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91.
In this study, the 54-year (1950 to 2003) monthly runoff series from February, April,August, and November, as well as the annual runoff series, measured at both Huayuankou and Lijin hydrological stations were chosen as representative data, and the continuous wavelet transform (CWT) was applied to analyze the impacts of human activities on the runoff regime of the middle and lower Yellow River. A point of change in 1970 was first determined, and the observed series before 1970 were considered natural runoff while those after 1970 were restored according to linear trends. Then, the CWT was applied to both the observed and restored runoff series to reveal their variations at multi-temporal scales, including the five temporal ranges of 1-4,6-8, 9-12, 16-22, and 22-30 years, and the trend at the temporal scale of 54 years. These analysis results are compared and discussed in detail. In conclusion, because of the impacts of human activities, there have been significant changes in the runoff regime in the middle and lower Yellow River since 1970. The decaying tendency of annual runoff has become more pronounced, and the inner-annual distribution of runoff has changed, but human activities have had little impact on the periodic characteristics of runoff. 相似文献
92.
径流曲线数模型(Soil Conservation Service Curve Number Model,简称SCS-CN模型)可以利用降雨资料估算径流,对水资源合理配置和山洪灾害预警具有重要意义,因为其方便计算、参数简单,而被广泛应用。目前标准SCS-CN模型在山区小流域的适用性欠佳,因此需要对模型参数进行优化以提高预测精度。本文以湖南省螺岭桥流域为例,根据实测降雨径流资料优化径流曲线数CN (Curve Number)查算表,并利用步长优化参数算法研究初损率对模型精度的影响,将优化模型的方法应用于湖南省凤凰小流域,验证该优化方法的可靠性。结果分析表明:与标准SCS-CN模型相比,优化后的SCS-CN模型效率系数NSE从0.576提升至0.813,决定系数R2为0.858。将模型优化方法验证于气候地形条件相似的凤凰流域,模型NSE值提高117%。通过预测径流深与实测径流深比较,优化模型模拟精度较为理想,对湖南省山区小流域场次降雨产流预报有一定的参考意义。 相似文献
93.
芮孝芳 《水利水电科技进展》2017,37(2):1-6
凭借"大数据"可以精细刻画降雨空间分布和下垫面空间变异性的优势,提出了"大数据"背景下考虑降雨空间分布和下垫面空间变异性对流域产汇流影响的计算方法,即单元嵌套网格剖分流域的方法。通过引入"网格水滴"的概念揭示了流域瞬时单位线的物理本质,对由RodriguezIturbe和Valdes所提出R-V地貌瞬时单位线理论进行补充,分析了等流时线法和单位线法的局限性,提出的单元嵌套网格产汇理论既克服了等流时线法和单位线法的缺点,也吸取了它们的优点,为在"大数据"支撑下统一等流时线和单位线法提供了可行性。 相似文献
94.
95.
Jinzhu Ma Lihua Chen Jianhua He Yurui Zhang Xianghu Li W. Mike Edmunds 《Water and Environment Journal》2013,27(1):86-98
The Mann–Kendall test, wavelet analysis was used to analyse the long‐term trends and periodicities in temperature, precipitation and streamflow in China's Shiyang River Basin since 1950. The Principal components analysis (PCA) was used to quantify the impacts of climate change and human activities on water resources. The annual mean air temperature has increased, consistent with increasing global temperatures. The annual precipitation fluctuated but has generally increased since the 1990s. The air temperature and precipitation showed changes on periods ranging from 2 to 28 years. The correlation between annual runoff and precipitation variation was 0.61 (P < 0.05), indicating precipitation is the main source of the runoff. Human activities played the dominant role in the lower reaches, accounting for 58.5% of the total effect. The results have important implications for water resources management to support harmonisation of the relationship between humans and nature to combat the effect of climate. 相似文献
96.
Sprinkling is often used in Scandinavia to protect round wood stored for industrial use from fungal and insect attack and drying cracks. Log yard runoff can be harmful for the water recipient due to eutrophication and oxygen depletion. A wetland system for treatment of log yard runoff is being evaluated in central Sweden. The purification capacity of a sloping couch grass (Elytrigia repens L.) field was examined when log yard runoff was applied to the field through a sprinkling system. Water samples were taken from groundwater pipes during four summer seasons (May to September, 2002–2005) and analysed for total organic carbon, total phosphorus (TP), total nitrogen and distillable phenols to evaluate the purification capacity of the infiltration wetland. Results from 2002 to 2004 were compared with results from 2005 when the irrigation intensity was considerably lower. Overall, the results showed good purification capacity although the concentrations of TP in the groundwater increased during 2005. The reduced hydraulic load did not increase purification. 相似文献
97.
《Urban Water Journal》2013,10(3):247-257
The current paper is the first study to report quality of urban runoff, focusing on the diffuse sources contributing to pollutant loads in the Delhi watershed. The quality of stormwater runoff from the urban watershed of Delhi was evaluated to assess the effects of different land-use practices on pollutant concentrations. Six sites within the Delhi watershed with different land-use characteristics were selected. The microbial quality of the urban runoff from sub-catchments of Delhi watershed is very poor with Faecal Coliform (FC) levels varying between 6 and 7 log orders. There was a good correlation between the chemical and biological quality of urban runoff with land-use characteristics such as impervious land and population density. Except for chemical oxygen demand all other parameters in urban runoff were found to exceed the effluent discharge standards set by the National River Conservation Directorate (NRCD), India. The public health risks associated with exposure to urban runoff via different routes have also been qualitatively estimated. 相似文献
98.
99.
《Urban Water Journal》2013,10(6):441-448
The levels of organonitrogen, organochlorine and organophosphorus pesticides were monitored in rain and roof runoff waters in Gdańsk (Poland) over a period of 6 months (October 2000 – March 2001). Buildings included in the study were of different ages, and covered with a variety of roofing materials. Samples were collected during the precipitation events. Pesticides were determined by gas chromatography combined with NPD and ECD detection. Bromofos, heptachlor epoxide and o,p′-DDE were detected the most often in the samples collected. In general, pesticide concentrations were higher in roof runoff than in rainwater. The type of the roofing material had a significant effect on the pesticide levels in runoff waters. The highest analyte levels were recorded in October and November, when the temperature was the highest. 相似文献
100.
《Urban Water Journal》2013,10(10):934-942
ABSTRACTNovel laboratory experiments were carried out to investigate the outflow process and the detention effects of a tray module of a blue roof (BR) system designed for runoff control from building roofs. The experiments revealed the outflow from the tray to decline during time, due to a number of complex dynamics occurring in proximity of the outlet orifice. The tests also showed the system to provide potential for relevant attenuation of the flow peak during inflow events (i.e. precipitation) of different magnitude. Based on regression analysis, an empirical relationship was developed for the evaluation of the tray outflow as a function of time, thus providing a tool for improved design of BRs. Finally, combination of the identified relationship with a routine for the water balance simulation of the tray was shown to describe reliably the detention process in the BR tray module. 相似文献