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111-5 station is the houndary between 0; strict Numbel"s 8 and 2 of '~ater Division N~ber 1 as ad~inistered by the State Engineer Of Colorado. The Chemical quality of groundwater as measured by dissolved solids concen- tr~t ions is 1 ess th~n 500 mg/l from Chatfi 1'1 d Reservoi r to Co I llIllb i ne Va 1- ley. From Col~bine Vall'!'yto Brighton thegroundwat'!'r in the alluviumof the South Pl atte River I)as a d i sso 1 ved soli ds concentr~t i on in excess 0 f I I I In Water District No. 8 (Chatfield to 19th Street) development of the South Platte alluvial groundwater resources is accomplished via wells constructed fOr municipal. irrigation, and other purposes. Nearly lOll alluvial wells in this reach have been used for water table measurements betwee nlg54and 1976. 500mg/l. Alluvial groundlOater development along the South Platte River has heen extensivedownstrearnoftgth Street to Baseline Road. In 19fi8 a survey of all alluvial wells in Water Distl"ict No. 2sho"",d 1,552 irrigation well registrations eaCh having an average yield of 1.8cfs. Bittinger estimated that there were al so an additional 260 commercial, industl"i al, ~nd munici~ pal wells each having an average yield of ~pprox imately 0.5 cfs. Within the reach from 19th Street to Ba~eline Road (City of Brighton) lies approx- imately 30 percent of themainstem of the South Platte River in District ~. 2. Bittinger estim~ted that in this sdllle re~ch the aVf>rage rumping withdrawals from this portion of the dyer alluvium amounted to 40,000 acre~feet per year. More detailed analyses which have been performed for specific O'/ate rsupply investigations indicate that. commencing ~t about 1.70 the dissolved sol ids cOficentr~tion is approximatel y 1,000 mg/1. Some variations in dissolved solidS concentration is found laterally within the aquifer, the better water quality existing in some places near the west edge of the alluvium. '~ell yields from the SOuth P1 atte all uvium ~re s~tisfactory for the ent ire 40 mile study reach. Individual pumping rates of from 500 to l,OOOgpn are common. There are at least 15 zones where the well yieldSranqebetween 1,000 and 1.500gpm,....ith sornewells pumping in excess of 1,500gp"'. The alluvium is hyrlraul ically connected to the surface ~tredlll of the South Platte River. Pumping of water from the wells causes a depletion to the surface flow. but the depletion is lagged over time. The water table adjacent to themainstE"llof the South Platte River. from Sand Creek to Brighton, i~ designated by the U. S. Geological Survey ~s being less than 5 feet below the ground surface. Surrounding. and adjacent to this zone of shallow water. and along the full reach of the river in the f1 oodp 1 a; n. the water tab le is de~ i gnated as bei ng from 5 to 10 feet deep. Along the right bank for the full river length from Sand Creek to Bri ghton. the alluvial groundwater extends eastward for, insorneplaces. as muCh as 7 rn j le~. Tlwrlugh tile City of Denver from Sand Creek to Big Ory Creek in Englewood. t~e depth to w~ter tab 1 I' adj acent to the ri ver is from 10 to 20 feet. From Big Dry Creek to Chatfield Reservoir the water table is again shallow. r~nging f~()I" 10 feet to less than ~ fe~t. Pumpi fig for one month, for i n~tance, may cau~e a depl et io" to the ri ver of ten to twenty percent of the amount pumped during the firstmOfith. The naldnce of the totdl drpletion ~dY cau~e an additional ~ix to twplv~ ~onth~ of river depletion while the drawdown aquifer is refilled, i.e., refill..d byd;rect 'echarqe frorn the river or from ioterceptiooof lateral 'echarge from the adjaceot laods. Within the aquifer, the water table slope is both towards the river and ~own<;tr""",. Th" rl""n,t.,.""," ,.""'pnopnt of th" <; I npp i <; gpnpr~ 11 y rJr~ 11 pl I,n the slope of the l"iver. I t