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<br />30. Schem.tic di.gram showing the western part of the Grand Valley, rel.tive loc.tions of surf.ce- <br />w.ter-sampling sites, and selenium concentrations in samples collected during synoptic surveys, <br /> <br />February-March 1992 ....................... ........ ........... ............................................ ............ .................... .......... ............. 65 <br />31. Schematic di.gram showing the eastern part of the Grand Valley, rel.tive loc.tions of surf.ce- <br />w.ter-sampling sites, and selenium concentrations in samples collected during synoptic surveys, <br /> <br />February-March 1992 ....... ......... ..... .......... ...................... ............................................................ ..... ....... .......... ...... 66 <br />32-43. Graphs showing: <br />32. Mean selenium concentr.tions in irrig.tion-drain.ge samples collected in March 1991 and in <br />February and March 1992.t the 20 reconnaissance sites in the Grand V.lley............................................... 67 <br />33. Selenium concentrations in samples from S.ltCreek.t site SC, Reed W.sh.t site RWI, and <br />Leach Creek.t site LCI, March 199I-AugustI992...................................................................................... 69 <br />34. Selenium lo.ds in the Uncompahgre River, February 19-20, 1992............................................................... 71 <br />35. Season.lly weighted mean selenium lo.ds for 12 sites in the Uncompahgre Project, 1991-92.................... 72 <br />36. Mean selenium loads of three sets of samples collecled in ]99]-92 for 20 sites in the Grand V.lley........... 75 <br />37. Selenium lo.ds in Salt Creek.t site SC, Reed Wash.t site RWI, Big Salt W.sh at site BSWI; <br />and Le.ch Creek.t site LCI, March 199 I-August 1992....................................................................... ........ 76 <br />38. Rel.tion of season.lly weighted mean selenium lo.d to drain.ge.basin .re. within the irrig.ted <br />are. for 20 b.sins in the Grand V.lley ............................................................................................................ 78 <br />39. Rel.tions of selenium concentration to specific conductance for Loutsenhizer Arroyo .nd <br /> <br />Reed Wash.......... ....... ......... ......... ...... ......... ..... .......................... ................................. .............. ............ ........... 81 <br />40. Rel.tions of selenium lo.d to dissolved-solids lo.d for Loutsenhizer Arroyo (site LZA I) .nd <br /> <br />Reed W.sh (site RWI) .................................................................................................................................... 83 <br />41. Rel.tion of estim.ted selenium yield based on s.mpling during 1991-92 to estimates of <br />dissolved-solids yield by the Bureau of Recl.mation for 15 b.sins in the Grand V.lley............................... 84 <br />42. Selenium and chloride concentr.tions in irrig.tion-drain.ge s.mples from the Grand Valley, <br />November 1991-March 1992, .nd the estim.ted ev.por.tive-<:oncentration line.......................................... 84 <br />43. Rel.tions of selenium to nitrile-plus-nitrate concentrations in w.ter s.mples collected during the <br />nonirrig.tion season from streams and ditches on the e.stern side of the Uncomp.hgre Project <br />and in the Grand V.lley north of the Color.do River, 1991-92..................................................................... 88 <br />44-47. M.ps showing: <br />44. Loc.tion of 1991 biota sampling sites on tributary streams in the Uncompahgre Project............................. 96 <br />45. Loc.tion of 1991 biota sampling sites .dj.centto the Uncompahgre Projecl................................................ 99 <br />46. Location of 1991 biota s.mpling siles on tributary streams in the Grand Valley........................................... 101 <br />47. Loc.lion of s.mpling sites on m.jor rivers where fish samples were collected in 1992................................ 105 <br />48-51. Gr.phs showing: <br />48. Me.n selenium concentr.tions in four fish-trophic groups in the Color.do, Nonh Fork of the <br />Gunnison, Gunnison, .nd Uncomp.hgre Rivers............................................................................................. 106 <br />49. Mean selenium concentrations in three fish-trophic groups collecled from four siles on the <br /> <br />Color.do Ri ver ...... ....... ................... .............. ....... ...... ................ .......... ............... .......... .......... .................. ...... ] 08 <br />50. Mean selenium concentr.tions in three fish-trophic groups collected from four sites in the <br /> <br />Gunnison River B.sin ..................................................................................................................................... 109 <br />51. Me.n selenium concentrations in three fish-trophic groups collected from three sites on the <br /> <br />Uncompahgre River... ................ ............ ...... ....... ........ ............... .......... .......... ..... ....... ........... ........... ..... .......... 110 <br />52. M.p showing loc.tion ofs.mpling sites.t wetl.nds in the Uncomp.hgre Project are.......................................... ] 16 <br />53. Map showing loc.tion of s.mpling sites at wetl.nds in the Grand Valley.............................................................. ] 19 <br /> <br />TABLES <br /> <br />I. Distribution of soil-s.mpling sites by geologic units in townships of the Uncompahgre Project are. .................. 18 <br />2. Geometric me.n .nd observed range of total- and w.ter-extractable selenium concentr.tions in soil <br />and total-selenium concentr.tions in .If.lf. for all samples from the Uncompahgre Project area, <br /> <br />by geologic unil............. ............. .............. ........ ........... ...... ........................... ............... ......... ........... ........................ 19 <br /> <br />VI CONTENTS <br />