Depth to Groundwater Screener — USGS Water Levels for Phase I ESA, Geotech & Dewatering

How deep is the water table at this address, when was it actually measured, and how much has it moved?

This actor answers that for any US coordinate from the USGS Water Data OGC API — the authoritative national record of groundwater levels. For each site you get the depth to water in feet below land surface, the date that measurement was taken, how old it is, its vertical datum and approval status, the shallowest and median depth across every well in the radius, and — optionally — the full observed fluctuation range from a well's complete history.

It is built around one uncomfortable fact about US groundwater data: most of it is old. A great many USGS wells were last measured in the 1960s, 1980s or 1990s. A screener that prints "depth to groundwater: 9.7 ft" without saying that the reading is from April 1962 is handing you a confident wrong answer. This one puts the date, the age in years, and an explicit staleness flag on every single row, and it will tell you plainly when every reading near your site is archival.

Who this is for

• Phase I ESA consultants — the ASTM E1527-21 §8.2.2 physical setting leg. Depth to groundwater and the inferred flow setting are part of every report, and this is the fastest defensible way to source it with a citation and a date.
• Geotechnical and civil engineers — seasonal high water table for foundation, basement, slab and pavement design.
• Dewatering and excavation contractors — turn on includeHistory and you get the observed min, max and total fluctuation over a well's whole record, which is what actually sizes a dewatering system. A single latest reading cannot give you that.
• Environmental engineers — vadose-zone thickness, contaminant-migration screening, monitoring-well network design.
• Land and site-selection teams — septic feasibility, stormwater infiltration, basement viability, and flagging artesian conditions before you buy.

What makes the answer trustworthy

Every actor in this portfolio is built to a simple rule: a crash is cheap, a confident wrong answer is expensive. Concretely, here:

• Only an ambient static water level is reported as depth to groundwater. USGS marks each reading with condition qualifiers. A pumping measurement is a drawn-down level, not the water table. A dry well means the water is deeper than the hole and USGS publishes no value at all — read carelessly, that null becomes "water at 0 ft", i.e. water at the surface, which is the exact opposite of the truth. Both are excluded from every depth statistic and reported separately.
• Artesian levels are preserved as negative numbers. A well whose water stands 81 ft above land surface reports -81.16, never 81.16 and never dropped.
• A water-level elevation is never silently turned into a depth. USGS publishes some levels as elevation above NAVD88, NGVD29 or local mean sea level. A depth is only derived when the well's own land-surface datum matches the measurement datum exactly — the NGVD29-to-NAVD88 offset is location-specific and is never assumed. When it can't be derived, you get null plus the reason, never a guess.
• null means "not checked". false/0 means "checked and negative". If USGS is unreachable the row says source_unavailable and carries no verdict at all. It will never tell you a site has deep groundwater because a request failed.
• Completeness is proven, not assumed. This API publishes no result total of any kind, so there is no server count to check against. The actor pages the cursor to exhaustion and proves termination from three independent signals that must agree — the final page carried no next link, the final page was short, and the unique feature IDs equal the sum of every page's count. It publishes that proof on the row in paging_exhaustion_proof, and if it cannot prove it, results_truncated is true.
• The live source is verified before any billable row. Every run checks that the four required collections still exist, that parameter code 72019 still means depth below land surface in feet, that two pinned canary wells return their pinned identity and earliest measurement (one with a record back to 1928), that a mid-Pacific control returns zero, and that a cursor walk really terminates. If any of that fails the run fails, emits nothing, and bills nothing.

Example input

{
  "assets": [
    { "lat": 40.7891, "lon": -73.1350, "label": "Long Island NY industrial parcel", "radiusMiles": 1 },
    { "lat": 39.7392, "lon": -104.9903, "label": "Denver CO redevelopment site", "radiusMiles": 1 },
    { "lat": 29.7604, "lon": -95.3698, "label": "Houston TX warehouse", "radiusMiles": 1 }
  ],
  "radiusMiles": 1,
  "includeWellDetail": true,
  "maxWellsPerAsset": 8,
  "includeHistory": true,
  "historyWellCount": 2,
  "maxAgeYearsForCurrent": 5,
  "shallowGroundwaterThresholdFeet": 15
}

assets is the only required field. Everything else has a sensible fallback applied in code (documented per field below) — deliberately not a schema default, because an Apify input-schema default is injected server-side into every run and would silently narrow queries you never asked to narrow.

What a result looks like

The three example sites above return three genuinely different answers, and the difference is the product:

Site	Depth to water	Measured	Age	data_currency_class	all_readings_stale
Long Island NY	shallow, coastal-plain water table	2026	weeks	current	false
Denver CO	~9.7 ft at the nearest well	April 1962	~64 yr	archival	true
Houston TX	Gulf Coast aquifer	2011	~15 yr	historical	true

All three are correct. Only one of them is a current condition, and the row tells you which.

Output fields

Two row types share one schema. record_type is asset_summary (one per site) or well (one per USGS monitoring location inside the radius, when includeWellDetail is on).

Site summary — the answer

Field	Meaning
screening_result	static_depth_available, readings_present_no_static_depth, no_water_level_data_in_radius, no_monitoring_locations_in_radius, or source_unavailable. The last one is not a negative finding.
nearest_static_depth_to_water_feet	The headline depth, in feet below land surface, at the nearest well with a usable static reading.
nearest_static_reading_date / _age_years	When that reading was taken, and how old it is. Always read these with the depth.
nearest_static_reading_approval	Approved or Provisional.
nearest_static_well_id / _name / _distance_feet / _bearing_compass	Which well it came from and where it is relative to your point.
nearest_static_well_depth_feet / _aquifer_code	Which aquifer that level represents.
shallowest_depth_to_water_feet	Shallowest static depth anywhere in the radius — usually the conservative number for excavation and basement work.
depth_to_water_min_feet / _max_feet / _median_feet / depth_readings_used	Distribution across the radius. A wide spread normally means multiple aquifers, not error.
most_recent_reading_date_in_radius / _age_years / _well_id	The honest answer to "how current is groundwater data here".
data_currency_class	current (<1 yr), recent (1–5), historical (5–20), archival (20+).
all_readings_stale / readings_within_max_age_count	Whether every reading near the site predates your maxAgeYearsForCurrent threshold.
shallow_groundwater_flag	Shallowest measured depth at or above your threshold. null — never false — when no usable depth was found.
artesian_conditions_present	A measured water level standing above land surface somewhere in the radius.
phase1_physical_setting_flag	Gated: true when shallow or artesian groundwater was measured, null whenever the data was not adequate to decide.
depth_data_adequate_for_verdict	Both sources answered and a usable static depth exists. Every flag above is gated on this.
monitoring_locations_in_radius / groundwater_wells_in_radius / locations_with_water_level_data / wells_with_static_depth_reading	The funnel from "sites nearby" to "sites that actually answer the question".
wells_with_elevation_only_reading / wells_with_depth_derived_from_elevation	Wells that publish an elevation rather than a depth, and how many allowed a datum-safe derivation.
dry_wells_observed / pumping_only_wells_observed / artesian_wells_observed / static_readings_provisional_count	Condition breakdown, so an excluded reading is visible rather than missing.
measurements_source_status / locations_source_status / history_source_status (+ _error)	Per-source outcome on every row.
query_complete / results_truncated / paging_* / server_total_available	The completeness proof described above. server_total_available is always false and says so deliberately.
usgs_api_root / usgs_api_version / collections_verified / parameter_codes_queried / drift_checks_ran / checked_at	Provenance.
api_rate_limit_remaining / api_key_supplied	Your remaining USGS quota for the hour. USGS only sends the quota header on an HTTP 429, so on a healthy run api_rate_limit_remaining is legitimately null — "not reported", never "zero left".
asset_label / asset_lat / asset_lon / search_radius_miles / error	Echo of your input, plus any per-site failure.

Per-well rows — the evidence

Field	Meaning
well_rank_by_distance	1 = nearest.
well_id / well_agency_code / well_site_number / well_name	USGS identity. Names are often survey-grid codes, not plain language.
well_site_type_code / well_site_type	GW (well), GW-TH (test hole), GW-MW, GW-EX, GW-HZ, GW-CR, GW-IW, or a non-groundwater type.
well_state / well_county / well_hydrologic_unit_code	Administrative and watershed context.
well_lat / well_lon / well_distance_feet / well_distance_miles / well_bearing_degrees / well_bearing_compass	True haversine distance and bearing — not the bounding box that fetched the candidate.
well_horizontal_accuracy / well_horizontal_method	How precisely USGS knows the position. Sites interpolated from a map can be off by a minute of arc, which matters when the well is close to your parcel.
well_constructed_depth_feet / hole_constructed_depth_feet / well_construction_date	Which aquifer the level represents.
land_surface_altitude_feet / _datum / _accuracy_feet / _method	Subtract depth from altitude for water-table elevation.
aquifer_code / national_aquifer_code / aquifer_type_code	Aquifer identity, where USGS publishes it.
static_depth_to_water_feet	Most recent ambient static depth. Negative = artesian.
static_reading_date / _age_years / _approval_status / _is_provisional / _qualifiers / _observing_procedure / _parameter_code / _unit	Full provenance of that number, including how it was measured.
latest_reading_date / _age_years / _value_raw / _unit / _parameter_code / _basis / _qualifiers / _is_static / _approval_status / _unusable_reason / _elevation_datum	The most recent record of any kind. It can be newer than the static reading when the last visit found the well pumping, dry or flowing. _value_raw is kept verbatim so nothing fetched is silently discarded.
depth_derived_from_elevation_feet / depth_derivation_datum / depth_derivation_blocked_reason	Datum-safe derivation, or the exact reason it was refused.
dry_observed / flowing_artesian_observed / pumping_observed / artesian_static_level / unknown_qualifier_seen	Conditions ever recorded at this well.
measurement_series_rows_seen / superseded_series_rows_seen	How many measurement series USGS returned for this well, and how many were older than the one used.
history_fetched / history_readings_fetched / history_static_depth_readings / history_min_depth_feet / history_max_depth_feet / history_median_depth_feet / history_fluctuation_feet / history_earliest_reading / history_latest_reading / history_truncated / history_source_error	With includeHistory: the observed range of water-table movement — the number dewatering and basement design actually need.

Use as an MCP tool

This actor is callable by AI agents through Apify's hosted MCP server, so an assistant can screen a site mid-conversation. Billing is unchanged when it is called as a tool, and a run that cannot answer fails without billing.

Claude Desktop / Claude Code / Cursor — add to your MCP config:

{
  "mcpServers": {
    "apify": {
      "command": "npx",
      "args": [
        "-y", "mcp-remote",
        "https://mcp.apify.com/sse?actors=malonestar/usgs-groundwater-depth-screener"
      ],
      "env": { "APIFY_TOKEN": "<your Apify token>" }
    }
  }
}

A worked agent prompt:

"We're doing a Phase I on 1400 Industrial Blvd, Long Island NY (40.7891, -73.1350). Screen depth to groundwater within a mile, tell me the shallowest measured water table and how old that measurement is, and flag whether any of it is current enough to cite."

Chaining with the rest of the Phase I shelf — these compose into one physical-setting and recognised-environmental-conditions workup for the same coordinate:

https://mcp.apify.com/sse?actors=malonestar/usgs-groundwater-depth-screener,malonestar/epa-contaminated-site-screener,malonestar/site-due-diligence-bundle

• epa-contaminated-site-screener — Superfund, RCRA, USTs, spills and ECHO enforcement around the same point. Depth to groundwater is what turns a nearby release into a plume question.
• site-due-diligence-bundle — the 20-layer one-call screen (flood, seismic, wetlands, karst, habitat, levees and more) with a composite site score.
• ssurgo-soil-suitability-screener — NRCS soil profile, hydric rating and depth to restrictive layer at the same coordinate.
• nhd-surface-water-404-screener — Clean Water Act §404 surface-water jurisdiction nearby.
• epa-drinking-water-quality-screener — SDWA violations and PFAS occurrence for the serving public water systems.
• usgs-historical-topo-records-review — historical topographic map coverage for the ASTM historical-use review.

FAQ

How do I find the depth to the water table at an address? Geocode it, pass the latitude and longitude in assets, and read nearest_static_depth_to_water_feet together with nearest_static_reading_date. For design work read shallowest_depth_to_water_feet — the conservative value across the whole radius.

Why is the measurement so old? Because that is genuinely the newest USGS has for that location. Most of the national groundwater network is measured periodically, and a great many wells were last visited decades ago. The actor never hides this: data_currency_class and all_readings_stale are on every row, and Denver's nearest reading really is from 1962.

Is this a current water level? Only when data_currency_class is current (under a year). Otherwise it is a historical measurement — still the best available evidence, and still what a Phase I cites, but it must be reported with its date.

What is the seasonal high water table? Turn on includeHistory. history_min_depth_feet is the shallowest level ever recorded at that well and history_fluctuation_feet is the total observed range. A single latest reading cannot tell you this.

Why does a well show no depth? Check latest_reading_unusable_reason and latest_reading_qualifiers. The common causes are a dry well (water deeper than the hole — USGS publishes no value), a flowing artesian well (nothing to measure), a pumping measurement (drawdown, not the water table), or a level published as an elevation whose datum does not match the well's own land-surface datum.

What does a negative depth mean? Artesian conditions — the water level stands above land surface. -81.16 means 81 ft above ground. These are real USGS values and are never clamped or dropped.

What if there are no wells nearby? no_monitoring_locations_in_radius with a count of 0. That is a verified negative: USGS answered and has nothing there. It is a different value from source_unavailable, which means USGS did not answer and nothing on the row is a finding.

Do I need an API key? No. The USGS OGC API is keyless. But the anonymous quota is 1,000 requests per hour per IP address, and Apify runs from shared addresses, so a busy hour can return HTTP 429 through no fault of your run. A free key from api.waterdata.usgs.gov/signup moves you to a private quota — pass it in the optional apiKey field.

How many rows will a run produce? One per site, plus one per monitoring location when includeWellDetail is on (capped by maxWellsPerAsset). Every row is a billable result, so leave well detail off for large portfolio screens.

Which USGS parameters are used? Depth below land surface: 72019 (feet), 30210 and 99019 (metres, converted). Water level elevation, reported but never implicitly converted to depth: 62610 (NGVD29), 62611 (NAVD88), 62612, 62613, 72150 and 72389 (local mean sea level).

Source and coverage

• USGS Water Data OGC API, https://api.waterdata.usgs.gov/ogcapi/v0 — collections monitoring-locations, latest-field-measurements, field-measurements and parameter-codes. Public domain, no key required.
• The legacy waterservices.usgs.gov/nwis/gwlevels service was decommissioned on 2026-06-01. This actor is built on the OGC API only and deliberately does not fall back to it.
• Coverage is the USGS national network — every state and territory, but density varies enormously. Urban and agricultural basins are well covered; some rural areas have no monitored well within miles. The row always tells you which situation you are in.
• Data is public domain (USGS). Please credit the U.S. Geological Survey when you republish it.

Limitations, stated plainly

• These are measurements, not a model. The actor reports what USGS measured at specific wells on specific dates. It does not interpolate a water-table surface to your parcel, and it does not infer a flow direction.
• Well depth matters. A 320 ft bedrock well and a 31 ft alluvial well a mile apart will report very different water levels, and both are correct. Use well_constructed_depth_feet and national_aquifer_code to work out which one is relevant to your excavation.
• Positional accuracy varies. Some sites were located by GPS, others interpolated from a paper map to the nearest minute of arc. well_horizontal_accuracy is on every row.
• No result total exists upstream. This API publishes no numberMatched, so completeness can only be established structurally. When it cannot be proven, results_truncated is true and the statistics on that row cover a subset.
• This is a screening tool. It does not replace a site-specific hydrogeologic investigation, a monitoring well, or a licensed professional's judgment.

Pricing

Pay per result — one charge per row emitted, with graduated discounts on paid Apify plans. A run that cannot answer fails loudly and bills nothing.

Complete field reference

Every field the dataset can contain, exactly as declared in the dataset schema. All fields except record_type tolerate null, and null always means "this was not checked" rather than "the answer is no".

Field	Type	Description
record_type	string	asset_summary or well. One asset_summary row per screened site; one well row per monitoring location inside the radius when includeWellDetail is on.
asset_label	string	The label you supplied for this site, echoed on every row so results can be joined back to your portfolio.
asset_lat	number	The WGS84 latitude that was screened, after numeric validation.
asset_lon	number	The WGS84 longitude that was screened, after numeric validation.
search_radius_miles	number	The radius in statute miles actually used for this site. A bbox is used to fetch candidates and every candidate is then re-filtered by true haversine distance, so this is a real circle and not a square.
screening_result	string	One of: static_depth_available (a usable static water level was found), readings_present_no_static_depth (water-level records exist but none is an ambient static depth), no_water_level_data_in_radius (monitoring locations exist but none publishes a water level - a verified negative), no_monitoring_locations_in_radius (USGS answered and has no sites here - a verified negative), source_unavailable (USGS did not answer; nothing here is a negative finding).
monitoring_locations_in_radius	integer	Count of USGS monitoring locations of any site type whose true haversine distance is within the radius. null when the locations source did not answer.
groundwater_wells_in_radius	integer	Of those, how many carry a GW* site type (well, test hole, extensometer, hyporheic-zone well and so on).
locations_with_water_level_data	integer	How many of the locations in radius published at least one water-level record of any kind.
wells_with_static_depth_reading	integer	How many published a reading usable as an ambient static depth below land surface. This is the denominator behind every depth statistic on this row.
wells_with_elevation_only_reading	integer	How many published a water-level ELEVATION but no usable depth. Reported so a zero depth count is never mistaken for an absence of groundwater data.
wells_with_depth_derived_from_elevation	integer	Of those, how many allowed a depth to be derived because the site altitude datum matched the measurement datum exactly. Derived depths never feed the headline fields.
dry_wells_observed	integer	How many locations in radius have a reading qualified Dry. A dry well means water is deeper than the hole; USGS publishes no value for it and neither does this actor.
pumping_only_wells_observed	integer	How many have readings only from a pumping well. A pumping level is a drawdown level, not the ambient water table, and is never reported as depth to groundwater.
artesian_wells_observed	integer	How many have a negative static depth, meaning the water level stands above land surface. USGS publishes these as genuine negative values and they are preserved, not clamped.
static_readings_provisional_count	integer	How many of the static readings used carry approval_status other than Approved. Provisional data has not completed USGS review.
nearest_static_depth_to_water_feet	number	Depth to water in feet below land surface at the NEAREST location that has a usable static reading. This is the headline number. It is a measurement from a specific date, not a current condition - always read it together with nearest_static_reading_age_years.
nearest_static_reading_date	string	The date and time that nearest static reading was taken (ISO 8601, UTC).
nearest_static_reading_age_years	number	How many years old that reading is as of this run. USGS groundwater records are historical: readings decades old are common and are reported as such rather than presented as current.
nearest_static_reading_approval	string	Approved or Provisional for the nearest static reading.
nearest_static_well_id	string	USGS monitoring location identifier of that well.
nearest_static_well_name	string	USGS name of that well.
nearest_static_well_distance_feet	number	True haversine distance from your coordinate to that well, in feet.
nearest_static_well_bearing_compass	string	Compass bearing from your coordinate to that well, to 16 points.
nearest_static_well_depth_feet	number	Constructed depth of that well in feet, where USGS publishes it. Tells you which aquifer the reading represents.
nearest_static_well_aquifer_code	string	USGS national aquifer code for that well, where published.
shallowest_depth_to_water_feet	number	The shallowest static depth to water found anywhere in the radius. For excavation, basement and dewatering screening this is usually more conservative than the nearest well.
shallowest_depth_well_id	string	Monitoring location that produced the shallowest depth.
shallowest_depth_reading_date	string	Date of the shallowest reading (ISO 8601, UTC).
depth_to_water_min_feet	number	Minimum static depth to water across every usable reading in the radius.
depth_to_water_max_feet	number	Maximum static depth to water across every usable reading in the radius. A wide min-max spread usually means multiple aquifers, not measurement error - check the per-well rows.
depth_to_water_median_feet	number	Median static depth to water across the radius.
depth_readings_used	integer	How many static depth values the statistics above were computed from.
most_recent_reading_date_in_radius	string	The single most recent water-level reading of any kind anywhere in the radius (ISO 8601, UTC). The honest answer to "how current is groundwater data here".
most_recent_reading_age_years	number	Age in years of that most recent reading.
most_recent_reading_well_id	string	Monitoring location that produced it.
data_currency_class	string	current (under 1 year), recent (1-5), historical (5-20) or archival (20+), from the most recent reading in the radius. null when nothing was read.
max_age_years_for_current	number	The maxAgeYearsForCurrent threshold this run used.
readings_within_max_age_count	integer	How many locations in radius have a latest reading no older than that threshold.
all_readings_stale	boolean	true when every location in radius has a latest reading older than the threshold - the data exists but describes a past condition. null when no reading was obtained at all.
shallow_groundwater_threshold_feet	number	The shallowGroundwaterThresholdFeet this run used.
shallow_groundwater_flag	boolean	true when the shallowest static depth in radius is at or above the threshold. null when no usable static depth was found - a site with no data is never flagged as having deep groundwater.
artesian_conditions_present	boolean	true when at least one static level in radius stands above land surface. null when the data was not adequate to decide.
phase1_physical_setting_flag	boolean	true when shallow or artesian groundwater was measured, so ASTM E1527-21 section 8.2.2 physical setting warrants a closer look. GATED: null whenever depth_data_adequate_for_verdict is false. It never reads false because a source was unavailable.
depth_data_adequate_for_verdict	boolean	true only when both upstream reads succeeded AND at least one usable static depth was obtained. Every flag above is gated on this.
measurements_source_status	string	ok or unavailable for the latest-field-measurements read. unavailable means no finding on this row is a negative.
locations_source_status	string	ok or unavailable for the monitoring-locations read.
history_source_status	string	ok, partial, unavailable or not_applicable for the optional per-well history read. null when includeHistory was off.
measurements_source_error	string	Verbatim error from the measurements read when it failed.
locations_source_error	string	Verbatim error from the locations read when it failed.
query_complete	boolean	true only when the cursor walk was PROVEN to have reached the end. This API publishes no numberMatched, so there is no server total to check against; completeness is established structurally from three signals that must agree - the final page carried no next link, the final page was short, and the unique feature ids equal the sum of every numberReturned.
results_truncated	boolean	The inverse of query_complete. When true the counts and statistics on this row are computed over a SUBSET and must not be read as exhaustive.
paging_pages_fetched	integer	How many pages the cursor walk consumed.
paging_rows_returned	integer	Sum of numberReturned across all pages.
paging_unique_ids	integer	Count of distinct feature ids collected. A gap between this and paging_rows_returned means cursor overlap or a dropped page.
paging_exhaustion_proof	string	JSON of the three exhaustion signals: noNextLink, shortFinalPage, idsMatchReturned. Published so completeness can be audited rather than trusted.
paging_incomplete_reasons	string	Why completeness could not be proven, when it could not.
server_total_available	boolean	Always false, and published deliberately. The USGS OGC API returns no numberMatched, so no free exact total exists for any query against it.
error	string	Set when this site could not be screened at all, for example an invalid coordinate.
usgs_api_root	string	The exact API root this row came from. The path is versioned and will move.
usgs_api_version	string	The OGC API version segment in use.
collections_verified	integer	How many collections the API advertised when the run started. The four this actor depends on are verified by name before any row is emitted.
parameter_codes_queried	string	The USGS parameter codes queried: depth-below-land-surface codes plus water-level elevation codes.
drift_checks_ran	boolean	false only when skipDriftChecks was deliberately set; then nothing on the row is guaranteed to come from an undegraded source.
checked_at	string	When this run queried USGS (ISO 8601, UTC).
api_rate_limit_remaining	integer	USGS x-ratelimit-remaining after this site. MEASURED: USGS sends this header only on an HTTP 429 response, not on successful ones, so on a healthy run it is legitimately null - null means "not reported", never "zero requests left". It populates when a run is being throttled. The anonymous quota is 1,000 requests per hour PER IP and Apify runs from shared addresses, so supplying your own free apiKey moves you to a private quota.
api_key_supplied	boolean	Whether this run used your own USGS API key.
well_rank_by_distance	integer	Rank of this monitoring location among those in radius, 1 = nearest.
well_id	string	USGS monitoring location identifier.
well_agency_code	string	Agency that operates the site.
well_site_number	string	USGS site number without the agency prefix.
well_name	string	USGS site name. Often a survey-grid code rather than a plain-language name.
well_site_type_code	string	GW (well), GW-TH (test hole), GW-MW (multiple wells), GW-EX, GW-HZ, GW-CR, GW-IW, or a non-groundwater type. A 72019 reading at a non-GW site is reported rather than hidden.
well_site_type	string	Plain-language site type.
well_state	string	State the site is in.
well_county	string	County the site is in.
well_hydrologic_unit_code	string	USGS hydrologic unit code (HUC) of the watershed the site sits in.
well_lat	number	WGS84 latitude of the site as published by USGS.
well_lon	number	WGS84 longitude of the site as published by USGS.
well_distance_feet	number	True haversine distance from your coordinate, in feet.
well_distance_miles	number	The same distance in statute miles.
well_bearing_degrees	number	Bearing from your coordinate to the site, degrees clockwise from true north.
well_bearing_compass	string	The same bearing as a 16-point compass label.
well_horizontal_accuracy	string	How precisely USGS knows the site position. Sites interpolated from a map can be off by a minute of arc, which matters when the site is close to your parcel.
well_horizontal_method	string	How the position was determined.
well_constructed_depth_feet	number	Constructed depth of the well in feet - which aquifer the water level represents.
hole_constructed_depth_feet	number	Depth of the drilled hole in feet, where published.
well_construction_date	string	Construction date, where published.
land_surface_altitude_feet	number	Land-surface altitude at the site in feet. Subtract the depth to water to get the water-table elevation.
land_surface_altitude_datum	string	The vertical datum that altitude is referenced to, usually NAVD88 or NGVD29. The two differ by a location-specific offset and are never reconciled silently.
land_surface_altitude_accuracy_feet	number	Stated accuracy of the altitude.
land_surface_altitude_method	string	How the altitude was determined.
aquifer_code	string	Local aquifer code, where published.
national_aquifer_code	string	USGS national aquifer code, where published.
aquifer_type_code	string	Aquifer type code (confined, unconfined and so on), where published.
static_depth_to_water_feet	number	The most recent AMBIENT STATIC depth to water at this site, in feet below land surface. Only a reading qualified Static counts. A negative value is real and means the water level stands above land surface (artesian).
static_reading_date	string	Date and time of that static reading (ISO 8601, UTC).
static_reading_age_years	number	Age of that static reading in years at run time.
static_reading_approval_status	string	Approved or Provisional.
static_reading_is_provisional	boolean	true when the static reading has not completed USGS review.
static_reading_qualifiers	string	USGS condition qualifiers on that reading, joined with +.
static_reading_observing_procedure	string	How it was measured - steel tape, electric tape, pressure transducer and so on.
static_reading_parameter_code	string	USGS parameter code behind the static depth. 72019 is feet below land surface.
static_reading_unit	string	Unit as published by USGS for that reading.
latest_reading_date	string	Date of the most recent water-level record of ANY kind at this site, static or not (ISO 8601, UTC). It can be newer than static_reading_date when the latest visit found the well pumping, dry or flowing.
latest_reading_age_years	number	Age of that latest reading in years.
latest_reading_value_raw	string	The value exactly as USGS published it, as a string. Kept verbatim so nothing fetched is silently discarded. It is null on every Dry and Flowing record - a null here is not a zero.
latest_reading_unit	string	Unit of that raw value.
latest_reading_parameter_code	string	USGS parameter code of the latest reading.
latest_reading_basis	string	measured_depth_below_land_surface or water_level_elevation. An elevation is not a depth and is never treated as one.
latest_reading_qualifiers	string	Condition qualifiers on the latest reading, joined with +. Measured values include Static, Above+Pumping, NoMeasurement+Dry and NoMeasurement+Flowing.
latest_reading_is_static	boolean	true only for an ambient static level. false when a qualifier rules it out (pumping, dry, flowing, surface-water affected, foreign substance). null when the qualifier set was empty or unrecognised - an unknown qualifier is never assumed to be static.
latest_reading_approval_status	string	Approved or Provisional for the latest reading.
latest_reading_unusable_reason	string	Why the latest reading yielded no depth, when it did not - for example "no value published (qualifier NoMeasurement+Dry)".
latest_reading_elevation_datum	string	For an elevation reading, the datum it is referenced to: NAVD88, NGVD29 or LMSL.
depth_derived_from_elevation_feet	number	Depth derived as land-surface altitude minus water-level elevation, and ONLY when the site altitude datum matches the measurement datum exactly. Never feeds the headline depth fields.
depth_derivation_datum	string	The datum both values shared when a derivation was possible.
depth_derivation_blocked_reason	string	Why a depth could not be derived from an elevation reading - most often a NGVD29 versus NAVD88 datum mismatch, whose offset is location-specific and is never assumed.
dry_observed	boolean	true when any reading at this site is qualified Dry - the tape reached the bottom without finding water, so the water table is DEEPER than the hole. USGS publishes no value for it. null when there were no readings at all.
flowing_artesian_observed	boolean	true when any reading is qualified Flowing - the well was discharging at surface, so no depth could be measured.
pumping_observed	boolean	true when any reading was taken while the well was pumping. Such a level is drawn down and is excluded from every depth statistic.
artesian_static_level	boolean	true when the static depth is negative, meaning the water level stands above land surface.
unknown_qualifier_seen	boolean	true when USGS returned a condition qualifier outside the verified closed vocabulary this actor ships. Such a reading is never classified as static.
measurement_series_rows_seen	integer	How many rows the latest-field-measurements collection returned for this site. It returns one row per measurement SERIES, and a site can have several.
superseded_series_rows_seen	integer	How many of those rows were older than the one used. The collection is NOT ordered, so the newest is selected by comparing timestamps rather than by taking the first row.
history_fetched	boolean	Whether a full reading history was retrieved for this site (includeHistory, nearest historyWellCount sites only).
history_readings_fetched	integer	How many historical records were retrieved.
history_static_depth_readings	integer	How many of them were usable static depths.
history_min_depth_feet	number	Shallowest static depth in the retrieved history - the seasonal high water table.
history_max_depth_feet	number	Deepest static depth in the retrieved history.
history_median_depth_feet	number	Median static depth across the retrieved history.
history_fluctuation_feet	number	max minus min - the observed range of water-table movement, which is what dewatering and basement design actually need.
history_earliest_reading	string	Earliest record in the retrieved history (ISO 8601, UTC).
history_latest_reading	string	Latest record in the retrieved history (ISO 8601, UTC).
history_truncated	boolean	true when more history exists than was retrieved. The history query is sorted, and this API cannot page a sorted query, so it is deliberately a single page and says so.
history_source_error	string	Verbatim error when the history read failed for this site.