aihydro-watershed 0.1.0

Watershed delineation + characterization — global pour-point delineation (NLDI + MERIT-Hydro), geomorphics, TWI, and watershed-scale hydrological signatures

aihydro-watershed

Watershed delineation + characterization for any point on Earth — as a standalone package.

Delineate a watershed from a USGS gauge or any global lat/lon pour point, then characterize it (geomorphics, topographic wetness index, terrain/runoff, watershed-scale hydrological signatures) — without installing the full AI-Hydro MCP hydrology stack.

Part of the AI-Hydro ecosystem. Carved out of aihydro-tools in Wave A of the ecosystem roadmap.

Install

# Delineation (fast tier: cloud DEM + pysheds + MERIT-Hydro/pyflwdir)
pip install "aihydro-watershed[delineation]"

# Characterization + signatures
pip install "aihydro-watershed[analysis]"

# Everything
pip install "aihydro-watershed[all]"

On Python 3.13, the analysis extra omits xrspatial (no wheel); use analysis-legacy on Python 3.10–3.12 if you need TWI via xarray-spatial.

Quick start

from aihydro_watershed.delineation.router import delineate_from_point

# CONUS pour point — uses NLDI automatically
result = delineate_from_point(40.7128, -74.0060, method="auto")
print(result.data["area_km2"])          # 1234.5
print(result.data["method_used"])       # "nldi_comid"

# Global pour point (Rhine at Cologne) — falls back to fast DEM tier
result = delineate_from_point(50.932, 6.970, method="auto")
print(result.data["area_km2"])

# Expected drainage area known? Pass it to improve COMID selection
result = delineate_from_point(39.27, -77.54, expected_area_km2=25_000)

Results are typed HydroResult (from aihydro-core) — provenance-stamped with tool path, version, parameters, and data sources.

What's inside

Subpackage	Capability
delineation	Global pour-point / gauge delineation. Three tiers: NLDI (CONUS NHD-indexed), MERIT-Hydro/pyflwdir (local flowdir cache), MERIT-Basins hybrid (vector topology + raster refinement). Auto-routing chooses the best available tier.
merit	MERIT-Hydro data management: regional basin cache, flowdir rasters, map layers, region presets.
characterize	Geomorphic parameters (28 indices), watershed attributes, topographic wetness index.
terrain	Curve number, event runoff (SCS-CN), RUSLE erosion.
signatures	Baseflow index (Lyne-Hollick), flow-duration curve, flood frequency (Gumbel/GEV), drought indices (SPI, SPEI, Palmer).

The flood-inundation suite is not part of this package.

Delineation tiers

1. nldi        — USGS NLDI NHD-indexed basin (CONUS only, < 1 s)
2. merit_gee   — MERIT-Hydro flowdir from Google Earth Engine (global, cloud)
3. local_merit — MERIT-Hydro flowdir from local cache (global, offline after download)
4. fast        — pysheds on cloud-fetched DEM tile (global, no MERIT cache needed)
auto           — tries tiers in order of accuracy; degrades gracefully on failures

Layering

Depends only downward:

aihydro-core  ←  contract (HydroResult / HydroMeta / ToolError)
aihydro-data  ←  data acquisition (streamflow, DEM, land cover, soil)
     ↑
aihydro-watershed   (this package)

The layering contract is enforced offline by tests/test_layering.py (AST walk, zero deps) and by import-linter for anyone who installs the dev extra.

Running tests

# Offline (layering guard — always passes, no network needed)
pytest tests/ -m "not live" -q

# Full suite including live API calls (requires network)
pytest tests/ -v

# Parity checks only (Wave A4 gate)
pytest tests/test_parity.py -m live -v

Status

v0.1.0. Wave A extraction complete (2026-06-21). All five subpackages (delineation, merit, characterize, terrain, signatures) are live. Compatibility shims remain in ai_hydro/analysis/ and ai_hydro/data/ of aihydro-tools for one release cycle; see MIGRATION.md.

Migration from aihydro-tools

If you previously imported from ai_hydro.analysis.* or ai_hydro.data.*, see MIGRATION.md for the one-line import changes.