HYDRO21737 - Laserfiche WebLink

Home Browse Search

Cotter Corporation Water Quality Assessment CO-0036251 Table A-8 Low Flows for the Dolores River at the confluence of East Paradox Creek and Bull Can on Z'oFlow " ~~ts~ ~ " its " ~' 't'~ a; a~ ~ "a~~ ~~ ~,, ~~~ ~ .~,,~a ~#c fir '~ ~ p ~ x 1 ~~~ ~.: a ~~ e~.~ .~r ~~~~ ~ nntral,, A T. ~,~ ~Jan ~ yy5.~ ~ ~ ~ web ~ iT1br~ .~~k ~ ~~Y ~Pl~r } ~ ,Mays .~ {{ t un ^~p~j ~~ J ~ JuI t' ~~ ~ ;~ ugr~ r~fSep ~ ~~c}[~^ ~ '~.'~ t , ~,. $~ 11' Y G b lty.C gtE{.. 1`~• tAec `~ y~,+'~4~~ yY l~~ 'i v ~ ~ q. . .}. ~' ~ .W . ~+ ST §~ ` ~ 9?P ~, ;Ei"'~p °d.{ . .Wt . . . 'i < t g W+4.. i ~IDg Ads, 9 n4__52+~"~_ ~' -~.. y ~ .~n'MY'ikh2 ss ~ ~ r c:uF.. . lE3 $ 0 30 32 44 21 14 8.0 25 32 21 26 30 22 Acute 30E3 Chronic 2S 30 32 44 25 25 2S 2S 36 29 29 30 30 During the months of January, February, and July, the acute low flow calculated by DFLOW exceeded the chronic low flow. In accordance with WQCD standazd procedures, the acute low flow was thus set equal to the chronic low flow for these months. IV. Technical Analysis Tn~ows and in-stream background data evaluated in sections II and III are ultimately used to _ determine the assimilative capacity of unnamed tributaries of East Paradox Creek and Bull Canyon, East Paradox Creek and BuII Canyon, and the Dolores River near the Cotter Corporation for pollutants of concern. For all parameters except ammonia, it is the WQCD's approach to conduct a technical analysis of stream assimilation capacityusing the lowest ofthe monthly low flows (referred to as the annual low flow) as calculated in the low flow analysis. For ammonia, it is the standard procedure of the WQCD to determine assimilative capacities for each month using the monthly low flows calculated in the low flow analysis, as the regulations allow the use of seasonal flows when establishing assimilative capacities: The WQCD's standard analysis consists of steady-state, mass-balance calculations for most pollutants and modeling for pollutants such as ammonia. The mass-balance equation is used by the WQCD to calculate the maximum allowable concentration ofpollutants in the effluent, and accounts for the upstream concentration of a pollutant, critical low flow (minimal dilution), effluent flow and the water quality standazd. The mass-balance equation is expressed as: MZ = M3Qs -M~Q~ Qz where: Q~ =Upstream low flow (lE3 or 30E3) Qz =Average daily effluent flow (design capacity) Qj =Downstream flow (Q~ + Qz) M~ = In-stream background pollutant concentrations Mz =Calculated maximum allowable effluent pollutant concentration Mj =Maximum allowable in-stream pollutant concentration (water quality standards) Appendix A Page 10 of 13 Final