Conflicts over water – diversion, depletion, degradation Introduction : when the ability to use water is diminished – through pollution, reduction in availability, or other harm – conflict usually results. Three sources of conflict: Diversion – re-allocation/transfer from one river basin (or aquifer) to another by tunnel, aqueduct, other means. Depletion – using up available supply without replenishment. Degradation – diminishing usefulness of water; e.g., through contaminants that cannot be easily removed, changing functioning of a water body.
Transcript
Conflicts over water – diversion, depletion, degradation
Introduction: when the ability to use water is diminished – through pollution, reduction in availability, or other harm – conflict usually results.
Three sources of conflict: Diversion – re-allocation/transfer from one river basin (or aquifer) to another
by tunnel, aqueduct, other means.
Depletion – using up available supply without replenishment.
Degradation – diminishing usefulness of water; e.g., through contaminants that cannot be easily removed, changing functioning of a water body.
Water diversion as source of conflict
Many early civilizations arose through ability to divert water for agriculture/public supply: e.g., Sumeria (Iraq), China, Egypt, Rome.
Diversion requires administrative as well as engineering skills.
Some (e.g., Karl Wittfogel – 1950s, Donald Worster – 1990s) believe large-scale diversion shaped authoritarian character of ancient societies by:
Built during Qin dynasty – 256 BC; near Chengdu, Sichuan Province
Diversion and California
Urban growth (e.g., San Francisco and Los Angeles) and agriculture (e.g., Imperial Valley) drove demand for long-distance diversions.
California’s experience illustrates impacts:
Water rights - mining, agriculture, urban use led to acquiring of water rights –outright or sometimes secretly – rights became enshrined in law.
Ecological effects – reducing stream flow; introducing “exotic” fish species: “Return flow” stipulations – e.g., Imperial Valley/Salton Sea. “Fish screens” – Great Plains; under discussion in N. California (CALFED).
Social & economic effects –reduction of regional income, economic opportunities, quality of life (e.g., Owens Valley).
Major diversions of water in California
Ecological issues - Salton Sea (formed 1905)
Contemporary problems:
• Nutrient inflow from surrounding farming regions
(eutrophication).
• High salinity due to evaporation & less inflow from Colorado River.
• Dust along shoreline where evaporation has occurred.
• Annual bird die-offs.
2005 photo
Hydraulic gold mining impacts (N. California, 1850s)
Placer County, CA – Sierra Nevada mountains
Socio-economic issues: Owens Valley
FROM: LA Department of Water and Power
Restoration efforts:1.Return flows of 15,000 acre/ft./yr.2.“Re-watering” portions of Owens and Mono Lakes, lower Owens River.3.Restock sport fisheries – bluegill, bass, trout.
What won’t be restored:1.Regional income.2.Population.3.Lands along valley that can be used for economic development.
Depletion of supplies – a growing problem
Surface and groundwater supplies can be diminished beyond natural ability to be replenished.
Groundwater examples:
Las Vegas, NV – until 1980s, received 30% of water from aquifers and springs; now 0%; 90% from Colorado River, rest from N. Nevada.
Subsidence and “fissuring’ caused by groundwater drawdown – N. Las Vegas
Lorenzi Park, west of downtown Las Vegas – one of last remaining “springs” At the original site of “The Meadows”
Mississippi River Embayment Aquifer system
Memphis, TN – draws 160 million gallons/day from aquifer system shared with other states– water levels are dropping; wells becoming deeper/more expensive to drill:
- Mississippi claims that 60/160 million g/d of Memphis’ water actually come from “beneath” northern part of their state – residents are losing 20% of their water due to Memphis’ pumping .
- February 2010: U.S. Supreme Court refused to overturn appellate court ruling in favor of Memphis: “Mississippi had not shown real or substantial injury.”
- If Memphis had lost, would have had to build a treatment plant and draw water from Mississippi River.
Memphis, Tennessee
Land Subsidence – San Joaquin ValleySan Joaquin Geological Survey
Solution? Reduce groundwater pumping; recharge aquifer with surface flow.
Evidence of land subsidence in San Joaquin Valley
(1925-1977)
Degrading riparian “function”
California example – Los Angeles River:
Until early 20th century – source of water supply for farms, orchards – through “zanjas” (ditches) used to move water.
1930s to 2000s – an urban “flood control” corridor to permit commercial & residential development.
The future (2000 and beyond)?
Los Angeles River – modern history
Near Griffith Park (c. 1900) Seasonal floods - 1941
Flooding – Arroyo Seco (1913)
Los Angeles River today
LA River Today – Glendale area
Los Angeles River Revitalization Master Plan
•City of LA; LADWP, Army Corps of Engineers, public interest groups. Goals:
--Remove channelization along 32 miles of river – from Canoga Park to Vernon.
--Re-plant native vegetation: develop “greenways” & parks.
--Achieve flood abatement, improve water quality, celebrate cultural heritage of river, foster civic pride.
Location map – Los Angeles River
“Virtual” future –courtesy Los Angeles River Revitalization Master Plan
A glimpse into the future? – Los Feliz area
Mouth of Los Angeles River – Long Beach
Golden Shore Marine Reserve – habitat restoration plan (2006)
Improved natural environment and a healthy, functioning River
Improved water quality throughout the River Corridor
Significant expansion of City’s open space system
Increased tourism and recreation-related revenues
Creation of new jobs
Increased economic investment and tax revenues
Benefits of Los Angeles River restoration (LARRMP)
Lessons – why we degrade rivers, how we can stop
• Changing urban needs influence how we value rivers.•Initial settlement•Industrialization•Post-industrialization
• Flood and drought influence perception of their usefulness; prompt us to harness and control them.
• Post industrial change makes people find new respect for natural amenities & desirability of rivers as recreational, aesthetic, and community development assets.
