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<br />';Water in the Balance';
<br />
<br />Colorado's Typical Wet and Dry Seasons by Basin
<br />
<br />It is common and necessary practice in watershed management to combine data from an entire basin including both
<br />high and low elevations. It is important to recognize, however, that the seasonality of precipitation may vary greatly
<br />within each basin, and that precipitation at different times of year across the basin may not be well correlated.
<br />
<br />For many water management and planning applications, Colorado is divided into seven water divisions (see figure).
<br />Each of these basins originate in high mountain environments and descend through mountain valleys and eventually
<br />drop to much lower elevations. Thus, we can roughly divide each basin into an upper and lower basin based on
<br />approximate elevation and mountain proximity. The table below is not definitive, but is meant to give a general picture
<br />of the typical wet and dry periods experienced across Colorado. WI t D'" V
<br />Water Division I a er iViSlOn
<br />South Platte, Upper: Wet Dec.-Apr., Dry June and again in Colorado, Upper: Wet late Nov.-Apr., Dry Jun-mid-Jul.
<br />Auu .-Oct. Colorado, Lower: On average, there is no clear wet or dry
<br />So';th Platte, Lower: Dry Nov.-Feb., Wet Apr.-Jul. season in the lower portion of th~ Colorado River basin.
<br />Water Division II Water DlVlsiOn VI
<br />Arkansas, Upper: Wet Dec.-Mar., Jul.-Aug., Dry (at the Yampa-White, Upper: Wet late Nov.-May, Dry mid-Jun.-
<br />highest mountains) May-Jun. Sep. (NOTE: The hIgh mountams of thIS basm mclude
<br />Arkansas, Lower: Dry Nov;-Feb., Wet May-Aug. some of the wettest areas of the state, receIvmg an average
<br />Water Division III of more than 50 inlyr of precipitation.)
<br />Rio Grande, Upper: Wet Dec.-Mar. and mid-Jul.-early Yampa-White, Lower: Similar to the lower portion ofthe
<br />Oct., Dry May-mid-July. Colorado River Basin, with no clear seasons, and less
<br />Rio Grande, Lower: Dry Nov.-Apr., Wet mid-Jul-Sep. lIkelIhood of receIVIng ram fro~ the summer monsoon.
<br />(NOTE: The San Luis Valley, which includes Great Sand Water DIVIsIOn VII
<br />Dunes National Monument, receives the least precipita- Sanjuan, Upper: Wet Dec.-Mar. and late Jul-early-Oct.,
<br />Dry May-early Jul. and mid-Oct-mid-Nov. (NOTE: The
<br />high mountains of this basin are also among the wettest in
<br />the state, receiving more than 50 inlyr average annual
<br />precipitation.)
<br />San Juan, Lower, Wet Dec.-Mar. and late Jul-early-Oct.,
<br />Dry May-early Jul. andmid-Oct-mid-Nov. (NOTE: similar
<br />to the upper basin, but less wet in the wet seasons.)
<br />
<br />tion in the state, with an annual average of less than eight
<br />
<br />inches of precipitation.)
<br />Water Division IV
<br />Gunnison, Upper: Wet mid-Nov.-Mar., Dry mid-May-mid-
<br />Jun. .
<br />Gunnison, Lower: No significant wet season. Dry late
<br />May-Jun, slightly wet mid-Jul-Aug
<br />
<br />Subbasin Ian Feb Mac Anr Mav lun lul Au. Sep I Oct Nov Dec
<br />Up. S. Platte
<br /> ,v,--" 0"<",-<>,,>>>:<<,>,,,"0"'0',"0<0> '0
<br />t.o. S. Platte "~v,,,y,'N~~V"'~ '-""8\/,; >n-'M>,c,',>:,',y<,>',', n\->",
<br />Up. Arkansas
<br /> '8",~,\O;'^',O)N';>A': ,,<,,:,'
<br />t.o. Arkansas ",,',,' ,,,",",!,",',",<1 cU>tU "'"',\V ,'.",",<-"',\VA~f" >~"'/.~,
<br />Up. Rio Gr.
<br /> .>":"",, ", '. -,-"":...,,,'
<br />Lo. Rio Gr.
<br /> , <'H-}",A,;..."~'''n''''w,, n"'!'''f,-,,-{,'''n,'n\ ",<" >-",,,!,V<"'<"~-""-"""-'-{>
<br />Up. Gunnison $
<br />t.o. Gunnison
<br /> 'of-x"'>",-_' V;,<__V-
<br />Up. Colorado
<br /> ',;\:;',-\:,,1\,,>,'<"""><
<br />t.o. Colorado I I
<br /> No clear wet or "y seasons.
<br />Up. Yam pa (>,' ;-x" _>'OYOXOX 'X<'Y~oY<'"}y",,,.~,
<br />Lo. Yam pa I I
<br /> No c1earwel or dry seasons
<br />Up. San Juan "'-">-'<'<',y-!;~ ,"'v''; ~, ' ,'" ~ tiE..
<br />t.o. San Juan m,
<br /> ,,;,>,\'<..',',,\.o_....',<t,\~;>,>,g,"',d,<_
<br />Legend: Wet , Dry ~ --"'_-; :~,~ f,,<.f_"W!_,~ ,I
<br />
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