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排序方式: 共有68条查询结果,搜索用时 15 毫秒
61.
62.
Jan‐Tai Kuo Wen‐Cheng Liu Ruey‐Tyng Lin Wu‐Seng Lung Ming‐Der Yang Chou‐Ping Yang Show‐Chyuan Chu 《Journal of the American Water Resources Association》2003,39(3):671-687
ABSTRACT: Field data collected from the Feitsui Reservoir in Taiwan indicate that the water is at a stage between mesotrophic and eutrophic. Recent measurements such as total phosphorus, chlorophyll a and Secchi depth levels suggest that the water quality has been declining. A two‐dimensional, laterally averaged, finite difference hydrodynamic and water quality model was used to simulate the water quality in the Feitsui Reservoir in an effort to determine sound water quality management strategies. The model was calibrated and verified using data collected in 1996 and 1997. The calibrated model was used to simulate algal biomass (in terms of chlorophyll a) levels under various wasteload reduction scenarios. Model results show that 50 percent reduction of the total phosphorus load will improve the existing water quality, shifting the trophic status from eutrophic/mesotrophic to oligotrophic. The modeling effort has yielded valuable information that can be used by decision makers for the evaluation of different management strategies of reducing watershed nutrient loads. 相似文献
63.
The paper describes the study of the hydrodynamic and transport features of the S. Gilla lagoon in Sardinia, Italy. The study,
aimed at assessing the environmental quality of the water body, involved extensive use of numerical models based on the shallow
water equations, thus enabling to simulate a number of different situations of practical interest. Based on field data, six
meteorological and hydrologic patterns were recognised which were assumed as representative of the various conditions occurring
in the four seasons. Typical winter conditions proved effective for the water refreshment, while the other seasonal patterns
induced a stronger internal mixing. Thus, unfavourable salinity distributions with respect to the fish farm activities, which
are carried out in the water body, were obtained with the winter pattern, whereas, on the other hand, a higher dilution of
pollutants discharged by the river inflows was achieved. In general, between dominant winds, southeast winds proved more effective
in forcing internal mixing than northwest winds. Two flood events with quite different return periods were also simulated,
in order to estimate the extent of the inundated areas and the salinity depletion. The consequent salinity recovery was simulated
both in natural conditions and with the discharge of salt sea water into the lagoon to accelerate the salinity re‐equilibrium.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
64.
65.
汉江流域水土流失特点及防治对策 总被引:11,自引:0,他引:11
贺素娣 《长江流域资源与环境》1997,6(3):271-276
汉江流域水土流失长期以来基本上没有得到有效控制,目前已成为区域经济建设和开发中的重大障碍之一。详细地阐述和分析了流域内水土流失发生规律和特点,指出了其潜在危险。随着治理的进一步深入、水土流失治理难度也在明显加大。介绍了若干项切实可行的防治措施。 相似文献
66.
Jung Hyun Choi Seon‐A. Jeong Seok Soon Park 《Journal of the American Water Resources Association》2007,43(6):1444-1454
Abstract: This research investigates possible impacts of enlarged water body according to dam reconstruction on the hydrodynamics and water quality of the reservoir using a laterally averaged, two‐dimensional hydrodynamic and transport model, CE‐QUAL‐W2. The lake was formed by the artificial dam in 1983 for agricultural water supply and is currently under consideration of reconstruction so as to expand the volume of reservoir for flood control as well as water supply in downstream areas. To calibrate and validate the model, field‐collected data were compared with model predictions for water level fluctuations and water temperature during the years of 2001 (from January to December) and 2003 (from March to November). The model results showed a good agreement with field measurements both in calibration and verification. Utilizing the model, impacts of dam reconstruction on the thermal hydrodynamics and turbid current were predicted. From the model results, dam reconstruction limited the depth of thermal stratification below 10 meter and formed steep temperature gradient between epilimnion and hypolimnion. The restricted thermal stratification persisted up to the end of September. This result indicated that thermal stratification would become stronger during summer and stay longer after dam reconstruction. In addition, the restricted thermal stratification caused vertical circulation of water mixing lower than 10 meter and isolated the upper water layer from the lower water layer which increased the volume of hypolimnetic water with low temperature. The vertical circulation near the surface also mitigated propagation of density plume within the depth of 10 m which would remain the hypolimnetic water clean. 相似文献
67.
以三峡水库典型支流库湾小江和香溪河为例,通过2020年蓄水期不同阶段的野外监测,对比分析了两条支流库湾的水动力过程、热分层、溶解氧时空差异及其对蓄水过程的响应.结果表明:(1)蓄水初期,小江库湾表层受大气复氧和浮游植物影响溶解氧较高(7.00~13.00 mg·L-1,其氧跃层出现在水深3~5 m处,5 m以下水域出现大面积缺氧(DO<2.00 mg·L-1),甚至无氧现象.香溪河库湾溶解氧在垂向上大致可以分为3层:表层富氧水体(8.00~12.00 mg·L-1)、中层水体(6.00~8.00 mg·L-1)和底层低氧水体(4.00~6.00 mg·L-1).(2)稳定的热分层为底层厌氧的形成提供了稳定的物理环境,而小江上游来流以及消落带植被分解增加了水体有机质的含量,可能是造成小江水体耗氧量增大、形成厌氧的内因;而香溪河因为长期存在的顺坡异重流补给,底层水体缺氧的风险较低.(3)持续的跟踪监测发现水库蓄水对支流库湾溶解氧起到了显著的补给作用,促使小江库湾厌氧现象在短期... 相似文献
68.
微生物在城市河流氮循环中发挥重要作用.由于河流的三维流动性,有必要明晰河流微生物组成和氮循环功能的垂向分布以及水动力因子对微生物来源和群落构建的影响.基于16S rRNA高通量测序技术,研究了北运河北京通州段水体和沉积物的细菌群落组成和氮循环功能,解析了环境要素和水动力因子对群落结构的影响,并对河流细菌进行了溯源.结果表明,沉积物细菌α多样性显著高于水体;从组成上来看,变形菌门(Proteobacteria)丰度最高,在水体和沉积物中的相对丰度分别为54.72%和32.36%. PICRUSt2功能解析表明,北运河有丰富的氮代谢功能,共获得47个氮代谢基因.水体和沉积物表现出相似的功能分布:反硝化作用、氮的同化和异化还原作用相关基因丰度较高,生物固氮和硝化作用相对较低.溯源分析表明,水体细菌来自上游、两岸和沉积物的比例分别为60.05%、37.93%和1.05%,而沉积物细菌来自上游、两岸和上覆水的比例分别为50.16%、45.55%和1.55%,细菌主要通过纵向和横向运移影响当地微生物群落的组成.环境因子、水动力因子和两者相互作用对水体细菌群落变化的解释率分别为44.22%、3.21... 相似文献