Google Earth Engine——WWF/HydroSHEDS/30ACC该数据集的分辨率为30弧秒。30角秒的数据集是水文条件下的DEM、排水（流）方向和流量累积。

HydroSHEDS is a mapping product that provides hydrographic information for regional and global-scale applications in a consistent format. It offers a suite of geo-referenced datasets (vector and raster) at various scales, including river networks, watershed boundaries, drainage directions, and flow accumulations. HydroSHEDS is based on elevation data obtained in 2000 by NASA's Shuttle Radar Topography Mission (SRTM).

This flow accumulation dataset defines the amount of upstream area (in number of cells) draining into each cell. The drainage direction layer is used to define which cells flow into the target cell. The number of accumulated cells is essentially a measure of the upstream catchment area. However, since the cell size of the HydroSHEDS data set depends on latitude, the cell accumulation value cannot directly be translated into drainage areas in square kilometers. Values range from 1 at topographic highs (river sources) to very large numbers (on the order of millions of cells) at the mouths of large rivers.

This dataset is at 30 arc-second resolution. The datasets available at 30 arc-seconds are the Hydrologically Conditioned DEM, Drainage (Flow) Direction, and Flow Accumulation.

Note that the quality of the HydroSHEDS data is significantly lower for regions above 60 degrees northern latitude as there is no underlying SRTM elevation data available and thus a coarser-resolution DEM was (HYDRO1k provided by USGS).

HydroSHEDS was developed by the World Wildlife Fund (WWF) Conservation Science Program in partnership with the U.S. Geological Survey, the International Centre for Tropical Agriculture, The Nature Conservancy, and the Center for Environmental Systems Research of the University of Kassel, Germany.

HydroSHEDS是一个制图产品，以一致的格式为区域和全球范围的应用提供水文信息。它提供了一套不同尺度的地理参考数据集（矢量和栅格），包括河流网络、流域边界、排水方向和流量积累。HydroSHEDS是基于2000年NASA的航天飞机雷达地形任务（SRTM）获得的高程数据。

这个流量累积数据集定义了排入每个单元的上游区域的数量（以单元数计）。排水方向层被用来定义哪些小区流入目标小区。累积单元的数量本质上是对上游集水区的测量。然而，由于HydroSHEDS数据集的单元大小取决于纬度，单元累积值不能直接转化为以平方公里为单位的排水面积。数值范围从地形高点（河流源头）的1到大河入海口的非常大的数字（数以百万计的单元）。

该数据集的分辨率为30弧秒。30角秒的数据集是水文条件下的DEM、排水（流）方向和流量累积。

请注意，在北纬60度以上的地区，HydroSHEDS数据的质量要低得多，因为没有底层的SRTM高程数据可用，因此要用更粗的分辨率DEM（美国地质调查局提供的HYDRO1k）。

HydroSHEDS是由世界自然基金会（WWF）保护科学项目与美国地质调查局、国际热带农业中心、大自然保护协会和德国卡塞尔大学环境系统研究中心合作开发的。

Dataset Availability

2000-02-11T00:00:00 - 2000-02-22T00:00:00

Dataset Provider

WWF

Collection Snippet

ee.Image("WWF/HydroSHEDS/30ACC")

Resolution

927.67 meters

Bands Table

* = Values are estimated

引用：

Lehner, B., Verdin, K., Jarvis, A. (2008): New global hydrography derived from spaceborne elevation data. Eos, Transactions, AGU, 89(10): 93-94.

代码：

var dataset = ee.Image('WWF/HydroSHEDS/30ACC');
var flowAccumulation = dataset.select('b1');
var flowAccumulationVis = {
  min: 0.0,
  max: 500.0,
  palette: [
    '000000', '023858', '006837', '1a9850', '66bd63', 'a6d96a', 'd9ef8b',
    'ffffbf', 'fee08b', 'fdae61', 'f46d43', 'd73027'
  ],
};
Map.setCenter(-121.652, 38.022, 8);
Map.addLayer(flowAccumulation, flowAccumulationVis, 'Flow Accumulation');