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建立三维水动力学模型分析中华鲟产卵栖息地水力因子的时空分布和中华鲟产卵时的适宜水力特性,为设计最佳的生态调度方案提供科技支撑。研究结果表明,中华鲟产卵栖息地的上产卵区水深和流速的变化主要受流量影响,涡量的变化主要受地形影响;中华鲟产卵前需要高流量脉冲刺激产卵。坝下与隔流堤之间流速和涡量值的大小与波动远大于其他区域,均值为2.4 m/s和11 m2/s。产卵栖息地水体表层、中层和底层的流速和水平涡量分布格局相似,均是在上产卵区值较大,空间分布多样性高。水体中层垂向涡量的值远大于底层和表层。产卵栖息地水体表层、中层和底层水力分布特征为中华鲟繁殖提供了有利的水力条件,体现出中华鲟对产卵栖息地不同功能区的自主选择性。 相似文献
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为了克服已有物理栖息地模型仅能在具有较完善监测资料河流使用的局限性,介绍了一种应用模糊逻辑的物理栖息地模拟方法。该方法以河道平面二维流场模拟结果为基础,将鱼类学和生态学专家的知识经验融入物理栖息地模型中,运用模糊逻辑推理计算栖息地各单元适宜度,最后根据加权可用面积、高适宜度面积比例与流量的关系曲线确定生态需水量。运用该方法对葛洲坝坝下中华鲟产卵栖息地进行模拟。研究结果表明,中华鲟产卵期适宜生态需水量为10 000~17 000 m3/s。分析认为该方法对监测资料依赖程度低,使用专家知识经验能够弥补数据不足造成的不利影响,具有一定的可行性及实用性。该研究有助于监测资料不足的河流开展生态保护及河流管理工作,并且能够为模糊数学理论在水生态学中的应用提供参考。 相似文献
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2006年9~10月在长江采集悬浮颗粒物样品,应用改进后的SEDEX法对磷的赋存形态进行了分析.结果表明,自生磷灰石磷是长江悬浮颗粒物中磷的主要赋存形态.涪陵至万州江段,碎屑磷灰石磷的含量较高,弱吸附态磷和有机磷含量较低,磷的赋存形态主要受悬浮颗粒物含量的影响;香溪至葛洲坝下江段,弱吸附态磷和有机磷含量较高,碎屑磷灰石磷含量较低,磷的赋存形态主要受浮游植物生长及泥沙粒径的影响;城陵矶至大通江段,有机磷、碎屑磷灰石磷和铁结合态磷含量较高,弱吸附态磷含量较低,磷的赋存形态主要受泥沙粒径和洞庭湖输入的影响.长江悬浮颗粒物中生物可利用磷占颗粒态磷的45.6%,长江上游水体中生物可利用磷含量较低,下游含量较高. 相似文献
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2012年7月,长江流域先后出现4次强降雨过程,发生了4次洪水,其中朱沱江段水位超过历史实测最高记录,寸滩江段发生1981年以来最大洪水,三峡水库出现建库以来最大入库洪峰;长江上游干流宜宾至寸滩江段全线超过保证水位,中游干流石首至螺山江段及洞庭湖全线超过警戒水位。在调控"2012·07"洪水过程中,三峡水库有效降低荆江江段最高水位超过2m,洪湖江段超过1m,避免了长江荆江江段出现接近保证水位的高水位,缩短了长江中下游超警江段240km,大大减轻了中下游的防洪压力。 相似文献
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定量评价三峡蓄水后长江中游流域水文情势的时空变化,为长江中游生态保护和区域水资源管理提供科学依据。采用变化范围法分析了长江干流5个水文站的流量、含沙量日均数据,定量评估了三峡工程蓄水后,长江中游水沙变化度最大的江段和水文指标类别,及其对应的生态影响。研究结果表明三峡蓄水后,下游河道含沙量的变化度远大于流量,除城陵矶站外,含沙量较蓄水前有了大幅度下降,宜昌站的含沙量下降幅度达到了一个数量级,洞庭湖对长江干流含沙量有明显的调蓄作用。流量的变化度随着与大坝距离的增加而减小,且在7~11月流量下降幅度明显。这些水文节律的变化将影响下游鱼类产卵栖息地以及滞洪区水生生物与周边植被的生长。 相似文献
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松花江水质污染严重,但其水质净化作用也很强,两者相互作用结果使哈尔滨江段上游断面江水基本符合地面二级水标准,下游断面基本符合地面三级水标准,把通过河底沉积物向漏斗渗透补给的江水中的污染质,大部分净化在含水层之外,对优质地下水起到了保护作用。 相似文献
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以黄河下游防洪工程体系为背景,系统研究了防洪工程体系减灾效益计算有关水文、水力学、工程、经济等方面的问题,提出了防洪工程体系减灾效益计算的整体思想,开发了相应的计算模型。研究中还开发了用于分析黄河下游防洪保护区12万km2范围决堤洪水成灾状况的二维非恒定流模型。结合黄河下游防洪保护区具体情况,提出了财产状况、洪灾损失率、地形地物数据等减灾效益计算的重要参数。实例计算结果表明:模型计算结果合理,对解决防洪工程体系减灾效益计算问题是非常有效的。 相似文献
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An extremely large rock avalanche occurred on April 9, 2000 at Yigong, Tibet, China. It started with an initial volume of material of 90?×?106 m3 comprising mainly of loose material lying on the channel bed. The rock avalanche travelled around 10 km in horizontal distance and formed a 2.5-km-long by 2.5-km-wide depositional fan with a final volume of approximately 300?×?106 m3. An energy-based debris flow runout model is used to simulate the movement process with a new entrainment model. The entrainment model considers both rolling and sliding motions in calculating the volume of eroded material. Entrainment calculation is governed by a second order partial differential equation which is solved using the finite difference method. During entrainment, it is considered that the total mass is changed due to basal erosion. Also the profile of the channel bed is adjusted accordingly due to erosion at the end of each calculation time step. For Yigong, the profile used in the simulation was extracted from a digital elevation model (DEM) with a resolution of 30 m?×?30 m. Measurements obtained from site investigation, including deposition depth and flow height at specific location, are used to verify the model. Ground elevation-based DEM before and after the event is also used to verify the simulation results where access was difficult. It is found that the calculated runout distance and the modified deposition height agree with the field observations. Moreover, the back-calculated flow characteristics based on field observations, such as flow velocity, are also used for model verifications. The results indicate that the new entrainment model is able to capture the entrainment volume and depth, runout distance, and deposition height for this case. 相似文献
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The 1100-year-old Acheron rock avalanche deposit lies in an active tectonic setting in Canterbury, New Zealand, and has a
volume of ten million cubic metres and a runout distance 3.5 km. The deposit comprises intensely fragmented greywacke rock,
and the processes of intense rock fragmentation during runout are postulated to have generated an isotropic dispersive stress.
Dynamic simulation shows that the runout can be explained as a flow of dry granular material with a normal coefficient of
friction, if the presence of an isotropic dispersive stress within the moving rock debris throughout the runout is assumed.
The dispersive stress distribution required to model the rock avalanche runout and match velocities calculated from run-up
traces is closely similar to that used to simulate the runout of the much larger Falling Mountain rock avalanche in a similar
lithologic and tectonic setting. Both events thus behaved in a fundamentally similar fashion. 相似文献
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选取山西南部典型岩溶泉龙子祠泉域为研究对象,利用1954-2018年65年长时序的泉水流量、降水监测数据及1990-2018年的开采数据,分析其动态特征及响应规律。结果表明:该泉域泉流量在2.94～8.39 m3·s-1之间波动,多年平均流量为4.74 m3·s-1;年内泉流量对降水补给响应有4个月的时间滞后性;开采量保持较高水平时,泉流量总体呈明显下降趋势。利用多元回归方法建立两个阶段（1954-1989年和1990-2018年）的数学模型,并对其进行模拟和误差分析,结果显示:第一阶段泉流量影响因素主要为前一年降水和前两年降水;1990年开始存在开采活动,第二阶段受降水和开采共同制约,与当年开采量负相关且受其影响最为强烈,其次受前一年和前两年降水影响;整个时间序列上流量误差为11.62%,模拟效果较好。 相似文献
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低扬程双向流道泵站是我国独创的泵站型式,为深入了解其流道内流场特性,首次运用基于壁面律的RNG κ-ε的湍流模型对流道进行数值模拟。计算采用交错网格的有限体积法求解三维不可压Navier Stokes方程。提出优化出水流道的目标函数,并依据数值模拟结果,预测出水流道水力损失。根据经验公式计算的水力损失和预测的出水流道水力损失两者较为接近,表明通过采用基于壁面律的RNG湍流模型能较好地预测出水流道的水力性能。考虑壁面律的RNG湍流模型在泵站流道内特性数值模拟和外特性预测研究方面有较好的推广价值。 相似文献
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New insight into the evolution of large-volume turbidity currents: comparison of turbidite shape and previous modelling results 总被引：2，自引：0，他引：2
The Marnoso Arenacea Formation provides the most extensive correlation of individual flow deposits (beds) yet documented in an ancient turbidite system. These correlations provide unusually detailed constraints on bed shape, which is used to deduce flow evolution and assess the validity of numerical and laboratory models. Bed volumes have an approximately log‐normal frequency distribution; a small number of flows dominated sediment supply to this non‐channelized basin plain. Turbidite sandstone within small‐volume (<0·7 km3) beds thins downflow in an approximately exponential fashion. This shape is a property of spatially depletive flows, and has been reproduced by previous mathematical models and laboratory experiments. Sandstone intervals in larger‐volume (0·7–7 km3) beds have a broad thickness maximum in their proximal part. Grain‐size trends within this broad thickness maximum indicate spatially near‐uniform flow for distances of ∼30 km, although the flow was temporally unsteady. Previous mathematical models and laboratory experiments have not reproduced this type of deposit shape. This may be because models fail to simulate the way in which near bed sediment concentration tends towards a constant value (saturates) in powerful flows. Alternatively, the discrepancy may be the result of relatively high ratios of flow thickness and sediment settling velocity in submarine flows, together with very gradual changes in sea‐floor gradient. Intra‐bed erosion, temporally varying discharge, and reworking of suspension fallout as bedload could also help to explain the discrepancy in deposit shape. Most large‐volume beds contain an internal erosion surface underlain by inversely graded sandstone, recording waxing and waning flow. It has been inferred previously that these characteristics are diagnostic of turbidites generated by hyperpycnal flood discharge. These turbidites are too voluminous to have been formed by hyperpycnal flows, unless such flows are capable of eroding cubic kilometres of sea‐floor sediment. It is more likely that these flows originated from submarine slope failure. Two beds comprise multiple sandstone intervals separated only by turbidite mudstone. These features suggest that the submarine slope failures occurred as either a waxing and waning event, or in a number of stages. 相似文献
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悦康药业在开发和生产过程中可能会对区域地下水环境造成影响。基于研究区水文地质条件,建立水文地质概念模型,分别对拟开采的第Ⅲ承压含水层,运用水流运动方程对项目开采15年后的地下水位进行模拟预测;运用溶质运移数学模型对药厂建成后污水处理站对潜水和第Ⅰ承压水进行污染物模拟预测。水位模拟结果表明,15年后含水层(组)中形成降落漏斗大于1 m的范围为0. 45 km~2,形成地面沉降的可能性较小。污染物模拟预测选取COD_(Mn)、氨氮作为预测因子,分别预测污染发生100天、720天及1 800天后污染物迁移情况。污染物模拟结果表明污水站溶质扩散范围较小,5年后COD_(Mn)最大迁移距离为40 m,中心体积质量降为5. 0 mg/L;氨氮最大迁移距离为35 m,中心体积质量降为0. 3 mg/L,对区域地下水水质影响不大。 相似文献