|
<br />; ~{.
<br />
<br />
<br />00302
<br />
<br />the drainage water with less ecological.
<br />damage. Severai laboratory investiga-
<br />tions have demonstrated that bacteria
<br />. can effectively reduce selenium, but
<br />this has not been adequately demon-
<br />strated in field tests (San Joaquin Val-
<br />ley Drainage Implementation Program
<br />1999). Because selenium removal re-
<br />duces hazards to wildlife but other-
<br />wise does not materially increase the
<br />monetary value of the water, costs for
<br />selenium trea tment cannot be offset by
<br />the production of a more valuable 'wap
<br />ter. Selenium concentrations can also
<br />be reduced in open systems such as
<br />flow-through wetlands, but this solu-
<br />tion can also pose hazards to wildlife.
<br />The benefits of treated water to wild-
<br />life must be weighed against the po-
<br />tential exposure of birds to toxicity as-
<br />sociated with a flow-through system.
<br />Off-site disposal. Salt balance on
<br />the West Side cannot be achieved
<br />without out-of-valley disposal. Unfor-
<br />tunately, this option has not underp
<br />gone scientific scrutiny concerning its
<br />ecological or economical viability.
<br />Such disposal is not available now, nor
<br />will it be in the immediate future.
<br />However, a decision by the U.S. Court
<br />of Appeals for the Ninth Circuit filed
<br />Feb. 4, 2000, (Firebaugh Canal Co. vs.
<br />USA, 95-15300) states that "the Gov-
<br />ernment must act promptly to provide
<br />drainage service." In the case, several
<br />Central VaHey water districts challenged
<br />the U.S. Bureau of Redamation's historic
<br />failure to provide for drainage facilities
<br />in California water contracts. The deci-
<br />sion aHows for a range of options to
<br />remove drainage water from the West
<br />Side, and does not rule out something
<br />other than the San Luis Drain. The
<br />means by which the Bureau will com-
<br />ply with this decision was uncertain at
<br />the time of this writing.
<br />Evaporation ponds. The only way
<br />to sustain agricultural production is to
<br />separate salts from productive agricul-
<br />tural lands. Even though there cannot
<br />be salt balance In the San Joaquin Val-
<br />ley without a means for salt disposal
<br />,utside the valley, growers can bal-
<br />ance salt on individual fields. Evapo-
<br />ration ponds are an option that perma-
<br />
<br />.....-
<br />
<br />
<br />In the future, Innovative approaches will be needed fa create new, highly productive
<br />habitat for wildlife In agricultural regions. At Tulare Lake Drainage District, a compen-
<br />sation habitat was constructed on about 307 acres to mitigate, for bird losses on 2,900
<br />acres of evaporation ponds, above.
<br />
<br />nently removes 5<'1lts from producti\"e
<br />farml-ilnd and accumulates "then).. on
<br />land selected for a pond; long.t~rm r~-
<br />111.0\"<'11 of the salts is another issue that
<br />must be resolved" Unf6rtunately, sele-
<br />nil'lm in c\'aportltion ponds cr,eiltes a
<br />significant bird hazard" A number of
<br />steps can be taken to reduce impacts to
<br />birds, including making the ponds less
<br />attractive to birds, using various meth-
<br />ods to scare them away, 'disrupting the
<br />selenium food chnin, and reducing sew
<br />lenium concentrntions by flowing wa-
<br />ter through constructed. wetlands prior
<br />to discharge into the en\porution
<br />ponds" A combination of such meth-
<br />ods can greatly reduce impacts on
<br />birds, but it l,\"ould be drtually impo:-:~
<br />sible to design a systl2'm th,1t is com-
<br />pIetd}' bird-sofe.
<br />Compensation hab.itat. Recent
<br />studies demonstrate thc1t compens<'l-
<br />tian habitat can be de:igned and operp
<br />ated successfully to support high den-
<br />sities of nesting wild birds. For
<br />example, Tul,1re Lake Drainage Disw
<br />trict (1999), which h." 2,900 acres of
<br />c\"aporation basins, constructed cOln-
<br />pensation habit<lt on 307 acres" The
<br />habit,lt is designed to be attr,1Cti\"e to
<br />birds, while e\'nporl1tiL1O ponds <'Ire
<br />
<br />m.:maged to discourage them" In 199-1,
<br />bdore cllmpensation habitat was ~on-
<br />structed, there were approximately
<br />2,200 nest starts on evaporation basins.
<br />In 1999, there ",..ere approxin1ately
<br />4,100 nest starts on the compensation
<br />habit,lt, and only about 200 on the
<br />evapor,ltion basins. Compensation
<br />habitat (,10 effectin?ly increase bird
<br />populotions. A policy drh'en by the
<br />goal of-enhancing bird numbers- to
<br />comp0nsate for the risk of bird dam-
<br />age incre,lses management options to.
<br />sustnin high agricultural productidty.
<br />
<br />Future in focus:
<br />Creatively managing salt
<br />
<br />The dilemma of dealing with salinity in
<br />irrigated regions h~ls historical roots dat-
<br />ing back to ivlesopotamia .1nd 2-400 13.C.
<br />In 21st.ccntury California, long-term ag-
<br />ricultural sustainability \dll nIso require
<br />salt bal,1nce on irrigated farmlands" The
<br />salt b~llance can be \"iewed regionally,
<br />with all salts introduced to a \"allev leav-
<br />ing the \.alley, or on a more locali~ed
<br />scale, \\'herebv all salts entering the field
<br />must It'.we the field by some cm"iron-
<br />ment.,ll~. accept,lble mealb"
<br />Salt b,llance c,m be achie\'ed in the
<br />Imperial Valley by using the Salton
<br />
<br />CALIFORNIA AGRICULTURE. MARCH-APRIL 2000 47
<br />
|