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河流泥沙磷迁移过程的数学模型研究 总被引:4,自引:2,他引:2
水体中磷的迁移转化过程,对于河流生态环境有着至关重要的影响。传统的水质模型缺乏对磷迁移转化过程机理和规律的深入探讨与分析。本文建立河流中水动力-泥沙-磷迁移过程的分相模型,在水流运动与泥沙输移模拟的基础上,从基本的化学反应出发,研究磷在河流中的迁移过程。首先,考虑天然河流中磷的来源及其不同形态,基于泥沙颗粒表面电荷非均匀分布的认识,利用修正后的表面络合模型研究悬移质泥沙对磷的吸附;其次,分析有氧与无氧条件下泥沙颗粒中铁/铝(氢)氧化物的不同形态,以描述磷在活性底泥层中的赋存形式;然后,重点关注河床冲淤变形,分析磷在河床表面的沉积与再释放。最后,本文设计磷水槽试验,分析泥沙颗粒运动对磷迁移的影响,并对模型进行验证。结果表明,泥沙运动对磷迁移有显著影响,磷浓度沿程分布与含沙量间存在较好的线性关系,尤其是溶解相磷;本文建立的模型可以合理地反映磷随着泥沙颗粒的迁移过程。 相似文献
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The Paraná upper reaches, above the confluence with the Paraguay River, drains a predominantly humid, tropical-subtropical basin that has been extensively altered by anthropogenic activities. Deforestation followed by intense mechanized agriculture has progressively increased in the last decades. Many industrial settlements and hydroelectric impoundments have been developed. Suspended matter, total phosphorus, and inorganic nitrogen exportation rates were estimated at 14 t km?2 y?1, 28kg TP km?2 y?1 and 188kg N km ?2 y?1 respectively. These rates are compartively low when compared to other areas of the world. It was estimated that riverine mass transport represented roughly 6 per cent of the phosphorus and 20 per cent of the nitrogen inputs in the basin. Mass transport of suspended matter and soluble reactive phosphorus are lower and inorganic nitrogen higher than in 1967–1969. Siltation in the man-made lakes reduced both suspended matter and phosphorus transport. Inorganic nitrogen increase is thought to be related to increased fertilizer inputs. 相似文献
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在模糊聚类法划分子区域的基础上,采用河套地区73个国家基本气象站1951—2014年气象数据,将Kendall-tau非参数检验方法,Sens斜率估计方法以及Savitzky-Golay平滑滤波方法相结合,分析该地区18个气温指数的变化趋势。结果表明:(1)在河套地区的干旱半干旱子区(地处黄河上游),湿润半湿润子区(地处黄河中下游),极端气温事件的变化趋势基本相近,但强度不同,空间分布不一致。(2)在时间尺度上,发现河套地区近60年存在极端气温事件上升趋势,说明河套地区与全球变暖之间有紧密的响应关系。(3)在空间尺度上,各个指数在河套地区分布差异明显。多个指数在干旱子区的变化率大于湿润子区;干旱区各个指数变化显著的气象站点的占比高于湿润子区。有些指数在个别小区域与整个河套地区变化趋势不同,可能存在的原因有城市热岛、山丘地局部小气候,但有待进一步分析验证。(4)气温日较差、平均最高气温、平均最低气温、日最低气温的极低值、日最低气温的极高值、日最高气温的极低值、日最高气温的极高值指数变化趋势都在2000年左右开始变缓,这可能与全球气候变暖减缓有关。 相似文献
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Methodologies to study the surface hydraulic behaviour of urban catchments during storm events 总被引:1,自引:0,他引:1
A good knowledge of the hydraulic behaviour of an urban catchment and its surface drainage system is an essential requirement to guarantee traffic and pedestrian safety. In many cases, inlets have been situated according to spatial density criteria. Indeed a more rational location of inlets on urban catchments must be defined according to an accurate analysis of the relationship between street flow and inlet hydraulic efficiency. Moreover we lack specific hazard criteria in terms of the maximum acceptable flow depths and velocities on the streets that do not cause problems to pedestrians. In this paper the results of two different experimental campaigns are presented. The first was carried out to evaluate inlet hydraulic efficiency; the second was carried out to address the pedestrian stability in urban flood conditions, whose aim was to propose new hazard criteria. On the basis of the experimental results, a methodology was developed to assess flood hazard in urban areas during storm events. If a refined topographic representation of urban areas is available, a two-dimensional numerical simulation of urban flooding can be performed using complete shallow water equations. According to this approach a numerical application for flood hazard assessment in a street of Barcelona is shown. 相似文献
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Extreme climate events threaten human health, economic development, and ecosystems. Many studies have been conducted on extreme precipitation and temperature changes in the Yarlung Zangbo River Basin (YZRB). However, little attention has been paid to compound climate extremes. In this study, the variations of wet/warm compound extreme events in summer and dry/cold compound extreme events in winter over the past 42 years in the YZRB were investigated using eight extreme climate indices that were estimated using monthly temperature and precipitation observations. The results showed that the numbers of frost days and ice days tended to decrease on the spatiotemporal scale, while the maximum values of daily maximum temperature and daily minimum temperature exhibited increasing trends. The frequency of wet/warm compound extreme events was significantly higher from 1998 to 2018 than from 1977 to 1997. Dry/cold compound extreme events became less frequent from 1998 to 2018 than from 1977 to 1997. The rate of increase of wet/warm compound extreme events was about ten times the absolute rate of decrease of dry/cold compound extreme events. With regard to the spatial pattern, the frequency of wet/warm compound extreme events increased significantly in almost all parts of the YZRB, while that of dry/cold compound extreme events decreased across the basin. This study helps to improve our understanding of the changes in compound precipitation and temperature extremes in the YZRB from a multivariable perspective. 相似文献
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1961—2016 年西宁市极端降水事件变化特征 总被引:1,自引:0,他引:1
为研究西宁市极端降水事件变化规律,利用西宁气象站 1961—2016 年逐日降水量序列资料,计算得出年总降水量、5 日最大降水量、极端降水量、日降水强度、持续降雨日数及大雨日数等 6 个极端降水指标的年际序列,应用线性倾向估计法、滑动平均法、Mann - Kendall 非参数检验法、Morlet小波分析、相关性分析等方法分析各极端降水指标的变化趋势、变化周期及各指标间变化一致性。结果表明,近 56 年间西宁市各极端降水指标呈波动式增加趋势,其中 PRCPTOT 的增加趋势显著,而其余各指标变化趋势不显著; PRCPTOT、RX5day、R95 及 SDII 序列在整个研究时段内均存在明显的突变现象,其中在 1960 年代后期及 1970 年代中期 RX5day 与 R95 发生了一致的突变,在 1980年代末和 1990 年代初,PRCPTOT、RX5day 与 SDII 发生了一致的突变; 在近 56 年间各极端降水指标的振荡变化均存在明显的主周期,其中除 SDII 外,从 1990 年代开始各指标多存在约 11—13 年的主周期,SDII 及 CWD 的振荡变化均在整个研究时段上存在 40 年及 29 年左右的主周期; 各极端降水指标与总降水量均呈一致的正相关性,对总降水量的变化具有较好的指示作用,RX5day、R95、SDII 及 R20mm 四个指标相互之间均存在显著的正相关性。研究结果可为区域水资源规划及洪旱灾害防御提供参考。 相似文献
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基于鄱阳湖流域14个国家气象站1961—2010年的日降水量数据,采用百分位法定义阈值,识别极端降水事件;采用线性回归方法进行趋势检验,进而对鄱阳湖流域1961—2010年极端降水的时空变化特征进行分析。结果表明,相比年降水,流域极端降水的变化趋势更为明显;1961—2010年鄱阳湖流域极端强降水强度呈显著增大趋势而极端强降水天数显著减小;极端降水强度增大的区域主要分布在赣江流域和抚河流域。1961—2010年鄱阳湖流域大部分站点极端降水不存在突变,降水在时间上有分布更加集中的趋势。鄱阳湖流域极端降水的上述变化,对流域水资源管理提出了更加严峻的挑战。 相似文献
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Sediment transport has implications for activities such as fishing, flood control, scour countermeasures, and dredging through altered flow depths and sediment transport, bank erosion, and bridge scour. To estimate the changes in sediment transport and bridge scour, river discharge, water surface slope, water temperature, and tailwater depth (to simulate sea‐level rise) were altered in existing sediment transport and scour models. It was found that (a) in uniform flow upstream of sea‐level rise effects, sediment transport is sensitive to discharge but not to temperature; (b) in non‐uniform flow affected by sea‐level rise, sediment transport is sensitive to water surface slope and discharge but not to temperature; (3) the discharge value to restore the sediment transport rate existing before sea‐level rise is proportional to the water surface slope ratio to the fourth power; (4) the discharge value to restore the bed sediment size existing before sea‐level rise is proportional to the water surface slope ratio to the three‐fourth power; (5) abutment scour is weakly inversely proportional to the water surface slope but more strongly proportional to the discharge in a logarithmic relation; (6) pier scour is weakly proportional to the water surface slope but more strongly proportional to the discharge in a logarithmic relation; and (7) the discharge to restore both abutment and pier scour depths to their original values prior to sea‐level rise is proportional to the water surface slope ratio to the 9/25th power. Full equations for each of these relationships are given in the article. These relationships can be used for future application and planning purposes. 相似文献
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为了探讨泄洪河道中苇草不同生长状态对过流的影响,作者通过淮河入江水道过流河工模型试验,探讨了苇草生长的三种状态下4个特征流量对应的水位流量关系,分析了苇草对河道过流的影响,为工程管理和防洪抢险等提供了理论依据。 相似文献
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(2002年) 1 1月1日,《长江河道采砂管理条例》(以下简称《条例》)正式施行.该《条例》是于2001年10月10日国务院第45次常务会议审议通过,2001年10月25日,朱镕基总理签署国务院第320号令颁布. 相似文献
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利用黄河流域1965-2012年252个观测站日降水资料,分析了黄河流域年极端降水、汛期日极端降水的时空分布特征。研究结果表明:黄河流域年极端降水在空间分布上呈现出从东南向西北递减的特点,不同区域的年极端降水强度有显著空间差异,下游大汶河年极端降水强度最大,内蒙杭锦后旗临河一带年极端降水强度最小。极端降水站数偏多的年份,该年黄河流域总降水量也趋于偏多。汛期日极端降水强度从黄河上游到下游逐渐增强,主要发生在7-8月。 相似文献
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黄河流域洪水对入海泥沙通量的影响 总被引:3,自引:1,他引:2
利用1950~1985年大样本洪水资料,研究了黄河流域洪水过程中三黑小所控制的流域水沙条件与入海泥沙通量和通量系数的关系,分析了泥沙通量与流域水量、沙量和平均流量的关系。在三黑小沙量与入海泥沙通量的关系中,从量上看,黄河下游河道具有“多来多排”的特性;从比例上看,具有“多来多淤”的特性。不同来源区洪水对泥沙通量和通量系数具有不同的影响,平均每场洪水泥沙通量按大小排序依次是:多沙粗沙区、下少沙区、上少沙区和多沙细沙区。通量系数按大小排序依次是:下少沙区、上少沙区、多沙细沙区和多沙粗沙区。 相似文献
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为有效推进特大干旱事件灾害孕育机理及其影响的研究,在回顾与展望特大干旱灾害的基础上,分别对其次生灾害孕育过程和对生态环境长期影响的研究进行梳理与评述,指出当前研究中存在的主要问题与薄弱环节,包括对特大干旱的聚焦不够、干旱灾害链及多灾种协同演进定量研究亟待深入、特大干旱对养分循环与生态过程的长期影响等方面的研究相对匮乏。认为特大干旱事件灾害孕育机理及影响方面的整体研究框架尚未确立,相应研究体系和技术方法体系也远未形成。建议未来着重研究特大干旱次生灾害的深层链式结构和复杂能量传递问题,有效揭示特大干旱事件灾害孕育机理与多灾种协同演进机制,进一步阐明特大干旱对水文生态过程和地表环境的多重影响。 相似文献
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利用VisualMODFLOW软件,模拟河流基流的减少、河流入渗的增加两个过程在抽水期间和抽水后期的地下水位场变化,直观的揭示了开采地下水对河道径流量的影响.得出:开采是导致研究区下游地下径流排泄量呈现逐年减小的趋势.从整体水均衡来看,模拟区含水层2001年至2004年都处于负均衡状态,说明该区地下水已出现超采现象. 相似文献