Video 3 C3: The connection between rivers/streams and groundwater Flashcards
(21 cards)
____ supply the majority of our water supply
rivers
how do rivers continue to flow when it isn’t raining?
groundwater
the land that a river drains is called…
the catchment
What is runoff, and what factors affect how much rainfall becomes runoff?
Runoff is the rainwater that flows downhill. The amount of runoff depends on:
- how much rain falls
- the time of year it happens
- the type of land on which it falls
runoff will be greater on ____ soil
bare
the percentage of the rock that is made up of spaces is known as…
porosity
water that has passed through the soil will continue to move down through the underlying rock, until it reaches a level where all the pore spaces are full. This level is called…
the water table level
the water moving in the rock below the water table is called…
groundwater
layers of rock that are permeable and allow a significant amount of water to flow through them are called…
aquifers
what are the two most important aquifers?
chalk and sandstone
When does rainwater usually reach and raise the water table?
It typically comes from winter rains, so the water table doesn’t rise until later in winter or even early spring.
When does the water table tend to be the highest/lowest (time of year)
Highest = spring (think of renforth wharf)
Lowest = summer or early fall
the shape of the water table follows that of…
the ground surface
Groundwater flows from areas where the water table is ____, to areas where its ____
high; low
what happens when the water table meets the ground surface?
The ground gets saturated and water appears at the surface, like in springs or seeping directly into rivers.
the time the groundwater takes to travel to the river depends on…
- how permeable the rock is
- if it follows a shallow or deep path
what does most rivers start as, and where?
a small boggy seep or springs high up in the catchment/watershed
what is a catchment?
another word for watershed; A catchment is the area of land where all the water collects and drains into the same point, like a river, lake, or reservoir
why is the groundwater of springs so pure/clear?
because of the filtering from its long travel time through the rock
why do streams dry up?
- Streams dry up when the water table drops below the level of the streambed, which often happens in summer. Since the soil and air are drier in summer, most rainfall evaporates or is absorbed by plants before it can reach the water table and feed the stream.
- also from man’s exploitation
rivers are threatened by…
- low flows
- straightening
- canalization
- urbanization
- industrialization
- agriculture (growing crops too close to rivers or allowing animals to damage the beds)
