What are environmental flows?

Environmental flows are the quantity, timing, and variability of water flow required to sustain freshwater ecosystems and the services they provide; managing them seeks to retain enough of the natural flow regime below dams and diversions to maintain river health.

How does vegetation affect hydrology?

Plants draw water from the soil and transpire it, influencing soil moisture, evapotranspiration, and the partitioning of rainfall; vegetation also affects infiltration and runoff, so changes in vegetation can substantially alter a catchment's water balance.

Ecohydrology

Ecohydrology studies the two-way interactions between water and ecosystems, from how soil moisture controls vegetation to how flow regimes structure rivers and wetlands.

Definition

Ecohydrology is the interdisciplinary study of the interactions between the hydrological cycle and ecosystems, examining how water availability and movement shape vegetation and aquatic life and how organisms in turn influence hydrological fluxes.

Scope

This topic covers the coupling of hydrological processes with vegetation and aquatic ecosystems, including soil-moisture dynamics in water-limited systems, vegetation feedbacks on the water balance, and environmental flows for river ecosystems. It is the ecological interface of hydrology, drawing on the water cycle, runoff, and flow-regime topics.

Core questions

How does soil moisture control vegetation in water-limited environments?
How does vegetation feed back on evapotranspiration and the water balance?
How do flow regimes structure river and wetland ecosystems?
What flows are needed to sustain freshwater ecosystems?

Key concepts

Soil-moisture dynamics
Plant water stress and water-use
Vegetation feedbacks on water balance
Riparian and wetland hydrology
Environmental (ecological) flows
Climate-soil-vegetation coupling

Key theories

Climate-soil-vegetation dynamics: Ecohydrology frames the coupled dynamics of climate, soil moisture, and vegetation, with stochastic rainfall driving soil-moisture fluctuations that control plant water stress and structure ecosystems in water-limited regions.
Environmental flows and the natural flow regime: The natural variability of river flows, in magnitude, timing, frequency, and duration, structures aquatic ecosystems, so maintaining environmental flows is central to ecohydrological management.

Clinical relevance

Ecohydrology informs the management of environmental flows below dams and diversions, the restoration of rivers and wetlands, the prediction of vegetation responses to drought and climate change, and the design of nature-based and water-sensitive approaches that account for the linkage of water and ecosystems.

History

Eagleson's work on ecological optimality in the 1980s and Rodriguez-Iturbe's framing of climate-soil-vegetation dynamics around 2000 established ecohydrology as a field; in parallel, the natural-flow-regime paradigm and environmental-flow science linked river ecology to hydrology, and the discipline has grown rapidly since.

Key figures

Ignacio Rodriguez-Iturbe
Peter S. Eagleson
N. LeRoy Poff

Seminal works

rodriguez2000
eagleson1982
poff1997

Frequently asked questions

What are environmental flows?: Environmental flows are the quantity, timing, and variability of water flow required to sustain freshwater ecosystems and the services they provide; managing them seeks to retain enough of the natural flow regime below dams and diversions to maintain river health.
How does vegetation affect hydrology?: Plants draw water from the soil and transpire it, influencing soil moisture, evapotranspiration, and the partitioning of rainfall; vegetation also affects infiltration and runoff, so changes in vegetation can substantially alter a catchment's water balance.