SWOT River Database (SWORD)

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 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 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_v2.nc (i.e. na_sword_v2.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]_v2.shp (i.e. na_sword_nodes_hb74_v2.shp; na_sword_reaches_hb74_v2.shp). 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/

若您的研究工作中使用了SWORD数据库，请引用如下文献：Altenau等人（2021）《地表水域与海洋地形（Surface Water and Ocean Topography, SWOT）任务河流数据库（SWORD）：面向卫星数据产品的全球河网》，《水资源研究》（Water Resources Research）。https://doi.org/10.1029/2021WR030054

1. 概述
即将于2022年发射的地表水域与海洋地形（Surface Water and Ocean Topography, SWOT）卫星任务，将极大拓展河流水表面高程（Water Surface Elevation, WSE）、河宽与河道坡度的观测能力。为支持灵活多样的前沿分析研究，SWOT任务将提供一系列相关数据产品，其中一类为针对每次SWOT过境场景、以矢量格式（shapefile）存储的河流矢量产品（JPL内部文档，2020b）。若该矢量数据产品支持对同一河道区域的河流节点（node）与河段（reach）进行多时序分析，其应用潜力将得到最大程度的发挥。这一目标需要预先定义SWOT河段与节点，以便将SWOT观测数据匹配至对应要素。SWORD河流数据库整合了多套全球河流与卫星相关数据集，用于构建构成SWOT河流矢量产品的节点与河段。SWORD以矢量格式（shapefile）与网络通用数据格式（netCDF）提供分辨率为200米的河流节点和约10公里的河段数据，附带水表面高程、河宽、坡度等水文变量，同时为宽度≥30米的全球河道提供统一的拓扑系统。

2. 数据格式
SWORD数据库以网络通用数据格式（netCDF）与矢量格式（shapefile）提供。所有文件均以两位字母的大洲标识符作为前缀："af"代表非洲，"as"代表亚洲/西伯利亚，"eu"代表欧洲/中东，"na"代表北美洲，"oc"代表大洋洲，"sa"代表南美洲。文件名的语法用于标识文件对应的区域信息，且在netCDF与shapefile两种格式间存在细微差异。
netCDF文件分为3个数据组：河道中心线（centerlines）、节点（nodes）与河段（reaches）。河道中心线组包含原始GRWL 30米分辨率河道中心线的位置信息，以及对应的河段与节点ID（Allen与Pavelsky，2018）。节点与河段组则包含分辨率约200米的节点和约10公里的河段对应的水文属性（详见下文属性说明）。netCDF文件按大洲尺度分发，文件名遵循如下约定：[大洲标识符]_sword_v2.nc（例如na_sword_v2.nc）。
SWORD的shapefile文件由4个核心文件组成（.dbf、.prj、.shp、.shx），其中节点与河段分别拥有独立的shapefile：节点以间距约200米的点要素表示，河段以多段线要素表示。所有shapefile均采用地理（纬度/经度）投影，基准面为WGS84。shapefile文件按大洲的HydroBASINS（Lehner与Grill，2013）Pfafstetter二级流域（hbXX）进行拆分，文件名约定如下：[大洲标识符]_sword_[nodes/reaches]_hb[XX]_v2.shp（例如na_sword_nodes_hb74_v2.shp；na_sword_reaches_hb74_v2.shp）。

3. 属性说明
以下为SWORD的netCDF与shapefile文件中包含的核心属性：
x：节点或河段的经度，取值范围为180°E至180°W，单位为十进制度。
y：节点或河段的纬度，取值范围为90°S至90°N，单位为十进制度。
node_id：每个节点的唯一标识，格式为`CBBBBBRRRRNNNT`，其中：C为大洲代码（对应Pfafstetter流域编码的首位数字），B为剩余的Pfafstetter流域编码（最高至6级），R为河段编号（在6级流域内从下游至上游依次递增分配），N为节点编号（在河段内从下游至上游依次递增分配），T为要素类型（1代表河道，3代表河道上的湖泊，4代表大坝或瀑布，5代表不可靠拓扑结构，6代表幽灵节点）。
node_length（仅节点文件包含）：沿GRWL河道中心线测量的节点长度，单位为米。
reach_id：每个河段的唯一标识，格式为`CBBBBBRRRRT`，其中：C为大洲代码（对应Pfafstetter流域编码的首位数字），B为剩余的Pfafstetter流域编码（最高至6级），R为河段编号（在6级流域内从下游至上游依次递增分配），T为要素类型（1代表河道，3代表河道上的湖泊，4代表大坝或瀑布，5代表不可靠拓扑结构，6代表幽灵河段）。
reach_length（仅河段文件包含）：沿GRWL河道中心线测量的河段长度，单位为米。
wse：节点或河段的平均水表面高程（WSE），数据源自MERIT Hydro数据集（Yamazaki等人，2019），基准面为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河道中心线沿线的WSE方差，单位为平方米。
width：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河道中心线沿线的河宽方差，单位为平方米。
max_width：节点或河段所在河道的最大河宽（包含江心洲与沙洲区域），单位为米。
facc：节点或河段的最大汇流面积，数据源自MERIT Hydro数据集（Yamazaki等人，2019），单位为平方千米。
n_chan_max：节点或河段所在河道的最大河道数量。
n_chan_mod：节点或河段所在河道的河道数量众数。
obstr_type：节点或河段的障碍物类型，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）获取。obstr_type的取值为：0 - 无障碍物，1 - 大坝，2 - 河道型大坝，3 - 船闸，4 - 低渗透性大坝，5 - 瀑布。
grod_id：当obstr_type取值为1-4时，对应节点或河段的唯一GROD标识。
hfalls_id：当obstr_type取值为5时，对应节点或河段的唯一HydroFALLS标识。
dist_out：节点或河段至河道出口的距离，单位为米。
type：节点或河段的类型标识：1 - 河道，2 - 河道旁湖泊，3 - 河道上湖泊，4 - 大坝或瀑布，5 - 不可靠拓扑结构，6 - 幽灵节点/河段。
lakeflag：GRWL水体标识，用于标记河段类型：0 - 河道，1 - 湖泊/水库，2 - 运河，3 - 受潮汐影响的河道。
manual_add（仅节点文件包含）：二进制标记，用于指示该节点是否被手动添加至公开的GRWL河道中心线（Allen与Pavelsky，2018）。此类节点最初被赋予河宽值1，后续已更新为对应河段的河宽值。
meand_len（仅节点文件包含）：节点所属弯道的长度，从弯道起点至终点的测量值，单位为米。若节点包含多个弯道，则meand_len为该节点所属所有弯道的平均长度，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的欧氏距离之比。
slope（仅河段文件包含）：沿GRWL河道中心线计算的河段平均坡度，采用线性回归方法计算，单位为米/千米。
n_nodes（仅河段文件包含）：每个河段包含的节点数量。
n_rch_up（仅河段文件包含）：每个河段的上游相邻河段数量。
n_rch_down（仅河段文件包含）：每个河段的下游相邻河段数量。
rch_id_up（仅河段文件包含）：上游相邻河段的ID列表。
rch_id_dn（仅河段文件包含）：下游相邻河段的ID列表。
swot_obs（仅河段文件包含）：在21天轨道周期内，可过境该河段的最大SWOT过境次数。
swot_orbits（仅河段文件包含）：在21天轨道周期内，可过境该河段的SWOT轨道轨迹列表。

4. 参考文献
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/