西藏扎布耶盐湖水位Winters和ARIMA模型分析

由于温室效应,气温加速上升,我国西部干旱一半干旱盐湖区盐湖水位出现加速下降或上升等变化．藏北高原湖泊众多,但都缺少湖水位的人工观测记录．中国地质科学院盐湖中心自1990年始在西藏扎布耶盐湖建立了长期科学观测站,进行水位动态观测,积累了连续13年珍贵的数据．如何根据湖泊水位历史记录数据,准确的定量预测水位中短期变化,是关系着盐湖资源开发命运的大事．本文用Winters线性和季节性指数平滑法、ARIMA乘积季节模型两种时间序列分析方法,根据西藏扎布耶盐湖1991年1月-2003年12月水位变化的时间序列数据,探讨了两种时间序列数据的预测方法在盐湖水位动态变化预测中的应用．     

抚仙湖历史水位反演与未来30年水位变化预测

在极端气候事件频发和人类活动加剧的背景下,抚仙湖水位波动显著,尤其是2009—2012年极端干旱事件的发生,使抚仙湖平均水位（1721.31 m）低于法定最低水位（1721.65 m）,给生态环境安全带来严重威胁.因此,找到合适有效的湖泊水位模拟方法,对气候变化影响下的未来水位进行预测,并做好相应的应对准备,对湖泊生态系统的保护至关重要.本文运用DYRESM水动力模型对抚仙湖1959—2050年水位进行了模拟.因抚仙湖流域尚无长时间序列的历史水文观测数据,故利用模型和水量补偿法对抚仙湖入湖水量进行反推,构建了降水量-入湖水量的回归方程,并通过有效的实测入湖水量和水位数据,对回归方程的精度进行了检验.利用全球气候模式BCC-CSM2-MR中SSP245和SSP585两种情景提供的未来气候预估数据,运用DYRESM预测了抚仙湖2021—2050年水位变化趋势.结果表明：（1）构建的DYRESM水动力模型和降水-入湖水量回归方程精度较高,模型结果能很好地反映抚仙湖水位的年际和年内变化趋势,且能有效捕捉到抚仙湖的水位峰值.（2）在SSP245和SSP585两种情景下,抚仙湖2021—2050年多年平均水位分别为1722.98和1723.93 m,较1959—2017年平均水位1721.77 m分别升高1.21和2.16 m.两种情景下抚仙湖未来水位均有部分时段超过法定最高蓄水位（1723.35 m）,但均高于法定最低水位.因此,未来气候变化对抚仙湖水量的影响有限,并不会导致水位过低,当水位超过法定最高蓄水位时,可通过控制出流闸门将水位调节在合理范围内.     

湖泊水情遥感研究进展

湖泊作为最直接的淡水资源之一,在人类的生产、生活各方面都占据至关重要的地位.受到全球气候变化与人类活动的影响,湖泊正在发生急剧变化,因而有必要对其进行快速、准确的时空变化监测,从而为水资源管理与保护、未来气候变化预警提供依据.遥感技术的产生与发展为大范围、实时动态的湖泊变化监测提供了难得的契机,它克服了人类对湖泊实地考察的局限性.本文对现有国内外湖泊水情遥感监测技术与方法进行了综合梳理,主要综述了国内外在湖泊水域范围提取、湖泊水位提取、湖泊水量估算、流域水文过程等方面的遥感研究进展情况,重点总结了该领域近年来提出的新方法和新技术.最后,结合当前遥感技术的发展,对未来遥感在湖泊动态变化监测中的应用潜力和趋势进行了简要论述,并对多源遥感数据融合与云计算平台的结合在地表水体连续变化监测中的应用进行了展望.     

洱海富营养化时间演变特征(1988-2013年)及社会经济驱动分析

基于1988-2013年的洱海流域社会经济统计数据与湖内水质历史监测数据,分析了社会经济指标和富营养化指标的逐年变化趋势,并借助Change-point Analyzer对指标进行了拐点分析.结果显示：过去25年洱海水体呈明显富营养化趋势,主要富营养化指标均出现过1次恶化拐点,总磷出现时间最早（1996年）,其次是高锰酸盐指数（1999年）,总氮、叶绿素a、透明度和综合营养状态指数则集中在2002-2003年期间出现拐点,叶绿素a浓度上升10余倍,透明度相应下降了近50%.流域主要社会经济指标出现了2~3次增长拐点,首次拐点集中出现在1994-1999年期间,明显早于富营养化指标恶化拐点出现时间.多元回归分析显示洱海总磷浓度受流域农作物种植业发展影响最大,其他水质指标则主要受流域畜牧业的影响.     

Satellite based estimates of terrestrial water storage variations in Turkey

In recent years, the Gravity Recovery and Climate Experiment (GRACE) has provided a new tool to study terrestrial water storage variations (TWS) at medium and large spatial scales, providing quantitative measures of TWS change. Linear trends in TWS variations in Turkey were estimated using GRACE observations for the period March 2003 to March 2009. GRACE showed a significant decrease in TWS in the southern part of the central Anatolian region up to a rate of 4 cm/year. The Global Land Data Assimilation System (GLDAS) model also captured this TWS decrease event but with underestimated trend values. The GLDAS model represents only a part of the total TWS variations, the sum of soil moisture (2 m column depth) and snow water equivalent, ignoring groundwater variations. Therefore, GLDAS model derived TWS variations were subtracted from GRACE derived TWS variations to estimate groundwater storage variations. Results revealed that decreasing trends of TWS observed by GRACE in the southern part of central Anatolia were largely explained by the decreasing trends of groundwater variations which were confirmed by the limited available well groundwater level data in the region.     

Characterisation of hydroclimatological trends and variability in the Lake Naivasha basin,Kenya

Recent hydro‐climatological trends and variability characteristics were investigated for the Lake Naivasha basin with the aim of understanding the changes in water balance components and their evolution over the past 50 years. Using a Bayesian change point analysis and modified Mann–Kendall tests, time series of annual mean, maximum, minimum, and seasonal precipitation and flow, as well as annual mean lake volumes, were analysed for the period 1960–2010 to uncover possible abrupt shifts and gradual trends. Double cumulative curve analysis was used to investigate the changes in hydrological response attributable to either human influence or climatic variability. The results indicate a significant decline in lake volumes at a mean rate of 9.35 × 10⁶ m³ year^?1. Most of the river gauging stations showed no evidence of trends in the annual mean and maximum flows as well as seasonal flows. Annual minimum flows, however, showed abrupt shifts and significant (upward/downward) trends at the main outlet stations. Precipitation in the basin showed no evidence of abrupt shifts, but a few stations showed gradual decline. The observed changes in precipitation could not explain the decline in both minimum flows and lake volumes. The findings show no evidence of any impact of climate change for the Lake Naivasha basin over the past 50 years. This implies that other factors, such as changes in land cover and infrastructure development, have been responsible for the observed changes in streamflow and lake volumes. Copyright © 2015 John Wiley & Sons, Ltd.     

Long-term Trends and Temporal Heterogeneity of Water Quality in Tidally Mixed Estuarine Waters

Dynamics of water quality in the Keonggi Bay, a shallow macrotidal temperate estuary of Yellow Sea, Korea were identified using the major water quality parameters such as dissolved oxygen (DO), ammonia, nitrate, phosphate, and chemical oxygen demand (COD). The study area during the last 18 years was in eutrophic and mesotrophic water in terms of the nutrient eutrophication index even with a slight decrease in DIN and COD concentrations during recent years. Monthly values of nitrate and ammonia significantly correlated with SS and salinity, respectively, indicating that re-suspension of sediment by vertical mixing and freshwater input are critical factors of monthly fluctuation in water quality. The lack of significant autocorrelation in water quality parameters suggested a significant tidal effect on temporal water quality fluctuation in the tidally mixed estuarine system. Principal component analysis (PCA) revealed a clear pattern of long-term trends of water quality. The early 1980s were the periods of best water quality, with worst conditions during the late 1980s and early 1990s. These long-term trends of water quality were well discriminated by PCA which can be further applied for the whole ecosystem interpretation with biological variables.     

Inter‐annual changes of alpine inland lake water storage on the Tibetan Plateau: Detection and analysis by integrating satellite altimetry and optical imagery

The effects of climate change have a substantial influence on the extremely vulnerable hydrologic environment of the Tibetan Plateau. The estimation of alpine inland lake water storage variations is essential to modeling the alpine hydrologic process and evaluating water resources. Due to a lack of historical hydrologic observations in this remote and inaccessible region, such estimations also fill a gap in studies on the continuous inter‐annual and seasonal changes in the inland lake water budget. Using Lake Siling Co as a case study, we derived a time‐series of lake surface extents from MODIS imagery, and scarce lake water level data from the satellite altimetry of two sensors (ICESat/GLAS and ENVISAT RA‐2) between 2001 and 2011. Then, based on the fact that the rise in lake water levels is tightly dependent on the expansion of the lake extent, we established an empirical model to simulate a continuous lake water level dataset corresponding to the lake area data during the lake's unfreezing period. Consequently, from three dimensions, the lake surface area, water level and water storage variations consistently revealed that Lake Siling Co exhibited a dramatic trend to expand, particularly from 2001 to 2006. Based on the statistical model and lake area measurements from Landsat images since 1972, the extrapolated lake water level and water storage indicate that the lake has maintained a continual expansion process and that the cumulative water storage variations during 1999–2011 account for 66.84% of the total lake water budget (26.87 km³) from 1972 to 2011. Copyright © 2013 John Wiley & Sons, Ltd.     

太湖水体氮、磷浓度演变趋势(1985-2015年)

分析了太湖水体氮、磷浓度1985-2015年的演变趋势.结果表明,近30年来,全太湖水体氮、磷指标总体呈先恶化、后好转的波动变化趋势.总氮（TN）浓度年均值在1.79～3.63 mg/L之间,30年平均值为2.62±0.03 mg/L,总磷（TP）浓度年均值在0.04～0.15 mg/L之间,30年平均值为0.086±0.001 mg/L,1996年全太湖TN （3.84 mg/L）和TP （0.15 mg/L）浓度年均值均达历史峰值.氮、磷逐月浓度变化情况显示,TN浓度呈明显季节性变化规律,最高值集中出现在3、4月,概率分别为67%和33%,最低值则分布在8、9、10、11月,概率分别为18%、41%、29%和12%,而TP浓度则没有明显的季节性变化规律.太湖各湖区水体氮、磷浓度变化空间异质性明显,西部水域和北部水域变化幅度大于东部水域、南部水域和湖心区.太湖水体氮、磷浓度的长期变化趋势显然和流域经济发展及各项环保管理措施的实施密切相关,同时也受到重大水情变化的影响.此外,在相对封闭的局部湖湾水体可以通过水利调度等综合治理措施短时期内改善氮、磷指标,但大太湖水质的改善任重而道远.     

Temporal trends of hydro-climatic variables and their relevance in water resource management

Identification of temporal changes in hydrological regimes of river basins is an important topic in contemporary hydrology because of the potential impacts of climate change on river flow regimes.For this purpose,long-term historical records of rainfall(P),runoff(Q)and other climatic factors were used to investigate hydrological variability and trends in the Tajan River Basin over the period 1969e1998.Actual evaporation(E),rainfall variability index(d),evaporation ratio(CE)and runoff ratio(CQ)were estimated from the available hydroclimatological records.Mann-Kendall trend analysis and nonparametric Sen's slope estimates were performed on the respective time series variables to detect monotonic trend direction and magnitude of change over time.Rainfall variability index showed that 1973 was the wettest year(δ=+2.039)while 1985 was the driest(δ=-1.584).Also,decades 69e78 and 89e98 were recognized as the wettest and driest decades respectively.The gradient of variation of climatological parameters showed that during the study period,all three parameters of rainfall,evaporation and runoff have decreased and the variations of rainfall and evaporation were significant at the 95%level.Investigation of hydrological changes due of dam construction(1999)showed that the amount and annual distribution of discharge were completely different pre and post-dam construction.Discharge decreased in high water months and increased in low water months to meet water supply demands,especially for agriculture.The relationship between temperature and rainfall trends is compared for three stations in Mazandaran Province(Gorgan,Babolsar and Ramsar)from 1956 to 2003 and nine other stations with different statistical periods of 19e36 years,relating trends to northern hemisphere and global trends.Decreases in temperature were accompanied by decreases in rainfall,and vice versa.These trends were not observed in northern hemisphere and world scales,where temperature increases are accompanied by decreases in rainfall.These variations of hydroclimatological parameters show undesirable water resources situations during the statistical periods if the trend continues severe water resource crises.     

滇池、抚仙湖、阳宗海长期水位变化(1988-2015年)及驱动因子

水位变化影响湖泊水质、水量和生态系统功能,是研究湖泊演变的重要内容,但目前针对滇中高原湖群水位变化特征还少见系统报道.本文选择滇池、抚仙湖、阳宗海3个滇中高原湖泊作为研究对象,基于1988-2015年实测水位数据和Mann-Kendall趋势检验法评估了3个湖泊水位变化特征;运用RClimDex模型获得了流域极端降水指标,结合其他指标构建了基于极端气象因子的湖泊水位驱动力指标体系;采用主成分-多元回归模型,解析了极端降水、蒸发等气象因子对滇中高原湖泊水位变化的贡献.结果表明：①滇池、抚仙湖、阳宗海水位年际波动不突出.滇池的年平均水位总体略呈上升趋势,年均上升0.025 m.阳宗海和抚仙湖水位无明显变化.②滇中高原湖泊流域的极端降水指数年际变化趋势不明显.滇池的蒸发量呈明显减小趋势,年均减小21.05 mm.抚仙湖蒸发量呈明显增加趋势,平均每年增加5.52 mm.阳宗海蒸发量的变化不明显.③气象指标可解释滇池水位变化的49.7%,滇池水位变化受气候变化和人类活动的综合影响;阳宗海和抚仙湖水位变化主要受气象条件控制,蒸发量、综合降水指标和连续降水指标对阳宗海水位变化的解释率高达93.3%;综合降水指标和干旱状况指标可以解释抚仙湖水位变化的64.5%.极端降水指标对解释高原湖泊水位变化具有重要作用.     

Relationships between snowpack,low flows and stream temperature in mountain watersheds of the US west coast

Water temperatures in mountain streams are likely to rise under future climate change, with negative impacts on ecosystems and water quality. However, it is difficult to predict which streams are most vulnerable due to sparse historical records of mountain stream temperatures as well as complex interactions between snowpack, groundwater, streamflow and water temperature. Minimum flow volumes are a potentially useful proxy for stream temperature, since daily streamflow records are much more common. We confirmed that there is a strong inverse relationship between annual low flows and peak water temperature using observed data from unimpaired streams throughout the montane regions of the United States' west coast. We then used linear models to explore the relationships between snowpack, potential evapotranspiration and other climate-related variables with annual low flow volumes and peak water temperatures. We also incorporated previous years' flow volumes into these models to account for groundwater carryover from year to year. We found that annual peak snowpack water storage is a strong predictor of summer low flows in the more arid watersheds studied. This relationship is mediated by atmospheric water demand and carryover subsurface water storage from previous years, such that multi-year droughts with high evapotranspiration lead to especially low flow volumes. We conclude that watershed management to help retain snow and increase baseflows may help counteract some of the streamflow temperature rises expected from a warming climate, especially in arid watersheds.     

Stage level,volume and time‐frequency information content of Lake Tana using stochastic and wavelet analysis methods

Lake Tana is the largest fresh water body situated in the north‐western highlands of Ethiopia. In addition to its ecological services, it serves for local transport, electric power generation, fishing, recreational purposes, and source of dry season irrigation water supply. Evidence shows that the lake has dried at least once at about 15,000–17,000 before present owing to a combination of high evaporation and low precipitation events. Past attempts to understand and simulate historical fluctuation of Lake Tana based on simplistic water balance approach of inflow, outflow, and storage have failed to capture well‐known events of drawdown and rise of the lake that have happened in the last 44 years. This study tested different stochastic methods of lake level and volume simulation for supporting Lake Tana operational planning decision support. Three stochastic methods (perturbations approach, Monte Carlo methods, and wavelet analysis) were employed for lake level and volume simulation, and the results were compared with the stage level measurements. Forty‐four years of daily, monthly, and mean annual lake level data have shown a Gaussian variation with goodness of fit at 0.01 significant levels of the Kolmogorov–Smirnov test. The stochastic simulations predicted the lake stage level of the 1972, 1984, and 2002/2003 historical droughts 99% of the time. The information content (frequency) of fluctuation of Lake Tana for various periods was resolved using Wigner's Time‐Frequency Decomposition method. The wavelet analysis agreed with the perturbations and Monte Carlo simulations resolving the time (1970s, 1980s, and 2000s) in which low frequency and high spectral power fluctuation has occurred. The Monte Carlo method has shown its superiority for risk analysis over perturbation and deterministic method whereas wavelet analysis reconstructed historical record of lake stage level at daily and monthly time scales. Copyright © 2012 John Wiley & Sons, Ltd.     

Spatiotemporal Analysis of Extracted Groundwater Volumes Estimated from Electricity Consumption

Land subsidence caused by groundwater overexploitation is a serious global problem. The acquisition of spatiotemporal pumping rates and volumes is a first step for water managers to develop a strategic plan for mitigating land subsidence. This study investigates an empirical formulation to estimate the monthly maximum pumped volume over a 10-year period based on electric power consumption data. A spatiotemporal variability analysis of monthly pumped volume is developed to provide an improved understanding of seasonal pumping patterns and the role of irrigation type. The analysis of regional pumped volume provides an approximation of the spatiotemporal patterns of the variations in pumped volume. Results show the effects of climate, seasonal changes in pumping from irrigation, and the local differences in pumping caused to crop types. A seasonal pumped volume peak occurs annually, with the highest and least pumped volumes occurring in March (highest peak) and September (lowest peak), respectively. However, the majority of the historical maximum pumped volumes have occurred during the last few years. Extracted volumes continue to increase in some locations. The analysis reveals increasing trends in pumping, thereby possibly providing the locations where increased effective stresses may lead to land subsidence.     

Trends in water quality variations in the Odra River the day before implementation of the Water Framework Directive

This paper contains an account of UN/EEC-sponsored research on water quality monitoring and assessments in the catchments areas of Europe's 10 transboundary rivers. In this context, water quality assessments established on the basis of monitoring data for Poland's rivers are discussed. Consideration is also given to the water quality assessment methods recommended by the EU Directives. The problem has been exemplified by the analysis of water quality variations in the transboundary river Odra in the time span of 1973–2003. For the years 1993–2003, the trends in water quality variations are calculated and the rates of variation are analysed. The points in time when the water quality will have attained the second class purity values are predicted, taking into account the requirements specified in Polish, Czech and German standards. Analysis of the trends in the variations of pollution parameters has revealed that the achievability of good water quality depends on the limit values adopted for the assessment.     

A 50-year record of nitrate concentrations in the Slapton Ley Catchment,Devon, United Kingdom

Slapton Ley, a coastal lake, is the largest natural body of fresh water in south-west England. There was concern in the 1960s that the lake was becoming increasingly eutrophic. To quantify inputs of water, sediment and nutrients into the lake, Slapton Ley Field Centre initiated a programme of weekly water quality sampling in September 1970. Of all the chemical properties which have been measured over the decades, the nitrate record has been the subject of more research than any other. The weekly monitoring has been supplemented by research projects aimed at understanding aspects of processes and patterns of nitrate delivery to the stream network. Three aspects of the nitrate record are reviewed: short-term process dynamics; the annual cycle of influent streams and the lake itself; and long-term trends. In the first two decades of monitoring, there was increasing concern about a trend of rising nitrate concentrations, an issue in most lowland rivers in the United Kingdom at the time. In the 1990s, nitrate concentrations levelled off and then have fallen steadily in recent years. In relation to eutrophication, there are clear signs of improvement in the influent streams, but concerns remain about water quality in the lake itself.     

引水等综合整治后杭州西湖氮、磷营养盐时空变化(1985—2013年)

经引水等综合整治后,西湖外湖、西里湖总磷(TP)浓度累计下降58%和78%,总氮(TN)浓度累计下降16.7%和7.7%,透明度提高100%~200%,富营养状态得到极大缓解.比较1986年治理前,西湖各湖区因来水、引水和排水格局差异较大,TP浓度的年内变化特点及驱动因素也存在较大差异:杨公堤以西的上游湖区因优质水源补充TP浓度总体较低,同时受流域降雨径流面源输入影响,呈现时段性升高;杨公堤和苏堤之间的中游湖区优质水源补充量最大,湖区水体更新最快,TP浓度最低且变化相对最为稳定;苏堤以东的外湖区水体更新相对最慢,在夏、秋高温季节因底泥污染释放,TP浓度出现峰值.因外来引水量大且未经脱氮处理,西湖各湖区TN年内变化基本与钱塘江取水口TN浓度变化一致,同时因流域降雨径流面源输入而出现时段性波动.基于TP质量平衡模型分析,各湖区水质空间差异主要受水体年交换次数影响,其次受单位水体的年污染负荷影响.     

Variation in riverine phosphorus between 1994 and 2003 as affected by land-use and loading reductions in six medium-sized to large German rivers

Land use and in-stream transformation exert great influence on concentrations and loads of phosphorus (P) in rivers. We aimed to display differences in the courses of total P (TP) and soluble reactive P (SRP) concentrations and loads in six medium-sized to large rivers in the central region of Germany, and to identify the reasons for different long-term trends. Therefore, we applied multivariate statistics to 10-year-time series (1994–2003) of TP, SRP, discharge (Q), water temperature (T), pH, dissolved organic carbon (DOC), total organic carbon (TOC), dissolved oxygen (DO), total iron (Fe), and total manganese (Mn). Statistical results were related to land use in the catchments of the rivers. TP concentrations ranged between 0.02 and 0.78 mg l⁻¹, and SRP concentrations ranged between 0.01 and 0.44 mg l⁻¹. Q correlated negatively with TP and SRP concentrations over the entire year. Furthermore, Fe correlated significantly and positively to TP and SRP and therefore, ferric hydroxides likely were the major P sorption sites. DOC showed significant positive correlation to SRP particularly in spring, indicating manure exposure in early spring as a major source of both, DOC and SRP. Significant negative correlations between DO and SRP in summer hint at internal P loading in rivers or in flushed lakes. Different forms of land use were the reasons of enhanced or retarded recovering from previous increases in P concentrations. High portions of arable land within some of the catchments impeded the process of decreases since 1996 because of remaining high-diffuse emissions from fertilized soils. Agricultural practices, exposing fertilizer to soils within the river catchments and high Q in early spring caused high TP and SRP loads to downstream systems, and evoked risks for downstream river reaches.