Transcript California Water Issues AGST 3000 Agriculture, Society and the Natural World www.water-ed.org/cabriefing.asp www.dwr.water.ca.gov/ Look at the those websites and… From the first site, read…”A Briefing on.

California Water Issues
AGST 3000
Agriculture, Society and the Natural
World
www.water-ed.org/cabriefing.asp
www.dwr.water.ca.gov/
Look at the those websites and…
From the first site, read…”A Briefing on California Water Issues”
Search the second sight and provide details on the Central Valley
Project:
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Who is the Central Valley Project operated by?
How many reservoirs are part of the CVP and how many acre feet
do they hold and are delivered in an average year?
In contrast, How many reservoirs are part of the State
Water Project and how many acre feet do they hold and are
delivered in an average year?
How many farmed acres does the CVP irrigate?
How many people does the CVP provide drinking water for?
In contrast, what percentage does the SWP deliver to urban vs.
agriculture?
Water Terminology
Acre-feet
An acre-foot equals the amount of water needed
to cover an acre of land to the depth of one foot
(326,000) and is approximately the amount of
water used by an average family of four during
two year period.
Overdraft
The deficit between pumped water from a
groundwater basin and the long-term recharge.
California’s Tug of Water
Geologic Tugs
Geologic Tug #1: The North 75%– 25% South
precipitation distribution circumstance
Geologic Tug #2: The Coast Range and Sierra
Nevada Mountains rain shadow effects
Geologic Tug #3: The Drought/Flood cycles
Geologic Tug #4: Calif. is the number 1 ground
water using state, but has little regulation
California’s Tug of Water
Water Use Tugs
Water Use Tug #1: 80% of water demand occurs south of
Sacramento North versus South
Water Use Tug #2: There is also an East versus West use
conflict
Water Use Tug #3: Water demand is highest in the
summer when availability is lowest
Water Use Tug #4: Environmentalists idea on water use
versus water developers ideas
Water Use Tug #5: Agriculture versus Urban use: who
gets how much and when, etc.?
Water Use Tug #6: What are the water rights for various
interest groups in the future?
Figure 1. Freshwater Consumption as a Percentage of Local
Average Annual Precipitation. (Source: USDA-NRCS, 2001)
California’s Water Supply
California’s ground water
California’s groundwater basins store about 850 million
acre-feet of water. (Less than 50% is unavailable for use
due to depth of water table.)
 Groundwater cannot be removed that will not be
replenished.
 15 million acre-feet of groundwater is pumped each year.
 20% of the state’s water requirements are met with
pumped groundwater.
 CA is operating on a 1.3 million acre-foot overdraft.
 CA groundwater is recharged by:
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1) Nature – rain & snow (7 million acre-foot annually)
2) After usage – agriculture & industry (6.65 million acre-feet
annually)
3) Recharge programs
California’s surface water
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Comes from an average annual statewide
precipitation of almost 24 inches. (Ranging from
almost nothing in the deserts to more than 100
inches in the northern mountains)
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Sixty percent of the precipitation is evaporated
or transpired by trees and vegetation. The
remaining forty percent equals about 71 million
acre-feet of stream flow.
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Colorado River flows diverted to California
supply 4.8 million acre-feet.
California’s surface water continued…
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Inflow streams from Oregon add an addition 1.4
million acre-feet.
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This means in an average year California has
available slightly more than 78 million acre-feet
of water.
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However, not all of this water can be collected
for use (almost 29 million acre-feet occurs in the
north coast region alone and much of it is
unavailable for use).
Agriculture is the largest user of CA
water supply.
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80% of developed supply
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28-35 million acre-feet depending on yearly rainfall
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Irrigated acres 2002-8,709,353
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Irrigated acreage is declining due to urban growth
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A large percentage of agriculture water percolates
back into ground or streams (around 5 million acrefeet contributes to re-charge)
1997-8,886,693
California Water Balance Summary
For Water Years 1998, 2000 and 2001
Where the Water Goes
1998 (Wet Year)
2000 (Avg Year)
2001 (Dry Year)
Total Supply
(Precipitation & Imports)
335.8 maf **
194.2 maf
145.5 maf
Dedicated Supply
(Includes Reuse)
97.5 maf
82.5 maf
65.1 maf
Distribution of Dedicated Supply to Various Applied Water Uses
Urban Uses
7.7 maf (8%)
8.8 maf (11%)
8.6 maf (13%)
Agricultural Uses
27.7 maf (28%)
34.3 maf (42%)
34.1 maf (52%)
Environmental Water *
62.1 maf (64%)
39.4 maf (47%)
22.4 maf (35%)
* Environmental water includes instream flows, wild & scenic flows, required
Delta Outflow and managed wetlands water use.
** million acre-feet
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CA urban use is about 7.8 million acre-feet.
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One acre of houses uses approximately the same
amount of water as an acre of agriculture crops
26 million acre-feet is diverted to environmental
uses during normal years less in drought years)
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9.56 million acre-feet for the Delta
17.8 for wild and scenic river flows
This amount is expected to increase
Regional water use:
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Central Valley
 Sacramento River
 South Coast
 Colorado River
19 million acre-feet
11.7 million acre-feet
4.6 million acre-feet
4 million acre-feet
The earth’s water supply…
 Salt
Water 97.2%
 Fresh Water 2.8%
 Ground Water 0.6%
 Lakes and Streams 0.01%
 Glaciers and Icecaps 2.2%
 Water Vapor 0.001%
Chronology of Water in
California
 Refer
to the handout
Class Discussion…after reviewing the
handout, in your opinion…
 What are some of the most significant
events?
 What is the most striking aspect of the
entire list of events?
WATER RESOURCE PROBLEMS
Too Much Water…
 Untimely
precipitation: India gets 90% of
its rainfall from June-Sept. – Monsoon
Season results in:
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Floods
Water logged soils
Leaches soil nutrients
Soil erosion
Figure 2. Excessive Erosion on Cropland, 1997. Each red dot
represents 5000 acres of highly erodible land and each yellow
dot represents 5000 acres of non-highly erodible (USDA-NRCS
2001)
Floods are also beneficial…
 Provide
nutrients to farmland located in
the flood plain
 Recharge groundwater
 Refill wetlands
 Keep waterways flooding during droughts
 Provide fish and wildlife habitat
Floodplains…
a magnet for human settlement
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Fertile soil
Close to water for domestic and agricultural uses
and as source of transportation
Usually a flat area suitable for farming, buildings,
highways, railroads, etc..
But, these areas are referred to as floodplains
for a reason
Floods kill many people annually and are
responsible for billions of $ in property damage
Too Little Fresh Water…
 Droughts
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Most damaging natural hazard
Since 70’s, 24,000 people/yr. killed
40% of world’s pop. live in 80 arid/semiarid
countries
At risk areas include…
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N. Africa, parts of India, N. China, Middle East,
Mexico, parts of W. U.S., & much of former
U.S.S.R.
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Potential causes
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Deforestation
Overgrazing
Desertification
Natural vegetation replacement
Impact of global warming
 Water will be a foreign policy issue
Water Issues
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Allocating more water for fish and wildlife
Population Growth
Water Conservation
The Bay-Delta
Colorado River
Water Marketing
Groundwater Overdraft and Contamination
Agricultural Drainage
Class Discussion…