Evapotranspiration (ET0/ETc)

Agriculture Math & Calculations Weather Credits / request: 3

Reference evapotranspiration ET0 (FAO-56) over a date range, plus crop water use ETc when crop/Kc is given. Decision support.

GET https://api.apikodu.com/api/v1/agriculture/evapotranspiration

Documentation

Overview

Reference evapotranspiration ET0 (FAO-56) over a date range. When crop or kc is given, crop water use ETc = ET0 × Kc is also returned. Decision support. Weather data © Copernicus ERA5 / ERA5-Land (contains modified Copernicus Climate Change Service information) / Open-Meteo / OpenWeather / MET Norway.

Authentication

Every request requires the x-api-key header. Credits used and remaining quota are returned in response headers (x-api-credits-used, x-api-remaining-credits, x-rate-limit-*).

Request

GET https://api.apikodu.com/api/v1/agriculture/evapotranspiration?latitude=39.92&longitude=32.87&fromDate=2026-07-01&toDate=2026-07-31&crop=maize

GET query.

Parameters

Name	Type	Required	Default	Options	Description
`latitude`	number	* Required	—	—	Point latitude -90..90. 0.1° cell.
`longitude`	number	* Required	—	—	Point longitude.
`fromDate`	string	* Required	`2026-07-01`	—	Start YYYY-MM-DD. Range ≤ 366 days.
`toDate`	string	* Required	`2026-07-31`	—	End YYYY-MM-DD.
`crop`	string	Optional	`maize`	`wheat` `barley` `maize` `sunflower` `cotton` `potato` `tomato` `rapeseed` `oats` `rye` `sugarbeet` `grape` `apple` `chickpea` `lentil`	Crop code. Kc is looked up from this (with stage) when kc is absent.
`kc`	number	Optional	—	—	Kc coefficient 0–2. Overrides crop/stage when given.
`stage`	string	Optional	`mid`	`initial` `mid` `late`	initial, mid or late. Default mid. Used with crop to pick Kc.

Response

Name	Type	Description
`et0Mm`	number	Total ET0 over the range, mm.
`et0MmPerDay`	number	Mean daily ET0 mm.
`kc`	number	Kc used. null when not found.
`stage`	string	Stage the Kc was taken from (when kc was not passed).
`etcMm`	number	Total ETc = ET0 × Kc mm. null without Kc.
`etcMmPerDay`	number	Mean daily ETc mm.
`crop`	string	Normalized crop code.
`fromDate`	string	Window start.
`toDate`	string	Window end.
`daysTotal`	integer	Calendar days in the window.
`daysWithData`	integer	Days ET0 was computed for.
`missingCount`	integer	Days without data.
`missingDates`	array	YYYY-MM-DD list of missing days (first 10).
`degradedCount`	integer	Days ET0 could not be computed because Tmax was missing.
`degradedDates`	array	YYYY-MM-DD list of degraded days (first 10).
`gridLatitude`	number	0.1° cell latitude.
`gridLongitude`	number	0.1° cell longitude.
`daily`	array	Daily ET0/ETc rows.
`daily[].date`	string	Day YYYY-MM-DD.
`daily[].et0Mm`	number	ET0 for that day, mm.
`daily[].etcMm`	number	ETc for that day, mm. null without Kc.
`method`	string	Calculation method: fao56-et0.
`source`	string	database: tarim_hava cell.
`disclaimer`	string	Decision-support disclaimer.

Errors

HTTP	code	Description
`400`	`-254`	fromDate/toDate missing, not YYYY-MM-DD, or range exceeds 366 days.
`400`	`-255`	latitude/longitude missing or out of range.
`400`	`-249`	kc outside 0–2 or stage invalid.
`400`	`-250`	Unknown crop.
`429`	`-316`	Daily new location (cell) limit (50) reached. Previously requested locations keep working; new locations next day (UTC). Retry-After header gives seconds until end of day.
`503`	`-256`	Cell created; Worker is filling history. Retry in a few minutes.
`400`	`-251`	No weather for this location/date.
`401`	`-100`	x-api-key is missing, empty, malformed, inactive, banned, expired, IP-restricted, or not allowed for this API.
`429`	`-221`	Per-minute request limit exceeded. Response headers: x-rate-limit-limit, x-rate-limit-remaining, x-rate-limit-reset.
`429`	—	Package credit quota cannot cover this request. Body may be { error, limit, currentUsage, requestCost } (no code field).
`500`	`-1`	Unexpected server error. message is a generic error text without technical details.

Notes

Success body is { data: { ... } }. Error body is { code, message }. code is an ApiResponseCode enum value (negative integer).

Sample response

{
  "data": {
    "et0Mm": 168.4,
    "et0MmPerDay": 5.61,
    "kc": 1.15,
    "stage": "mid",
    "etcMm": 193.66,
    "etcMmPerDay": 6.46,
    "crop": "maize",
    "fromDate": "2026-07-01",
    "toDate": "2026-07-30",
    "daysTotal": 30,
    "daysWithData": 30,
    "missingCount": 0,
    "missingDates": [],
    "degradedCount": 0,
    "degradedDates": [],
    "gridLatitude": 39.90,
    "gridLongitude": 32.90,
    "daily": [
      {
        "date": "2026-07-01",
        "et0Mm": 5.20,
        "etcMm": 5.98
      },
      {
        "date": "2026-07-02",
        "et0Mm": 6.63,
        "etcMm": 7.62
      }
    ],
    "method": "fao56-et0",
    "source": "database",
    "disclaimer": "Decision support only. Not agronomic advice. Weather data: Copernicus ERA5 / ERA5-Land, Open-Meteo, OpenWeather, MET Norway. Contains modified Copernicus Climate Change Service information."
  }
}

Code samples

  
      const response = await fetch('https://api.apikodu.com/api/v1/agriculture/evapotranspiration', {
        method: 'GET',
        headers: {
          'x-api-key': 'YOUR_API_KEY'
        }
      });

      const data = await response.json();
      console.log(data);

  
      import requests

      headers = {
          'x-api-key': 'YOUR_API_KEY'
      }

      response = requests.get('https://api.apikodu.com/api/v1/agriculture/evapotranspiration', headers=headers)
      print(response.json())

  
      using var client = new HttpClient();
      client.DefaultRequestHeaders.Add("x-api-key", "YOUR_API_KEY");

      var response = await client.GetStringAsync("https://api.apikodu.com/api/v1/agriculture/evapotranspiration");
      Console.WriteLine(response);

  
      $response = file_get_contents('https://api.apikodu.com/api/v1/agriculture/evapotranspiration', false, stream_context_create([
          'http' => [
              'header' => "x-api-key: YOUR_API_KEY"
          ]
      ]));

      print_r(json_decode($response, true));

  
      curl -X GET 'https://api.apikodu.com/api/v1/agriculture/evapotranspiration' \
        -H 'x-api-key: YOUR_API_KEY'

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