近60年来长江河口河势变化及其对水动力和盐水入侵的影响Ⅱ.水动力

本文基于本系列论文Ⅰ中数值化的长江河口20世纪50年代、70年代海图获得的岸线和水深资料,以及2012年水深实测资料,设置不同年代模式网格,考虑径流量、潮汐和风应力作用,建立长江河口水动力和盐水入侵三维数值模式,模拟和分析不同年代潮汐潮流、单宽余通量、分汊口水通量和分流比,及其河势变化对它们的影响。最大潮差在3个年代间的变化主要在北支区域,50年代至70年代,北支潮差减小,减小区域集中在北支中段,2012年相比70年代北支潮差增大。单宽水通量在50年代北港大于南港,北支下段向上游输运、上段量值较小,在70年代南港大于北港,北支下段量值较小、上段向下游,在2012年南北港水通量较为接近,北港稍大,整个北支水通量向上游。定量给出了50、70年代和2012年南北支、南北港大潮期间和小潮期间涨潮、落潮和净水量和分流比,结合河势变化分析了不同年代间的变化原因。     

河西走廊西端灌丛沙丘发育过程及其对沙漠化的指示意义

在风沙活动强烈的荒漠地区开展环境变化研究常缺乏符合要求的地质测年材料。灌丛沙丘是干旱区发育的一种特殊生物地貌类型,具有计年和储存环境信息的功能,可以用来重建沙丘的发育过程和过去的环境变化。以河西走廊西端花海盆地发育的灌丛沙丘沉积剖面为研究对象,基于AMS¹⁴C年代学及沉积物粒度、碳酸盐含量、地球化学元素等代用指标的分析,与文献记载、沙漠化监测数据和近几十年的器测气象资料对比分析,试图揭示区域灌丛沙丘的发育过程及其环境指示意义。结果表明：花海盆地灌丛沙丘的发育时间已超过800 年;20世纪60年代中后期至70年代早期人类活动的干扰曾使灌丛沙丘的堆积过程中断,但丰富的物源随后又促使灌丛沙丘再次快速发育。沙丘物源曾发生过剧烈的变化,使得灌丛沙丘沉积物中的粗颗粒组分和中值粒径并不适于作为环境代用指标重建区域的风沙环境变化,而细颗粒组分（<63 μm和<10 μm）和碳酸盐含量的变化,则揭示了研究区在20世纪70-80年代（沙丘高度300~420 cm）时获得了丰富的物质来源。灌丛沙丘沉积物中的Zr/Rb比值,能够作为良好的环境代用指标指示1970-1988年（沙丘高度300~420 cm）区域处在风沙活动较强烈的环境;近几十年花海盆地土地沙漠化明显,尤其是20世纪70年代和80年代。灌丛沙丘可以作为有较高可信度的地质记录载体,在河西走廊西端重建较长时间尺度的、高分辨率的区域气候环境演变历史。     

Perennial frost blisters of the outer Mackenzie Delta,western Arctic coast,Canada

Saturated floodplains in Arctic deltas provide conditions favourable for frost mound growth. Little work has been reported from these settings to determine the origin of frost mounds and the controls on their distribution, to assess the longevity of individual mounds, or to quantify variation of mound distribution over time. A case study is presented on low mounds in low‐centred syngenetic ice‐wedge polygons of Big Lake Delta Plain, outer Mackenzie Delta. In 2008 and 2009, 12 mounds were examined by drilling to describe their morphologic variations and to investigate their growth processes. The mounds, containing a core of ice 15 to 58 cm thick, were less than 1 m high and 3 · 7 to 8 · 5 m in diameter; other mounds were over 10 m long. Organic inclusions in the ice, bubble densities, electrical conductivity profiles, and ice‐crystal structure indicated that the mounds were hydrostatic frost blisters. Up to six frost blisters were found within individual polygons due to the relatively small volume of water needed to create each mound. Frost‐blister densities, of greater than 1700 km^–2, increased toward the wet centres of alluvial islands down gentle topographic gradients. The frost blisters were perennial, with individuals remaining identifiable on aerial photographs and satellite images for up to 10 years. Frost blisters collapsed along dilation cracks opened by hydrostatic uplift and by thawing from their sides caused by snow drifting and water ponding. Cyclical growth and decay of the mounds may degrade the visible polygonal network over time. Copyright © 2013 John Wiley & Sons, Ltd.     

Riparian responses to reduced flood flows: comparing and contrasting narrowleaf and broadleaf cottonwoods

Abstract

To enable assessment of risks of water management to riparian ecosystems at a regional scale, we developed a quantile-regression model of abundance of broadleaf cottonwoods (Populus deltoides and P. fremontii) as a function of flood flow attenuation. To test whether this model was transferrable to narrowleaf cottonwood (Populus angustifolia), we measured narrowleaf abundance along 39 river reaches in northwestern Colorado, USA. The model performed well for narrowleaf in all 32 reaches where reservoir storage was <75% of mean annual flow. Field data did not fit the model at four of seven reaches where reservoir storage was >90% of mean annual flow. In these four reaches, narrowleaf was abundant despite peak flow attenuation of 45–61%. Poor model performance in these four reaches may be explained in part by a pulse of narrowleaf cottonwood expansion as a response to channel narrowing and in part by differences between narrowleaf and broadleaf cottonwood response to floods and drought.

Editor Z.W. Kundzewicz; Guest editor M. Acreman

Citation Wilding, T.K., Sanderson, J.S., Merritt, D.M., Rood, S.B., and Poff, N.L., 2014. Riparian responses to reduced flood flows: comparing and contrasting narrowleaf and broadleaf cottonwoods. Hydrological Sciences Journal, 59 (3–4), 605–617.     

青海省共和-玉树高速公路新建块石路基下的温度状况分析

块石路基是多年冻土区应用最为广泛的多年冻土路基形式. 为了研究多年冻土区修筑高速公路后块石路基的效果,选取青海省新建共和-玉树高速公路3个块石路基监测断面的实测资料,对路基修筑初期多年冻土温度状况进行了分析. 结果表明：路基修筑初期路基中心原天然地表下0.5 m处仍表现出季节变化规律,至原多年冻土上限深度处,温度波动幅度急剧减小. 块石路基的保温效果与年平均地温密切相关,年平均地温越低,对冻土的保护效果越显著. 受阴阳坡效应的影响,左路肩/坡脚温度高于右路肩/坡脚. 左右路肩及中心孔下多年冻土上限都得到不同程度的抬升,抬升幅度主要受路基高度影响,与多年冻土年平均地温没有必然关系.     

季节性冻土区水文特性及模型研究进展

简要评述了寒区冻土水文的研究进展情况,在分析季节性冻土的冻融水文过程和特点的基础上,系统归纳与总结了季节性冻融土壤条件下的融雪径流的产流模型、入渗规律及预报模型、对非寒区水文模型改进后应用到寒区的探讨及定量研究冻土水分迁移运动的数值模拟方法,并提出未来研究方向:开发更加逼近真实情况的水文水利模型;野外大田实验数据的监测采集并确定水文模型的参数;将水文模型与冻土水分迁移模型的完善结合.     

基于TRMM卫星雷达降雨的流域陆面水文过程

利用热带降雨观测计划(TRMM)卫星雷达降雨数据驱动分布式陆面水文模型,研究流域尺度陆面水文过程,评估该数据在水文模拟与预报等研究领域的性能。通过与实测雨量资料比较,验证TRMM卫星雷达降雨数据的质量。分别将TRMM卫星雷达降雨与观测降雨作为耦合模型的气象输入,模拟和研究淮河流域1998~2003年的陆面水文过程时空变化。结果表明,TRMM卫星雷达降雨数据能够很好地描述降雨的时空分布,利用TRMM降雨模拟的结果与利用观测降雨模拟的结果精度相当;模拟流量与实测资料基本吻合。卫星雷达降雨数据在陆面水文过程研究中具有广泛的应用前景。     

SWAT模型及其应用研究进展

SWAT（Soil and Water Assessment Tool）模型是近几年发展迅速、影响较大的水文模型,主要用于模拟预测各种管理措施及气候变化对水资源供给的影响,评价流域非点源污染等。本文通过对SWAT模型的发展历史及该模型在水文、气候变化、非点源污染和输入参数对模拟结果的影响等几个主要方面的研究,总结了模型的优势,以及在使用该模型时需要注意的主要问题。SWAT 模型在国内的应用主要侧重于水文及非点源污染研究,研究多是以模型作为手段,改进工作不多,建议今后根据研究区域的需要,对模型作相应的改进,以更好地服务于研究项目。     

Relating a recruitment shift of Patagonian grenadier (Macruronus magellanicus Lönnberg) to large-scale environmental changes off Southern Chile

The SE Pacific stock of Patagonian grenadier (Macruronus magellanicus) showed evidence of an abrupt reduction in recruitment after 2000. This drop exceeded expectations from changes in the spawning stock biomass (SSB), indicating a change in the stock-recruitment relationship (S-R). We evaluated whether variability in recruitment could be explained by concurrent changes in three environmental indices: sea-surface temperature anomaly (SSTA); southern oscillation index (SOI); and latitudinal position of the west wind drift bifurcation (WWDL). Continuous and discrete effects of these indices were tested as covariates in linear log-log and non-linear Ricker's S-R models. Discrete effects represented regime shifts detected in SSTA (1998), SOI (1998) and WWDL (1995). While SSTA was the only continuous variable found to be significant, the discrete 1998 regime shift supported the most informative model. The best Ricker's model considered a discrete intercept change in the same year: 1998. Although a spurious correlation between SSTA and S-R changes is possible, SSTA may be reflecting major physical or biological changes relevant to M. magellanicus juveniles in the SE Pacific.     

Compared performance of a conceptual and a mechanistic hydrologic models of a green roof

In order to investigate the hydrologic response of a green roof system within the urban environment, a monitoring campaign is carried out at the green roof site of the University of Genova (Italy). Experimental data confirm that the green roof is able to significantly mitigate the generation of runoff with median values of retained volume and peak reduction, respectively, equal to 94 and 98%. A conceptual linear reservoir and a simple mechanistic (Hydrus‐1D) models are implemented to simulate the hydrologic behaviour of the system; each model is calibrated and validated based on experimental data collected at the green roof site. The hydrographs simulated with both hydrologic models reproduce with acceptable matching capabilities the experimental measurements, as confirmed by the Nash‐Sutcliffe Efficiency index generally greater than 0·60. Although the relative percentage differences evaluated for the selected hydrograph variables (the total effluent volume, the peak flow rate and the hydrograph centroid) demonstrate that the mechanistic model is more accurate, prediction errors of the conceptual model are generally limited when compared with the observed hydrologic performance. Results of the present comparison are useful in supporting conceptual model selection in case the hydrologic response is addressed for hydrologic performance assessment. Copyright © 2011 John Wiley & Sons, Ltd.