持措施因子和生物措施因子同样对土壤侵蚀区的分布范围及强度影响较大。研究结果对我国东北地区防治水土流失、减少河流泥沙、改善和恢复黑土肥力具有重要意义。     

中国农业碳排放绩效评价及随机性收敛研究——基于SBM-Undesirable模型与面板单位根检验

当前,全局层面及工业视角下的碳排放绩效评价和收敛性分析已趋于成熟,但农业碳排放方面的研究尚十分薄弱。为补充相关研究,对区域农业碳排放总量、绩效及两者的收敛趋势有更清晰的认识,本文在测算2000—2014年我国30个省市农业碳排放总量的基础上,运用SBM-Undesirable模型计算农业碳排放绩效,并通过面板单位根检验方法对全国和各区域的农业碳排放总量及绩效进行了随机性收敛检验。结果显示:1)2000—2014年间,全国农业碳排放量整体呈递增趋势,但各区域排放量差异明显。比较中部与全国、东部和西部各年总量均值,发现2000年的差值分别为3.357 4?106 t,3.965 0?106 t和5.904 7?106 t,到2014年,差距扩大至5.244 8?106 t,7.351 2?106 t和7.681 0?106 t,对应增长比例分别为56.2%、85.4%和30.0%。2)各区域农业碳排放绩效存在显著差异。绩效均值折线图显示,东部平均绩效较高,15年来基本稳定在0.8左右;西部和中部绩效均值较低,绝大多数年份处于0.3~0.5,但西部不断改善,中部则持续下降。3)对总量进行收敛性检验,发现全国、西部、中部呈现明显的随机性分异,仅东部出现随机性趋同;在绩效的收敛性检验中,全国范围内不存在随机性收敛,但东部、中部、西部各自呈俱乐部式随机性收敛态势。随机性收敛检验结果表明,中国农业碳排放总量和绩效不会自动降低到稳态水平,有必要进行相关政策干预,以缩小各省市间的差距。本研究为制定区域间差异化和区域内统一性农业减排政策奠定了基础。     

红壤丘陵区典型小流域侵蚀景观时空变化分析——以福建长汀县朱溪河小流域为例

基于1999年和2007年2期数字化侵蚀景观类型图,在ArcGIS 9．0的支持下,提取朱溪河小流域侵蚀景观类型转移矩阵,并结合重心模型,从时间和空间上对侵蚀景观动态变化进行定量分析,结果表明：1）1999年、2007年朱溪河小流域侵蚀景观基质均为微度侵蚀,轻度、中度、强度、极强度和剧烈侵蚀作为斑块单元镶嵌其中;2）1999—2007年,微度和轻度侵蚀的面积均有显著增加,其中微度侵蚀面积增加量最大,主要由轻度转化而来,且主要分布于小流域东部;中度、强度、极强度和剧烈侵蚀面积均有减少,其中剧烈侵蚀面积减少率最大,主要向轻度转化,且高度聚集于小流域上游的游屋圳和高陂坡次一级小流域;3）1999-2007年期间,剧烈侵蚀重心迁移距离最大,轻度、中度和极强度的重心向西南偏移,微度重心向东北偏移,强度重心向东南偏移。人类活动是该流域侵蚀景观时空变化的主要驱动因素。     

麦田土壤水分时空变异特性及CA-Markov模型模拟预报

为揭示农田土壤水分时空变异特征,精准预测土壤含水量,该研究以河北省太行山山前平原井灌区典型麦田为例,在监测土壤水分的基础上,采用时间稳定性指数法、空间自相关性评价法研究土壤水分时空分布规律,构建了适用于模拟预报田间水分时空变化的CA-Markov 模型,并将该模型的模拟预报效果与HYDRUS 模型进行比较。结果表明：随着土层深度的增加,土壤水分等值线由密变疏,变异系数逐渐减小。随着小麦生育期的推移,前期监测的土壤水分稳定性高于后期;在土壤较湿润的情况下,土壤水分空间相关性较强,土壤水分全局Moran’s I 指数随小麦生育期的推移呈现先增大后变小的规律。CA-Markov 模型模拟预报的各土壤相对湿度等级面积误差的平均值为1.61%,比HYDRUS 模型模拟预报的面积误差平均值（10.86%）小9.25个百分点; CA-Markov 模型对研究区4月下旬、5月上旬的土壤水分干旱等级预测的空间分布Kappa 系数分别为 89.31%、91.46%。该模型可综合考虑麦田墒情的时空变化及随机特性,模拟预测土壤墒情的精度较高、效果良好,可以作为麦田水分管理的重要工具。     

皇甫川流域降水和人类活动对水沙变化的定量分析

采用线性趋势法、非参数Mann-Kendall趋势检验法、累积距平法及径流历时曲线法分析皇甫川流域1955-2010年水沙变化特征,通过水文分析法定量评价降水和人类活动对水沙变化的贡献率.结果表明:皇甫川流域径流量和输沙量均呈急剧减少趋势,尤其在20世纪80年代之后,减少更加显著,近10年(2000-2010)的平均径流量与输沙量相当于1950-1959年的约20％;皇甫站径流量和输沙量均在1979年发生突变;在变化期1980-2010年,人类活动对流域水沙变化的贡献占主导因素,约为70％,而降水所占比例为30％左右;自20世纪80年代始,大规模的水土保持措施(如退耕还林(草)、梯田建设、水库淤地坝等工程)等人类活动是流域水沙锐减的主要影响因素.     

基于多源数据的中原黄泛区土壤盐分空间变异分析

为研究中原黄泛区土壤盐分空间变异,以河南省封丘县为研究区,综合考虑引起土壤盐渍化的土壤盐分、地形、地下水位及矿化度、植被情况及其他影响因素,基于遥感影像和磁感式探测获得的土壤表观电导率等多源数据建立了区域土壤盐分综合评估模型,并对研究区分层土壤盐分空间变异进行评估。结果表明:对于0~60 cm土层利用多源数据进行模型构建中土壤表观电导率与光谱指数占主要比例,模型对于各层土壤盐分的评价精度0~60 cm土层优于≥60~120 cm土层。土壤盐分含量随着深度的增加而增大,变异系数在0.22~0.28之间,属中等变异强度。土壤盐分主要集中分布在研究区北部与东南部,尤其是东南角黄河沿线区域,且随着土壤剖面显示出从表现到深层逐渐增加的趋势。利用多源数据建立的分层土壤盐分综合评估模型对于区域土壤盐分解析具有较高精度。该研究为中原黄泛区土壤盐化消减与土壤质量提升提供了可靠新方法。     

改进YOLOv5测量田间小麦单位面积穗数

单位面积穗数是决定小麦产量的主要因素之一。针对人工清点小麦穗数的方法容易受主观因素影响、效率低和图像处理方法鲜有进行系统部署等问题,提出一种注意力模块（Convolutional Block Attention Module,CBAM）与YOLOv5相结合的CBAM-YOLOv5网络结构,通过对特征图进行自适应特征细化,实现更准确的单位面积穗数测量。该研究以本地采集小麦图像数据和网络公开小麦图像数据为数据集,设置输入图像分辨率为1 280,得到CBAM-YOLOv5模型,可以达到0.904的F1分数和0.902的平均精度,测试集计数的平均相对误差为2.56%,平均每幅图像耗时0.045 s,综合对比,CBAM-YOLOv5模型具有显著优势。模型放置于服务器,结合手机端软件和辅助装置,形成单位面积穗数测量系统,实现育种小区麦穗图像实时采集、处理和计数,计数的平均相对误差为2.80%,抗环境干扰性强。该研究方法与装置可以实现田间小麦单位面积穗数的实时在线检测,降低主观误差,具有较高的准确率及较强的鲁棒性,为小麦单位面积穗数快速、准确估测提供一种新的技术和装备支撑。     

蒲河流域氮污染负荷模拟及时空分布

目前世界上许多国家仍面临严重的非点源污染问题,其中氮素污染负荷仍是水资源研究与环境治理方面的重点问题。利用SWAT模型,结合地形地貌、土地利用、气候条件等因素对氮污染负荷进行模拟及时空分布研究,对非点源污染治理具有重要意义。在辽宁省沈阳市蒲河流域基础资料搜集基础上,应用GIS结合SWAT构建模拟研究数据库,根据蒲河水系分布将流域划分为23个小流域215个水文响应单元,分别对氮素形态、氮污染负荷贡献率、氮污染关键区以及流域氮污染的时空分布等进行模拟研究。结果表明:1)氮以有机氮、NH4+-N、NO3--N、NO2--N的形式存在于水体中,NO3--N含量最高。2)时间上,TN量在年内各月呈波动变化,且TN流失具有明显滞后性。3)空间上,流域有机氮和NO3--N整体呈现由东北向西南扩散,上游及中游地区含氮量高于下游地区,1号子流域为氮素污染关键区,3、9、10号为次要关键区,TN贡献区主要集中在流域出口至马家窝棚水域。     

坡地水土保持型生态农业体系建设研究

研究了坡地水土保持型生态农业模式构建及其技术体系与调控机制、坡地水土保持型生态农业建设评价指标体系,并结合案例简析了坡地水土保持型生态农业优化模式构建。     

哈尔滨市耕地利用效益特征分析

提高耕地利用效益是缓解粮食供应压力的有效手段。以黑龙江省粮食主产区哈尔滨市为例,从经济效益、社会效益及生态效益3个方面构建耕地利用效益评价指标体系,以哈尔滨市1997-2006年的数据为基础,运用熵值法确定各指标权重,并通过建立协调度模型,定量评价出1997-2006年哈尔滨市耕地利用效益系统协调度。结果表明:1997-2006年哈尔滨市耕地利用系统协调度处于波动状态,耕地综合利用效益并不稳定,但总体呈上升趋势。耕地利用经济效益和社会效益协调度变化不大,综合效益与生态效益的协调度曲线走势趋同,表明哈尔滨市耕地利用综合效益主要受生态效益的影响。最后从根本上提出有效措施实现哈尔滨市耕地利用效益的提高。     

有机肥施用模式对环水有机蔬菜种植氮磷径流的影响

在水环境敏感区域以有机生产代替常规集约化农业,对保护生态环境、提高水库水质和保障居民饮用水安全具有重要意义。实际生产中,如果为追求产量盲目施用有机肥会增加氮磷径流流失风险。为在保障产量的前提下减少氮磷流失,本研究于昆明松华坝水库集水区,以不施肥(CK)和常规施用化肥(CF)为对照,在有机生产方式下设置不同类型有机肥[牛粪(DMC)、鸡粪(CMC)以及二者与豆饼的混合有机肥(HH)]及用量(与CF处理等氮素投入100%、80%和60%)的有机肥施用模式,共计11个处理(CK、CF、0.6DMC、0.8DMC、DMC、0.6CMC、0.8CMC、CMC、0.6HH、0.8HH、HH),分析其对土壤径流氮磷流失阻控效果和作物产量的影响。研究结果表明,在有机种植方式下,施用有机肥可使施肥初期(0～25d)总氮径流浓度比常规施化肥降低26.3%～73.9%,生育期总氮累积浓度降低32.8%～67.0%。单施牛粪和鸡粪导致径流水总磷浓度比CF提高49.1%和12.3%,施用混合有机肥或减氮施用牛粪和鸡粪总磷浓度则比CF处理降低15.8%～52.5%。氮素投入水平和施肥类型对径流水氮磷浓度、土壤硝态氮和速效磷含量有显著影响。等氮素投入下不同肥料类型的径流水总氮浓度为化肥牛粪混合有机肥鸡粪,总磷浓度为牛粪鸡粪混合有机肥化肥;土壤硝态氮含量为化肥牛粪、鸡粪混合有机肥,速效磷含量为鸡粪牛粪混合有机肥化肥。以60%氮素水平施用有机肥对径流水氮磷累积浓度和土壤硝态氮含量削减效果最佳,但土壤速效磷仍有累积风险。混合有机肥处理的青花菜产量最高,而单施牛粪或鸡粪存在减产风险。综合来看,与常规施用化肥相比, 60%氮素投入加牛粪、鸡粪和豆饼混合有机肥的施肥模式可在产量提高16.7%的前提下,使径流水总氮、硝态氮、氨态氮浓度分别降低66.5%(18.94mg·L~(–1))、67.2%(11.11 mg·L~(–1))和66.2%(6.57 mg·L~(–1)),总磷降低52.5%(0.5 mg·L~(–1)),可作为推荐施肥类型和用量在松华坝流域有机蔬菜生产进行推广。