SWOT River Database (SWORD)

** IMPORTANT UPDATE: ** Until now, the project and public versions of SWORD have been kept separate while algorithms were being developed in preparation for SWOT launch. Now that the SWOT mission is here, we have decided to publish the project version of SWORD which is why the version numbers jump after v2. The primary difference between the project and public versions of SWORD are extra "filler" variables in the NetCDF format that will be used for calculating discharge. Everything else, reach definition, attribute values, etc. are the same between the two versions. For details on the filler variables please reference the Product Description Document provided with the downloads. If you use the SWORD Database in your work, please cite: Altenau et al., (2021) The Surface Water and Ocean Topography (SWOT) Mission River Database (SWORD): A Global River Network for Satellite Data Products. Water Resources Research. https://doi.org/10.1029/2021WR030054 You can also visit www.swordexplorer.com to explore the current version of SWORD before downloading. 1. Summary: The upcoming Surface Water and Ocean Topography (SWOT) satellite mission, planned to launch in 2022, will vastly expand observations of river water surface elevation (WSE), width, and slope. In order to facilitate a wide range of new analyses with flexibility, the SWOT mission will provide a range of relevant data products. One product the SWOT mission will provide are river vector products stored in shapefile format for each SWOT overpass (JPL Internal Document, 2020b). The SWOT vector data products will be most broadly useful if they allow multitemporal analysis of river nodes and reaches covering the same river areas. Doing so requires defining SWOT reaches and nodes a priori, so that SWOT data can be assigned to them. The SWOt River Database (SWORD) combines multiple global river- and satellite-related datasets to define the nodes and reaches that will constitute SWOT river vector data products. SWORD provides high-resolution river nodes (200 m) and reaches (~10 km) in shapefile and netCDF formats with attached hydrologic variables (WSE, width, slope, etc.) as well as a consistent topological system for global rivers 30 m wide and greater. 2. Data Formats: The SWORD database is provided in netCDF, geopackage, and shapefile formats. All files start with a two-digit continent identifier (“af” – Africa, “as” – Asia / Siberia, “eu” – Europe / Middle East, “na” – North America, “oc” – Oceania, “sa” – South America). File syntax denotes the regional information for each file and varies slightly between netCDF and shapefile formats. NetCDF files are structured in 3 groups: centerlines, nodes, and reaches. The centerline group contains location information and associated reach and node ids along the original GRWL 30 m centerlines (Allen and Pavelsky, 2018). Node and reach groups contain hydrologic attributes at the ~200 m node and ~10 km reach locations (see description of attributes below). NetCDFs are distributed at continental scales with a filename convention as follows: [continent]_sword_v14.nc (i.e. na_sword_v14.nc). SWORD shapefiles consist of four main files (.dbf, .prj, .shp, .shx). There are separate shapefiles for nodes and reaches, where nodes are represented as ~200 m spaced points and reaches are represented as polylines. All shapefiles are in geographic (latitude/longitude) projection, referenced to datum WGS84. Shapefiles are split into HydroBASINS (Lehner and Grill, 2013) Pfafstetter level 2 basins (hbXX) for each continent with a naming convention as follows: [continent]_sword_[nodes/reaches]_hb[XX]_v14.shp (i.e. na_sword_nodes_hb74_v14.shp; na_sword_reaches_hb74_v14.shp). SWORD geopackage files are split into two files for nodes and reaches per continental region, where nodes are represented as 200 m spaced points and reaches are represented as polylines. All geopackage files are in geographic (latitude/longitude) projection, referenced to datum WGS84. Geopackage file names are distributed at continental scales and are defined by a two-digit identifier (Table 2): [continent]_sword_[nodes/reaches]_v14.gpkg (i.e. na_sword_nodes_v14.gpkg; na_sword_reaches_v14.gpkg). 3. Attribute Description: This list contains the primary attributes contained in the SWORD netCDFs and shapefiles. x: Longitude of the node or reach ranging from 180°E to 180°W (units: decimal degrees). y: Latitude of the node or reach ranging from 90°S to 90°N (units: decimal degrees). node_id: ID of each node. The format of the id is as follows: CBBBBBRRRRNNNT where C = Continent (the first number of the Pfafstetter basin code), B = Remaining Pfafstetter basin code up to level 6, R = Reach number (assigned sequentially within a level 6 basin starting at the downstream end working upstream), N = Node number (assigned sequentially within a reach starting at the downstream end working upstream), T = Type (1 – river, 3 – lake on river, 4 – dam or waterfall, 5 – unreliable topology, 6 – ghost node). node_length (node files only): Node length measured along the GRWL centerline points (units: meters). reach_id: ID of each reach. The format of the id is as follows: CBBBBBRRRRT where C = Continent (the first number of the Pfafstetter basin code), B = Remaining Pfafstetter basin codes up to level 6, R = Reach number (assigned sequentially within a level 6 basin starting at the downstream end working upstream, T = Type (1 – river, 3 – lake on river, 4 – dam or waterfall, 5 – unreliable topology, 6 – ghost reach). reach_length (reach files only): Reach length measured along the GRWL centerline points (units: meters). wse: Average water surface elevation (WSE) value for a node or reach. WSEs are extracted from the MERIT Hydro dataset (Yamazaki et al., 2019) and referenced to the EGM96 geoid (units: meters). wse_var: WSE variance along the GRWL centerline points used to calculate the average WSE for each node or reach (units: square meters). width: Average width for a node or reach (units: meters). width_var: Width variance along the GRWL centerline points used to calculate the average width for each node or reach (units: square meters). max_width: Maximum width value across the channel for each node or reach that includes island and bar areas (units: meters). facc: Maximum flow accumulation value for a node or reach. Flow accumulation values are extracted from the MERIT Hydro dataset (Yamazaki et al., 2019) (units: square kilometers). n_chan_max: Maximum number of channels for each node or reach. n_chan_mod: Mode of the number of channels for each node or reach. obstr_type: Type of obstruction for each node or reach based on the Globale Obstruction Database (GROD, Whittemore et al., 2020) and HydroFALLS data (http://wp.geog.mcgill.ca/hydrolab/hydrofalls). Obstr_type values: 0 - No Dam, 1 - Dam, 2 - Channel Dam, 3 - Lock, 4 - Low Permeable Dam, 5 - Waterfall. grod_id: The unique GROD ID for each node or reach with obstr_type values 1-4. hfalls_id: The unique HydroFALLS ID for each node or reach with obstr_type value 5. dist_out: Distance from the river outlet for each node or reach (units: meters). type: Type identifier for a node or reach: 1 – river, 2 – lake off river, 3 – lake on river, 4 – dam or waterfall, 5 – unreliable topology, 6 – ghost reach/node. lakeflag: GRWL water body identifier for each reach: 0 – river, 1 – lake/reservoir, 2 – canal, 3 – tidally influenced river. manual_add (node files only): Binary flag indicating whether the node was manually added to the public GRWL centerlines (Allen and Pavelsky, 2018). These nodes were originally given a width = 1, but have since been updated to have the reach width values. meand_len (node files only): Length of the meander that a node belongs to, measured from beginning of the meander to its end in meters. For nodes longer than one meander, the meander length will represent the average length of all meanders belonging to the node (units: meters). sinuosity (node files only): The total reach length the node belongs to divided by the Euclidean distance between the reach end points. slope (reach files only): Reach average slope calculated along the GRWL centerline points. Slopes are calculated using a linear regression (units: meters/kilometer). n_nodes (reach files only): Number of nodes associated with each reach. n_rch_up (reach files only): Number of upstream reaches for each reach. n_rch_down (reach files only): Number of downstream reaches for each reach. rch_id_up (reach files only): Reach IDs of the upstream neighboring reaches. rch_id_dn (reach files only): Reach IDs of the downstream neighboring reaches. swot_obs (reach files only): The maximum number of SWOT passes to intersect each reach during the 21 day orbit cycle. swot_orbits (reach files only): A list of the SWOT orbit tracks that intersect each reach during the 21 day orbit cycle. 4. References: Allen, G. H., & Pavelsky, T. M. (2018). Global extent of rivers and streams. Science, 361(6402), 585-588. Altenau, E. H., Pavelsky, T. M., Durand, M. T., Yang X., Frasson, R. P. d. M., & Bendezu, L. (2021). The Surface Water and Ocean Topography (SWOT) Mission River Database (SWORD): A global river network for satellite data products”. Water Resources Research. Biancamaria, S., Lettenmaier, D. P., & Pavelsky, T. M. (2016). The SWOT mission and its capabilities for land hydrology. In Remote Sensing and Water Resources (pp. 117-147). Springer, Cham. JPL Internal Document (2020b). Surface Water and Ocean Topography Mission Level 2 KaRIn high rate river single pass vector product, JPL D-56413, Rev. A, https://podaac-tools.jpl.nasa.gov/drive/files/misc/web/misc/swot_mission_docs/pdd/D-56413_SWOT_Product_Description_L2_HR_RiverSP_20200825a.pdf Lehner, B., Grill G. (2013): Global river hydrography and network routing: baseline data and new approaches to study the world’s large river systems. Hydrological Processes, 27(15): 2171–2186. Data is available at www.hydrosheds.org. Tessler, Z. D., Vörösmarty, C. J., Grossberg, M., Gladkova, I., Aizenman, H., Syvitski, J. P. M., & Foufoula-Georgiou, E. (2015). Profiling risk and sustainability in coastal deltas of the world. Science, 349(6248), 638-643. Whittemore, A., Ross, M. R., Dolan, W., Langhorst, T., Yang, X., Pawar, S., Jorissen, M., Lawton, E., Januchowski-Hartley, S., & Pavelsky, T. (2020). A Participatory Science Approach to Expanding Instream Infrastructure Inventories. Earth's Future, 8(11), e2020EF001558. Yamazaki, D., Ikeshima, D., Sosa, J., Bates, P. D., Allen, G., & Pavelsky, T. (2019). MERIT Hydro: A high-resolution global hydrography map based on latest topography datasets. Water Resources Research. https://doi.org/10.1029/2019WR024873. Yang, X., Pavelsky, T. M., Allen, G. H. (2019). The past and future of global river ice. Nature. SWOT Orbits: https://www.aviso.altimetry.fr/en/missions/future-missions/swot/orbit.html HydroFALLS: http://wp.geog.mcgill.ca/hydrolab/hydrofalls/

【重要更新】
此前，在为表面水与海洋地形（Surface Water and Ocean Topography, SWOT）任务发射筹备算法期间，本项目版SWORD与公开版SWORD一直处于分离状态。如今SWOT任务已正式启动，我们决定发布项目版SWORD，这也是v2版本后版本号大幅跃升的原因。SWORD项目版与公开版的核心差异仅在于NetCDF格式中用于流量计算的额外"填充"变量。其余内容，包括河段定义、属性值等，两个版本完全一致。关于填充变量的详细信息，请参考下载包附带的产品说明文档。若您在研究中使用了SWORD数据库，请引用以下文献：Altenau等人（2021）《表面水与海洋地形（SWOT）任务河流数据库（SWORD）：面向卫星数据产品的全球河网》，刊载于*Water Resources Research*，DOI: https://doi.org/10.1029/2021WR030054。您也可以访问www.swordexplorer.com，在下载前预览SWORD的当前版本。

1. 数据集概述
即将于2022年发射的SWOT卫星任务，将大幅拓展对河流水面高程（Water Surface Elevation, WSE）、河宽及坡度的观测覆盖范围。为支持灵活多样的新型分析研究，SWOT任务将提供一系列相关数据产品。其中一类产品为针对每次SWOT过境场景的矢量河网数据，以shapefile格式存储（JPL内部文档，2020b）。若要实现对同一河域内的河节点与河段的多时相分析，SWOT矢量数据产品需具备广泛适用性，这要求预先定义SWOT河段与节点，以便将SWOT观测数据匹配至这些预定义单元。SWOT河流数据库（SWORD）整合了多套全球河流与卫星相关数据集，用于定义构成SWOT矢量河网数据产品的节点与河段。SWORD提供分辨率达200米的河节点和约10公里的河段，支持shapefile与NetCDF两种格式，附带水文变量（如WSE、河宽、坡度等），并为宽度≥30米的全球河流构建了统一的拓扑系统。

2. 数据格式
SWORD数据库以NetCDF、地理包（geopackage）及shapefile三种格式提供。所有文件均以两位大陆标识符作为前缀（"af"对应非洲，"as"对应亚洲/西伯利亚，"eu"对应欧洲/中东，"na"对应北美洲，"oc"对应大洋洲，"sa"对应南美洲）。文件名语法用于标识文件所属区域，NetCDF与shapefile格式的命名规则略有差异。NetCDF文件包含三个分组：中心线（centerlines）、节点（nodes）与河段（reaches）。中心线分组包含原始全球河流与湖泊中心线（Global River and Lake Centerlines, GRWL）30米中心线的位置信息，以及对应河段与节点的ID。节点与河段分组则包含约200米节点和约10公里河段的水文属性（详见下文属性说明）。NetCDF文件按大陆尺度分发，命名约定为：[continent]_sword_v[version].nc（例如na_sword_v14.nc）。
SWORD的shapefile文件包含四个核心文件（.dbf、.prj、.shp、.shx），节点与河段分别拥有独立的shapefile：节点为间隔约200米的点要素，河段为多段线要素。所有shapefile均采用地理坐标系（纬度/经度），基准面为WGS84。shapefile按HydroBASINS（Lehner与Grill，2013）的Pfafstetter二级流域（hbXX）进行拆分，命名约定为：[continent]_sword_[nodes/reaches]_hb[XX]_v[version].shp（例如na_sword_nodes_hb74_v14.shp；na_sword_reaches_hb74_v14.shp）。
SWORD地理包文件按大陆尺度拆分，分为节点与河段两个文件：节点为间隔200米的点要素，河段为多段线要素。所有地理包文件均采用地理坐标系（纬度/经度），基准面为WGS84。地理包文件的命名约定为：[continent]_sword_[nodes/reaches]_v[version].gpkg（例如na_sword_nodes_v14.gpkg；na_sword_reaches_v14.gpkg）。

3. 属性说明
以下为SWORD的NetCDF与shapefile文件中包含的主要属性：
x：河节点或河段的经度，范围为180°E至180°W，单位为十进制度。
y：河节点或河段的纬度，范围为90°S至90°N，单位为十进制度。
node_id：每个河节点的ID，格式为CBBBBBRRRRNNNT，其中：C为大陆代码（即Pfafstetter流域代码的首位数字）；B为剩余的Pfafstetter流域代码（最高至6级）；R为河段编号（在6级流域内从下游向上游依次编号）；N为节点编号（在河段内从下游向上游依次编号）；T为类型代码（1 – 河流，3 – 河上湖泊，4 – 水坝或瀑布，5 – 拓扑结构不可靠，6 – 虚拟节点）。
node_length（仅节点文件包含）：沿GRWL中心线测量的节点长度，单位为米。
reach_id：每个河段的ID，格式为CBBBBBRRRRT，其中：C为大陆代码（即Pfafstetter流域代码的首位数字）；B为剩余的Pfafstetter流域代码（最高至6级）；R为河段编号（在6级流域内从下游向上游依次编号）；T为类型代码（1 – 河流，3 – 河上湖泊，4 – 水坝或瀑布，5 – 拓扑结构不可靠，6 – 虚拟河段）。
reach_length（仅河段文件包含）：沿GRWL中心线测量的河段长度，单位为米。
wse：河节点或河段的平均水面高程（Water Surface Elevation, WSE）。WSE数据提取自MERIT Hydro数据集（Yamazaki等人，2019），基准为EGM96大地水准面，单位为米。
wse_var：用于计算节点或河段平均WSE的GRWL中心线点上的WSE方差，单位为平方米。
width：河节点或河段的平均河宽，单位为米。
width_var：用于计算节点或河段平均河宽的GRWL中心线点上的河宽方差，单位为平方米。
max_width：节点或河段的河道最大宽度（包含岛屿与沙洲区域），单位为米。
facc：河节点或河段的最大汇流面积，数据提取自MERIT Hydro数据集（Yamazaki等人，2019），单位为平方千米。
n_chan_max：节点或河段的最大河道数量。
n_chan_mod：节点或河段的河道数量众数。
obstr_type：基于全球障碍物数据库（Global Obstruction Database, GROD，Whittemore等人，2020）与HydroFALLS数据（http://wp.geog.mcgill.ca/hydrolab/hydrofalls）得到的节点或河段障碍物类型。obstr_type取值：0 – 无障碍物，1 – 水坝，2 – 河道水坝，3 – 船闸，4 – 低渗透性水坝，5 – 瀑布。
grod_id：obstr_type取值为1-4的节点或河段对应的唯一GROD ID。
hfalls_id：obstr_type取值为5的节点或河段对应的唯一HydroFALLS ID。
dist_out：河节点或河段至河流出口的距离，单位为米。
type：节点或河段的类型标识符：1 – 河流，2 – 河外湖泊，3 – 河上湖泊，4 – 水坝或瀑布，5 – 拓扑结构不可靠，6 – 虚拟河段/节点。
lakeflag：GRWL水体标识符，用于标识河段类型：0 – 河流，1 – 湖泊/水库，2 – 运河，3 – 受潮汐影响的河流。
manual_add（仅节点文件包含）：二进制标记，用于标识该节点是否手动添加至公开的GRWL中心线（Allen与Pavelsky，2018）。此类节点最初被赋予宽度值1，后续已更新为对应河段的河宽值。
meand_len（仅节点文件包含）：节点所属河湾的长度，从河湾起点至终点的测量值，单位为米。若节点跨越多个河湾，则meand_len为该节点所属所有河湾的平均长度，单位为米。
sinuosity（仅节点文件包含）：节点所属河段的总长度与河段端点间欧氏距离的比值。
slope（仅河段文件包含）：沿GRWL中心线计算的河段平均坡度，通过线性回归方法得到，单位为米/千米。
n_nodes（仅河段文件包含）：每个河段关联的节点数量。
n_rch_up（仅河段文件包含）：每个河段的上游河段数量。
n_rch_down（仅河段文件包含）：每个河段的下游河段数量。
rch_id_up（仅河段文件包含）：上游相邻河段的ID。
rch_id_dn（仅河段文件包含）：下游相邻河段的ID。
swot_obs（仅河段文件包含）：21天轨道周期内，可与该河段相交的SWOT过境次数最大值。
swot_orbits（仅河段文件包含）：21天轨道周期内，可与该河段相交的所有SWOT轨道轨迹列表。

4. 参考文献
1. Allen, G. H., & Pavelsky, T. M. (2018). Global extent of rivers and streams. *Science*, 361(6402), 585-588.
2. Altenau, E. H., Pavelsky, T. M., Durand, M. T., Yang X., Frasson, R. P. d. M., & Bendezu, L. (2021). The Surface Water and Ocean Topography (SWOT) Mission River Database (SWORD): A global river network for satellite data products. *Water Resources Research*.
3. Biancamaria, S., Lettenmaier, D. P., & Pavelsky, T. M. (2016). The SWOT mission and its capabilities for land hydrology. In *Remote Sensing and Water Resources* (pp. 117-147). Springer, Cham.
4. JPL Internal Document (2020b). Surface Water and Ocean Topography Mission Level 2 KaRIn high rate river single pass vector product, JPL D-56413, Rev. A, https://podaac-tools.jpl.nasa.gov/drive/files/misc/web/misc/swot_mission_docs/pdd/D-56413_SWOT_Product_Description_L2_HR_RiverSP_20200825a.pdf
5. Lehner, B., Grill G. (2013): Global river hydrography and network routing: baseline data and new approaches to study the world’s large river systems. *Hydrological Processes*, 27(15): 2171–2186. 数据可从www.hydrosheds.org获取。
6. Tessler, Z. D., Vörösmarty, C. J., Grossberg, M., Gladkova, I., Aizenman, H., Syvitski, J. P. M., & Foufoula-Georgiou, E. (2015). Profiling risk and sustainability in coastal deltas of the world. *Science*, 349(6248), 638-643.
7. Whittemore, A., Ross, M. R., Dolan, W., Langhorst, T., Yang, X., Pawar, S., Jorissen, M., Lawton, E., Januchowski-Hartley, S., & Pavelsky, T. (2020). A Participatory Science Approach to Expanding Instream Infrastructure Inventories. *Earth's Future*, 8(11), e2020EF001558.
8. Yamazaki, D., Ikeshima, D., Sosa, J., Bates, P. D., Allen, G., & Pavelsky, T. (2019). MERIT Hydro: A high-resolution global hydrography map based on latest topography datasets. *Water Resources Research*. https://doi.org/10.1029/2019WR024873.
9. Yang, X., Pavelsky, T. M., Allen, G. H. (2019). The past and future of global river ice. *Nature*.
10. SWOT Orbits: https://www.aviso.altimetry.fr/en/missions/future-missions/swot/orbit.html
11. HydroFALLS: http://wp.geog.mcgill.ca/hydrolab/hydrofalls/

搜集汇总

背景与挑战

背景概述

SWOT River Database (SWORD) 是一个为SWOT卫星任务设计的全球河流网络数据库，旨在提供高分辨率（节点约200米，河段约10公里）的河流向量数据，以支持河流水表面高程、宽度和坡度等多时相分析。数据集以netCDF、geopackage和shapefile格式提供，覆盖全球各大洲，并整合了MERIT Hydro、GRWL等全球数据集的水文属性，如水位、宽度、坡度和拓扑信息，适用于水文研究和卫星数据产品开发。