1958—2017年太湖蒸发量年际变化趋势及主控因子

湖泊蒸发对气候变化非常敏感, 是水文循环响应气候变化的指示因子, 因此研究湖泊蒸发的控制因素, 对于理解区域水文循环有重要意义. 本文利用太湖中尺度涡度通量网避风港站观测数据校正JRA-55再分析资料, 驱动CLM4.0-LISSS模型, 并利用2012—2017年涡度相关通量数据和湖表面温度数据检验模型模拟蒸发结果, 验证了该模型在太湖的适用性; 估算了1958—2017年间太湖的湖面蒸发量, 并利用Manner-Kendall趋势检验分析了湖面蒸发的变化趋势, 寻找太湖实际蒸发的年际变化的主控因子. 结果如下: 校正后的JRA-55再分析资料模拟的太湖蒸发与观测值之间存在季节偏差, 但是季节偏差在年尺度上相互抵消, 再分析资料可用于年际尺度太湖蒸发变化的模拟; 1958—2017年间太湖蒸发量以1977年为界, 先下降(-3.6 mm/a), 后增加(2.3 mm/a); 多元逐步回归结果表明, 向下的短波辐射是太湖1958—2017年间太湖蒸发变化的主控因子, 向下的长波辐射、气温、比湿也对湖泊蒸发年际变化有一定影响, 但是风速对蒸发量的年际变化影响不大.     

用稳定同位素方法估算大型浅水湖泊蒸发量——以太湖为例

湖泊蒸发量的准确估算对于水文学、气象学和湖泊学等研究有重要的意义.基于2013-2015年太湖水量收支资料、气象观测数据和稳定同位素观测资料,采用稳定同位素质量守恒模型、水量平衡法和Priestley-Taylor模型估算太湖蒸发量,分析太湖蒸发量的季节变化和年际变化特征,并以Priestley-Taylor模型结果为参考值,评价水量平衡法和同位素质量守恒方程的计算精度.结果表明:5-9月太湖蒸发量较高,冬季最低.2013-2015年太湖年总蒸发量分别为1069、894和935 mm,蒸发量的年际变化受到天气条件的影响.2013年12月2014年11月期间,用Priestley-Taylor模型计算的湖泊蒸发量为885 mm;同位素质量守恒模型的估算结果较一致,为893 mm;而水量平衡方程的估算结果明显偏高,为1247 mm.     

洱海湖气界面水汽和二氧化碳通量交换特征

基于2012年涡动相关法取得的洱海湖气之间湍流通量资料,计算了湖面反照率、空气动力学粗糙度和整体输送系数等湖气交换过程的基本物理参数;分析高原湖泊表面动量通量、感热通量、潜热通量和二氧化碳通量的变化特征及其主要的控制因子;采用神经网络法对缺失蒸发量数据进行填补,估算了洱海湖面全年蒸发量。2012年全年蒸发量为（1165±15）mm,大于年实际降水量（2012年的年降水量为818mm）。洱海局地环流在全年范围内较显著;全年主导风向为东南（谷风／湖风）和西北风（山风／陆风）。高原湖泊感热通量通常只有每平方米几十瓦,通常午后感热通量为负值;即湖面向大气输送热量。夏季湖泊大气界面感热通量最大值出现在清晨,与湖气温差的出现时间一致;在白天湖面的有效能量主要分配为潜热通量;湖气温差和水汽压差分别是感热通量和潜热通量日变化的主要控制因子。湖气界面二氧化碳通量除夏季存在弱的吸收外,其余季节（冬季）表现为弱的排放。湖面反照率的季节变化规律与太阳高度角的季节变动有关,同时湖面反照率与水的浑浊度等有关。与实际观测得到的湖面反照率相比,CLM4湖泊模式在冬季低估（夏季高估）了湖面反照率。     

四万年以来青海湖的三期高湖面及其降水量研究

孢粉学、地貌学与沉积学的证据揭示了青海湖自４０ｋａＢＰ以来经历了至少三期高湖面,即３０－４０ｋａＢＰ,１１－１３ｋａＢＰ,７．５－５ｋａＢＰ。其中第一期与第三期的高湖面是全球性暖温气候的产物,第二期的高湖面同暖温气修及高山区冰川消融均有关系。根据Ｍ．Ｎ．Ｂｙｄｕｋｋｏ（Ｍ．И．Ｂｙлｂｉｋｏ）公式和Ｊ．Ｅ．Ｋｕｔｚｂａｃｈ公式计算年蒸发量,依据封闭流域全流域水面平衡模式,模拟了青海湖在第一期与第三     

近20年青海湖湖水面积变化遥感

采用NOAA/AVHRR资料,对青海湖湖面进行水体判识,并利用线性混合模式对混合象元进行处理,定量估算了近20年青海湖湖水面积并分析了变化趋势,表明近20年青海湖湖水面积在不断减小,每年减少约4km2,并且青海湖干涸部分主要在其北部.进一步采用主成分分析和回归分析方法对青海湖地区降水、气温和蒸发量做了初步气候分析,表明青海湖地区降水减少、气温升高、蒸发量增加是青海湖湖水面积逐年减少的主要原因.     

高温微风条件下太湖流域风场时空特征分析

适宜太湖蓝藻水华大面积形成的诸多因素中,气象因素主要是高温、微风.据此对太湖周边17个常规气象观测站的7年报文资料进行筛选,选择的17个站点同时满足时间为14点、气温大于2590、风速小于等于4m/s的风场进行分析,研究发现太湖流域风场空间特征以东南风居多,而且不同风向的背景风场吹过水面后.在下风向湖面及湖岸附近都存在...     

人类活动对青海湖水位下降的影响

青海湖是我国最大的内陆湖泊,位于青藏高原的东北隅。近三十年来由于自然要素和人为活动的影响,湖周生态环境急剧退化,湖水位下降达3.35m,湖面收缩约300多km~2。根据调查研究以及其他方面的资料。青海湖多年平均亏水量4.36×10~8m~3,而人为活动耗水量占亏水量的8.7％。仅占湖面蒸发量的1％。所以,人为耗水与湖水位波动无明显相关,湖水位下降虽然是综合效应,但主导因素是气候变化,并导致湖周生态环境的恶化。     

太湖和大浦河口风成流、风涌水的数值模拟及其单站验证

介绍了太湖风成流和风涌水的数值摸拟工作。使用两种不同水平分辨率的数值模式,利用中日合作研究组在大浦河口实测的水位、湖流和风的资料对模拟结果进行了验证。结果指出,模式对风涌水及流向有较好的预报能力,流速的预报尚待进一步改进。     

太湖水面太阳辐射中的光合有效成份

本文利用睛空大气辐射传输分光参数化模式,讨论了到达太湖水面太阳总辐射中光合有效成分所占比例的日变化状况。辐射传输计算所涉及的气象参数采用无锡地区气象站资料;水体反射仅考虑有风浪状况下的水平Fresnel反射。两次湖面实测太阳总辐射日变化曲线与计算值对比分析表明,计算结果基本上能反映晴空条件下太湖水面辐射状况。本文结果对利用总辐射值估算水体生态研究中感兴趣的光合有效成份有一定参考价值。     

东南极拉斯曼丘陵区的湖泊

拉斯曼丘陵区的湖泊均为淡水湖,总数近150个,湖泊总面积6.3km~2,占陆地总面积的3.15％。东部地区湖泊数量少但多深大湖,西部地区数量多但多浅小湖。湖泊地貌发育初始,A_1/A_c之值较大,湖岸地貌形态不发育,全年封冻期长达300天,限制了湖水动力对地貌和沉积物形成的作用强度,冰雪融水量与湖面蒸发量控制了湖水平衡和湖面变化过程。湖积物厚度小,颗粒粗,分选差,风力混杂堆积作用明显。夏季水温变化复杂,并常有明显的逆温现象。水体pH值介于6.0～8.0之间,Na~+占绝对优势。     

Evaporation estimation on Lake Titicaca: a synthesis review and modelling

The aim of this study was to validate evaporation models that can be used for palaeo‐reconstructions of large lake water levels. Lake Titicaca, located in a high‐altitude semi‐arid tropical area in the northern Andean Altiplano, was the object of this case study. As annual evaporation is about 90% of lake output, the lake water balance depends heavily on the yearly and monthly evaporation flux. At the interannual scale, evaporation estimation presents great variability, ranging from 1350 to 1900 mm year^?1. It has been found that evaporation is closely related to lake rainfall by a decreasing relationship integrating the implicit effect of nebulosity and humidity. At the seasonal scale, two monthly evaporation data sets were used: pan observations and estimations derived from the lake energy budget. Comparison between these data sets shows that (i) there is one maximum per year for pan evaporation and two maxima per year for lake evaporation, and (ii) pan evaporation is greater than lake evaporation by about 100 mm year^?1. These differences, mainly due to a water depth scale factor, have been simulated with a simple thermal model θ_w(h, t) of a free‐surface water column. This shows that pan evaporation (h = 0·20 m) is strongly correlated with direct solar radiation, whereas the additional maximum of lake evaporation (h = 40 m) is related to the heat restitution towards the atmosphere from the water body at the end of summer. Finally, five monthly evaporation models were tested in order to obtain the optimal efficiency/complexity ratio. When the forcing variables are limited to those that are most readily available in the past, i.e. air temperature and solar radiation, the best results are obtained with the radiative Abtew model (r = 0·70) and with the Makkink radiative/air temperature model (r = 0·67). Copyright © 2007 John Wiley & Sons, Ltd.     

ESTIMATION OF LAKE EVAPORATION FROM A SHALLOW LAKE IN CENTRAL SWEDEN BY OXYGEN-18

Lake evaporation has been estimated for a shallow lake using a combination of water and isotope mass balance, accounting for the isotopic non-steady state of lake water. The main feature of the isotope method is that inflows need not be measured. Knowledge of their isotopic content is sufficient. Oxygen-18 content, i.e. (δ¹⁸O), of lake water, inflows and outflow was measured on a weekly basis, whereas for precipitation it was monitored daily. The discharge from the lake was also recorded daily. Lake water level, relative humidity, air, and lake water surface temperatures were recorded by a logger. The weather data were recorded on a small island in the lake. It was observed that the lake is isotopically well mixed. Furthermore, the atmospheric moisture was not always in isotopic equilibrium with the precipitation. Daily lake evaporation was estimated as an average of six to eight days depending upon the field logistics. Lake evaporation varied from 0.6 to about 5.4 mm/day during the experimental period. It was found that evaporation estimates are very sensitive to small variations in δ¹⁸O of lake evaporate. Induced changes of 10% in δ¹⁸O of lake evaporate caused errors in evaporation estimates of 9–31%, while similar induced changes in δ¹⁸O of inflows caused errors of 8–18%. Thus, an accurate experimental determination of δ¹⁸O of lake evaporate is relatively more important.     

Estimating daily lake evaporation from biweekly energy‐budget data

Estimates of daily lake evaporation based on energy‐budget data are poor because of large errors associated with quantifying change in lake heat storage over periods of less than about 10 days. Energy‐budget evaporation was determined during approximately biweekly periods at a northern Minnesota, USA, lake for 5 years. Various combinations of shortwave radiation, air temperature, wind speed, lake‐surface temperature, and vapour‐pressure difference were related to energy‐budget evaporation using linear‐regression models in an effort to determine daily evaporation without requiring the heat‐storage term. The model that combined the product of shortwave radiation and air temperature with the product of vapour‐pressure difference and wind speed provided the second best fit based on statistics but provided the best daily data based on comparisons with evaporation determined with the eddy‐covariance method. Best‐model daily values ranged from ?0.6 to 7.1 mm/day over a 5‐year period. Daily averages of best‐model evaporation and eddy‐covariance evaporation were nearly identical for all 28 days of comparisons with a standard deviation of the differences between the two methods of 0.68 mm/day. Best‐model daily evaporation also was compared with two other evaporation models, Jensen–Haise and a mass‐transfer model. Best‐model daily values were substantially improved relative to Jensen–Haise and mass‐transfer values when daily values were summed over biweekly energy‐budget periods for comparison with energy‐budget results.     

Net groundwater inflow in an enclosed lake: from synoptic variations to climatic projections

Using lake Stechlin in northeastern Germany as an example of a small groundwater‐feed lake without surface inflows and outflows, we estimated the temporal scales and the variability ranges of the net groundwater contribution to the lake water budget. High‐resolution water level measurements by a bottom‐mounted pressure logger provided the background for the estimation of the total lake water budget. This method has demonstrated reliability for estimation of lake level variations during periods ranging from subdiurnal to perennial. The typical amplitudes of the synoptic‐to‐perennial variability characterizing the groundwater climate of lake Stechlin are estimated by comparing the two subsequent years 2006 and 2007; one of these years shows an extremely high, and the other an extremely low, annual precipitation–evaporation balance. The net groundwater flow, estimated as the difference between the total water budget and the precipitation–evaporation balance at the surface, revealed synoptic effects of lake water exfiltration into the groundwater aquifer following strong precipitation events. Perennial variations between wet and dry years superimposed seasonal oscillations. The probable origin of the latter is seasonality in the groundwater level on the watershed, although the exact amplitudes are subject to further quantification on account of seasonality in the evaporation estimation error. The results emphasize the non‐stationary behaviour of groundwater flow on timescales shorter than climatic ones. The analysis yielded a net quantitative relationship between groundwater flow and water balance at the lake surface: The water level changes in the lake due to evaporation and precipitation are damped to 60% because of the lake–groundwater exchange by means of intermittent infiltration and exfiltration events. Assuming the remaining 40% of the surface water budget may potentially result in perennial water level variability, we estimated an effect of the precipitation decrease on the lake water budget as predicted by the regional climate scenarios for the next century. Copyright © 2012 John Wiley & Sons, Ltd.     

湖泊蒸发观测与计算方法研究进展

湖泊蒸发是连接湖泊水分循环与能量平衡的关键纽带之一,认识湖泊蒸发过程对于理解湖-气间相互作用机制十分重要。然而,由于湖泊的形态结构、地理位置和气候背景不同,各湖泊在不同时间尺度上的蒸发特征不同。湖泊蒸发存在复杂的物理驱动过程、时间尺度相关的反馈以及空间异质性。准确地捕捉并量化湖泊蒸发过程,仍是湖沼学、水文学和气象学等学科的重要研究内容。本文首先介绍了湖泊蒸发的主要观测手段,然后概述了湖泊蒸发在日内、季节、年际、年代际四种不同时间尺度的变化特征;梳理了不同时间尺度各要素对湖泊蒸发的影响,以及湖泊蒸发与湖泊面积和深度等形态结构特性及纬度和海拔等地理因素之间的关系;对自涡度相关技术等高精度仪器应用以来的湖泊蒸发研究进展做出了总结。     

Water balance of Lake Victoria: update to 2000 and climate change modelling to 2100 / Bilan hydrologique du Lac Victoria: mise à jour jusqu’en 2000 et modélisation des impacts du changement climatique jusqu’en 2100

Abstract

Abstract An annual water balance model of Lake Victoria is derived for the period 1925–2000. Regression techniques are used to derive annual inputs to the water balance, based on lake rainfall data, measured and derived inflows and estimated evaporation during the historical period. This approach acknowledges that runoff is a nonlinear function of lake rainfall. A longer inflow series is produced here which is representative of the whole inflow to the lake, rather than just from individual tributaries. The results show a good simulation of annual lake levels and outflows and capture the high lake level in 1997–1998. Climate change scenarios, from a recent global climate model experiment, are applied to the lake rainfall inflow series and evaporation data to estimate future water balances of the lake. The scenarios produce a potential fall in lake levels by the 2030s horizon, and a rise by the 2080s horizon. A discussion of the application of climate change data to this complex hydrological system is presented.     

Hydrological processes of a closed catchment‐lake system in a semi‐arid Mediterranean environment

Data collected in 4 years of field observations were used in conjunction with continuous simulation models to study, at the small‐basin scale, the water balance of a closed catchment‐lake system in a semi‐arid Mediterranean environment. The open water evaporation was computed with the Penman equation, using the data set collected in the middle of the lake. The surface runoff was partly measured at the main tributary and partly simulated using a distributed, catchment, hydrological model, calibrated with the observed discharge. The simplified structure of the developed modelling mainly concerns soil moisture dynamics and bedrock hydraulics, whereas the flow components are physically based. The calibration produced high efficiency coefficients and showed that surface runoff is greatly affected by soil water percolation into fractured bedrock. The bedrock reduces the storm‐flow peaks and the interflow and has important multi‐year effects on the annual runoff coefficients. The net subsurface outflow from the lake was calculated as the residual of the lake water balance. It was almost constant in the dry seasons and increased in the wet seasons, because of the moistening of the unsaturated soil. During the years of observation, rainfall 30% higher than average caused abundant runoff and a continuous rise in the lake water levels. The analysis allows to predict that, in years with lower than the average rainfall, runoff will be drastically reduced and will not be able to compensate for negative balance between precipitation and lake evaporation. Such highly unsteady situations, with great fluctuations in lake levels, are typical of closed catchment‐lake systems in the semi‐arid Mediterranean environment. Copyright © 2012 John Wiley & Sons, Ltd.     

Artificial neural networks and empirical equations to estimate daily evaporation: application to Lake Vegoritis,Greece

ABSTRACT

Evaporation is one of the most important components in the energy and water budgets of lakes and is a primary process of water loss from their surfaces. An artificial neural network (ANN) technique is used in this study to estimate daily evaporation from Lake Vegoritis in northern Greece and is compared with the classical empirical methods of Penman, Priestley-Taylor and the mass transfer method. Estimation of the evaporation over the lake is based on the energy budget method in combination with a mathematical model of water temperature distribution in the lake. Daily datasets of air temperature, relative humidity, wind velocity, sunshine hours and evaporation are used for training and testing of ANN models. Several input combinations and different ANN architectures are tested to detect the most suitable model for predicting lake evaporation. The best structure obtained for the ANN evaporation model is 4-4-1, with root mean square error (RMSE) from 0.69 to 1.35 mm d^?1 and correlation coefficient from 0.79 to 0.92.

EDITOR M.C. Acreman

ASSOCIATE EDITOR not assigned     

Application of a spreadsheet hydrological model for computing the long-term water balance of Lake Awassa,Ethiopia

Abstract

The water balance of the closed freshwater Lake Awassa was estimated using a spreadsheet hydrological model based on long-term monthly hydrometeorological data. The model uses monthly evaporation, river discharge and precipitation data as input. The net groundwater flux is obtained from model simulation as a residual of other water balance components. The result revealed that evaporation, precipitation, and runoff constitute 131, 106 and 83 × 10⁶ m³ of the annual water balance of the lake, respectively. The annual net groundwater outflow from the lake to adjacent basins is 58 × 10⁶ m³. The simulated and recorded lake levels fit well for much of the simulation period (1981–1999). However, for recent years, the simulated and recorded levels do not fit well. This may be explained in terms of the combined effects of land-use change and neotectonism, which have affected the long-term average water balance. With detailed long-term hydrogeological and meteorological data, investigation of the subsurface hydrodynamics, and including the effect of land-use change and tectonism on surface water and groundwater fluxes, the water balance model can be used efficiently for water management practice. The result of this study is expected to play a positive role in future sustainable use of water resources in the catchment.     

Missing role of groundwater in water and nutrient cycles in the shallow eutrophic lake Kasumigaura,Japan

A process‐based model was developed, NICE‐LAKE (NIES (National Institute for Environmental Studies) Integrated Catchment‐based Ecohydrology), which includes interactions between surface water, canopy, unsaturated water, aquifer, lake and rivers, and used it to model the shallow eutrophic Lake Kasumigaura in Japan. By estimating the spatial distribution of the hydrological cycle, the model shows that groundwater withdrawal greatly affects groundwater distribution and seepage and indirectly influences lake water level. The simulated seepage agrees excellently with the budget‐derived value calculated from the observed groundwater level, lake level and isotope analyses. The model showed that groundwater seepage and groundwater concentrations are important contributors to the eutrophication of Lake Kasumigaura, an important contribution not recognized in previous studies of the lake. Groundwater entering the lake from the north side is contaminated with high concentrations of nitrate and ammonia from intensive pig and cattle raising and cultivated fields. The simulation showed that this high nitrogen load plays an important role in the eutrophication of the lake (the nitrogen load in inflowing groundwater is 30% of river inflow and 4 times that from wastewater treatment plants) in spite of government policies to prevent overland flow of nutrients into the lake. Our results show that NICE‐LAKE is a powerful tool for forecasting how the water quality of the lake will be affected by the (illegal) disposal of animal excreta in the surrounding open fields. Copyright © 2007 John Wiley & Sons, Ltd.