Geoskill: Watershed Delineation

Automated watershed delineation from DEM. Computes D8 flow direction, flow accumulation, delineates watersheds from outlet points, extracts stream networks, and generates statistics. Use when the user wants to delineate a watershed, compute flow accumulation, extract streams, or analyze hydrological characteristics from a DEM.

Watershed Delineation

Automated watershed analysis from DEM using D8 algorithm.

CLI Usage

bash

python scripts/watershed_delineation.py --dem dem.tif
python scripts/watershed_delineation.py --dem dem.tif --outlet-row 50 --outlet-col 60
python scripts/watershed_delineation.py --dem dem.tif --stream-threshold 50
python scripts/watershed_delineation.py --synthetic --output-dir ./out

数据下载

本 skill 可自动从 Microsoft Planetary Computer 下载 DEM (无需 API key):

bash

# 自动下载 Copernicus DEM GLO-30
python scripts/watershed_delineation.py \
    --bbox 116.30,39.85,116.45,39.95 \
    --date-range 2020-01-01,2020-12-31 \
    --output-dir ./ws-auto

下载的内容:

• Copernicus DEM GLO-30 (cop-dem-glo-30) — 替换 --dem

下载元数据（data_source, fetched_at, collection, dem_downloaded）会写入 output-manifest.json。

Parameters

Flag	Type	Default	Description
--dem	path	(required, or use --synthetic)	Input DEM raster (GeoTIFF)
--outlet-row	int	None	Outlet row in DEM grid (default: max accumulation)
--outlet-col	int	None	Outlet column in DEM grid (default: max accumulation)
--stream-threshold	int	100	Stream threshold in accumulation pixels
--output-dir / -o	path	watershed-output	Output directory
--synthetic	flag	False	Run with synthetic demo data (no real inputs needed)
--version	flag	-	Show version and exit

Output

File	Description
flow_direction.tif	D8 flow direction raster
flow_accumulation.tif	Flow accumulation raster
watershed.tif	Watershed mask
streams.tif	Stream network
report.html	Statistics report
output-manifest.json	Machine-readable manifest

Exit Codes

Code	Meaning
0	Success
2	Argument error
3	Dependency missing
7	Processing failure

数据下载

本 skill 可自动从 Microsoft Planetary Computer 下载数据 (无需 API key):

bash

python watershed_delineation.py --bbox 116,39,117,40 --date-range 2024-06-01,2024-06-30 --output-dir <tmp>

• --bbox W,S,E,N: WGS-84 边界框 (西, 南, 东, 北)
• --date-range START,END: 日期范围 (YYYY-MM-DD,YYYY-MM-DD)
• --aoi-file <path.geojson>: 替代 --bbox 的 GeoJSON 多边形
• --cache-dir <path>: 缓存目录 (默认 ~/.geoskill_cache)

当用户只给 --bbox + --date-range (没有 --dem) 时，skill 自动下载数据。 当用户给 --dem 时，走原文件路径 (向后兼容)。