feat(wateruse): add water-use module for the USGS NWDC API

Add `dataretrieval.wateruse` for USGS National Water Availability Assessment
Data Companion (NWDC) water-use estimates — modeled on a HUC12 grid and
queryable by state, county, or hydrologic unit. This is the modern replacement
for the defunct legacy NWIS water-use service (`nwis.get_water_use` now points
callers here).

    from dataretrieval import wateruse

    df, md = wateruse.get_wateruse(
        model="wu-public-supply-wd",
        variable=["pswdtot", "pswdgw", "pswdsw"],
        state="RI",
        start_date="2020-01",
        time_resolution="monthly",
    )

The NWDC is a plain CSV REST service, not an OGC API Features collection, so the
module supplies the NWDC-specific pieces (CSV parsing, the RFC 8288 Link-header
pagination cursor, the `{detail}` error envelope, and state/county/huc location
builders) but reuses the OGC engine's generic transport rather than
re-implementing it: the shared pager (`_paginate`), the Jupyter-safe anyio sync
bridge (`_run_sync`), response/frame aggregation, and `_default_headers`. It
keeps the package conventions where they fit — a `(DataFrame, BaseMetadata)`
return, the typed `DataRetrievalError` taxonomy (surfacing the NWDC `detail`),
`API_USGS_PAT` token support, idiomatic snake_case params, and `state` /
`county` / `huc` selectors that each accept a value or a list (a list fans out
one concurrent request per location). Large areas paginate transparently.

A `FutureWarning` flags the module as experimental, since the NWDC service is
new and still changing.

Extracting the reusable engine seams also de-duplicated the engine itself
(~-66 LOC, behavior-preserving): `planning._merge_response` now backs both
pagination and fan-out aggregation; a generic `utils.Ambient[T]`
contextvar-with-scope helper collapses the per-call ambients; and
`x-ratelimit-remaining` now reports the lowest value any concurrent sub-request
saw (the quota actually left after a fan-out), fixing a latent inaccuracy in the
OGC chunker too.

Includes offline pytest-httpx coverage, a reference page, a README example, and
a demo notebook.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sjb14HkwuCydKSKMsaXsgd

Author: thodson-usgs

AGENTS.md

@@ -6,7 +6,7 @@
 - Exclude `.claude/worktrees/` from searches and edits; it contains stale worktrees that pollute results.
 
 ## Example Notebooks
-- `demos/*.ipynb` — top-level Water Data tour: `USGS_WaterData_Introduction_Examples.ipynb` is the entry point; `_ContinuousData_`, `_DailyStatistics_`, `_DiscreteSamples_`, `_ReferenceLists_` cover individual collections; `WaterData_demo.ipynb`, `peak_streamflow_trends.ipynb`, and `R Python Vignette equivalents.ipynb` are standalone walkthroughs.
+- `demos/*.ipynb` — top-level Water Data tour: `USGS_WaterData_Introduction_Examples.ipynb` is the entry point; `_ContinuousData_`, `_DailyStatistics_`, `_DiscreteSamples_`, `_ReferenceLists_` cover individual collections; `WaterData_demo.ipynb`, `peak_streamflow_trends.ipynb`, `USGS_WaterUse_Examples.ipynb` (NWDC water-use data via `wateruse.get_wateruse`), and `R Python Vignette equivalents.ipynb` are standalone walkthroughs.
 - `demos/hydroshare/*.ipynb` — per-service HydroShare examples (NLDI, NWIS WaterUse, and Water Data DailyValues / GroundwaterLevels / Measurements / ParameterCodes / Peaks / Ratings / Samples / SiteInfo / SiteInventory / Statistics / UnitValues). Mirror these when adding examples for a new collection.
 - `demos/nwqn_data_pull/` — non-notebook example: a lithops/Docker batch pipeline (`retrieve_nwqn_samples.py`, `retrieve_nwqn_streamflow.py`) with its own `README.md`.
 - Any `Untitled*.ipynb`, `*_test.ipynb`, or notebooks not listed here are untracked local scratch; ignore them.

README.md

@@ -133,7 +133,7 @@ sites, metadata = ngwmn.get_sites(state='Wisconsin')
 
 print(f"Found {len(sites)} NGWMN sites in Wisconsin")
 
-# Pull water levels from the first twenty sites over a time window. 
+# Pull water levels from the first twenty sites over a time window.
 water_levels, metadata = ngwmn.get_water_level(
     monitoring_location_id=sites['monitoring_location_id'][:20],
     datetime=['2022-01-01', '2024-01-01']
@@ -192,6 +192,31 @@ flowlines = nldi.get_flowlines(
 print(f"Found {len(flowlines)} upstream tributaries within 50km")
 ```
 
+### Water Use (NWDC)
+
+Retrieve modeled water-use estimates from the National Water Availability
+Assessment Data Companion:
+
+```python
+from dataretrieval import wateruse
+
+# Monthly public-supply withdrawals for Rhode Island, split into
+# groundwater and surface-water sources (returns a DataFrame and metadata).
+df, metadata = wateruse.get_wateruse(
+    model='wu-public-supply-wd',
+    variable=['pswdtot', 'pswdgw', 'pswdsw'],
+    state='RI',  # name/postal/FIPS; pass a list to fan out over several areas
+    start_date='2020-01',
+    time_resolution='monthly',
+)
+
+print(f"Retrieved {len(df)} records across {df['huc12_id'].nunique()} watersheds")
+
+# Aggregate the HUC12 grid to a statewide monthly total (million gallons/day)
+statewide = df.groupby('year_month')['pswdtot_mgd'].sum()
+print(statewide.head())
+```
+
 ## Available Data Services
 
 ### Modern USGS Water Data APIs (Recommended) — `dataretrieval.waterdata`
@@ -232,6 +257,13 @@ print(f"Found {len(flowlines)} upstream tributaries within 50km")
 - `get_features`: Find monitoring sites, dams, and other features along the network
 - `get_features_by_data_source`: Features from a specific data source
 
+### Water Use (NWDC)
+- **Public supply**: Modeled public-supply withdrawals and consumptive use
+- **Irrigation**: Modeled irrigation withdrawals and consumptive use
+- **Thermoelectric**: Modeled thermoelectric-power water use
+- **HUC12 estimates**: National coverage on a 12-digit hydrologic-unit grid,
+  summarizable to counties, states, or coarser hydrologic units
+
 ## More Examples
 
 Explore additional examples in the

dataretrieval/__init__.py

@@ -11,7 +11,8 @@
     df, meta = nwis.get_dv(sites="05427718")
 
 Available service modules: ``waterdata``, ``wqp`` (Water Quality Portal),
-``nldi``, ``streamstats``, and the deprecated ``nwis``.
+``wateruse`` (NWDC water-use data), ``nldi``, ``streamstats``, and the
+deprecated ``nwis``.
 
 ``nldi`` requires geopandas (``pip install dataretrieval[nldi]``) and is
 imported on demand: ``from dataretrieval import nldi``.
@@ -62,6 +63,7 @@
     streamstats,
     utils,
     waterdata,
+    wateruse,
     wqp,
 )
 
@@ -72,6 +74,7 @@
     "streamstats",
     "utils",
     "waterdata",
+    "wateruse",
     "wqp",
     # error taxonomy (canonical home: ``dataretrieval.exceptions``), re-exported
     # so callers can ``except dataretrieval.DataRetrievalError``

dataretrieval/nwis.py

@@ -741,8 +741,17 @@ def get_pmcodes(**kwargs: Any) -> NoReturn:
 
 
 def get_water_use(**kwargs: Any) -> NoReturn:
-    """Defunct: no current replacement."""
-    raise NameError("`nwis.get_water_use` is defunct.")
+    """Defunct: use ``dataretrieval.wateruse.get_wateruse`` instead.
+
+    The legacy NWIS water-use service has been retired. Modeled water-use
+    estimates are now served by the National Water Availability Assessment Data
+    Companion (NWDC); retrieve them with
+    :func:`dataretrieval.wateruse.get_wateruse`.
+    """
+    raise NameError(
+        "`nwis.get_water_use` is defunct; use "
+        "`dataretrieval.wateruse.get_wateruse` instead."
+    )
 
 
 @_deprecated

dataretrieval/ogc/chunking.py

@@ -69,15 +69,14 @@
 import functools
 import os
 from collections.abc import Callable, Iterator
-from contextlib import contextmanager
-from contextvars import ContextVar, copy_context
+from contextvars import copy_context
 from typing import Any, cast
 
 import httpx
 import pandas as pd
 from anyio.from_thread import start_blocking_portal
 
-from dataretrieval.utils import HTTPX_DEFAULTS
+from dataretrieval.utils import HTTPX_DEFAULTS, Ambient
 
 from . import progress as _progress
 from .interruptions import (
@@ -106,9 +105,6 @@
 _OGC_URL_BYTE_LIMIT = 8000
 
 
-# Response header USGS uses to advertise remaining hourly quota.
-_QUOTA_HEADER = "x-ratelimit-remaining"
-
 # Fan-out concurrency cap, read at call time (not import) so test
 # ``monkeypatch.setenv`` applies. Value grammar in :func:`_read_concurrency_env`;
 # the concurrency model is in the module docstring.
@@ -152,38 +148,11 @@ def _read_concurrency_env() -> int | None:
     return value
 
 
-# Shared per-call ``httpx.AsyncClient``, published via :func:`_publish`
-# during ``ChunkedCall._run`` so paginated-loop helpers (``_walk_pages``)
-# reuse the same connection pool across every sub-request. ``None``
-# outside a chunked call — paginated helpers then open their own
-# short-lived client.
-_chunked_client: ContextVar[httpx.AsyncClient | None] = ContextVar(
-    "_chunked_client", default=None
-)
-
-
-@contextmanager
-def _publish(client: httpx.AsyncClient) -> Iterator[None]:
-    """
-    Publish ``client`` on the ``_chunked_client`` ContextVar so the
-    paginated-loop helpers can borrow it via :func:`get_active_client`
-    for the duration of the ``with`` block.
-
-    Parameters
-    ----------
-    client : httpx.AsyncClient
-        The client to publish.
-
-    Yields
-    ------
-    None
-        Yields once, for the duration of the bind.
-    """
-    token = _chunked_client.set(client)
-    try:
-        yield
-    finally:
-        _chunked_client.reset(token)
+# Shared per-call ``httpx.AsyncClient``, scoped via ``with _chunked_client(c):``
+# during ``ChunkedCall._run`` so paginated-loop helpers (``_walk_pages``) reuse
+# the same connection pool across every sub-request. ``None`` outside a chunked
+# call — paginated helpers then open their own short-lived client.
+_chunked_client: Ambient[httpx.AsyncClient | None] = Ambient("_chunked_client", None)
 
 
 def get_active_client() -> httpx.AsyncClient | None:
@@ -197,8 +166,8 @@ def get_active_client() -> httpx.AsyncClient | None:
     Returns
     -------
     httpx.AsyncClient or None
-        The client published via :func:`_publish` if currently inside a
-        :class:`ChunkedCall` run; ``None`` otherwise.
+        The client scoped via ``with _chunked_client(...)`` if currently inside
+        a :class:`ChunkedCall` run; ``None`` otherwise.
     """
     return _chunked_client.get()
 
@@ -541,7 +510,7 @@ async def _run(self, max_concurrent: int | None) -> tuple[pd.DataFrame, Any]:
         )
 
         async with httpx.AsyncClient(limits=limits, **HTTPX_DEFAULTS) as client:
-            with _publish(client):
+            with _chunked_client(client):
                 reporter = _progress.current()
                 if reporter is not None:
                     reporter.set_chunks(self.plan.total)