NorthPlatteBasinWaterSupplyandNeedsReport

• Basin Roundtable: North Platte
• Title: Water Supply & Needs Report for the North Platte Basin
• Date: 6/1/2006
• Author: CDM
• Basin Roundtables - Doc Type: Needs Assessment Documents

Section 3
Physical Environment of the North Platte Basin

f Sit d USGS St

G

the North Platte River Basin

Table 3 2 S

.

USGS Site
Number

Mean Annual
Streamflow
(AFY)

Drainage
s m'l

Site Name

Laramie River near Glendevey
Sand Creek at Colorado-Wyoming State
Line
North Platte River near Northgate

T 06657500
06659580

I 06620000

Source. USGS NWIS web/HydroBase database

3.2.7 Groundwater

The more important aquifers in the basin include:

. Valley-fill alluvium
. North Park Formation
. Coalmont Formation

Figure 3-6 shows the location of the significant aquifers
in the basin separated into two groups: alluvial (valley-fill
alluvium) and bedrock (North Park and Coalmont). The
valley-fill alluvium is composed of sand, gravel, clay, and
silt and is 80 feet thick in some areas (Pearl 197 4). The
North Park Formation is a 2,000-foot layer of calcareous
sandstone with interbedded layers of siltstone, clay, and
volcanic ash. Well yields from this aquifer are typically
less than 50 gallons per minute (gpm) (Pearl 1974). The
Coalmont Formation is a 6,000 to 9,000 foot layer of
sandstone, shale, conglomerate, and coal beds. This is
the primary aquifer in the basin, and well yields are
generally less than 10 gpm (Pearl 1974). The Coalmont
Formation is estimated to contain 120 million AF of
recoverable groundwater; however, only 39 million AF
are considered to be economical for withdrawal (CGS
2003). Figure 3-34 also shows the location of wells with
permitted or decreed capacities greater than or equal to
500 gpm. In the North Platte Basin there is only one such
well located to the west of South Delaney Lake.

Groundwater recharge and discharge are assumed to be
equal as there has been no substantial change in the
volume of storage in the North Park Basin. The volume
of water withdrawn each year is very small compared to
the total volume of groundwater storage (CGS 2003).

S:\1177\Basin Reports\North Platte\S3_North Platte.doc

Mean Annual
Streamflow
(cfs)

52,312 T
7,518

Period of
Record (Years)

I es
101
29

T

72
10

1904-1982
1968-2002

310,389 I

I

1915-2002

1,431

429

3.2.8 Water Quality

The North Platte and its tributaries are generally of high-
quality water (CDPHE 2002). Elevated levels of total
dissolved solids (TDS) are of concern in portions of the
basin's groundwater resources affected by coal mining
(CGS 2003). The basin has very few permitted
wastewater discharges; stream erosion and sediment are
the primary water quality issues of concern in the basin.
The state's 2002 303(d) list did not include any listings in
the North Platte Basin. However, the proposed 2004
303(d) list includes impairment of tributaries to the North
Platte in the Illinois River drainage for iron, and Spring
Creek for dissolved oxygen. Stream segments proposed
for listing via the 2004 303(d) list and the accompanying
Monitoring and Evaluation list are described in Colorado
Water Quality Control Commission (WQCC) Regulations
93 and 94.

3.2.9 Areas of Environmental Concern
,

Special Attention Areas, and

Threatened and Endangered

Species

As mentioned above, an area of environmental concern
in the North Platte Basin is the high TDS concentrations
in groundwater in certain historic coal mine areas. There
are no federal and/or state listed fish species found in the
North Platte Basin. However, some other species are
federally and/or state listed as threatened and
endangered species in the North Platte Basin. A
complete list of these species can be found in
Appendix C of the SWSI Report Figure 3-7 shows areas
of environmental concern in the North Platte Basin.

CONI

3-3