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RULE 2 PERMITS
<br />The upland plateau region is characterized by generally flat, low-lying mesas divided by meandering
<br />streams with shallow gradients. The valleys of the larger streams, including Milk Creek and the Yampa
<br />River are typically broad, with aggrading of the alluvial/colluvial materials. Erosion and sloughing of
<br />stream banks is often severe due to the abundance of unconsolidated materials in the valley bottom, and
<br />typically results in increasing sediment loads to the drainages (CDM, 1985b).
<br />The climate in the region is semi -arid, characterized by low precipitation, large daily temperature
<br />fluctuations, low humidity, and abundant sunshine. Precipitation averages about 18 inches per year, with
<br />most precipitation falling in the form of snow generally between the months of October and April.
<br />Surface flows in the general area are dominated by runoff events resulting from either snowmelt or
<br />rainfall.
<br />Stream flows vary widely within the Lower Yampa River basin, primarily due to differing climatic,
<br />physiographic, and geomorphic conditions. Stream flow in the montane areas is generally a result of
<br />snowmelt in the spring/early summer months, and thunderstorms in the summer months. The streams are
<br />usually intermittent; since there is a lack of significant spring/seep discharge and a lack of storage in the
<br />valley fill deposits. This type of stream regime is typical of the principal drainages in the area (CDM,
<br />1985b).
<br />Surface water resources in the general area include the drainages of Wilson Creek, Collom Gulch, and
<br />Jubb Creek, perennial streams; and Taylor Creek, Little Collom Gulch, Straight Gulch, Morgan Gulch,
<br />and the East and West Forks of Jubb Creek, minor ephemeral or intermittent drainages. Based on
<br />monitoring data discussed below, the upper reaches of Collom Gulch and Jubb Creek are also intermittent
<br />in some years. These drainages are illustrated on Map IOB. Wilson Creek is a tributary to Milk Creek,
<br />which has its confluence with the Yampa River about 13 miles southwest of Craig, Colorado, and about 7
<br />miles north of the Colowyo permit area.
<br />Surface Water Quantity — Surface water monitoring in the general area, permit area, and permit revision
<br />areas has been conducted since 1975, including studies by the U.S. Geological Survey (USGS), and those
<br />commissioned or conducted by Colowyo. The USGS has monitored hydrologic conditions in the Lower
<br />Yampa River basin at several gaging stations since as early as 1947. The data collected at the gaging
<br />stations in the general area are summarized in Table 2.04.7-45. Flows measured in Good Spring, Taylor,
<br />Wilson, and Jubb Creeks near Axial, Colorado, for the period of record ranged from minimal/no flow, to
<br />a peak flow of 94 cubic feet per second (cfs), measured in Wilson Creek. The USGS discontinued water
<br />quantity monitoring at last of these stations in 1992.
<br />Engineering Science (ES) measured parameters in area streams and springs from 1978 through 1982 (ES,
<br />1982), for comparison with the USGS-measured stream parameters from 1974 until 1981 in the same
<br />streams. The report concluded that Taylor, Jubb, Good Spring, and Wilson creeks all have low
<br />baseflows, with mean flow of 1.0 cfs or less in all three drainages. It also concluded that there were no
<br />conflicts between the ES data and USGS data.
<br />Colowyo investigated baseline streamflow conditions for streams in the general area from September
<br />1996 to September 1997 (Jubb Creek and forks only), from December 2004 through May 2006 and
<br />March of 2012 through April of 2015. Surface water monitoring locations were established in Collom
<br />Gulch, Little Collom Gulch, Straight Gulch, and Jubb Creek as part of this study. Water Management
<br />Consultants (WMC) reported on those efforts up to May 2005 in their Pre -Feasibility Hydrology Report,
<br />included herein as Exhibit 7, Item 21 (WMC, 2005). Surface water monitoring locations applicable to the
<br />Collom permit expansion area are summarized in Table 2.04.7-46, and monitoring results are summarized
<br />in Table 2.04.7-48. Surface water monitoring locations are depicted on Map l OB.
<br />Collom — Rule 2, Page 29 Revision Date: 4/7/17
<br />Revision No.: RN -07
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