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The other half of the salinity problem comes
from people. Long-term indoor water conservation measures—ultra-low-flush
toilets and low-flow showerheads—reduce water use, resulting in an
increase in the salinity concentration of residential wastewater. Water
softeners, which use salt to reduce the "hardness" of water,
add additional salt concentrations to water that eventually ends up in
Southern California's many groundwater basins.
Agriculture also contributes to the salinity of the Colorado. Apply water
to the land and as much as two-thirds will be used to meet the needs of
the crop or is lost through evaporation. The rest (1/3 of water) seeps
deep into the underground aquifer and eventually makes its way to the
river. That's salt concentration.
Add the two sources of salt together and you get water
with a salinity level of 720 milligrams per liter (mg/L)—that's like
having about 700 pounds of salt delivered to your home every year. Not
much if you compare it to the Pacific Ocean at 25,000 to 35,000 mg/L.
But if you operate a wastewater treatment plant or a groundwater recharge
facility, that's high enough to grab your attention.
The United
States agreed in 1974 to various measures to help reduce salinity in the
Colorado River water flowing to Mexico. The seven basin states—Colorado,
New Mexico, Utah and Wyoming in the upper basin and Arizona, California
and Nevada in the lower basin—created the Colorado River Basin Salinity
Control Forum the following year to reduce salinity and recommend water
quality standards for various points along the Colorado. The forum adopted
specific standards in 1999 for Hoover Dam, Parker Dam and Imperial Dam
and current measures prevent 700,000 tons of salt from reaching the river
each year. The Colorado River Basin Salinity Control Act, which was signed
by President Nixon in 1974, authorized several measures to prevent salt
from reaching the river, such as getting farmers to switch from flood
irrigation to using sprinklers and lining canals to prevent salts leaching
from the soil.
Increases in oil and gas drilling in the West - encouraged by the current
Bush administration—are seen as another potential threat to Colorado
River salinity. Drillers routinely find brine—or highly salty water.
Old practices allowed brine solutions to be simply dumped onto the ground
or fed back to rivers. Water managers are now seeking rules to force treatment
of brine water before it re-enters the aquifers.
Looking for leaders, solutions
The May 31 Salinity Summit, organized by the Salinity Management Coalition
of Southern California, is the second session in two years to deal with
the high costs of salty water impacting the world's 11th largest economy.
The coalition is now seeking to become a formal organization, raising
money to hire an executive director and initiating some regionally beneficial
programs.
Metropolitan began looking for new solutions to the salt problem a couple
of years back. To improve the quality of the water delivered to its 26
member public agencies, Metropolitan's board of directors adopted an action
plan setting a salinity target of 500 mg/L—anything above 300 mg/L is
considered hard water. That's achieved by blending higher salinity Colorado
River with lower salinity water delivered through the California Aqueduct.
The trade-off, however, is a risk to supply reliability. During years
of low rainfall, the State Water Project supply may be insufficient and
saltier. Under favorable conditions, Metropolitan would meet its salinity
standard year round. During less favorable times, emphasis would be placed
on reducing salinity from April through September to support irrigation
with recycled water.
