New graphical methods for estimating aquifer hydraulic parameters using pumping tests with exponentially decreasing rates     

Chao Zhuang  Zhifang Zhou  Hongbin Zhan  Jinguo Wang  Yabing Li  Zhi Dou 《水文研究》2019,33(17):2314-2322

Actual pumping tests may involve continuously decreasing rates over a certain period of time, and the hydraulic conductivity (K) and specific storage (S_s) of the tested confined aquifer cannot be interpreted from the classical constant‐rate test model. In this study, we revisit the aquifer drawdown characteristics of a pumping test with an exponentially decreasing rate using the dimensionless analytical solution for such a variable‐rate model. The drawdown may decrease with time for a short period of time at intermediate pumping times for such pumping tests. A larger ratio of initial to final pumping rate and a smaller radial distance of the observation well will enhance the decreasing feature. A larger decay constant results in an earlier decrease, but it weakens the extent of such a decrease. Based on the proposed dimensionless transformation, we have proposed two graphical methods for estimating K and S_s of the tested aquifer. The first is a new type curve method that does not employ the well function as commonly done in standard type curve analysis. Another is a new analytic method that takes advantage of the decreasing features of aquifer drawdown during the intermediate pumping stage. We have demonstrated the applicability and robustness of the two new graphical methods for aquifer characterization through a synthetic pumping test.  相似文献   

两种造礁石珊瑚对海水酸化和溶解有机碳加富的响应*     

郭亚娟  周伟华  袁翔城  廖健祖  江雷  黄晖 《热带海洋学报》2018,37(1):57-63

文章选择鹿回头近岸海域常见的板叶角蜂巢珊瑚(Favites complanata)和十字牡丹珊瑚(Pavona decussata)为研究对象, 采用室内连续培养的方法, 探究两种不同造礁石珊瑚对酸化和溶解有机碳(DOC)加富的响应。结果表明: 酸化(pH 7.6)并不会影响两种珊瑚的钙化速率和生长速率; 但DOC加富(524.03±78.42μmol•L^-1)使两种珊瑚的钙化速率分别降低67%和47%、生长速率降低59%和40%。当二者共同作用时, 两种珊瑚的钙化速率降低30%和11%、生长速率降低46%和59%, 大多没有DOC单独作用时强烈, 表现出一定的拮抗作用。两种珊瑚共生虫黄藻叶绿素荧光指数(F_v/F_m)均升高后降低, 板叶角蜂巢珊瑚F_v/F_m最先降低。实验表明, 这两种珊瑚虽然对海洋酸化的敏感度不高, 但是对有机物加富有不同的响应, 板叶角蜂巢珊瑚更为敏感, 可能导致这两种珊瑚在未来环境变化中有不同命运。  相似文献   

Temporal and spatial variation of soil erosion in wooded rangelands of southwest Spain     

Judit Rubio-Delgado  Susanne Schnabel  Álvaro Gómez-Gutiérrez  Joaquín Francisco Lavado-Contador 《地球表面变化过程与地形》2019,44(11):2141-2155

Changes in land use are common in Mediterranean areas and are reported as having produced changes in the intensity of soil erosion. Dehesas are rangelands with a disperse tree cover, widespread in the south-western part of the Iberian Peninsula and similar ecosystems are also common in other areas with a Mediterranean climate. The aim of the present study is to analyse temporal and spatial variations of soil erosion rates estimated along three hillsides, located in two farms (Buitrera and Parapuños) in southwest Spain. To understand the temporal variation, soil erosion rates were studied in light of land use-management changes that took place during the last few centuries. Results indicate very low erosion rates prior to the 18^th century in both farms. In Buitrera, a first increase of soil loss rates was identified during the period 1831-1897, amounting to 7.4 t ha^-1 y^-1. A further increase took place during the 20^th century, reaching a mean erosion rate of 29.1 t ha^-1 y^-1. In Parapuños, data points to a significant increase from 1881 onwards, with an estimated mean erosion rate of 18.5 t ha^-1 y^-1. Those increases were presumably connected with an intensification of land use, such as cultivation and excessive livestock populations. Regarding spatial variation, the bare surface and the erosive power of run-off along the hillsides accounts for 76% of the soil erosion rates dispersion. At a local scale, the variability of erosion rates could not be explained, because of (i) uncertainty related to the micromorphology of the past soil surface and (ii) the role of tillage erosion in the past. However, the results obtained offer valuable data on the temporal and spatial variation of erosion rates in dehesas at the hillslope scale and a similar approach could be used for other rangelands with a disperse tree cover. © 2019 John Wiley & Sons, Ltd.  相似文献   

长江口水下三角洲泥质区近期沉积物粒度变化特征及其影响因素   总被引：4，自引：0，他引：4  

张瑞  汪亚平  高建华  潘少明 《海洋地质与第四纪地质》2011,(5):9-16

河口水下三角洲是河流和海洋环境共同作用的产物,沉积地层中蕴藏了许多环境变化信息.在长江口水下三角洲泥质区采集了柱样SC09,首先利用放射性同位素210Pb确定了沉积柱样的平均沉积速率,其次对沉积柱样以0.2 cm间隔进行高分辨率取样,获得了沉积物粒度参数,然后提取了沉积物粒度敏感组分,并对其进行了经验模态分解(EMD)...  相似文献   

内蒙古固阳盆地东北缘更新统洪积物地层的发现及研究意义     

蔡雄飞  智铎强  罗中杰  吴义布 《地层学杂志》2011,(2):172-178

关于内蒙古高原的隆升,长期以来研究较少,从更新世的冲、洪积物分布在现今1600～1700m海拔高程的山顶上出发,发现固阳盆地东北缘更新统的洪积物的沉积类型、沉积特点和粗碎屑岩系的组分以及孢粉的资料,无不与内蒙古高原隆升紧密相关.内蒙古高原隆升不是孤立的,而是受青藏高原隆升的控制,它们几乎是同步的或者说紧密相连的.  相似文献   

Mapping of erosion rates in marly badlands based on a coupling of anatomical changes in exposed roots with slope maps derived from LiDAR data     

Jérôme Lopez Saez  Christophe Corona  Markus Stoffel  Georges Rovéra  Laurent Astrade  Frédéric Berger 《地球表面变化过程与地形》2011,36(9):1162-1171

Black marls form very extensive outcrops in the Alps and constitute some of the most eroded terrains, thus causing major problems of sedimentation in artificial storage systems (e.g. reservoirs) and river systems. In the experimental catchments near Draix (France), soil erosion rates have been measured in the past at the plot scale through a detailed monitoring of surface elevation changes and at the catchment scale through continuous monitoring of sediment yield in traps at basin outlets. More recently, erosion rates have been determined by means of dendrogeomorphic techniques in three monitored catchments of the Draix basin. A total of 48 exposed roots of Scots pine have been sampled and anatomical variations in annual growth rings resulting from denudation analysed. At the plot scale, average medium‐term soil erosion rates derived from exposed roots vary between 1·8 and 13·8 mm yr^?1 (average: 5·9 mm yr^?1) and values are significantly correlated with slope angle. The dendrogeomorphic record of point‐scale soil erosion rates matches very well with soil erosion rates measured in the Draix basins. Based on the point‐scale measurements and dendrogeomorphic results obtained at the point scale, a linear regression model involving slope angle was derived and coupled to high‐resolution slope maps obtained from a LiDAR‐generated digital elevation model so as to generate high‐resolution soil erosion maps. The resulting regression model is statistically significant and average soil erosion rates obtained from the areal erosion map (5·8, 5·2 and 6·2 mm yr^?1 for the Roubine, Moulin and Laval catchments, respectively) prove to be well in concert with average annual erosion rates measured in traps at the outlet of these catchments since 1985 (6·3, 4·1 and 6·4 mm yr^?1). This contribution demonstrates that dendrogeomorphic analyses of roots clearly have significant potential and that they are a powerful tool for the quantification and mapping of soil erosion rates in areas where measurements of past erosion is lacking. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Variability in erosion rates related to the state of landscape transience in the semi‐arid Chilean Andes     

Germán Aguilar  Rodrigo Riquelme  Joseph Martinod  José Darrozes  Eric Maire 《地球表面变化过程与地形》2011,36(13):1736-1748

We quantify erosion rates in the higher sectors of the Huasco Valley, in the Main Cordillera of the semi‐arid Andes of Chile, using elevation differences between three successive geomorphic markers (pediments and paleo‐valleys) and the present day valley. Available Ar‐Ar ages of Neogene pediments are used to estimate mean erosion rates for the three periods (16 to 13 My, 13 to 8 My, and following 8 My). The landscape of the Huasco Valley is in a transient state, as indicated by well‐preserved pediment surfaces in interfluves, valleys deeply incised by fluvial and glacial erosion and scarped head‐valleys that represent the current knickzones. Higher erosion rates (45–75 m/My) are calculated for the more recent period (< 8 My) during which deep incision developed compared to previous periods (6–31 m/My). Quantitative data indicate that glaciers had a much higher erosional capability than fluvial activity in the higher sectors of the Main Cordillera. Comparison with erosion rates calculated in other drainage basins of the Chilean Andes suggests that the variability of erosion rates depends on the landscape's transient erosive state. The landscape's geomorphologic response to the uplift of the Main Cordillera results in the retreat of a knickzone, for which retreat velocity depends on precipitation rate pattern and glacial erosion intensity. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

多点激励下连续桥梁地震响应特性研究     

何浩祥  闫维明 《地震学刊》2011,(1):44-49

地震动在强度和频率等方面均具有非平稳特性,导致多跨桥梁的动力响应非常复杂。为了研究多跨连续桥梁在多点地震动激励下的反应,首先提出了评价多点地震动非平稳性的3个指标：幅值绝对值的标准差、方向离散度和穿零率。根据桥梁多点激励运动方程的特点,阐述了广义振型参与系数矩阵的意义,及其与传统振型参与系数矩阵的联系和区别。根据多点地震动非平稳性的特性,对不同支点施加异向及不同幅值的位移或加速度,研究了不同跨数连续梁桥的多点激励响应规律。结果表明,随着连续梁桥跨数的增多,桥梁在多点地震激励下的响应趋于复杂多变,受具体地震动的非平稳性影响越发明显。  相似文献   

用拉萨点大地测量资料检测青藏高原地壳的增厚   总被引：3，自引：0，他引：3  

邢乐林  孙文科  李辉  杨光亮 《测绘学报》2011,40(1):41-44

青藏高原地壳的隆升与增厚,是一个复杂的热点问题.印度板块和欧亚板块的碰撞挤压导致地壳的隆升与增厚,已被地质、构造学等方面资料证实,但利用大地测量资料定量确定高原地下地壳增厚速率的很少.基于此,利用高精度绝对重力测量资料及GPS结果定量检测高原拉萨点地下地壳增厚速率((3.9±0.8)cm/a),并给出简单的动力学模型,...  相似文献   

中国省域离婚率的时空格局及趋同演变研究   总被引：1，自引：0，他引：1  

白彩全  陈昶  丁一帆  吴启焰 《测绘科学》2015,(11):48-53

针对现有离婚率研究时间、空间割裂,整体性探讨不足及实证研究缺乏的问题,该文运用空间自相关、空间马尔可夫链等空间统计方法对中国大陆各省域1979—2012年离婚率数据的时空分布及趋同演变进行了研究,结果发现:除东北、西北地区离婚率一直居高不下之外,中国大陆高离婚率地区逐步向中部延伸并聚集,离婚率存在着较强的空间自相关且空间聚集现象明显;省域离婚率的"两极分化"现象和"俱乐部趋同"现象均经历了由弱到强再减弱的波动变化趋势。  相似文献