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1.
Integration of the MODIS Snow Cover Produced Into Snowmelt Runoff Modeling   总被引：1，自引：0，他引：1  
Because of the difficulty of monitoring and measuring snow cover in mountainous watersheds, satellite images are used as an alternative to mapping snow cover to replace the ground operations in the watershed. Snow cover is one of the most important data in simulation snowmelt runoff. The daily snow cover maps are received from Moderate Resolution Imaging Spectroradiometer (MODIS), and are used in deriving the snow depletion curve, which is one of the input parameters of the snowmelt runoff model (SRM). Simulating Snowmelt runoff is presented using SRM model as one of the major applications of satellite images processing and extracting snow cover in the Ghara - Chay watershed. The first results of modeling process show that MODIS snow covered area product can be used for simulation and forecast of snowmelt runoff in Ghara - Chay watershed. The studies found that the SCA results were more reliable in the study area.  相似文献   

2.
Extensive, complex supraglacial river networks form on the southwest Greenland ice sheet (GrIS) surface each melt season. These networks are the dominant pathways for surface meltwater transport on this part of the ice sheet, but their fluvial morphometry has received little study. This paper utilizes high-resolution (2 m) WorldView-1/2 images, digital elevation models, and GIS tools to present a detailed morphometric characterization (river number, river length, Strahler stream order, width, depth, bifurcation ratio, braiding index, drainage density, slope, and relief ratio) for 523 GrIS supraglacial river networks. A new algorithm is presented to determine Strahler stream order in supraglacial environments. Results show that (1) Supraglacial river networks are broadly similar to terrestrial landscapes in that they follow Horton’s laws (river number, mean river length, and slope versus stream order), widen downstream, and have comparable mean bifurcation ratios (3.7 ± 1.9) and braiding indices; (2) unlike terrestrial systems, supraglacial drainage densities (0.90–4.75 km/km2) have no correlation with elevation relief, but instead display a weakly inverse correlation with ice surface elevation; (3) both well-developed (e.g., fifth-order) and discrete (e.g., first-order) supraglacial river networks form on the ice sheet, with the latter associated with short flow distances upstream of a terminal moulin; (4) mean river flow widths increase substantially, but flow depths only modestly, with increasing stream order. Viewed collectively, the 523 supraglacial river networks studied here display fluvial morphometries both similar and dissimilar to terrestrial systems, with moulin capture an important physical process driving the latter.  相似文献   

3.
Thar desert spreads in western part of Rajasthan, northern part of Gujarat, and some parts of Punjab and Haryana. The terrain is dominated by slightly sloping plains, broken by some dunes and low barren hills. The area is characterized by low average annual rainfall which is erratic in distribution and intensity. Drought will remain a major hindrance for agricultural production in Thar desert. Due to water stress condition, many watershed based development activities has been adopted by government and non-government organizations for the growth and sustainable development of this region. The need of this hour is preparation of a national level watershed atlas of 1:50,000 scale because majority of thematic maps are being produced presently on same or 1:10,000 scale. The manual delineation of watershed boundary in flat terrain based on topographic map will be time consuming and less accurate in the absence of prominent contour lines. Automated approach for watershed delineation using Digital Elevation Model (DEM) along a suitable algorithm has the advantage because the output is not only less time consuming but also independent from human decisions. Hence, a case study has been carried out in Churu sub-basin part of Indus basin which is located in Thar desert region. Depression less DEM with different spatial resolutions was used as input in hydrology tool of ArcGIS spatial analyst function for characterization of watersheds. The Churu sub-basin has been divided into various numbers of watersheds with an average size of 600 km2. These watershed boundaries have been validated with respect to high resolution satellite imageries (IRS P6 LISS IV), Survey of India toposheets, ancillary data and limited field checks.  相似文献   

4.
Land cover changes within watersheds have the potential to produce dramatic changes in surface hydrology, namely runoff, in the event of storms. The Mid-Cibolo Creek watershed in south-central Texas has experienced extensive land-cover change in the past two decades due to mass residential development and land clearing in the wake of urban growth along the I-35 corridor. This study determined land-cover changes within the basin using supervised classification to classify land cover from LANDSAT images for the years 1986 and 1999. Changes in runoff volume were then calculated using the Soil Conservation Service (SCS) runoff equation for a series of rainfall scenarios. The results showed that an overall increase in impervious cover and decrease in natural vegetative cover has occurred leading to larger runoff volumes for all storm scenarios. The findings are important for watershed scale urban expansion and land clearing practices as current methods suggest that flood risk is increased.  相似文献   

5.
Land cover conversion is known to alter the hydrologic regimes of watersheds. While connections between land cover and runoff are generally known, not all land cover alterations result in detectable changes in streamflow, and the quantity of land cover change required to yield a detectable change in streamflow is unknown over a range of watersheds. The connection between land cover change and streamflow was explored for a Hydro-Climatic Data Network (HCDN) watershed. HCDN is a database of USGS gauged streams commonly used to assess the influence of climatic change on streamflow. Watersheds included in the HCDN have been screened to represent "unimpaired" streamflow. Implicit in this definition is the assumption that land cover is relatively unaltered over the streamflow time series. Imagery from the North American Landscape Characterization (NALC) project was analyzed to detect land cover change from 1972 to 1992 in an Oregon watershed selected from the HCDN. A post-classification change detection yielded a 44% rate of landscape change over 20 years. Changes in land cover classes by dominant soil types were paired with the L-THIA model of Purdue University to quantify the effect of land cover change on runoff. Despite land cover changes, simulations confirmed that runoff remained unchanged. This report summarizes recommended steps for applying NALC imagery to detection of landscape change in other watersheds.  相似文献   

6.
Soil erosion is a prominent cause of land degradation and desertification in Mediterranean countries. The detrimental effects of soil erosion are exemplified in climate (in particular climate change), topography, human activities, and natural disasters. Forest fires, which are an integral part of Mediterranean ecosystems, are responsible for the destruction of above-and below-ground vegetation that protects against soil erosion. Under this perspective, the estimation of potential soil erosion, especially after fire events, is critical for identifying watersheds that require management to prevent sediment loss, flooding, and increased ecosystem degradation. The objective of this study was to model the potential post-fire soil erosion risk following a large and intensive wildland fire, in order to prioritize protection and management actions at the watershed level in a Mediterranean landscape. Burn severity and preand post-fire land cover/uses were mapped using an ASTER image acquired two years before the fire, air photos acquired shortly after the fire, and a Landsat TM image acquired within one month after-fire. We estimated pre-and post-fire sediment loss using an integrated GIS-based approach, and additionally we analyzed landscape erosion patterns. The overall accuracy of the severity map reached 83%. Severe and heavy potential erosion classes covered approximately 90% of the total area following the fire, compared to 55% before. The fire had a profound effect on the spatial erosion pattern by altering the distribution of the potential erosion classes in 21 out of 24 watersheds, and seven watersheds were identified as being the most vulnerable to post-fire soil erosion. The spatial pattern of the erosion process is important because landscape cover heterogeneity induced especially by fire is a dominant factor controlling runoff generation and erosion rate, and should be considered in post-fire erosion risk assessment.  相似文献   

7.
This study investigates the changes in simulated watershed runoff from the Agricultural NonPoint Source (AGNPS) pollution model as a function of model input cell size resolution for eight different cell sizes (30 m, 60 m, 120 m, 210 m, 240 m, 480 m, 960 m, and 1920 m) for the Little River Watershed (Georgia, USA). Overland cell runoff (area-weighted cell runoff), total runoff volume, clustering statistics, and hot spot patterns were examined for the different cell sizes and trends identified. Total runoff volumes decreased with increasing cell size. Using data sets of 210-m cell size or smaller in conjunction with a representative watershed boundary allows one to model the runoff volumes within 0.2 percent accuracy. The runoff clustering statistics decrease with increasing cell size; a cell size of 960 m or smaller is necessary to indicate significant high-runoff clustering. Runoff hot spot areas have a decreasing trend with increasing cell size; a cell size of 240 m or smaller is required to detect important hot spots. Conclusions regarding cell size effects on runoff estimation cannot be applied to local watershed areas due to the inconsistent changes of runoff volume with cell size; but, optimal cells sizes for clustering and hot spot analyses are applicable to local watershed areas due to the consistent trends.  相似文献   

8.
In the present study, prioritization of sub-watersheds was carried out on the basis of sediment production rate. Further, basic hydrologic information such as peak rate of runoff and annual surface water potential were also assessed for the study watersheds and these are essential requisites for effective watershed management. The 10 sub watersheds of Tarai development project area are selected for the present study. Morphometric parameters pertaining to study area are used in the estimation of sediment production rate. The sediment production rate in the study area varies between 2.45 to 11.0 ha-m/100 km2/year. The remote sensing data has been utilized for generating land use/land cover data which is an essential prerequisite for land and water resource planning and development. The remote sensing data can especially play significant role in collection of real time information from remote areas of river basins for generation of parameters required for hydrologic modeling.  相似文献   

9.
Sedimentation of water bodies is governed by the erosional processes occurring at the watershed level. In this research, a method is proposed for assessing the sediment yield of the mountainous watersheds surrounding the Wular lake in Kashmir Himalaya, using geoinformatics and geostatistics. This method is empirical and semi-quantitative in approach and takes into account the weightage-based influence of the parameters governing the watershed sediment yield. The results of this study reveal that out of the six surrounding watersheds of the Wular Lake, Madhumati watershed with the highest sediment yield index, SYI (39.78) drains maximum sediments into the Lake followed by Arin (39.27), Ferozpur (34.30), Wular II (32.53), Wular I (24.65) and Gundar (23.43) in the event of a same intensity storm. The proposed method is reasonably a better approach in the data-scarce Himalayan region and shall be a useful tool for watershed management in other regions with similar geographic setting.  相似文献   

10.
The precise delineation of coastal areas subject to past, present, and future erosive processes plays a fundamental role in coastal risk management. Within this framework, satellite data represent a valuable synoptic and multi-temporal information source. Therefore, this research integrated remote sensing and GIS techniques for mapping and modeling shoreline evolution through time. Long-term shoreline’s proxy rates of advance and retreat were determined using Landsat data from the mid-1980s to 2011 and subsequently, a short-term scenario (3 years) was predicted and validated. Two different coastal environments, Oceanic and Mediterranean, were investigated. In the first, different proxies were analyzed, thereby enabling a multi-proxy analysis. Findings showed that the method provided more accurate results in higher energy environments (Oceanic) and where the coastline is not urbanized. Results also highlighted the importance of performing multi-proxy analyses in given study areas, to more reliably define shoreline modeling. Importantly, during the analyses, particular attention was given to assessing uncertainty, which is crucial when outcomes of scientific research are considered for management.  相似文献   

11.
‘Watershed Management’ has assumed urgency for planned development of land and water resources and to arrest land degradation process to preserve environment and ecological balance. Decision support to such management planning requires scientific knowledge of resources information, expected runoff and sediment yield, priority classification of watersheds for conservation planning, monitoring of watershed for environmental impact assessment and technologies of GIS for data base creation, scenario development and appropriate decision making. Remote sensing technique is ideally suited to evolve such a management strategy. Scientific basis of this approach is explained.  相似文献   

12.
In order to check the premature siltation of the reservoirs, the Government of India has launched the schemes of soil conservation and integrated watershed management in the catchments of River Valley Projects (RVPs) and Flood Prone Rivers. However, due to lack of sufficient funds and manpower for surveys and soil and water conservation programmes, a priority approach for treatment of the watersheds was developed and followed for implementation of soil conservation and watershed management schemes in India.

This paper deals with the prioritisation of watersheds using GIS approach in a part of Musi river catchment in RR district of Andhra Pradesh. The GIS software package, ARC/INFO version 5.0, was used to digitize, edit, display, analyse and plot the maps. It was concluded that by the creation of computerised data base for the maps, the composite map generation and calculation of area statistics are performed much faster and more accurately compared to the conventional method.  相似文献   

13.
We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.  相似文献   

14.
Signs of long-term glaciological processes and past ice-sheet structure are preserved in the internal layer manifestations of the Greenland ice sheet. Internal layer data have been collected over a substantial portion of the Greenland ice sheet using the University of Kansas ice-sounding radar. In this letter, these layers are traced along thousands of kilometers of flight lines from the ice divide toward Jakobshavn, which is the most active glacier in Greenland. The authors determine the traced radar layers' age at the Greenland Ice Core Project (GRIP) site using the GRIP core age-depth relationship. Inasmuch as the depth varies spatially for a layer of a specific dated age, an age-depth relationship for each location along the flight lines of this letter can be found using the traced layers. Thirty-one points where flight lines cross over one another were analyzed. From the flight line crossover analysis, a 9-m maximum difference (< 1%) was found  相似文献   

15.
A case study has been conducted to identify suitable sites for water harvesting structures in Soankhad watershed, Punjab using information technologies such as Remote Sensing and Geographical Information System (RS-GIS). The IRS-1C, P6 satellite imagery of the Soankhad watershed was used. The various Thematic maps such as land use map, hydrological soil group map, slope map and DEM map were prepared for selecting suitable site for construction of water harvesting structures. The suitable sites were not found for nala bunding and farm ponds due to steep slope, less soil thickness and high runoff velocity. Fourteen check dams and six percolation tanks were proposed for the construction as per Integrated Mission for Sustainable Development (IMSD) guidelines. The water balance study of the Soankhad watershed was also computed with monthly mean temperature and rainfall data using TM model. The average runoff for the wet season (July–September) 1996 was computed to be about 1543.82 mm and the total runoff volume from the Soankhad watershed was estimated to be about 143.52 Mm3.  相似文献   

16.
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.  相似文献   

17.
利用TechDemoSat-1低轨道卫星采集的卫星反射信号生成的时延多普勒图（delay-doppler map,DDM）探测北极格陵兰岛（Greenland）地区的海冰分布。由于卫星散射信号在海冰和海水上分别遵循相干散射和漫散射模型,与海水相比,海冰的时延多普勒图扩散较少,所以从海水到海冰的过渡会导致时延多普勒图中高于一定能量值的像素数量减小。提出了一种基于相邻DDM像素数量比值的检测方法,通过采用一定阈值来区分海冰和海水的时延多普勒图,用于分析格陵兰岛地区海冰的分布情况。还利用多期数据分析了格陵兰岛地区海冰分布随时间的变化。通过与美国国家冰雪数据中心提供的数据比对,利用数学统计方法对本文提出的方法性能进行了评估。结果显示,该方法的判断成功率可以达到98.76%~99.21%,整体评估成功率约为99.09%。  相似文献   

18.
非航海用DDM向航海应用转换的方法   总被引：1，自引：0，他引：1  
针对非航海用数字水深模型（DDM）不能直接应用于航海上的这一问题,提出了一种基于水深不确定度拟合面的非航海用DDM向航海应用转换的方法。采用不确定度合成方法计算原始水深不确定度对非航海用DDM建模点的传递不确定度;利用测试点检验法估算非航海用DDM网格的地形描述不确定度,进而合成建模点的综合不确定度;基于模型网格双线性法构建非航海用DDM的水深不确定度拟合面,并推估模型内任一点的水深不确定度,以提高转换后非航海用DDM的深度保证率。试验证明：所提方法切实可行,能够较大程度地提高转换后非航海用DDM的深度保证率,以满足舰船的安全航海需求。  相似文献   

19.
Runoff modelling of a small watershed using satellite data and GIS   总被引：1，自引：0，他引：1  
This study was conducted for the Nagwan watershed of the Damodar Valley Corporation (DVC), Hazaribagh, Bihar, India. Geographic Information System (GIS) was used to extract the hydrological parameters of the watershed from the remote sensing and field data. The Digital Elevation Model (DEM) was prepared using contour map (Survey of India, 1:50000 scale) of the watershed. The EASI/PACE GIS software was used to extract the topographic features and to delineate watershed and overland flow-paths from the DEM. Land use classification were generated from data of Indian Remote Sensing Satellite (IRS-1B—LISS—II) to compute runoff Curve Number (CN). Data extracted from contour map, soil map and satellite imagery, viz. drainage basin area, basin shape, average slope of the watershed, main stream channel slope, land use, hydrological soil groups and CN were used for developing an empirical model for surface runoff prediction. It was found that the model can predict runoff reasonably well and is well suited for the Nagwan watershed. Design of conservation structures can be done and their effects on direct runoff can be evaluated using the model. In broader sense it could be concluded that model can be applied for estimating runoff and evaluating its effect on structures of the Nagwan watershed.  相似文献   

20.
The planning of conservation measures to conserve water and soil resources taking hydrological planning unit as micro-watershed is considered to be effective. The automated watershed delineation technique using the spline interpolated filled digital elevation model (DEM) is effective in converging slopes of the area in which the stream patterns match with the manually digitized stream patterns of the topographical map. The various vector spatial layers like the slope/aspect, land-use/land-cover, runoff potential, soil erosion potential and the associated attribute information governing the criteria for different conservation structures can act as input layers in integrated spatial analysis module in GIS environment to evolve derived layers indicating the locations of conservation sites meeting the requisite criteria. The reliability of suitable conservation sites suggested out of integrated spatial GIS analysis could be ascertained using the multi criteria analysis incorporating the various factors controlling soil erosion process in the micro-watershed groups. The details of the above work are discussed in the paper.  相似文献   

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