Catchment infiltration II: Contributing areas

This study considers two issues of interest to the hydrologic and geographical information systems community. One deals with identifying the spatial distribution of infiltration and runoff contributing areas. The other addresses process modelling within a GIS framework. The study operates on the premise that partitioning of precipitation into runoff or infiltration depends on rainfall intensity and on soil properties. The problem is that neither local rainfall intensity, nor soil properties such as infiltration capacity and macroporosity are known well enough for all points of a catchment and need to be estimated. We infer local intensity from the interpolated distribution of cumulated rain depths over the catchment and record duration at the official met site. Measured values of sorptivity and hydraulic conductivity define infiltration. Negative head infiltration describes macroporosity. To scale-up measured point values to larger areas and to model infiltration and macropore continuity at a catchment scale we use geostatistical kriging and conditional simulation together with standard GIS techniques of overlay manipulation. Results delineate areas contributing to runoff and infiltration and relate them to macroporosity. By intersecting overlays of precipitation with those of infiltration we create alternate GIS masks targeting specific portions of the watershed as either runoff or infiltration contributing zones. Choice of cell size and time interval define the scales of averaging for the application. Kriged surfaces illustrate the distribution of catchment infiltration, while conditional simulation provides a mechanism to define model uncertainty.     

从规则格网DEM自动提取汇水区域及其子区域的方法

从DEM自动提取的汇水区域及其子区域信息对进一步的水文分析有着重要的辅助作用.在经过洼地处理的DEM及得到水流方向矩阵的基础上,本文提出并实现了一种汇水区域及其子区域的提取算法.该算法首先提取整个DEM区域内每条河流的汇水区域,然后按照不同的要求划分子区域.经过试验,与现有的方法相比,该算法在提取效率和结果准确性方面都有明显提高.     

Determination of run-off factor of the Tons Catchment using aerial photographs

Run-off is an important element of the hydrologic studies of any given basin. As such the estimation of the run-off factor of a catchment becomes imperative for determination of the total quantity of its surface run-off. The traditional ground survey methods of hydrologic studies of river basins are gradually getting replaced by more economical and reasonably accurate methods mostly based on aerial photographs. This paper deals with an experiment carried out on the Tons Catchment for determination of its run-off factor with the help of aerial photographs using the photo-interpretation and analysis techniques. The resultant values of the surface runoff have compared very well with the observed flow at Kisau gauging station. This indicates that a suitable methodology can be developed to estimate the discharge of the catchment of Indian rivers, where the run-off data is not available, with reasonable accuracy using the aerial photographs.     

半方差函数与Moran’s I在土壤微量元素空间分布研究中的应用——以寿光市为例

利用半方差函数与Moran’s I两种空间分析方法,研究了山东省寿光市土壤中微量元素的空间分布特征,以探讨不同空间分析方法的差异性与准确性。结果表明,无论表层土壤还是深层土壤,半方差函数分析得到的土壤微量元素的空间相关距离大约为20~60 km,而空间自相关图获得的正自相关距离为20~25km,负自相关距离为25~55 km。除深层土壤中的Zn元素外,其他元素均达到了显著的自相关水平。空间自相关方法对土壤微量元素空间相关性的判断要优于半方差函数法。     

Landcover Classification in the Taieri River Catchment,New Zealand: A Focus on the Riparian Zone

Abstract

Riparian vegetation has a fundamental influence on the biological, chemical and physical nature of rivers. The quantification of riparian landcover is now recognised as being essential to the holistic study of the ecosystem characteristics of rivers. Medium resolution satellite imagery is now commonly used as an efficient and cost effective method for mapping vegetation cover; however such data often lack the resolution to provide accurate information about vegetation cover within riparian corridors. To assess this, we measure the accuracy of SPOT multispectral satellite imagery for classification of riparian vegetation along the Taieri River in New Zealand. In this paper, we discuss different sampling strategies for the classification of riparian zones. We conclude that SPOT multispectral imagery requires considerable interpretative analysis before being adequate to produce sufficiently detailed maps of riparian vegetation required for use in stream ecological research.     

Using Passive Microwave Response to Soil Moisture Change for Soil Mapping: A Case Study for the Livingstone Creek Catchment

The 46-$hbox{km}^{2}$ Livingstone Creek Catchment in southeastern Australia was flown with a passive microwave airborne remote sensor four times throughout the three-week National Airborne Field Experiment in 2006, with a spatial resolution of $sim$200 m. Both continuous and discrete measurements of soil moisture were taken to help with interpretation of results. The catchment was experiencing extreme drought conditions leading up to the experiment, and as a result, ground cover in the catchment was minimal with many paddocks consisting of sparse dry stubble and grass. During the experiment period of November 2006, 30 mm of rainfall occurred, with the catchment going from parched dry conditions to surface wet conditions and back to dry conditions again in a short period of time. Changes in moisture responses observed by the airborne passive microwave sensor were field verified to reflect the different geology, soil, and landform elements of the catchment. Consequently, this study suggests that passive microwave remote sensing has potential as a tool to assist with soil mapping, through detecting changes in soil moisture spatial and temporal patterns.      

数字龙江地理空间框架建设一期工程1:10000地形图更新区域两种基础影像数据布点情况分析

根据三江平原测区常规框幅式航摄像片与佳木斯测区推扫式航摄影像数据不同,分析两种布点方案特点,阐述外业像控点工作量。     

微地图符号的视觉变量及其应用

视觉变量是微地图在设计表达过程中的关键部分,该文针对现有视觉变量研究成果并不完全适用于微地图这一问题,研究并提出了微地图符号的视觉变量.通过对比分析微地图与常用地图的不同,得到了微地图符号简单化、多元化、个性化、模块化的特点,在此基础上提出了符合微地图符号特点的视觉变量表达方式;考虑用户、环境、地物3个方面的影响,应用微地图视觉变量设计了微地图符号;实现了校园导航微地图的设计,并运用问卷调查验证了微地图视觉变量表达及应用的合理性.结果表明,提出的理论及方法能较好地表达微地图内容,能够为微地图的应用提供理论支持.     

冠层反射光谱对植被理化参数的全局敏感性分析

植被理化参数与许多有关植物物质能量交换的生态过程密切相关,定量分析植被反射光谱对理化参数的敏感性是遥感反演理化参数含量的前提。本文采用EFAST(Extended Fourier Amplitude Sensitivity Test)全局敏感性分析方法,利用PROSAIL辐射传输模型分析了冠层疏密程度对叶片生化组分含量、冠层结构以及土壤背景等多种参数敏感性的影响,并对植被理化参数反演所需先验知识的精度问题进行了初步探讨。研究表明:(1)对于较为稠密的冠层,可见光波段的冠层反射率主要受叶绿素含量的影响,近红外和中红外波段的冠层反射率主要受干物质量和含水量的影响;(2)对于稀疏的冠层,LAI是影响400—2500 nm波段范围内冠层反射率的最重要参数,土壤湿度次之,叶片生化参数对冠层反射率的敏感性较低;(3)在已知稀疏冠层LAI的情况下进一步确定土壤的干湿状态,可显著提高冠层反射率对叶绿素含量的敏感度,有助于稀疏冠层叶绿素含量的反演。     

市政排水管网节点汇水面积自动化计算的方法和应用

针对排水管网节点汇水面积的自动化计算问题,提出了将排水管网图转化为有向图,首先运用图论中的广度优先搜索算法得到任意指定节点的上游节点,然后计算其上游节点各关联边,最后根据上游节点及其关联边的汇水面积得到该节点总的汇水面积的方法。     

随机变量非线性变换统计性质的高精度逼近算法

应用扩展卡尔曼滤波对非线性系统进行状态估计时 ,要对系统的动力方程进行线性化 ,这就为状态的估计带来一定的误差。本文首先对非线性变换的函数进行级数展开 ,获得了随机变量经非线性变换后的真实均值和协方差表达式 ,并得到一阶线性化的均值和协方差 ,然后提出了一种精度更高的变换算法用以逼近非线性变换后的真实均值和协方差 ,理论分析和数值试验都表明新算法不仅具有更高的精度 ,而且更容易实现     

地图水系综合中等高线簇与河网协同的汇水区域提取方法

在地图水系自动综合中河流选取需要建立对不同河流重要性程度的有效判别。由于河流汇水区域直接反映河流的作用空间,因而其面积大小成为关键性的量化指标。目前基于河流的汇水区域自动提取方法主要从河流单一要素出发,按“空间均衡竞争”思想平分河流之间的区域,由于未考虑地形因素使得提取的汇水区域往往存在偏差,而传统基于DEM的汇水区域提取虽然考虑了地形,但没有与河流目标建立显性的对应关系。河流是一种天然的沟谷地性线,与山脊线具有对生互补的空间耦合关系,本文提出了一种等高线簇与河网双要素协同的河流汇水区域提取方法,该方法对河流与等高线的目标集合构建约束Delaunay三角网(CD-TIN)并将三角形分类,对不同类型的三角形分别采用骨架线提取规则与梯度向量引导的分水线搜索规则提取分水线段,连接形成网络结构并依此计算各河段的汇水区域。实验结果表明,本算法能更准确地提取河流汇水区域,从而为河流综合选取提供有效支持。     

Run-off potential indices of watersheds in Tilaiya Catchment,Bihar (India) through use of remote sensing and implementation of GIS

The present study was aimed at assessing the potential of remote sensing data in providing input to the SCS model developed by USDA and exploring the possibilities of improving the model through implementation of a GIS package. Subsequently, prioritization of watersheds in Tilaiya Catchment area (Bihar, India) based on their run-off potential indices was envisaged. The results demonstrated the capability of Landsat data in providing multithematic maps which could be used to provide input to the run-off model. Implementation of the GIS package enabled computation of run-off potential indices on pixed-by-pixel basis imparting physically distributed approach to the model.     

Hydrological excitation of polar motion by different variables from the GLDAS models

Continental hydrological loading by land water, snow and ice is a process that is important for the full understanding of the excitation of polar motion. In this study, we compute different estimations of hydrological excitation functions of polar motion (as hydrological angular momentum, HAM) using various variables from the Global Land Data Assimilation System (GLDAS) models of the land-based hydrosphere. The main aim of this study is to show the influence of variables from different hydrological processes including evapotranspiration, runoff, snowmelt and soil moisture, on polar motion excitations at annual and short-term timescales. Hydrological excitation functions of polar motion are determined using selected variables of these GLDAS realizations. Furthermore, we use time-variable gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE) to determine the hydrological mass effects on polar motion excitation. We first conduct an intercomparison of the maps of variations of regional hydrological excitation functions, timing and phase diagrams of different regional and global HAMs. Next, we estimate the hydrological signal in geodetically observed polar motion excitation as a residual by subtracting the contributions of atmospheric angular momentum and oceanic angular momentum. Finally, the hydrological excitations are compared with those hydrological signals determined from residuals of the observed polar motion excitation series. The results will help us understand the relative importance of polar motion excitation within the individual hydrological processes, based on hydrological modeling. This method will allow us to estimate how well the polar motion excitation budget in the seasonal and inter-annual spectral ranges can be closed.     

Fields as a framework for integrating GIS and environmental process models. Part 2: Specifying field variables

In Part 1 of this paper, the concept of a field variable was described. In Part 2, the way in which a field variable might be specified is outlined. Field variables can be declared like other data types in any standard computing language. Specifications of field variables must include several special properties which are used to express the relationship between the physical field and the discrete data model. Field variable properties determine how the spatial data can be manipulated. For example, specifying a cellgrid spatial data model requires information about grid orientation and origin and the size of cells, while specifying a polygon data model requires information about the minimum distance over which variation is recorded. In either case, this information can be used to select appropriate conversion procedures between spatial data models using similarly specified conversion matrices and rules. The use of field variables has pedagogic as well as practical value. New operations allowed include field functions such as those for determining integrals, slope, and aspect, and reserved variables such as latitude and longitude.