A New Non-stationary Hydrological Drought Index Encompassing Climate Indices and Modified Reservoir Index as Covariates

Due to accelerating climate variability and intensified anthropogenic activities, the hypothesis of stationarity of data series is no longer applicable, questioning the reliability of the traditional drought index. Thus, it is critical to develop a non-stationary hydrological drought index that takes into account the joint impacts of climate and anthropogenic changes in a drought assessment framework. In this study, using the Generalized Additive Model for Location, Scale and Shape (GAMLSS), a new Non-stationary Standardized Runoff Index (NSRI) was developed combining climate indices (CI) and modified reservoir index (MRI) as explanatory variables. This novel index was applied to the hydrological drought assessment of the Hanjiang River basin (HRB) in China, and its reliability was assessed by comparing with the traditional Standardized Runoff Index (SRI). Results indicated that the optimal non-stationary model with CI and MRI as covariates performed better than did other models. Furthermore, NSRI was more robust in identifying extreme drought events and was more effective in the study region than the conventional SRI. In addition, based on the method of Breaks for Additive Seasonal and Trend (BFAST), it was found that there were two change points in 1981 and 2003 for the NSRI series at four hydrological stations in the HRB, which indicated that hydrological drought in the basin had a prominent non-stationary behavior. Our findings may provide significant information for regional drought assessment and water resources management from a changing environment perspective.

     

Analysis of Impacts of Climate Change and Human Activities on Hydrological Drought: a Case Study in the Wei River Basin,China

Climate change and human activity are the two major drivers that can alter hydrological cycle processes and influence the characteristics of hydrological drought in river basins. The present study selects the Wei River Basin (WRB) as a case study region in which to assess the impacts of climate change and human activity on hydrological drought based on the Standardized Runoff Index (SRI) on different time scales. The Generalized Additive Models in Location, Scale and Shape (GAMLSS) are used to construct a time-dependent SRI (SRI_var) considering the non-stationarity of runoff series under changing environmental conditions. The results indicate that the SRI_var is more robust and reliable than the traditional SRI. We also determine that different driving factors can influence the hydrological drought evolution on different time scales. On shorter time scales, the effects of human activity on hydrological drought are stronger than those of climate change; on longer time scales, climate change is considered to be the dominant factor. The results presented in this study are beneficial for providing a reference for hydrological drought analysis by considering non-stationarity as well as investigating how hydrological drought responds to climate change and human activity on various time scales, thereby providing scientific information for drought forecasting and water resources management over different time scales under non-stationary conditions.     

Assessment of Probabilistic Multi-Index Drought Using a Dynamic Naive Bayesian Classifier

The proper consideration of all plausible feature spaces of the hydrological cycle and inherent uncertainty in preceding developed drought indices is inevitable for comprehensive drought assessment. Therefore, this study employed the Dynamic Naive Bayesian Classifier (DNBC) for multi-index probabilistic drought assessment by integrating various drought indices (i.e., Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI), and Normalized Vegetation Supply Water Index (NVSWI)) as indicators of different feature spaces (i.e., meteorological, hydrological, and agricultural) contributing to drought occurrence. The overall results showed that the proposed model was able to account for various physical forms of drought in probabilistic drought assessment, to accurately detect a drought event better than (or occasionally equal to) any single drought index, to provide useful information for assessing potential drought risk, and to precisely capture drought persistence in terms of drought state transition probability in drought monitoring. This easily produced an alternative method for comprehensive drought assessment with combined use of different drought indices.     

A Review of AI Methods for the Prediction of High-Flow Extremal Hydrology

Forecasting systems for foreseeing water levels and flow rates have become necessary to mitigate climate change negative impacts. Most of these systems are based on powerful tools such as Artificial Intelligence (AI) methods. This paper presents a comprehensive review of AI methods for high-flow extremes prediction. The review starts with an overview of the state-of-the-art AI techniques and examples of their application, followed by a SWOT analysis to benchmark their predictive capability based on set of criteria. Finally, the most suitable AI methods for short-term and/or long-term prediction, based on a rigorous suitability assessment are proposed. As a result, Fourteen AI methods have been identified. Their evaluation revealed that the methods that averagely behave the best for achieving high-flow extremes prediction are ANNs, SVMs, wavelets and Bayesian methods, at all-time scales. The latter, as stochastic methods, have the privilege by their cheap computation cost, their reliability and ability to handle hydrological uncertainty, and their capacity to perform causal relationships between features. This study also urges researchers to further explore the predictive potential of decision trees, ensembles, CNNs, MARS, GP and agent-based methods for high-flow extremes.

     

Comparison of Meteorological,Hydrological and Agricultural Drought Responses to Climate Change and Uncertainty Assessment

A comparison study of meteorological, hydrological and agricultural drought responses to climate change resulting from different General Circulation Models (GCMs), emission scenarios and hydrological models is presented. Drought variations from 1961–2000 to 2061–2100 in Huai River basin above Bengbu station in China are investigated. Meteorological drought is recognized by the Standardized Precipitation Index (SPI) while hydrological drought and agricultural drought are indexed with a similar standardized procedure by the Standardized Runoff Index (SRI) and Standardized Soil Water Index (SSWI). The results generally approve that hydrological and agricultural drought could still pose greater threats to local water resources management in the future, even with a more steady background to meteorological drought. However, the various drought responses to climate change indicate that uncertainty arises in the propagation of drought from meteorological to hydrological and agricultural systems with respect to alternative climates. The uncertainty in hydrological model structure, as well as the uncertainties in GCM and emission scenario, are aggregated to the results and lead to much wider variations in hydrological and agricultural drought characteristics. Our results also reveal that the selection of hydrological models can induce fundamental differences in drought simulations, and the role of hydrological model uncertainty may become dominating among the three uncertainty sources while recognizing frequency of extreme drought and maximum drought duration.     

Hydrological Drought Class Transition Using SPI and SRI Time Series by Loglinear Regression

Loglinear models for three-dimensional contingency tables was used with data from 21 rainfall stations and 7 hydrometric stations in the Luanhe river basin, northeast China, for short term prediction of drought severity class. Loglinear models were fitted to drought class transitions derived from standardized precipitation index (SPI) and standardized runoff index (SRI) time series to find which series was more suitable for hydrological drought class prediction 1 and 2 months ahead, respectively. Expected frequencies for two consecutive transitions between drought classes were first calculated, and based on this the predicted drought classes 1 and 2 months ahead were obtained. The results showed that despite the contingency tables of drought class transitions presented the maintenance of the precedent drought class, results of three-dimensional loglinear modeling presented good results when comparing predicted and observed drought classes. Only for a few cases predictions did not fully match the observed drought class, mainly for 2-month lead and when the SRI values are near the limit of the severity class predicted by SRI time series. Based on the correlation analysis of SPI and SRI, we presented the well-known method of hydrological drought class prediction by SPI time series. It was found that, using loglinear regression method, the accuracy of predictions for 2-month lead predicted by SPI time series was higher than those predicted by SRI time series. When we divided the SPI and SRI time series into 2 sub-periods (pre- and post-1980 where land cover changed), we got the same drought class prediction as that predicted by the entire SPI and SRI time series, which illustrated that changes in land use did not affect predictions of hydrological drought classes in the Luanhe river basin. It could be concluded that loglinear prediction of drought class transitions is a useful tool for short term hydrological drought warning, and the results could provide significant information for water resources managers and policy makers to mitigate drought effects.     

Construction of an optimized comprehensive drought index for agricultural watersheds in cold regions and its applicability analysisEI北大核心CSCD

以挠力河流域为寒区农业流域典型区,构建融合多源信息的综合干旱指数用于寒区农业流域干旱特征的评估,并分析其适用性。基于构建的SWAT模型模拟挠力河流域水文气象要素,计算单一的标准化降水蒸散发指数(SPEI)、标准化土壤湿度指数(SSI)和标准化径流指数(SRI),运用主成分分析法和熵权法分别对3种单一干旱指数赋权,通过最小偏差法计算最优组合权重,构建融合气象干旱、农业干旱和水文干旱信息的综合干旱指数(OCDI)。结果表明:OCDI的干旱事件监测结果与历史干旱事件吻合度较高,综合考虑多时间尺度下的OCDI对于挠力河流域干旱状况描述更为准确和全面;3种单一干旱指数监测的干旱程度空间分布差异明显,融合多源信息的OCDI能够从气象干旱、农业干旱和水文干旱多角度揭示挠力河流域综合干旱特征;OCDI与不同类型单一干旱指数均有较高的相关性,在挠力河流域上游对于干旱的综合表征能力更优且年尺度的OCDI综合表征能力优于季尺度和月尺度;OCDI能够较好地识别和区分该流域的综合干旱程度,随着OCDI所识别综合干旱程度的加重,流域实际受旱面积相应增大。     

Temporal Hydrologic Alterations Coupled with Climate Variability and Drought for Transboundary River Basins

Climate change (CC) and drought episode impacts linked with anthropogenic pressure have become an increasing concern for policy makers and water resources managers. The current research presents a comprehensive methodology but simple approach for predicting the annual streamflow alteration based on drought indices and hydrological alteration indicators. This has been achieved depending on the evaluation of drought severity and CC impacts during the human intervention periods to separate the influence of climatic abnormality and measure the hydrologic deviations as a result of streamflow regulation configurations. As a representative case study, the Lesser Zab River Basin in northern Iraq has been chosen. In order to analyse the natural flow regime, 34 hydrological years of streamflow (1931–1965) prior to the main dam construction were assessed. The Indicators of Hydrologic Alteration (IHA) method has been applied to quantify the hydrological alterations of various flow characteristics. In addition, an easy approach for hydrological drought prediction in relatively small basins grounded on meteorological parameters during the early months of the hydrological year has been presented. The prediction was accomplished by implementing the one-dimensional drought examination and the reconnaissance drought index (RDI) for evaluating the severity of meteorological drought. The proposed methodology is founded on linear regression relations connecting the RDI of 3, 6, and 12 months and the streamflow drought index (SDI). The results are critical for circumstances where an early exploration of meteorological drought is obtainable. Outcomes assist water resources managers, engineers, policy makers and decision-makers responsible for mitigating the effects of CC.     

干旱传播研究进展与展望Ⅱ −影响因素与干旱传播研究展望

在回顾干旱传播概念和内涵的基础上，明确提出干旱传播全环节的详细定义，阐述干旱传播的累积、衰减、 滞后及延长特征，并重点就累积性与滞后性提炼了有关进展。按干旱传播环节、干旱传播时空特征两种方法划分 干旱传播的类型，从线性回归、对数函数、小波分析、Copula 函数、因果分析、贝叶斯网络和随机森林 7 个方面、 从单一水文模型模拟和多个模型集合模拟两大方面，分别归纳统计方法、水文模拟方法在干旱传播研究领域的应     

区域干旱特征分析与预测研究

在分析区域干旱特征的基础上．以邢台市1959年实测降水量系列为样本．利用灰色理论和方法建立GM（1,1）预测模型并进行预测。通过对计算结果进行历史拟合和精度检验分析．模型精度高适用性好,预测结果与实际状况吻合,符合区域干旱的灰色特性。     

基于Shapley值的西安市生活需水量组合预测研究

利用等维灰数递补法、非线性回归、广义回归神经网络等3种方法进行了西安市生活需水量预测,比较了不同方法的预测误差,然后根据各种方法对总预测值的信息贡献能力形成Shapley值组合需水量预测方法,计算了不同预测方法的Shapley值及其组合权重,形成组合预测需水量模型。预测结果表明:组合方法误差曲线平缓、平均误差值较小,具有一定的预测精度,适用于需水量的中短期预测。     

Hydro-Climatological Drought Analyses and Projections Using Meteorological and Hydrological Drought Indices: A Case Study in Blue River Basin, Oklahoma

Understanding the characteristics of historical droughts will benefit water resource managers because it will reveal the possible impacts that future changes in climate may have on drought, and subsequently, the availability of water resources. The goal of this study was to reconstruct historical drought occurrences and assess future drought risk for the drought-prone Blue River Basin in Oklahoma, under a likely changing climate using three types of drought indices, i.e., Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI) and Standardized Runoff Index (SRI). No similar research has been conducted in this region previously. Monthly precipitation and temperature data from the observational period 1950?C1999 and over the projection period 2010?C2099 from 16 statistically downscaled Global Climate Models (GCM) were used to compute the duration, severity, and extent of meteorological droughts. Additionally, soil moisture, evapotranspiration (ET), and runoff data from the well-calibrated Thornthwaite Monthly Water Balance Model were used to examine drought from a hydrological perspective. The results show that the three indices captured the historical droughts for the past 50?years and suggest that more severe droughts of wider extent are very likely to occur over the next 90?years in the Blue River Basin, especially in the later part of the 21st century. In fact, all three indices display lower minimum values than those ever recorded in the past 50?years. This study also found that SRI and SPI (PDSI) had a correlation coefficient of 0.81 (0.78) with a 2-month (no appreciable) lag time over the 1950?C2099 time period across the basin. There was relatively lower correlation between SPI and PDSI over the same period. Although this study recommends that PDSI and SRI are the most suitable indices for assessing future drought risks under an increasingly warmer climate, more drought indices from ecological and socioeconomic perspectives should be investigated and compared to provide a complete picture of drought and its potential impacts on the dynamically coupled nature-human system.     

变化环境下时变标准化径流指数的构建与应用

变化环境下,干旱指数可能表现出非一致性特征。本文假设径流序列为二阶非平稳序列,建立以时间为协变量的时变矩GAMLSS模型,该模型采用非一致性Gamma分布拟合实测径流序列,并基于该模型计算出的时变标准化径流指数SRIt,与传统指数SRI进行对比分析,以验证其合理性与必要性。结果表明:基于时变矩模型的时变标准化径流指数SRIt更适应于潘家口水库流域变化环境下水文干旱的评价。时变标准化径流指数SRIt的值整体上比基于一致性模型的指数SRI偏小,即所表示的干旱程度更加严重,主要是因为时变矩GAMLSS模型能够反映出变化环境下径流序列的变化趋势,该趋势是影响径流的一系列因素共同导致的,如气候变化,人类活动等。而在受这些因素的影响下,潘家口水库流域的水文干旱事件频率增加,严重程度增强。     

基于最大熵原理的水文干旱指标计算方法研究

确定水文变量的概率分布,是计算各类标准化干旱指标的关键。提出了基于最大熵原理(POME)的月径流分布构建方法,采用多阶矩作为求解最大熵的约束条件,以拉格朗日乘子法估计分布参数,计算了不同时间尺度的标准化径流干旱指数SDI,评估了汉江30个子流域历史水文干旱情势。结果表明:与Normal、Gamma、Weibull、Pearson TypeⅢ等常用概率分布相比,POME分布模型可以最大程度地利用实测水文数据中的信息,有效拟合不同时间尺度的累积月径流量,表现出良好的适用性;随着时间尺度的增大,采用不同分布拟合同一尺度的月径流量,差别逐渐减小,月径流量概率分布特征趋于正态化。成果可为推求干旱指标,研究干旱特征的统计规律,进行干旱频率分析等提供新的手段。     

A New Method for Joint Frequency Analysis of Modified Precipitation Anomaly Percentage and Streamflow Drought Index Based on the Conditional Density of Copula Functions

In this study, a new method was proposed to model the occurrence of related variables based on the conditional density of copula functions. The proposed method was adopted to investigate the dynamics of meteorological and hydrological droughts in the Zarinehroud basin, southeast of Lake Urmia, during the period 1994–2015. For this purpose, the modified precipitation anomaly percentage and streamflow drought indices were extracted. Finally, the joint frequency analysis of duration-duration and severity-severity characteristics of meteorological and hydrological droughts was analyzed. Analysis of 7 different copulas used to create the joint distribution in the Zarinehroud basin indicated that the Frank copula had the best performance in describing the relationship between the meteorological and hydrological drought severities and durations. By examining the results of the bivariate analysis of duration-duration of meteorological and hydrological droughts at different stations, the expected meteorological and hydrological drought durations were estimated in the years ahead. For example, at Chalkhmaz station, 4- to 7-month duration for the hydrological drought and 9- to 12-month duration for the meteorological drought is expected in the years ahead. The joint frequency analysis of drought characteristics allows to determine the meteorological and hydrological drought characteristics at a single station at the same time using joint probabilities. Also, the results indicated that by knowing the conditional density, the hydrological drought characteristics can be easily estimated for the given meteorological drought characteristics. This could provide users and researchers useful information about the probabilistic behavior of drought characteristics for optimal operation of surface water.

     

抚河流域气象干旱向水文干旱传播的影响机制研究

气象干旱是水文干旱发生的前兆,探究影响气象干旱向水文干旱传播的主要因素对建立有效的基于气象干旱的水文干旱监测预警具有重要意义。以抚河流域为例,采用标准化降水指数和标准化径流指数分别评估气象干旱和水文干旱,并构建基于流域分布式二元水循环模型的干旱传播评估方法,采用多因素综合影响贡献量分解法量化气候变化和人类活动对干旱传播变化的贡献。结果表明：建立的抚河流域分布式二元水循环模型模拟流域出口断面流量的纳什效率系数大于0.85,相对误差在5%之内;气象干旱向水文干旱传播关系变化的时间是1980s—1990s。相对于1956—1990年,1991—2019年气象干旱向水文干旱的传播率降低了8.3%;在气象干旱向水文干旱传播的影响中,气候变化的减缓作用占主导地位,贡献量为-9.9%;其次是人类活动的加剧作用,贡献量为1.6%;降水作为干旱的主要致灾因子,变化期增加了144.3 mm,这对于减弱气象干旱向水文干旱传播的敏感性起到主要作用。     

叶尔羌河流域主要水文要素变化分析

本文选取叶尔羌河流域的卡群水文站,2001~2012年的降水、蒸发、及流量资料,利用累积距平法、Mann-Kendall趋势检验法及变差系数对该流域各要素的变化情况进行分析计算。结果表明:该流域年降水量变化基本稳定;年蒸发量序列有缓慢增加趋势;年径流量丰枯变化较小,利用累积距平法分析得到,卡群站年径流量丰枯变化较频繁,Kendall秩次相关检验表明,卡群水文站年径流量无显著增加趋势。     

基于标准水资源指数(SWRI)的流域水文干旱评估——以海河北系为例

构建了一个新的水文干旱评估指标——标准水资源指数(SWRI),结合分布式水循环模型、Copula函数及统计检验等方法,形成了一套完整的水文干旱识别、评估及特征分析的基本框架。以海河北系为例,定量识别了1956—2009年间的水文干旱事件,并对其干旱特征及变化规律进行了剖析。结果表明:海河北系近54年发生的34次水文干旱主要集中在短历时、低强度、小面积区间内,空间上主要分布在张家口、大同及北京等地区;干旱指标的联动关系上,干旱历时、强度与面积指标间呈显著的线性或指数相关关系,90%的水文干旱历时低于40个月、干旱面积占比不超过43%,干旱强度低于9.0;在给定的干旱特征指标值(如干旱面积)条件下,另一干旱指标值越大(如强度越大)干旱发生概率越小,且存在明显的特征区间;单变量水文干旱重现期介于联合重现期和同现重现期之间。     

An automatic parameter calibration method for the SWAT model in runoff simulation

Runoff simulation is highly significant for hydrological monitoring, flood peak simulation, water resource management, and basin protection. Runoff simulation by distributed hydrological models, such as the soil and water assessment tool (SWAT) model which is the most widely used, is becoming a hotspot for hydrological forecasting research. However, parameter calibration is inefficient and inaccurate for the SWAT model. An automatic parameter calibration (APC) method of the SWAT model was developed by hybrid of the genetic algorithm (GA) and particle swarm optimization (PSO). Multi‐station and multi‐period runoff simulation and accuracy analysis were conducted in the basin of the Zhangjiang River on the basis of this hybrid algorithm. For example, in the Yaoxiaba Station, the calibration results produced an R² of 0.87 and Nash Sutcliffe efficiency (NSE) index of 0.85, while verification results revealed an R² of 0.83 and NSE of 0.83. Results of this study show that the proposed method can effectively improve the efficiency and simulation accuracy of the model parameters. It can be concluded that the feasibility and applicability of GA‐PSO as an APC method for the SWAT model were confirmed via case studies. The proposed method can provide theoretical guidance for many hydrological research fields, such as hydrological simulation, flood prevention, and forecasting.     

枯水期径流量的中长期预估模式

为建立水文干旱预测系统，采用灰色系统理论中灰关联度分析的方法，对枯水期径流量的预估模式进行了探讨，并提出用层次分析法来考虑各影响因子对径流量的不同影响程度，这一尝试为水文干旱的预测提供了条件。