WSP04876 - Laserfiche WebLink

Home Browse Search

. PART VI EVALUATION OF EXISTING SALINITY CONDITIONS discuss~d in Part IX. Gorge Bnd Lake Powe 11 cond i t ions. The selective salinity routing observed in Flaming in the 1970's may not he representative of future """ C,;1 tv When higher TDS waters jeet to bank storage, chemical reduction, and various biological remain in the pree i pi t at ion, act ivit ies. reservoirs, they are sub- 10n exchange I ox idat ion . . In addition, it 1S possible that the sedimentation processes in the reservoirs may influence both TDS and the ratio of dissolved ions. Suspended sediment which is subject to m('chanical degradat ion in a rlver environment may continue to release salts and exchange ions (sodium exchanged for calcium); ho....ever. once settled out in the reservoir these salts and ion exchange capabilities may be isolated. Sediment stored in reservoirs may contain salts which would have been released with con- tinued mechanical breakdown in a riverine environment. Reservoir studies are discussed in detail in Part IX. 3. Irrigation and Increased Depletions . Most of the irrigation projects that deplete water and increase salt pickup to the river were largely in place before 1965. Moreover, like the newly inundated soils in reservoirs, the irrigated lands are also subject to a l~ach-out period. In cases where lands with poor drainage stored salt. th~se areas were taken out of production. In addition, irrigation practices changed significantly during the 1960-30 period, with canal and lateral lining, sprinkling systems, gated pipe, and trickle systems being introduced. These changes should result in reduced return flows and salt pickup. la.rgely percent. Projected unrealized; water deplet ions through the total depletions increased 1965-80 period were bv approximately 12 1970-1979 1960-1969 1950-1959 1940-1949 1930-1939 1920-1929 1910-1919 1900-1909 1/ 2/ Average annual depletions by (1,000 acre-feet) Upper Basin 3,565 2,538 2,043 1,894 1,712 1,998 1,656 1,001 Estimated from best available Lacking some years of data. bas in LOwer Bas\n 6, l36..!..' 6 1191/2/ , -- 4, 757~..I 3.776 3,676 3,662 3,643 3,3nY data. . Previous Reclamati.on salinity projections have been too high, largely because the depletion projections were also too high. Transbasin diversions and increased reservoir evaporation account for the majority 29