Unit 10 - Water

Part I: Part I: Water Supply, Water Supply, Use and ManagementUse and Management

An Arizona Watershed

So what is a watershed?So what is a watershed?

Watershed (review)• An area of land that drains into a lake or a river.An area of land that drains into a lake or a river.• ItIt is a basin-like landform defined by highpoints and is a basin-like landform defined by highpoints and

ridgelines that descend into lower elevations and stream ridgelines that descend into lower elevations and stream valleys. valleys.

• A watershed carries water "shed" from the land after rain A watershed carries water "shed" from the land after rain falls and snow melts. Drop by drop, water is channeled into falls and snow melts. Drop by drop, water is channeled into soils, groundwaters, creeks, and streams, making its way to soils, groundwaters, creeks, and streams, making its way to larger rivers and eventually the sea. larger rivers and eventually the sea.

• Remember: Remember: Water is a universal solvent, affected by all that Water is a universal solvent, affected by all that it comes in contact with: the land it traverses, and the soils it comes in contact with: the land it traverses, and the soils through which it travels. through which it travels.

• The The most most important thing about watersheds is: important thing about watersheds is: what we do on the land affects water quality what we do on the land affects water quality for all communities living downstream. for all communities living downstream.

http://techalive.mtu.edu/meec/module01/whatiswatershed.htm http://watershedmg.org/content/view/20/33/

The Hydrologic Cycle

On a separate sheet of paper please On a separate sheet of paper please draw out the steps of the hydrologic draw out the steps of the hydrologic cycle.cycle.

The Hydrologic Cycle

Water Locations

• Where is water located?Where is water located?– Oceans: 97%Oceans: 97%– Ice caps & glaciers: 2%Ice caps & glaciers: 2%

• 99% of our water is NOT useable!99% of our water is NOT useable!

– We are all competing for 1%We are all competing for 1%

– Atmosphere: .001% (residence time 9 days)Atmosphere: .001% (residence time 9 days)• This small amount is responsible for producing all This small amount is responsible for producing all

of our freshwater resources through precipitation.of our freshwater resources through precipitation.

Groundwater and StreamsGroundwaterGroundwater

– Water found below the Earth’s surface, within the zone of Water found below the Earth’s surface, within the zone of saturation, below the water tablesaturation, below the water table

– Define the following (page 436) in your own words: wDefine the following (page 436) in your own words: water ater table, recharge zones, discharge zones, table, recharge zones, discharge zones, vadose zone, vadose zone, aquifer, cone of depressionaquifer, cone of depression

Two Types of Streams:Two Types of Streams:1.1. Effluent StreamEffluent Stream

– A type of stream where flow is maintained during the dry A type of stream where flow is maintained during the dry season by groundwater seepage into the channelseason by groundwater seepage into the channel..

– A stream the flows all year round is______________.A stream the flows all year round is______________.

2.2. Influent StreamInfluent Stream– A type of stream that is everywhere above the groundwater A type of stream that is everywhere above the groundwater

table and flows in direct response to precipitationtable and flows in direct response to precipitation– A stream the does not flow all year round______________.A stream the does not flow all year round______________.

Interaction between Surface Water and Groundwater

• If the groundwater is lowered what effects If the groundwater is lowered what effects might that have on effluent streams?might that have on effluent streams?

• What might cause reduction in What might cause reduction in groundwater?groundwater?

Water Supply: A U.S. Example

• Water budget Water budget – a model that balances the inputs, outputs and storage of a model that balances the inputs, outputs and storage of

water in a system.water in a system.

– Defines the natural variability and availability of waterDefines the natural variability and availability of water

• Over 99% of the Earth’s water is unavailable or Over 99% of the Earth’s water is unavailable or unsuitable for beneficial human useunsuitable for beneficial human use

• It is expected that the total water withdrawn from It is expected that the total water withdrawn from streams and groundwater in the U.S will decrease streams and groundwater in the U.S will decrease but the consumptive use will increasebut the consumptive use will increase

Water Use

• Off-stream use: Off-stream use: – water removed from it’s source for usewater removed from it’s source for use

• In-stream use: In-stream use: – the use of rivers for navigation, hydroelectric the use of rivers for navigation, hydroelectric

power generation, fish and wildlife habitats and power generation, fish and wildlife habitats and recreationrecreation

Water Conservation

- the careful use and protection of water the careful use and protection of water resourcesresources

- Agricultural UseAgricultural Use

- Domestic UseDomestic Use

- Industry and Manufacturing UseIndustry and Manufacturing Use

- Perception and Water UsePerception and Water Use

Possible Future Improvements

Sustainable Water Use

• The use of water resources by people in a The use of water resources by people in a way that allows society to develop and way that allows society to develop and flourish into an indefinite future without flourish into an indefinite future without degrading the various components of the degrading the various components of the hydrologic cycle or the ecological systems hydrologic cycle or the ecological systems that depend on itthat depend on it

Wetlands• Areas that are inundated by water or where Areas that are inundated by water or where

the land is saturated to a depth of a few the land is saturated to a depth of a few centimeters for at least a few days per yearcentimeters for at least a few days per year

• Wetlands serve a variety of functions that Wetlands serve a variety of functions that benefit ecosystems and peoplebenefit ecosystems and people

Channelization and the Environment

• Channelization: Channelization: – An engineering technique that consists of An engineering technique that consists of

straightening, deepening, widening, clearing, or straightening, deepening, widening, clearing, or lining existing stream channelslining existing stream channels

– Purpose:Purpose:• Control floods, improve drainage, etc.Control floods, improve drainage, etc.

Channelization Summary• Humans often decide that a stream should flow Humans often decide that a stream should flow

along a specified path for such reasons as flood along a specified path for such reasons as flood control, enhancement of drainage, control of control, enhancement of drainage, control of erosion, increasing access to the floodplain for erosion, increasing access to the floodplain for development, or improvement of the development, or improvement of the appearance of the channel. Such channel appearance of the channel. Such channel modifications involve measures such as the modifications involve measures such as the straightening the channel, deepening or straightening the channel, deepening or widening the channel, clearing vegetation from widening the channel, clearing vegetation from the banks, or lining the channel with concrete. the banks, or lining the channel with concrete. These modifications are referred to as These modifications are referred to as channelization. channelization.

Benefits of Channelization

• In order to control floods, channel modification In order to control floods, channel modification should involve increasing the channel cross-should involve increasing the channel cross-sectional area, so that higher discharge will not sectional area, so that higher discharge will not increase the stage of the river.  Straighter channels increase the stage of the river.  Straighter channels also allow higher velocity flow and, enable the also allow higher velocity flow and, enable the stream to drain faster when discharge increases.  stream to drain faster when discharge increases.  Lining the channel with concrete provides a Lining the channel with concrete provides a smoother surface over which the water can flow, smoother surface over which the water can flow, thereby reducing friction and also increasing the thereby reducing friction and also increasing the velocity of the stream. They also allow development velocity of the stream. They also allow development of floodplains.  of floodplains. 

Problems with Channelization• While channelization for flood control may reduce the While channelization for flood control may reduce the

incidence of flooding in the channelized area, it often results in incidence of flooding in the channelized area, it often results in more severe flooding both upstream and downstream from the more severe flooding both upstream and downstream from the channelized area.  channelized area. 

• Channelization can also interfere with the natural habitat of the Channelization can also interfere with the natural habitat of the stream system and decrease the aesthetic value of the stream. stream system and decrease the aesthetic value of the stream.

• Channelized steams often have poor in-stream habitat for Channelized steams often have poor in-stream habitat for aquatic organisms, they can be a barrier to fish migrations and aquatic organisms, they can be a barrier to fish migrations and in areas where the riparian buffer has been removed, the water in areas where the riparian buffer has been removed, the water in the stream can be heated by the sun during the day reducing in the stream can be heated by the sun during the day reducing its oxygen holding capacity and raising water temperatures its oxygen holding capacity and raising water temperatures above the tolerance limits of some fish species. In addition, above the tolerance limits of some fish species. In addition, while channelization may be able to reduce flooding in one while channelization may be able to reduce flooding in one specific stream reach, often it increases flooding downstream. specific stream reach, often it increases flooding downstream.

Flooding

• The most universal natural hazard in the The most universal natural hazard in the worldworld

• The frequency and severity are increased by The frequency and severity are increased by urbanizationurbanization

• Avoid building on floodplainsAvoid building on floodplains

Desalination as a Water Source• Desalination: a technology to remove salt from waterDesalination: a technology to remove salt from water• Increased costIncreased cost• Yuma desalinization plantYuma desalinization plant

– A desalinization plant, one of the largest in the world, built to take salt out A desalinization plant, one of the largest in the world, built to take salt out of the Colorado River before it trickles into Mexico. The plant, constructed of the Colorado River before it trickles into Mexico. The plant, constructed by the Federal government for $256 million, was promised to Mexico by the Federal government for $256 million, was promised to Mexico because the river is so salty by the time it crosses the border that Mexican because the river is so salty by the time it crosses the border that Mexican farmers find it dangerous to use on their crops. This was due to salt farmers find it dangerous to use on their crops. This was due to salt contamination from throughout the lower Colorado region desert contamination from throughout the lower Colorado region desert agriculture, but primarily from the intensive agriculture in the arid Welton agriculture, but primarily from the intensive agriculture in the arid Welton Mohawk district, east of Yuma, which flushes the salt--the residue from Mohawk district, east of Yuma, which flushes the salt--the residue from evaporation--out of its fields, directly into the Colorado.evaporation--out of its fields, directly into the Colorado.

– TThe plant, conceived of in the late 1970's, and finished in 1992, operated for he plant, conceived of in the late 1970's, and finished in 1992, operated for only eight months, before laying idle again, due to a number of factors, only eight months, before laying idle again, due to a number of factors, including flood damage on some of the region's drainage ditches, wet including flood damage on some of the region's drainage ditches, wet weather naturally diluting the salty water, and the $30 million annual weather naturally diluting the salty water, and the $30 million annual expense of operating the plant. expense of operating the plant.