甘肃省黄土高原区典型城市雨洪与积水模拟研究

近年来,受气候变化影响,黄土高原城市区极端暴雨事件持续多发,引起诸多城市内涝等水灾害问题,严重影响社会、经济发展.选取甘肃省黄土高原地区典型新建城市区为研究对象,基于历史实测降雨、径流数据及地形等基础数据,构建黄土高原沟壑区城市暴雨洪水模拟模型(Seorm Water Management Model,SWMM),研究...     

知识窗

北京时间的由来电台报告时间总是说:现在是北京时间××时。“北京时间”又是怎样来的呢?原来,地球上不同地点的人,看到太阳通过天体子午线的时刻(即正午12时)是不一样的。为了统一,天文学家规定东西两地相隔经度15°,时间就差1小时。地球自转1周为360°,一天分成24小时,所以地球1小时就等于自转15°。国际上把全球分为24个“时区”,我国使用的是东经120°的标准时间,属于东8区,“北京时间”就是东8区时间。什么是发达国家和发展中国家发达国家是指那些经济上发达,生产力发展快,人民生活水平高的国家,也称工业国家,包括北美的美国、加拿大,…     

基于GIS及综合权重法的甘肃黄土高原区山洪灾害风险区划研究

针对甘肃黄土高原区特殊地形地貌特点,通过对山洪灾害形成因素分析,确定将研究区的高程、坡度、汇流累积量、河网密度、年平均降雨量、1 h临界雨量、人口密度、耕地面积占比、人均GDP 9项指标作为山洪灾害主要影响因子,通过危险性和易损性分析建立山洪灾害风险区划模型,运用层次分析法及熵权法综合确定指标权重,利用Arc GIS软件进行空间插值和栅格图层计算完成山洪灾害风险区划图,结果表明:甘肃黄土高原区的山洪灾害风险区划指数按照从高到低划分为5个等级,从西北向东南呈明显递增的分布特征,高风险区主要分布在降雨较多的陇东黄土高原及西南部的临夏州一带、较高风险区主要分布在黄土高原的中南部、中风险区分布于黄土高原的中部一带、较低风险区和低危险区分布在黄土高原的西北部分县(区),最终通过65年历史山洪灾害验证分析,甘肃黄土高原区山洪灾害风险区划结果符合实际情况,可以为山洪灾害风险管理提供支撑。     

考虑两流区影响的分布式水文模型及其应用

黄土塬区土层巨厚，土壤入渗过程包括优先流和基质流，但其两流区入渗过程不同于山区等区域。目前，分布式水文模型在黄土高原应用时未考虑优先流对降雨入渗过程的影响，造成模型在黄土高原应用时模拟失真，精度较低，大大限制了流域分布式水文模型的广泛适用性。基于传统降雨入渗模型（Green-Ampt模型），研究通过引入总土壤饱和含水量和土壤总饱和导水系数，改进分布式水文模型，构建黄土塬区两流区WEP分布式水文模型。选择黑河流域作为研究区域，分别利用改进前、后的WEP模型模拟研究区的降雨径流过程，对比验证WEP模型改进后的适用性。结果表明：与传统WEP模型相比，通过考虑两流区影响：对于月径流而言，流域断面逐月径流量相对误差绝对值均小于0.05%,Nash-Sutcliffe效率系数均大于0.69；而未改进模型的相对误差为0.06%～0.24%,Nash-Sutcliffe效率系数在0.66～0.70之间；改进后的模型率定期Nash-Sutcliffe效率系数由0.66升高至0.69，相对误差绝对值由0.24%降低到0.05%，在验证期内Nash-Sutcliffe效率系数由0.70提升到0.73，相对误...     

青海省干旱灾害时间序列分形特征研究

采用标度变换法,计算了1470—1970年青海省总体干旱灾害、各等级旱灾及旱季序列的时间分维数,并探讨了各等级旱灾及旱季序列时间分维的动态变化特征。结果表明,干旱灾害时间序列存在自相似性,具有分形特征。各等级旱灾以及各旱季时间分维数与其发生频次正相关。不同等级干旱灾害的时间重演规律不同,旱灾程度越重,无标度区越宽、分维值越低;旱灾程度越轻,无标度区越窄、分维值越高。旱灾序列时间分维数与区域气候条件有关。研究时段内,总体旱灾和轻度旱灾的发生趋向混沌无序化,短周期更加明显;中度旱灾变化较无序;春旱趋向混沌无序的平衡态,夏旱则出现短周期与长周期、有序与无序的交替现象。     

基于Meta-Analysis的气象与环境因素对玉米氮素利用的研究

运用Meta-Analysis法研究玉米氮肥利用与气象和环境因素的关系。结果表明,在砂质粘壤土和粉砂壤土中玉米氮素利用的响应比最大;地理纬度为39°—42°N时,玉米氮素利用的响应比最大;气象因素对玉米氮素利用的影响为:在玉米生长前2个月,降雨均匀度对玉米氮素利用的影响较气温和降雨量大,在玉米生长中期,降雨量对玉米氮素利用的影响最大;在玉米生长后期,降雨均匀度、气温和降雨量都对玉米氮素利用的响应比有重要影响。     

天然降雨对黄土坡地土壤侵蚀和养分流失的影响

选渭北旱原东部合阳县甘井镇为试验地,以研究天然降雨和坡度对黄土高原土壤侵蚀以及土壤养分流失的影响。研究区的径流小区被设置为5°、10°、15°3个坡度的坡面,采用径流场观测法,对一定降雨条件下的产流产沙量以及土壤养分流失量进行测定研究。实验结果表明：在相同坡度的径流小区中,产流量、产沙量以及土壤养分的流失量均随着降雨量...     

压片式微喷带单孔水量分布特性试验研究

试验研究了不同工作压力(0.1MPa和0.15 MPa)、不同喷射角度(43°、65°和79°)和不同喷孔直径(0.5、0.6和0.7mm)对压片式微喷带水量分布的影响。试验结果表明,干燥区宽度、湿润区长度和湿润区面积主要受喷射角度影响,均随喷射角度的增大而减小;湿润区宽度相对稳定,但在0.15MPa下,随着喷孔直径的增大有明显的增加趋势;平均灌水强度随着喷射角度、喷孔直径和工作压力的增大均有增加趋势,其中喷射角度影响最为明显。     

黄泛区潮土土壤水和地下水的动态变化及其对降雨的响应

基于时间序列分析方法,在1999年10月至2000年9月豫北平原潮土土壤水、地下水位观测资料的基础上,分析了降雨(包括灌溉)动态和土壤水、地下水位动态的相关关系,揭示了该地区土壤水、地下水位对降雨的响应及其动态变化规律。结果表明,该地区土壤水、地下水位序列为自相关序列,时间相关域为1～2个滞后时间距;土壤水、地下水位对降雨的初始响应时间都在1周以内,并基本随土层深度增加而增大。     

立体雾培墙定植角度对生菜生长的影响

在温室立体雾培墙系统中，研究了不同栽培角度对大速生生菜生长情况和品质的影响。在试验处理中，定植角度90°（与水平面夹角，以下相同）不利于生菜根系的生长和叶片数的增加，定植角度90°的生菜的硝态氮含量较低，同时，其叶绿素含量和可溶性蛋白含量与水平定植45°相比，也显著降低；水平定植60°有利于生菜根系的生长；水平定植45°的生菜的生长情况和品质较优，其中，与水平定植角度90°处理相比，叶绿素含量和可溶性蛋白含量显著提高。试验证明：选择合适的定植角度有利于生菜的栽培，其中，在墙面栽培中，定植角度45°优先考虑。     

Quantifying risk for water harvesting under semi-arid conditions: Part I. Rainfall intensity generation

Rainfall intensity is the most important factor for runoff estimations, however rainfall intensity data is often unavailable. Rainfall disaggregation techniques are appropriate for use in problems where design storms are required. Rainfall intensity patterns within storms and then the validity of a stochastic rainfall intensity model were, therefore, studied on the highveld of South Africa. Rainfall intensity data collected for 30 years at two semi-arid sites, Bloemfontein (29°S, 26°E) and Pretoria (26°S, 28°E) were analysed using dimensionless hyetographs. No difference was found in either seasonal or geographic variability for the two sites, indicating that intensity patterns within rainfall events across the highveld was identical. The stochastic rainfall intensity model was shown to produce acceptable results. From these results, it has been concluded that one model can be used to generate rainfall intensities for the highveld.     

人工模拟暴雨条件下紫色土坡耕地入渗过程研究

结合室内物理化学试验等研究手段,运用人工模拟降雨法,分别探讨了不同暴雨强度,地面坡度及聚丙烯酰胺(PAM)加入量对紫色土坡耕地降雨入渗率的影响.研究结果表明,随着降雨强度的增大,稳定入渗率有增大的趋势;在0°～10°范围内随着坡度的增大紫色土坡面入渗量随之增加;PAM的加入可以较大程度促进土壤水分的入渗,提高稳定入渗率...     

雨滴打击对黄土坡面细沟侵蚀特征的影响

基于模拟降雨试验和纱网覆盖消除雨滴打击作用的试验方法,研究雨滴打击对黄土坡面细沟侵蚀特征的影响。试验包括3种黄土高原代表性的侵蚀性降雨强度(50、75、100 mm/h)和3个细沟侵蚀发生最常见的坡度(10°、15°和20°)。结果表明,与有雨滴打击试验处理相比,纱网覆盖消除雨滴打击后,坡面径流稳定产流率和含沙量均明显减小;坡面侵蚀量和细沟侵蚀量分别减少28.1%~47.7%和20.2%~38.6%;而细沟侵蚀对坡面侵蚀的贡献率增加。消除雨滴打击后,坡度对细沟侵蚀的影响与有雨滴打击时相同,而降雨强度对细沟侵蚀的影响增加。有、无雨滴打击试验处理的细沟密度和割裂度均随着降雨强度和坡度的增加而增大;而细沟倾斜度的变化较为复杂,所以细沟密度和割裂度可作为描述细沟形态的最佳指标。试验结果还表明,雨滴打击对细沟沟槽形状也有间接影响,即消除雨滴打击后,细沟宽度和深度的变异程度减小,沟槽形状更为规则。同时,有雨滴打击试验处理的细沟宽深比随着坡度和降雨强度的增加而减小,而无雨滴打击试验处理的细沟宽深比随着坡度的增加而减小,随着降雨强度的增加呈微弱的增加趋势。     

自然降雨对紫色土坡耕地氮磷流失的影响

在三峡库区主要土壤类型(紫色土)、不同坡度(15°、25°)、不同种植模式(柑桔-牧草、蔬菜-马铃薯、玉米-小麦)上建立径流池,研究自然降雨条件下土壤氮磷流失特点。结果表明,土壤氮、磷流失量和流失率在降雨量增加到一定程度时即达最大值,继续增加降雨量,氮、磷流失量和流失率呈下降趋势。氮、磷流失量和流失率同72h内降雨量呈S曲线关系。径流水中总氮(磷)量和浓度同坡度和种植模式无显著性差异。径流水中总氮(磷)浓度随降雨量增加无明显增加趋势,径流水中总氮流失量随降雨量的增加也无明显增加趋势,但径流水中总磷流失量随降雨量的增加呈直线增加。     

Time trend in reference evapotranspiration: analysis of a long series of agrometeorological measurements in Southern Italy

This study aims to evaluate the potential effects of the climatic variations on the reference evapotranspiration (ET₀) and, consequently, on the crop water requirements in the Apulian Tavoliere, one of the largest irrigated districts of Southern Italy. To reach this purpose, both climatic parameters (air temperature and rainfall) and estimated water requirements of ??processing?? tomato (among the most representative irrigated crops in the district since the mid-1970s and, therefore, chosen as a study-case) were analyzed in order to find out if a time trend exists or does not. The analysis covered the period from 1957 to 2008. The analysis showed that the rainfall amounts decreased (?3.4 mm per year in the analyzed period), while air temperature increased (0.18 °C and 0.25?°C per decade for minimum and maximum, respectively). As a consequence of the climatic variation during the considered period, a growth trend of the ET₀ (1.4 mm per year) and water deficit (3.2 mm per year) took place. As a consequence, the water amounts for irrigating the same crop in the considered period were growing. This increased consumption is in agreement with the perception of the farmers of the district but never documented. Through the FAO AquaCrop model, the tomato irrigation water requirements have been simulated during the considered period. The trend analysis of the seasonal evapotranspiration values simulated in 52 years confirmed the increase in tomato water requirements (0.7 mm per year).     

双燃料发动机燃烧噪声特性及影响因素分析

从时域和频域两方面综合评价双燃料发动机的燃烧噪声,分析转速、负荷、供油提前角以及生物质气替代率等因素对燃烧噪声的影响,并与柴油机的相关数据进行比较,结果表明:在21℃A供油提前角时,转速对整个频率范围内气缸压力级的影响较小,在相同转速下随负荷的增加,生物质气替代率下降,燃烧总声压级普遍增大;而当供油提前角增大至24℃A时,两种机型的气缸压力级频谱曲线变化强烈,转速的增大使其在高频范围内呈振荡式发展,负荷的增加使其在低、中频范围内增大.     

雨型对东北典型黑土区顺坡垄作坡面土壤侵蚀的影响

基于人工模拟降雨试验,研究了雨型对东北黑土区顺坡垄作坡面土壤侵蚀的影响。根据典型黑土区侵蚀性降雨标准及雨型特征,试验设计了总降雨量相同(降雨量为87.5 mm)的5种不同雨型,即增强型(降雨过程中降雨强度分布为50-75-100-125 mm/h)、减弱型(降雨过程中降雨强度分布为125-100-75-50 mm/h)、峰值型(降雨过程中降雨强度分布为50-75-100-125-100-75-50 mm/h)、谷值型(降雨过程中降雨强度分布为100-75-50-75-100 mm/h)和均匀型(降雨过程中降雨强度保持75 mm/h不变),以及1个坡度(即顺坡垄作改横坡垄作的临界坡度5°)。结果表明,受前期预降雨的影响,各雨型处理的顺坡垄作坡面径流量差异较小,但坡面侵蚀量存在明显差异,其中峰值型雨型引起的坡面侵蚀量最大,分别是谷值型、减弱型、均匀型和增强型雨型处理下的1.20、1.63、1.78、1.80倍。引起侵蚀量较大的雨型(峰值型、谷值型和减弱型)在典型黑土区天然降雨中出现频次超过70%,这可能是该区夏季顺坡垄作坡面侵蚀作用强烈的重要原因之一。同一降雨强度在不同雨型中出现的时序不同,其产生的径流量和侵蚀量对总径流量和总侵蚀量的贡献率也不相同。除125 mm/h外,同一降雨强度出现在起始阶段产生的侵蚀量对坡面总侵蚀量的贡献率显著大于其出现在其他阶段对坡面总侵蚀量的贡献率。     

基于WA-SVM的流域降雨序列预测研

为了提高降雨中长期预测精度，将小波分析和支持向量机回归方法引入水文序列预测领域，给出了两种方法的思路和特点。在此基础上，尝试建立了基于小波分析-支持向量机（WA-SVM）的降雨量序列预测模型。通过小波分解，将原始复杂的降雨序列分解到不同的频率层次，对每层得到的分解序列分别采用支持向量机回归方法进行预测，最后合成原始序列的预测值。将该模型应用于实际流域月降雨量预测，并与单独支持向量机回归方法预测结果进行比较，表明该方法预测精度有明显提高。     

Estimation of water levels in a main drainage canal in a flat low-lying agricultural area using artificial neural network models

The Chiyoda basin is located in the Saga Prefecture of the Kyushu Island, Japan, and lies next to the tidal compartment of the Chikugo River, into which excess water in the basin is drained away. This basin has a total area of approximately 1100 ha and is a typical flat and low-lying agricultural area. The estimation of the water levels at the gates and along the main drainage canal is a crucial issue that has recently been the subject of much research. At these locations farmers and managers need to control the operation of the irrigation and drainage systems during periods of cultivation. An attempt has been made to apply a feed-forward artificial neural network (FFANN) to model and estimate the water levels in the main drainage canal. The study indicated that the artificial neural network (ANN) could successfully model the complex relationship between rainfall and water levels in this flat and low-lying agricultural area. Input variables and the model structure were selected and optimized by trial and error, and the accuracy of the model was then evaluated by comparing the simulated water levels with the observed ones during an irrigation period in July 2007. The water levels at two locations, located upstream and downstream of a main drainage canal, were investigated by using a time series at intervals of 20, 30, and 60 min. At these intervals, rainfall and tide water levels in the Chikugo River were measured, and the backward time-step numbers of the input variables of rainfall and tide water level were searched. For the upstream location, the optimal combination yielding good agreement between the observed and estimated water levels was obtained when the interval of the time series was 60 min. The number of backward time-steps of the input variables of rainfall and tide water level were 5 and 4, respectively. In contrast to the downstream location, the optimal combination was obtained for the interval time series of 20 min with 4 backward time-steps for both the input variables of rainfall and tide water level. The present study could provide farmers and managers with a useful tool for controlling water distribution in the drainage basin, and reduce the cost of installing water level observation points at many locations in the main drainage canal.     

A comparison of the Priestley-Taylor and Penman methods for estimating reference crop evapotranspiration in tropical countries

An equation for Potential Evaporation (PE) proposed by Priestley and Taylor in 1972 has fewer data requirements than the well established Penman Potential Transpiration (Et) equation. From their definitions, PE and Et values should both provide acceptable estimates of Reference Crop Evapotranspiration (ETo), as defined by Doorenbos and Pruitt. Analysis of mean monthly climatic data from 30 tropical stations, widely spread within the latitude zone 25°N to 25°S, showed that PE and Et estimates agreed closely when monthly rainfall exceeded monthly Et. The minimum data requirements for the Priestley-Taylor equation are daily net radiation and mean air temperature. The Penman equation additionally requires daily data for humidity and run of wind. As reliable field net radiometers become more widely available, the Priestley-Taylor PE equation offers a satisfactory alternative to the Penman Et equation for estimating ETo in humid tropical climates.