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<br />'.1" <br />"- <br />"') <br />:.-t <br />~.! <br />..--., <br />,- <br /> <br />incr-eased their- efficiency in 1990 but thr-ee sites <11, 15, 32) <br />r-educed their- efficiency in 1990 compar-ed to 1989. This could be due <br />to cr-op change (alfalfa to cor-n in site 15 and beans to small gr-ain in <br />site 32) in 1990. Site 11 did not have any cr-op or- oper-ator- change. <br /> <br />The r-educed efficiency in 1990 could be par-tly due the ear-Iy star-t of <br />the ir-r-igation season by two weeks. Because of the dr-y winter- and <br />spr-ing, the water- was let in the canal two weeks ahead of nor-mal so <br />that far-mer-s could star-t ir-r-igating ear-Iy. Mor-e water- was applied <br />than needed at that time, and might have dr-opped the ir-r-igation <br />efficiency. Fur-ther-, because of the dr-y weather-, far-mer-s anticipated <br />water- cuts dur-ing peak ir-r-igation season. Consequently, a few far-mer-s <br />ir-r-igated consider-ably longer- than nor-mal dur-ing late spr-ing and ear-Iy <br />summer. <br /> <br />In 1990, the var-iation in efficiencies for- individual ir-r-igations <br />r-anged fr-om 3% to 89% for- sur-face ir-r-igation and fr-om 14% to about 93% <br />for- spr-inkler-s (Refer- to Appendix B for- mor-e detai Is on individual <br />ir-r-igations). The sites with poor- ir-r-igation efficiencies gener-ally <br />wer-e ir-r-igated sooner- and longer- than needed. Impr-oper- schedul ing and <br />long set times caused excessive deep per-colation on some of the sites. <br />Ir-r-igation efficiencies can be impr-oved at some sites with better- <br />ir-r-igation scheduling and adjusting set times or- inflow r-ates. <br /> <br />Deep Per-colation: <br /> <br />For- an effective sal inity contr-ol pr-ogr-am, both deep per-colation and <br />seepage need to be contr-olled and r-educed. In the Gr-and Valley, deep <br />per-colation losses come fr-om on-far-m ir-r-igation pr-actices. The <br />seasonal deep per-colation losses for- the var-ious sites ar-e shown in <br />Table 2 which has been extr-acted fr-om individual ir-r-igation summar-ies <br />pr-ovided in Appendix B. The deep per-colation data ar-e impor-tant for- <br />salinity contr-ol. <br /> <br />The aver-age annua I deep per-co I at ion in the Gr-and Va II ey was est i mated <br />to be 11 acr-e inches per- acr-e, which r-esults in about four- tons of <br />salt pickup per- acr-e foot r-eaching the Color-ado River-. However-, <br />monitor-ing data for- the last six year-s indicate the aver-age deep <br />percolation to be slightly over- 16 acr-e inches per- acr-e <Table 4). <br /> <br />In 1990, the aver-age deep per-colation for- all 25 sites was 17.0 inches <br />CTable 2). When only the 22 sur-face ir-r-igated sites ar-e taken into <br />account, the aver-age deep per-colation is 17.9 inches <Table 2). The <br />aver-age for- the thr-ee spr-inkler- and micr-ospr-ay sites is 10.9 inches <br />CTable 2). A compar-ison of six year-s of deep per-colation data CTable <br />4) shows that deep per-colation dur-ing 1990 incr-eased compar-ed to 1986 <br />thr-ough 1989, but is less than that of 1985. The deep per-colation <br />values shown on Tables 2 and 4 ar-e aver-age values obtained fr-om both <br />sur-face and spr-inkler- ;r-r-igated sites. Incr-eased deep per-colation in <br /> <br />17 <br />