Introduction Flashcards
Give some examples of why knowledge of hydrology is useful
Design and operation of water resources, wastewater treatment, irrigation, flood risk, navigation, pollution control etc
What does the water cycle describe?
Continuous movement of water on, above, and below earth surface.
What drives the water cycle?
The Sun
Describe the key processes of the hydrological cycle
Sun drives the water cycle.
Water evaporates as vapor into the air.
Rising currents take the vapor up into the atmosphere where cooler temperatures cause it to condense into clouds.
Air currents move clouds around the globe, where they collide, grow, and fall out the sky as precipitation.
Precipitation can fall as snow and accumulate on ice caps for thousands of years.
Precipitation falls back into the oceans or onto land where the rain flows as surface runoff or soaks into the ground as infiltration.
Runoff and groundwater can be stored in freshwater lakes whereas infiltration can replenish aquifers which store large amounts of freshwater underground.
Over time all the rain flows returns into the ocean and the cycle is repeated.
What ways can water evaporate into vapor?
Ice and snow sublimates directly into water vapor.
Sun evaporates water from water bodies.
Evapotranspiration is water transpired from plants and evaporated from soil.
Describe where precipitation can fall and where it moves.
Falls into oceans or onto land.
If falls as snow will accumulate on ice caps and glaciers for thousands of years.
If falls on land will flow over ground as surface runoff into rivers which head towards the ocean eventually.
Lots of runoff soaks into ground as infiltration with some infiltrating deep into ground to replenish aquifers. Some groundwater that remains close to surface can seep into surface water bodies as groundwater discharge or as freshwater springs.
Water returns to oceans over time
What is precipitation?
Condensed water vapor that falls to the earth surface.
What is runoff?
The way water moves across land.
What can happen to runoff as it flows?
Infiltrate into the ground, evaporate into the air, become stored in lakes or reservoirs, be extracted for agricultural or other human uses.
What is infiltration?
Flow of water from ground surface into the ground.
What happens once water become infiltrated?
Water becomes soil moisture or groundwater.
What is subsurface flow?
Flow of water underground in the vadose zone and aquifers.
What is the vadose zone?
Water from infiltration that is above the water zone.
What is an aquifer?
Water below ground that is a zone of saturation and can be used as a water supply.
How can subsurface water return to the surface?
As a spring or from being pumped or eventually seeping into oceans.
What is evaporation?
Transformation of water from liquid to gas.
What is evapotranspiration?
Transpiration from plants combined with evaporation from solar energy.
What are common units of:
1. Flow rate or discharge
2. Precipitations
3. Volumes
4. Rainfall
- m3/s
- mm
- m3 or l
- cm/hour
What is residence time?
Average duration for a water molecule to pass through a water body.
What is equation for residence time?
t = V / Q
Why is residence time useful?
Can help define water quality.
What is an important point to note about the water cycle?
The total amount of water available to the earth is finite and conserved. Although global hydrological cycle remains constant the distribution varies across the world.
How can water storage be expressed?
Q1-Q2 = dS/dt
I-O = change S
V1-V0 = change S
What is a catchment?
An extent of land where water from rain or snow melt drains downhill into a body of water.
