黑河干流正义峡-狼心山段河道渗漏量计算及模拟

综合考虑来水条件和渗漏容量,利用平均水面宽度与渗漏率的乘积求得单位长度渗漏量,采用水面宽度的变化表征渗漏面随水流起伏变化,建立了黑河正义峡-狼心山段河道渗漏模型,模拟了2005-2013年河段渗漏量变化;并以此建立了河道前期过水和未过水条件下正义峡流量和正义峡-狼心山段渗漏量之间的关系。结果表明：（1）强烈渗漏条件下天然河道水流演进模型对正义峡-狼心山段渗漏模拟效果较好,总体误差小于5%;（2）模型模拟的2005-2013年年均渗漏量为2.69×10⁸ m³,与以水量平衡计算的年均2.84×10⁸ m³大致相当,绝对误差为0.15×10⁸ m³,表明模型模拟的结果较好;（3）正义峡流量和正义峡-狼心山段河道渗漏量呈显著的指数关系,实际调度工作中,可利用该模型计算渗漏量并预测下游的来水过程。     

洞庭湖生态经济区生态服务供需平衡研究

基于洞庭湖生态经济区土地覆被类型和土地利用现状,测算并研究区域内供给服务、调节服务、支持服务和文化服务及生态服务总量供给的价值当量;根据国家相关建设指标规定和人均资源消耗量,估算各项生态服务需求量价值当量;进而对区域内生态服务的供—需盈亏状态进行分析。结果表明：① 洞庭湖生态经济区各项生态服务及生态服务总量供需状况良好,供需比均大于1.2;② 不同生态服务供需状况存在差异,支持服务（1.46）>调节服务（1.44）>供给服务（1.39）>文化服务（1.28）;③ 供需比在空间上整体呈现“四周高中间低”的分布模式,北侧荆州供需比偏低;④ 城乡供需状况差异显著。本次研究囿于行政边界,基于自然边界的供需状况研究有待深入。     

Evaluating five remote sensing based single-source surface energy balance models for estimating daily evapotranspiration in a humid subtropical climate

In the last two decades, a number of single-source surface energy balance (SEB) models have been proposed for mapping evapotranspiration (ET); however, there is no clear guidance on which models are preferable under different conditions. In this paper, we tested five models-Surface Energy Balance Algorithm for Land (SEBAL), Mapping ET at high Resolution with Internalized Calibration (METRIC), Simplified Surface Energy Balance Index (S-SEBI), Surface Energy Balance System (SEBS), and operational Simplified Surface Energy Balance (SSEBop)—to identify the single-source SEB models most appropriate for use in the humid southeastern United States. ET predictions from these models were compared with measured ET at four sites (marsh, grass, and citrus surfaces) for 149 cloud-free Landsat image acquisition days between 2000 and 2010. The overall model evaluation statistics showed that SEBS generally outperformed the other models in terms of estimating daily ET from different land covers (e.g., the root mean squared error (RMSE) was 0.74 mm day⁻¹). SSEBop was consistently the worst performing model and overestimated ET at all sites (RMSE = 1.67 mm day⁻¹), while the other models typically fell in between SSEBop and SEBS. However, for short grass conditions, SEBAL, METRIC, and S-SEBI appear to work much better than SEBS. Overall, our study suggests that SEBS may be the best SEB model in humid regions, although it may require modifications to work better over short vegetation.     

Remote sensing of alpine glaciers in visible and infrared wavelengths: a survey of advances and prospects

Remote sensing is an efficient tool for temporal monitoring of inaccessible alpine glacial terrain. This study discusses the methods of remote sensing in visible and infrared (IR) wavelengths, which are helpful in providing important information about alpine glaciers. The scope of this study covers recent advances and prospects in optical and thermal remote sensing of glacier facies, glacier velocity, mass balance, glacial hazards and automated mapping techniques. The technology is ever evolving with the advent of new remote sensors capturing data in visible/IR wavelengths and better digital computing technology. An extensive list of significant studies further helps the reader to explore a particular topic of interest. We survey recent advances in this field and additionally highlight the emerging prospects.     

Ice Mass Variation in Antarctica from GRACE Over 2002–2011

We detect the mass balance of the Antarctica ice sheet from GRACE for the recent period July 2002 through March 2011. Land hydrology contamination was corrected through global hydrological models and glacial isostatic adjustment (GIA) of the solid Earth since last deglaciation using the IJ05 model, and then a forward model was employed to adjust to bias due to smoothing filters and GRACE's limited resolution. The results show that there are two significant turning points for ice mass losses or gains near the early 2006 and the end of 2008. The ice mass losses in West Antarctica have accelerated dramatically during 2009–2011, while in East Antarctica the rate is positive, mainly caused by snow accumulation. Over the whole studying period, ice loss rates in West Antarctica (?108 ± 36 Gt/yr) are still significantly larger than the increase in East Antarctica (+72 ± 24) Gt/yr. Thus, the total Antarctica contribution to sea level rise is slightly negative ?0.18 ± 0.02 mm/yr. The rapid change of the regional ice mass in Antarctic, in the course of only several years, suggests that the Antarctica ice sheet mass balance is more sensitive to regional climate conditions than considered before.     

Deuterium‐excess determination of evaporation to inflow ratios of an alpine lake: Implications for water balance and modeling

The numerous lakes on the Tibetan Plateau play an important role in the regional hydrological cycle and water resources, but systematic observations of the lake water balance are scarce on the Tibetan Plateau. Here, we present a detailed study on the water cycle of Cona Lake, at the headwaters of the Nujiang‐Salween River, based on 3 years (2011–2013) of observations of δ¹⁸O and δ²H, including samples from precipitation, lake water, and outlet surface water. Short‐term atmospheric water vapor was also sampled for isotope analyses. The δ²H–δ¹⁸O relationship in lake water (δ²H = 6.67δ¹⁸O ? 20.37) differed from that of local precipitation (δ²H = 8.29δ¹⁸O + 12.50), and the deuterium excess (d‐excess) in the lake water (?7.5‰) was significantly lower than in local precipitation (10.7‰), indicating an evaporative isotope enrichment in lake water. The ratio of evaporation to inflow (E /I ) of the lake water was calculated using both d‐excess and δ¹⁸O. The E /I ratios of Cona lake ranged from 0.24 to 0.27 during the 3 years. Observations of atmospheric water vapor isotopic composition (δ _A ) improved the accuracy in E /I ratio estimate over a simple precipitation equilibrium model, though a correction factor method provided nearly identical estimates of E /I ratio. The work demonstrates the feasibility of d‐excess in the study of the water cycle for lakes in other regions of the world and provides recommendations on sampling strategies for accurate calculations of E /I ratio.     

Modélisation du bilan hydrologique de la partie sud de la Mer d'Aral entre 1993 et 2001 / Hydrological balance modelling of the southern Aral Sea between 1993 and 2001

Abstract

Since the beginning of the 1990s, the Aral Sea is made of two separate entities: the Small Aral in the north and the Great Aral in the south. In this study, the water and salt balance of the Great Aral is analysed using newly available data: on the one hand, altimetric data of the sea level provided by the TOPEX/Poseidon satellite; and on the other, climate data provided by the ECMWF and NOAA within the framework of global climate re-analysis. These data indicate that the Great Aral received a mean groundwater inflow of about 4 km³ year^-1 between 1993 and 2001. Without this contribution, the Aral Sea would disappear even faster than is being observed today. Moreover, the temporal resolution of the data shows a systematic phase difference between the model prediction and satellite measurements. This phase shift is considered to be due to the formation of temporary lakes between the last station measuring the Amu-Darya discharge and its mouth in the Great Aral.     

Ephemeral stream chemistry below the elevation of near‐zero net infiltration

Stormwater along ephemeral arroyos and areal infiltration in nearby boreholes were studied in the Amargosa Desert Region of Southern Nevada, USA. Chemical composition of ephemeral stream runoff was measured at elevations below where areal infiltration generally occurs in arid environments using lysimeters designed for this study. Borehole cuttings from several wells were evaluated in terms of chloride migration. Analysis of the borehole data indicates that net areal infiltration has been insignificant for the past 10 000+ years. This is associated with an environment where chloride and other soluble salts accumulate in shallow sediments and potentially in runoff waters. Measured storm events during the 4‐year study period were small and localized but sufficient to produce surface runoff, at least near the lysimeters. Composition of storm runoff captured by the lysimeters was found to be a combination of the water chemistry types found in precipitation and from leaching tests of near‐surface sediments. All major cations and bicarbonate increased relative to chloride when precipitation interacted with sediments to form ephemeral stream runoff. The changes were consistent with calculated saturation indices. Despite the long‐term accumulation of chloride in soils and deep sediments caused by complete evapotranspiration of infiltrating precipitation, runoff waters were characterized by low chloride and total dissolved solids. This study presents a limitation of the chloride mass‐balance method, as chloride and water migration were disassociated from each other in the study area. Copyright © 2014 John Wiley & Sons, Ltd.     

Heat exchange processes and thermal dynamics of a glacier‐fed alpine stream

Glacier‐fed river thermal regimes vary markedly in space and time; however, knowledge is limited on the fundamental processes controlling alpine stream temperature dynamics. To address the research gap, this study quantified heat exchanges at the water surface and bed of the Taillon glacier‐fed stream, French Pyrénées. Hydro‐meteorological observations were recorded at 15‐min intervals across two summer melt seasons (2010 and 2011), and energy balance components were measured or estimated based on site‐specific data. Averaged over both seasons, net radiation was the largest heat source (~80% of total flux); sensible heat (~13%) and friction (~3%) were also sources, while heat exchange across the channel–streambed interface was negligible (<1%). Latent heat displayed distinct interannual variability and contributed 5% in 2010 compared with 0.03% in 2011. At the sub‐seasonal scale, latent heat shifted from source to sink, possibly linked to the retreating valley snowline that changed temperature and humidity gradients. These findings represent the first, multiyear study of the heat exchange processes operating in a glacier‐fed stream, providing fundamental process understanding; the research highlights the direct control antecedent (winter) conditions that have on energy exchange and stream temperature during summer months. In particular, the timing and volume of snowfall/snowmelt can drive thermal dynamics by the following: (1) altering the length of the stream network exposed to the atmosphere and (2) controlling the volume and timing of cold water advection downstream. Finally, this study highlights the need to develop long‐term hydro‐meteorological monitoring stations to improve the understanding of these highly dynamic, climatically sensitive systems. Copyright © 2015 John Wiley & Sons, Ltd.     

A hydrologic assessment of a saline‐spring fen in the Athabasca oil sands region,Alberta, Canada – a potential analogue for oil sands reclamation

Canada's post‐mined oil sands will have a higher concentration of salts compared with freshwater peatlands that dominate the landscape. While rare, naturally occurring saline wetlands do exist in Alberta's Boreal Plains and may function as analogues for reclamation, however, little is known about their hydrology. This paper investigates the geochemical and hydrologic characteristics of a natural saline‐spring peatland in Alberta's oil sands region. The fen is located within a saline groundwater discharge area connected to the erosional edge of the Grand Rapids Formation. Na⁺ (195–25,680 mgl^?1) and Cl^? (1785–56,249 mg l^?1) were the dominant salts, and the fen transitioned sharply to freshwater along its margins because in part of subsurface mineral ridges that restricted shallow groundwater exchange. Salinity decreased from hypersaline to brackish along the local groundwater flow path but no active spring outlets were observed over the two‐year study. Vertical groundwater discharge was minimal because of the very low permeability of the underlying sediments. Subsurface storage was exceeded during periods of high flow, resulting in flooding and surface runoff that was enhanced by the ephemerally connected pond network. These findings have implications for reclamation, as mechanisms such as subsurface mineral ridges may function as effective saline groundwater‐control structures in the post‐mined environment. Incorporating saline wetlands into regional monitoring networks will help to better quantify natural discharge, which has implications for belowground wastewater storage related to in situ bitumen extraction. Copyright © 2015 John Wiley & Sons, Ltd.