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1.
在用马斯京根法进行河道流量演算时,由于传统的试算法在精度和客观性上的欠缺,目前广泛使用最小二乘法来进行优化计算.在应用最小二乘法时,发现选择不同的目标函数会对最终的流量计算结果的精度产生影响.因此,本文应用了两种目标函数:河槽蓄量误差最小和出流量误差最小,推导了它们在最小二乘意义上的流量演进参数解析式,进而研究了对流量计算精度的影响.对3场洪水过程的模拟结果表明,以出流量误差最小为目标函数所获得的流量计算精度更高:与河槽蓄量误差最小相比,相对平均绝对误差分别降低了4%,25%和25%,说明使用出流量误差最小作为优化的目标函数更为有效. 相似文献
2.
地球物理反演是指根据一组观测结果来估计假设的地下模型的参数。因为模型所伴隋的响应可能是模型参数的非线性函数,因此在反演中非线性最小二乘方法是有用的。反演的一种普通类型是利用马奎特—列文伯格法实现迭代的阻尼最小二乘。通常,这种方法是通过常规的方法解有关的法方程来实现的。然而对于同样的法方程采用奇异值分解法(SVD)在计算精度上就会有明显的提高。迭代的最小二乘模拟在地球物理的多种问题中得到了应用,用两个实例来说明:(1)地震子波的反褶积;(2)根据地表重力资料推断一个隐伏台阶的位置。再广而言之,非线性最小二乘反演可以用于估计任意一组能得出适当数学描述的地球物理观测结果所对应的地下模型。 相似文献
3.
化非线性为线性的加权回归方法及其应用 总被引：1，自引：0，他引：1
一、引言回归分析是处理相关关系的一种数理统计方法,它在水文上应用很广泛。例如,插补展延水文特征值系列、经验公式的选配、观测数据的分析与处理等。对于线性关系,最小二乘法能给出直接的解析解。而非线性关系,最小二乘法不能象处理线性函数那样给出直接的 相似文献
4.
提出根据非稳定流抽水试验资料确定含水层参数的优化算法。该法不同于现有的配线法,其根据最小二乘法及0.618法原理进行优化计算,从而确定承压含水层的导水系数和弹性给水度及渗透系数等。优点是计算结果比较客观,计算精度比较高。给出了实例计算及与其他相比较的结果。 相似文献
5.
最小二乘配点法是用于地下水流计算的一种新型、高效的无网格方法。此方法是在径向基函数配点法的基础上,对计算域进行节点离散,并布置辅助点,近似函数仍然通过节点构造,微分方程在节点和辅助点上都严格满足,从而计算精度更高。而且此方法不需要背景网格,效率高,形式简单。利用该方法计算地下水流向河、渠中的非承压含水层稳定流和非稳定流问题,算例表明,该方法有很好的精度且计算量小,比径向基函数配点法有更精确的结果。 相似文献
6.
本文系“陆地卫星影象结合常规资料初步探索黄河流域产沙分布规律”一文之续.文中按照水文要素、下垫面组成和水文站网分布,将流域划分为若干地区,采用多元回归的方法求解输沙模数,并根据最小二乘法来优选。经计算证明,该法推求各控制站的输沙量,具有一定精度。不但解决了无资料地区输沙模数的内插问题,而且对由卫片确定的侵蚀类型区界线也是一种较好的验证. 相似文献
7.
8.
最小二乘配点无网格法是一种新型高效的无网格法。该方法除节点外又在研究域内引入辅助点,近似函数仍然只通过节点构造,微分方程在所有节点和辅助点上满足。本文将最小二乘配点无网格法应用于非均质多孔介质中的二维地下水稳定流问题,推导了计算格式、编制了相应的计算程序。算例结果表明,最小二乘配点无网格法算法简单,有较高的精度且节省计算量。 相似文献
9.
为了能够根据监测数据推测被测量变化规律及准确预测未来变化，针对常规最小二乘法拟合精度较差的情况，提出利用带权优化方法在常规非线性拟合基础上进行优化处理。通过对工程实际监测数据的计算验证表明，带权优化得到的拟合曲线，拟合精度与预测效果均有明显提高。 相似文献
10.
回归计算中，由于资料和计算上的误差，使结果也产生一定的误差，通常，采用最小二乘法或最小一乘法来估计回归模型中的参数，即是取目标函数为最小来实现的，如果使目标函数在允许的误差范围内变化，则参数会有相应的变幅，本文探讨了两变数回归时参数估计的灵敏度，在相关关系不甚密切时，误差对结果的影响是较大的。 相似文献
11.
降雨输入对分布式流域水文模拟具有重要影响。针对流域降雨资料不完整的情况,以武烈河流域为例,基于反距离加权平均法对雨量站降雨资料进行插补延长,并结合SWAT模型研究了降雨输入不确定性对分布式流域水文模拟的影响。结果表明:不同降雨输入对流域平均降雨量的影响较小,但基于气象站资料的降雨数据在降雨空间差异显著的年份会明显低估面雨量,且在夏季汛期表现更为显著;不同降雨输入对分布式流域水文模拟的影响较大;在雨量站降雨资料不完整的情况下,通过对雨量站降雨数据进行插补延长,相对于直接利用气象站降雨资料,在一定程度上可以提高径流模拟精度,满足降雨资料欠缺流域分布式水文模拟的实际需求。 相似文献
12.
依据钦州市58a平均降雨量和3条入海河流控制站径流量长序列资料,采用滑动平均、线性回归、Spearman、M-K及R/S法综合分析降雨径流的趋势性及突变特征。结果表明,钦州市降雨量总体呈弱增加趋势,增加率为0.742mm/10a,而茅岭江、钦江、大风江流域径流量存在总体减少趋势,减少率分别为0.2×108m~3/10a、1.1×108m~3/10a、0.4×108m~3/10a。运用复Molet小波分析多时间尺度周期性,降雨量序列存在5个时间尺度,22a和15a时间尺度分别为序列第一、三主周期;径流量序列存在3个时间尺度,其中22a和8a时间尺度分别为径流量序列第一、二主周期。 相似文献
13.
The time series of Indian summer monsoon rainfall for the period 1871–1989 has been analysed using the method of deterministic
chaos. It is found that a strange attractor underlies the time series implying the existence of a prediction function. This
function has been approximated by a second-degree polynomial, involving the rainfalls of the past seven years and the coefficients
have been estimated by least squares fit. The interannual variations of actual and computed rainfalls have been presented
for a comparative study. 相似文献
14.
Ayman G. Awadallah Mahmoud S. Farahat Mohammed Haggag 《Arabian Journal of Geosciences》2017,10(9):214
The soil conservation service curve number (SCS-CN) method is one of the most commonly used methods to compute the direct runoff from a rainfall event. Since the method was established, numerous researches were undertaken to improve the method through accurate estimation of its parameter and especially the curve number (CN). However, the essence of the SCS method, as an event-based Hortonian mechanism method, remained unchanged. The main assumption of the method related to the rainfall input is that the rainfall is continuous in time and uniform over the watershed. Mohammad and Adamowski (2015) paper apparently used the SCS method to estimate the annual runoff using the annual rainfall as one cumulative rainfall input value, which is a violation of the event-based principle of the method and of the assumption of the continuity of the rainfall event.To re-estimate the average annual runoff more realistically for the Asir region, Saudi Arabia, daily rainfall data from 14 rainfall stations are used for calculating the resulting runoff depths, on a daily event-by-event rainfall basis, throughout the whole simulation period. The resulting runoff depths are added for each year, and the total cumulative annual runoff values for each year are averaged to get the average annual runoff. The runoff values based on the previously mentioned procedure are an upper limit of the actual average annual runoff as the underlying SCS equations discard evaporation and similar long-term losses. Nevertheless, the average runoff values obtained in the discussion paper are an order of magnitude (at least five to tenfold) lower than the ones of the original paper. An equation is proposed to obtain a more realistic estimate of the average annual runoff, to be used with the average annual rainfall as an input, if the annual value is the only available rainfall information. 相似文献
15.
以大通河流域享堂水文站1950~2005年实测径流数据为基础,综合运用趋势分析、累积距平、R/S分析、Morlet小波分析、降水-径流深度双累积曲线等数理统计方法,研究了大通河流域径流的年内分配、年际变化和周期振荡特征、并定量分析了气候因素和人类活动因素对径流变化的影响。结果表明:（1）大通河径流年内主要集中在510月,占年径流总量的82%左右。1950~2005年,大通河流域年径流呈微弱减少趋势,递减率为-0.55×108m3/10a（R2=0.025,P=0.249）,Hurst指数为0.58,表明未来一段时间内径流仍可能呈减少趋势;（2）1950~2005年,大通河流域年径流在27a时间尺度上周期震荡明显,经历了"多-少-多-少-多-少-多"7个循环交替;（3）大通河流域降水-径流深度双累积曲线在1994年发生显著偏移,1994年之前径流变化主要受降水影响,1994年以后,径流变化主要受人类活动影响。 相似文献
16.
Quantitatively analyze the impact of land use/land cover change on annual runoff decrease 总被引：1，自引：0，他引：1
Annual runoff in Luanhe river basin was detected a downward trend and caused water crisis in Tianjin, China. To quantify the decreased runoff volume, Mann–Kendall test and Pettitt test were employed to check whether there existed significant trend and change points for annual rainfall and runoff time series in Panjiakou reservoir basin and 8 sub-watersheds. It was found that the annual runoff time series had a significant downward trend at 5 % confidence level, and the change point was at 1979 in Panjiakou reservoir watershed. Then double mass curve of annual rainfall and annual runoff was plotted, and two lines were fitted before and after 1979, respectively. Based on this method, the comprehensive effects of land use/land cover change on annual runoff were estimated. To further quantify the contributions of each main factor to annual runoff decrease, water stored in check dams and social water use in different periods were surveyed first. And then multi-linear regression was used to develop the relations between annual runoff and the driven factors. Water area decrease was identified to be the main factor contributing to annual runoff reduction. The results in this study can provide valuable information for water resources planners and policy makers. 相似文献
17.
将黄河流域主要控制站/区间的降雨、径流、洪水资料系列延长至2010年并分析其变化特点,在对实测径流还原的基础上,通过降雨径流关系变化分析下垫面变化对径流系列一致性影响,并采用多种方法进行一致性处理,提出3种下垫面情景的天然径流系列并推荐近期I下垫面情景的黄河设计径流成果。分析了影响洪水一致性的因素,对主要影响因素进行还原,对影响黄河中下游常遇洪水量级的因素进行还现,提出黄河流域各站天然设计洪水及中游现状下垫面5年一遇及以下设计洪水。 相似文献
18.
Abdelkader Elouissi Mohammed Habi Boumedienne Benaricha Sid Ahmed Boualem 《Arabian Journal of Geosciences》2017,10(22):496
This work describes the climate change impact study on rainfall patterns in Macta watershed, located in the northwest of Algeria. The monthly rainfall data collection, verification and validation have built a database with 42 stations, each with 42 years of observations from 1970 to 2011. The study of annual total rainfall has identified a downward trend and quantifies the deficits that are within the observation time series. The division of the annual rainfall series into four periods allowed to highlighting the increase in inter-year temporal variability with the coefficient of variation increases from 17 to 27%. The study shows an annual rainfall deficit increment from 13 to 25%. The standard deviation values decrease significantly for the last two periods showing a spatial variability. Multivariate statistical study by the hierarchical clustering method resulted in the formation of station groups indicating the unification of monthly rainfall patterns. 相似文献
19.
The Tarim River lies in the inland area of Northwest China, which has a semiarid or arid climate. Because of relatively scarce precipitation in this area, the main water resource is runoff from a mountainous drainage basin. It is very important to ascertain variations of regular hydrologic and meteorological time series data. Through the use of monthly precipitation and hydrologic data in the three headstream mountain areas of the Tarim River over the past 50 years, this work analyzes the variation of a drought–flood index and annual runoff volume, along with spatio-temporal structures of the index related to runoff at multiple time scales, via non-parametric testing and a wavelet transform method. Wavelet transform can clearly demonstrate many characteristics of the time series, including trend, shift, and major periods. Based on the analysis, the following conclusions can be drawn: (1) the drought–flood indices showed increasing trends for the Aksu and Yarkand rivers, and rose non-significantly for Hotan River. The indices of the three headstreams changed remarkably (p < 0.05) in 1986. The curves of wavelet variance show that significant periods of the indices are 4 and 8 years for Aksu and Hotan rivers, and 8 and 10 years for Yarkand River; (2) runoff of the Aksu and Hotan rivers had significant periods of 6 and 8 years, plus 3 and 9 years for Hotan River; (3) there was significant correlation between the drought–flood indices and annual runoff volume in the three headstreams. The results provide important information toward achieving predictability of flood and drought in Northwest China. 相似文献
20.
天山北坡玛纳斯河355a来年径流量的重建与分析 总被引：11，自引：2，他引：9
玛纳斯河树轮年表序列与该河肯斯瓦特水文站年径流总量相关显著,使用5个树轮年表序列较好地重建出天山北坡玛纳斯河肯斯瓦特水文站355a来的年径流总量,解释方差达61%.355a重建流量变化表明:1)玛纳斯河年径流总量355a来大致经历了11个偏枯水期和10个偏丰水期,最长的偏丰水期为1670-1699年,持续了30a,最长的偏枯水期为1949-1994年,持续了46a;2)最显著的两个百年流量变枯趋势为1872-1995年和1671-1775年,径流量减少率分别为0.19×108m3·(10a)-1和0.26×108m3·(10a)-1;3)在1711-1712年、1872年重建流量发生过两次突变,前者年径流量由多到少突变,后者相反;4)重建流量最丰水的年代为17世纪80-90年代,比现今偏多17.9%～18.1%,最枯水的年代为19世纪60年代,比现今偏少16.7%;5)重建流量存在着58～59、9.6、27.2、16.9、4.8、4.3、2.9～3.0a的变化周期. 相似文献