1

Hydrologic Cycle

Pat Ellsworth, ITEP

&

Robert K. HallUSEPA Region IX

hall.robertk@epa.gov

2

Hydrologic Cycle “Hydrologic cycle”—circulation and conservation of

earth's water

Begins with evaporation of water from earth (20%) and ocean (80%) surface

As moist air rises, it cools, and water vapor condenses to form clouds

Moisture is transported around globe via oceanic gyres (N and S hemispheres) until it returns to surface as precipitation

3

Once water reaches the groundEvaporates back into atmosphereRuns off into streams and lakes,

eventually back to oceanPenetrates surface, becomes groundwater

Groundwater willSeep into lakes, rivers, streamsReturn to atmosphere through

transpiration

Hydrologic Cycle (cont.)

4

Earth’s Water Budget

Diagram adapted from: Peixoto and Kettani (1973). http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/home.rxml

(97.5%)

(2.4%)

(0.001%)

5

Evaporation 80%

Eva

pora

tion

20%

(inla

nd w

ater

and

veg

etat

ion)

Adapted from The Hydrologic Cycle. Illustration by Tom Schultz

Condensation

Condensation

Convection

Transport

(rain, hail, sleet, snow, freezing rain)

Zone of AerationZone of Saturation

Surface Layer

Ground water flow

Eva

pora

tion

10%

6

Hyporheic ZoneRegion beneath and lateral/adjacent to stream

bed

Mixing of shallow groundwater and surface water

Hyporheic flow is important for Surface water/groundwater interactions Fish spawning Benthic macroinvertebrate distribution and community

structure

7

Hyporheic Zone (cont.)

Adapted from National park Service (http://www.nps.gov/archive/sitk/Natural%20Resources/Stream%20Ecology/Stream/hyporheic.htm)

HyporheicFlow

RHEIC Z

ONE

8

Ecological FunctionNatural riparian-wetland areas characterized by

interactions of vegetation, soils, hydrology

Riparian-wetland areas function properly with adequate vegetation, landform, or large woody debris Dissipates stream energy associated with high waterflows

Reduces erosion, improves water quality….

Changes in ecological function result from alterations (e.g., fire, invasive species, anthropogenic activity)

9

Ecological Function (cont.)

Human influences accelerate changes in ecosystem character

Over time, ecosystems develop spatial patterns characteristic of human disturbance and alterations

Necessary to recognize Different geographic patterns and How they respond to alterations and

resource-management activities

10

Illustration by Tom Schultz www.buffer.forestry.iastate.edu/Photogallery/...

11

Riparian Function

Functional Nonfunctional

Functional at Risk

12

Impacts: Watershed Morphology and Invasive Species Classification:

Humboldt River, NV

Area shown is part of the Special Recreation Management Area Near Elko, NVSource: BLM Nevada State Office and BAE Systems Advanced Technologies Inc.

13

ConclusionHydrologic Cycle

Impacts to the Hydrologic Cycle

PreservationTribal-oriented Best Management Practices

(BMPs) to achieve ecological function