USA SSURGO - Soil Hydrologic Group

When rain falls over land, a portion of it runs off into stream channels and storm water systems while the remainder infiltrates into the soil or returns to the atmosphere directly through evaporation. Physical properties of soil affect the rate that water is absorbed and the amount of runoff produced by a storm. Hydrologic soil group provides an index of the rate that water infiltrates a soil and is an input to rainfall-runoff models that are used to predict potential stream flow. For more information on using hydrologic soil group in hydrologic modeling see the publication Urban Hydrology for Small Watersheds (Natural Resources Conservation Service, United States Department of Agriculture, Technical Release–55). Dataset Summary Phenomenon Mapped: Soil hydrologic group Geographic Extent: Contiguous United States, Alaska, Hawaii, Puerto Rico, Guam, US Virgin Islands, Northern Mariana Islands, Republic of Palau, Republic of the Marshall Islands, Federated States of Micronesia, and American Samoa. Projection: Web Mercator Auxiliary Sphere Data Coordinate System: WKID 5070 USA Contiguous Albers Equal Area Conic USGS version (contiguous US, Puerto Rico, US Virgin Islands), WKID 3338 WGS 1984 Albers (Alaska), WKID 4326 WGS 1984 Decimal Degrees (Guam, Republic of the Marshall Islands, Northern Mariana Islands, Republic of Palau, Federated States of Micronesia, American Samoa, and Hawaii). Units: Classes Cell Size: 30 meters Source Type: Discrete Pixel Type: Unsigned integer Source: Natural Resources Conservation Service Update Frequency: Annual Publication Date: December 2025 Data from the gNATSGO database was used to create the layer. This layer is derived from the 30m rasters produced by the Natural Resources Conservation Service (NRCS). The value for hydrologic group is derived from the gSSURGO map unit aggregated attribute table field Hydrologic Group - Dominant Conditions(hydgrpdcd). The seven classes of hydrologic soil group followed by definitions: Group A - Group A soils consist of deep, well drained sands or gravelly sands with high infiltration and low runoff rates. Group B - Group B soils consist of deep well drained soils with a moderately fine to moderately coarse texture and a moderate rate of infiltration and runoff. Group C - Group C consists of soils with a layer that impedes the downward movement of water or fine textured soils and a slow rate of infiltration. Group D - Group D consists of soils with a very slow infiltration rate and high runoff potential. This group is composed of clays that have a high shrink-swell potential, soils with a high water table, soils that have a clay pan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. Group A/D - Group A/D soils naturally have a very slow infiltration rate due to a high water table but will have high infiltration and low runoff rates if drained. Group B/D - Group B/D soils naturally have a very slow infiltration rate due to a high water table but will have a moderate rate of infiltration and runoff if drained. Group C/D - Group C/D soils naturally have a very slow infiltration rate due to a high water table but will have a slow rate of infiltration if drained. What can you do with this layer? This layer is suitable for both visualization and analysis acrossthe ArcGIS system. This layer can be combined with your data and other layers from the ArcGIS Living Atlas of the World in ArcGIS Online and ArcGIS Pro to create powerful web maps that can be used alone or in a story map or other application. Because this layer is part of the ArcGIS Living Atlas of the World it is easy to add to your map: In ArcGIS Online, you can add this layer to a map by selectingAddthenBrowse Living Atlas Layers. A window will open. Type "soil hydrologic group" in the search box and browse to the layer. Select the layer then clickAdd to Map. In ArcGIS Pro, open a map and selectAdd Datafrom the Map Tab. SelectDataat the top of the drop down menu. The Add Data dialog box will open on the left side of the box, expandPortalif necessary, then selectLiving Atlas. Type "soil hydrologic group" in the search box, browse to the layer then click OK. In ArcGIS Pro you can use the built-in raster functions or create your own to create custom extracts of the data. Imagery layers provide fast, powerful inputs to geoprocessing tools, models, or Python scripts in Pro. Online you can filter the layer to show subsets of the data using the filter button and the layer's built-in raster functions. The ArcGIS Living Atlas of the World provides an easy way to explore many otherbeautiful and authoritative maps on hundreds of topics like this one. Questions? Please leave a comment below if you have a question about this layer, and we will get back to you as soon as possible.

当降水降落在陆地区域时，一部分会汇入河道与雨水管网，其余部分则渗入土壤，或直接通过蒸发返回大气。土壤的物理特性会影响水分下渗速率与暴雨产生的径流量。水文土壤组（Hydrologic Soil Group）为土壤水分下渗速率提供了量化指标，同时也是用于预测潜在河道流量的降雨-径流模型的输入参数之一。如需了解在水文建模中使用水文土壤组的更多信息，请参阅《小流域城市水文学》（美国农业部自然资源保护服务局，技术报告第55号，Urban Hydrology for Small Watersheds (Natural Resources Conservation Service, United States Department of Agriculture, Technical Release–55)）。

# 数据集摘要
## 测绘对象：水文土壤组
## 地理覆盖范围：美国本土、阿拉斯加、夏威夷、波多黎各、关岛、美属维尔京群岛、北马里亚纳群岛、帕劳共和国、马绍尔群岛共和国、密克罗尼西亚联邦和美属萨摩亚。
## 投影：Web Mercator辅助球体
## 数据坐标系：WKID 5070 美国本土阿尔伯斯等面积圆锥投影（美国本土、波多黎各、美属维尔京群岛）；WKID 3338 WGS 1984 阿尔伯斯投影（阿拉斯加）；WKID 4326 WGS 1984 十进制度（关岛、马绍尔群岛共和国、北马里亚纳群岛、帕劳共和国、密克罗尼西亚联邦、美属萨摩亚及夏威夷）。
## 单位：分类等级
## 像元大小：30米
## 源数据类型：离散型
## 像元类型：无符号整数
## 数据来源：美国农业部自然资源保护服务局（Natural Resources Conservation Service, NRCS）
## 更新频率：年度更新
## 发布日期：2025年12月

本数据集基于gNATSGO数据库制作，由美国农业部自然资源保护服务局（NRCS）生成的30米栅格数据衍生而来。水文土壤组的属性值取自gSSURGO制图单元聚合属性表中的「水文组-主导条件（Hydrologic Group - Dominant Conditions, hydgrpdcd）」字段。

水文土壤组共分为7类，具体定义如下：
1. **A组**：A组土壤为深层、排水良好的砂土或砾石砂土，下渗速率高，径流量低。
2. **B组**：B组土壤为深层排水良好的土壤，质地介于中细至中粗粒之间，下渗与径流量速率中等。
3. **C组**：C组土壤存在阻碍水分下渗的土层，或为细粒质地土壤，下渗速率缓慢。
4. **D组**：D组土壤下渗速率极慢，径流潜力高。该组包含具有高胀缩性的黏土、地下水位较高的土壤、表层或近表层存在黏磐或黏土层的土壤，以及覆盖近乎不透水层的浅层土壤。
5. **A/D组**：A/D组土壤因地下水位较高，天然下渗速率极慢，但经排水处理后下渗速率提升，径流量降低。
6. **B/D组**：B/D组土壤因地下水位较高，天然下渗速率极慢，但经排水处理后下渗与径流量速率达到中等水平。
7. **C/D组**：C/D组土壤因地下水位较高，天然下渗速率极慢，但经排水处理后下渗速率仍较为缓慢。

## 本数据集的应用场景
该图层适用于ArcGIS生态系统内的可视化与分析工作。可将其与自有数据及ArcGIS世界生活地图集（ArcGIS Living Atlas of the World）中的其他图层结合，在ArcGIS Online或ArcGIS Pro中创建功能强大的Web地图，可独立使用，或集成至故事地图或其他应用程序中。由于本图层属于ArcGIS世界生活地图集的一部分，添加至地图的操作十分便捷：
- 在ArcGIS Online中：点击「添加」，选择「浏览生活地图图层」，在弹出窗口的搜索框中输入“土壤水文组”，找到对应图层后点击「添加至地图」即可。
- 在ArcGIS Pro中：打开地图后，点击「地图」选项卡中的「添加数据」，在下拉菜单中选择「数据」，在左侧弹出的「添加数据」对话框中，展开「门户」后选择「生活地图」，在搜索框输入“土壤水文组”，找到目标图层后点击「确定」。在ArcGIS Pro中，可使用内置栅格工具或自定义工具对数据进行定制化提取。影像图层可为Pro中的地理处理工具、模型或Python脚本提供高效且强大的输入源。在ArcGIS Online中，可通过筛选按钮与图层内置的栅格函数，对数据子集进行可视化筛选。ArcGIS世界生活地图集提供了便捷途径，可探索数百个主题下的众多优质权威地图。

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