基于Copula的区域水文干旱频率分析

以径流量为水文干旱指标,通过径流量距平百分率和径流量累积频率两种方法识别水文干旱特征变量,并以适线法确定单个干旱特征变量的分布曲线,在此基础上利用Archimedean Copula函数构建了干旱历时与干旱烈度间的联合分布,并计算干旱重现期。应用研究结果表明:用Copula函数,得以上两种识别法提取的干旱历时和干旱烈度的联合概率分布,其重现期计算结果与区域实际受旱状况相符,其中径流量距平百分率法相对更优、更直观;适线法避免了基于样本数据估计分布函数参数的不合理性,使基于Copula函数的频率分析结果更可靠。     

Comparative assessment of three approaches for deriving stream power plots along long profiles in the upper Hunter River catchment, New South Wales, Australia

The downstream distribution of stream power is derived and analysed for 11 different streams in the upper Hunter River catchment, Australia. Stream long profiles were produced in a GIS environment using DEM data and catchment area–discharge analysis. These profiles were analysed using three approaches, namely long profile smoothing, curve fitting and a theoretical model. The methodology for deriving stream power profiles using these three approaches is discussed. The long profile smoothing method provides a good approximation of the subcatchment variability in stream power trends. The curve fitting method shows that higher-order exponential curves provide a better fit for long profile data. For the streams of the upper Hunter River catchment, second-order exponential curves fit well with significantly less error. The curve fitting method predicts a bimodal (upstream and midstream) distribution of stream power, which is a deviation from our earlier understanding of a single midstream peak. The theoretical approach provides a mathematical expression of the observed bimodal stream power distribution. The bimodal distribution emphasises the erosion potential of headwater reaches. The resultant stream power distribution provides a catchment-scale characterisation of the distribution of available energy in any given system. Using these approaches, the variability of stream power in headwater reaches is explained by discharge variability, while variability in midstream and downstream reaches is related to high variability in channel gradient.     

近年我国区域水文研究的若干进展

我国区域水文学的研究是在解放后其正发展起来的。尽管迄今人们对区域水文学仍有不同的认识,例如区域水文学是否可以与水文地理学等同,或是区域水文学是否应隶属于区域地理学等等,但是作为水文学的分支学科是无疑的。区域水文学从整体的观点来研究区域水文情势。区城可以是功能区,如城市、出口加工中心区等,或为自然景观区,如干旱区、喀斯特区等,也可以是行政区。目前,许多水文水利工作者已在致力于区域水文学的研究。     

近数十年湘江流域河流水文变化规律

湘江是长江中游主要支流之一，作者从制约河川水文要素变化的自然环境因素着手，依据湘江流域有代表性水文测站多年实测水文气象资料，较全面地分析了河川径流，水位，暴雨洪水，泥沙。水化学等水文要素的组成，发展与变化规律。     

中国人口疏密区分界线的历史变迁及数学拟合与地理意义

采用历史时间断面方法和现代空间分析方法,对中国西汉、西晋、唐代、北宋、明代、清代、现代7个时间断面的人口分布进行分析。结果发现：① 中国人口疏密区的分界线就是中国农牧区的分界线,中国人口分布的大格局由中国农耕区和畜牧区的空间分异奠定,理论上中国人口疏密区分界线就是中国农牧交错带的拟合线。② 两千多年的历史证明,中国农牧交错带是一个弧状地带,不能用直线拟合,只能用弧线拟合;“沈天大弧线”（沈阳—天水—大理弧线）是该交错带的函数拟合线,“山兰防弧线”（山海关—兰州—防城港弧线）是该交错带的内缘拟合线,也是中原王朝衰弱时期的农牧分界线;“沈兰西弧线”（沈阳—兰州—西双版纳弧线）是该交错带的外缘拟合线,也是中原王朝强盛时期的农牧分界线;直线的“爱辉—腾冲线”理论上不能拟合弧状的中国农牧交错带,但因为它碰巧是中国农牧交错带的函数拟合线的切线,因而也能较好地刻画中国人口的宏观分异格局。③ 中国人口疏密区分界线有着丰富的地理学意义：一是分界线本身就是农牧业分界线;二是分界线与海岸线围成的区域是中国的“国家核心区”;三是分界线最大限度地刻画了中国东南和西北的自然地理和人文地理的分异。     

潮白河径流分布规律及人类活动对径流的影响分析

利用潮白河五个水文站1956年以来的径流资料,应用多种数值分析方法,详细分析了潮白河径流的年际、年内分配规律,计算了人类活动对径流的影响。结果表明,潮白河径流的年际变化剧烈,丰水时段历时很短,而枯水时段历时很长。应用累积滤波器和肯德尔秩次相关法,对年径流变化趋势所作的定性和定量的结果表明,潮白河年径流总体呈减少趋势,且减少趋势显著。根据年径流累积曲线和回归分析,人类活动是引起潮白河径流减少的主要因素。     

塔里木河中下游地下水化学及其演变特征分析

 通过对塔里木河中下游14个断面57眼地下水监测井样品离子化学成分分析,探讨了塔里木河中下游地下水化学成分特点、水化学类型及演化规律。结果表明：塔里木河中下游各断面地下水pH值变化不大,矿化度和各离子差异明显,地下水水样以Na⁺、Cl^-占绝对优势;矿化度较低的断面其离子浓度变化较小,反之,矿化度高的断面其离子浓度变化幅度较大;从塔里木河中游沙吉利克断面至铁依孜断面地下水化学类型由以Cl-SO₄-Na、Cl-Na-Mg和Cl-SO₄-Na-Mg型水为主,逐渐过渡为以Cl-SO₄-Na-Mg和Cl-Na型水为主,在下游阿克敦断面至考干断面地下水化学类型由以Cl-SO₄-Na-Mg、Cl-Na-Mg型水为主过渡为以Cl-Na、Cl-HCO₃-Na和Cl-Na-Mg为主;时间上,2006年中游断面沿河道地下水化学类型由Cl-SO₄-HCO₃-Na型过渡为Cl-SO₄-Na-Mg型再到Cl-Na型水,而2010年则由Cl-SO₄-Na型过渡为Cl-SO₄-Na-Mg型再到Cl-Na型水,在下游,2006年沿河道地下水化学类型由Cl-SO₄-Na型过渡为Cl-SO₄-Na-Mg型再到Cl-Na（Mg）型水,2010年则由Cl-SO₄-Na-Mg型直接过渡为Cl-Na-Mg型和Cl-Na型水。塔里木河中下游水样化学组成均落在Gibbs提出的Boomerang Envelope模型上翼,暗示研究区水样化学组成受到蒸发/结晶作用影响。另外,土地利用变化、灌溉、施肥等人为活动的影响不容忽视。     

不同概率分布函数降雨极值的适用性分析

极端降雨极值发生的重现期是流域与城市防洪设施规划设计标准需要参考的最重要参数之一。利用常用的5种水文统计学分布函数,选取中国十大流域内10个站点不同时段的最大降雨极值序列进行拟合,并检验筛选不同站点的适用性分布函数。结果表明：10个站点拟合优度检验拟合效果较好,曲线差异度较小的分布依次为广义极值分布、对数正态分布、皮尔逊III分布;不同站点适宜性曲线的差异程度不同。研究结果可为区域降雨极值序列的拟合提供参考,即不同的区域、不同的季节、不同时长的降雨极值序列都应寻找其较适宜的分布函数并采用多种检验方法来拟合,以降低不确定性。     

流域水文模型计算域离散方法

常用的概念性水文模型 ,能够很好地模拟水文时间变化过程 ,但没有考虑水文变量和水文参数的空间变化与空间不均匀性。随着空间数据的获取手段的增多以及空间离散技术的发展 ,考虑水文参数和水文变量空间变化的分布式水文模型得到了极大的发展。本文详细介绍了分布式流域水文模型中用到的几种不同计算域离散方法 ,并讨论了河道汇流模型中常用到的有结构网格和无结构离散网格。地理信息系统技术对计算域离散有辅助作用 ,其有利于无结构离散网格的自动生成和交互修改 ,并可结合遥感技术 ,使水文模型能获取精确的空间分布的水文参数和水文变量。     

Quantitative reconstruction of lake conductivity in the Quaternary of the Near East (Israel) using ostracods

Surface sediments, water samples and environmental data from 37 lakes, ponds and streams in Israel were analysed to determine the main variables controlling ostracod species distributions. Multivariate statistical analysis revealed that the greatest amounts of variation in the distribution of the ostracod taxa among the 37 water bodies were explained by the host water δD value (12.9%), water temperature (11.0%), mean January air temperature (10.5%), electrical conductivity (9.5%), and the Mg and NO₃ concentrations (7.8 and 7.1%, ion concentrations as % of the anions or cations). A supplementary data set comprising ostracod species composition and electrical conductivity readings for 24 water bodies was available from previous research and was merged with the 37 samples data set to develop an ostracod-based transfer function for the reconstruction of electrical conductivities. A weighted averaging partial least squares regression (WA-PLS) provided the best results with a relatively high coefficient of determination (r ²) between measured and inferred electrical conductivity values of 0.73, a root mean square error of prediction of 0.13 (13.4% of gradient length) and a maximum bias of 0.24 (23.9% of gradient length), as assessed by leave-one-out cross-validation based on 56 water bodies. The application of the EC transfer function onto (sub)fossil ostracod assemblages from Holocene and early to mid Pleistocene lake sediments provided EC values consistent with other proxies and demonstrated that Quaternary ostracod assemblages from subaqueous sediments can now be used to trace the hydrological history of water bodies in the Near East. A better understanding of past hydrological conditions in response to the natural climate variability is crucial in regions that face restricted water resources and rising demands in times of rapid climate and environmental change.