---
source: https://iinventedlight.com/library/notes/evapotranspiration.md
title: "Evapotranspiration"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "US government work, public domain; restated in our own words"
attribution: "Summary by iinventedlight (AI-assisted). Sources: USGS, Evapotranspiration and the Water Cycle, US government work, public domain; USGS, Evaporation and the Water Cycle, US government work, public domain."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-04
as_of: 2026-11-04
confidence: medium
untested: "No observation or experiment was done; only the fetched government pages were read."
category: coverage-gaps
topic_area: "water: water cycle"
tags: ['water', 'water-cycle', 'evaporation', 'plants']
sources:
  - id: S1
    title: "Evapotranspiration and the Water Cycle"
    publisher: USGS
    url: https://www.usgs.gov/special-topics/water-science-school/science/evapotranspiration-and-water-cycle
    accessed: 2026-11-04
    license: "US government work, public domain"
  - id: S2
    title: "Evaporation and the Water Cycle"
    publisher: USGS
    url: https://www.usgs.gov/special-topics/water-science-school/science/evaporation-and-water-cycle
    accessed: 2026-11-04
    license: "US government work, public domain"
---
# Evapotranspiration

**Answer:** Evapotranspiration (ET) is the total of all processes that move water from land to the atmosphere: evaporation from soil, water bodies and wet surfaces, plus transpiration, water released by plants through their leaves.

## Evaporation

Evaporation turns liquid water into water vapor using heat energy. It is the main way water leaves the surface for the atmosphere, especially from the oceans.

## Transpiration

Plants draw water from the soil through roots and release vapor through small pores in their leaves. Because it is hard to separate from evaporation in the field, scientists usually measure the two together as ET.

## What ET includes

- Evaporation from the soil surface.
- Evaporation from the capillary fringe above the water table.
- Evaporation from lakes, rivers and other water bodies.
- Transpiration from plants.

## Why it matters

ET drives how much water farms and landscapes need, and it is a major part of each region's water budget.

## Claims
- id: C1
  claim: Evapotranspiration moves water from land to atmosphere via evaporation and transpiration.
  source: S1
  evidence: "by which water moves from the land surface to the atmosphere via evaporation and transpiration"
- id: C2
  claim: ET includes evaporation from the capillary fringe of the groundwater table.
  source: S1
  evidence: "evaporation from the capillary fringe of the groundwater table"
- id: C3
  claim: Evaporation changes liquid water to gaseous water.
  source: S2
  evidence: "Evaporation is the process that changes liquid water to gaseous water (water vapor)."
- id: C4
  claim: Water moves from Earth's surface to the atmosphere via evaporation.
  source: S2
  evidence: "Water moves from the Earth’s surface to the atmosphere via evaporation."

## Sources
- [S1] Evapotranspiration and the Water Cycle. USGS. https://www.usgs.gov/special-topics/water-science-school/science/evapotranspiration-and-water-cycle . License: US government work, public domain. Accessed 2026-11-04.
- [S2] Evaporation and the Water Cycle. USGS. https://www.usgs.gov/special-topics/water-science-school/science/evaporation-and-water-cycle . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).