DWCZ CO - Coal Creek (CC)

Coal Creek (CC) is a high-elevation, headwater tributary to the Upper Colorado Basin located in the Ruby-Anthracite Range in the central Colorado Rocky Mountains. The CC watershed is 53 km2 in area and ranges in elevation from 2712 to 3668 meters. CC originates near Lake Irwin and enters the Slate River near the town of Crested Butte before joining East River and eventually the Gunnison River. The watershed is seasonally snow-covered from November through June. The average temperature is 0.9˚C and it receives around 670 mm of precipitation each year, about 66% of which falls as snow (Carroll et al, 2018). The remaining precipitation falls during the summer monsoon season (July through September). Although monsoon rains comprise nearly 40% of the annual precipitation, they contribute minimally to the streamflow because the moisture is taken up by vegetation and lost via evapotranspiration (Carroll et al, 2020). Vegetation in the basin is strongly aspect driven, with north facing aspects dominated by evergreen forest (65%) and south facing aspects dominated by deciduous (9%) and herbaceous (20%) vegetation. High elevation ridges are barren (3%) (Zhi et al, 2019). Discharge in CC is dominated by snowmelt, with average peak flow occurring in June in response to snowmelt. Flows recede throughout the summer and fall, with small peaks in flow due to monsoon events. CC reaches baseflow conditions by early September and they persist throughout the winter until the onset of snowmelt in April. The lower CC watershed is underlain predominately by sandstone (Mesaverde Formation) with glacial till deposits occurring near the streambed. The upper portion of the watershed is underlain by mafic intrusive plutonic rock, emplaced during the Middle Tertiary. Areas of the upper north slope of the watershed are underlain by mudstone (Wasatch Formation).

煤溪（Coal Creek, CC）是坐落于科罗拉多州中部落基山脉鲁比-无烟煤岭（Ruby-Anthracite Range）的上科罗拉多流域的高海拔源头支流。该流域面积达53平方千米，海拔范围介于2712米至3668米之间。煤溪发源于埃尔温湖（Lake Irwin）附近，在克雷斯特德比特（Crested Butte）镇附近汇入斯莱特河（Slate River），随后与东河（East River）汇合，最终注入甘尼森河（Gunnison River）。该流域每年11月至次年6月为季节性积雪覆盖期。流域年均气温0.9℃，年降水量约670毫米，其中约66%以降雪形式降落（Carroll等，2018）。剩余降水多集中于夏季季风期（7月至9月）。尽管季风降雨占年降水量的近40%，但因水分被植被吸收并通过蒸散作用散失，其对溪流径流的贡献极小（Carroll等，2020）。流域内植被分布显著受坡向调控：北坡以常绿林为主（占比65%），南坡则以落叶林（9%）和草本植被（20%）为主；高海拔山脊区域为裸岩地带（占比3%）（Zhi等，2019）。煤溪的径流主要由融雪补给，平均峰值流量出现在6月，对应融雪过程。夏季至秋季径流逐渐衰减，季风事件会带来小型流量峰值。煤溪在9月初达到基流状态，并持续整个冬季，直至次年4月融雪期启动。煤溪下游流域的基底主要为砂岩，赋存梅萨韦尔德组（Mesaverde Formation）地层，河床附近分布有冰碛沉积物；流域上游区域的基底为中第三纪侵位的镁铁质侵入深成岩；流域北坡上部区域的基底则为沃萨奇组（Wasatch Formation）地层。