2007-11-01_PERMIT FILE - C1982056A ‎(4)‎

• Permit No: C1982056A
• IBM Index Class Name: Permit File
• Doc Date: 11/1/2007
• Section_Exhibit Name: 2.06 Special Categories of Mining
• Media Type: D
• Archive: Yes

Calculation of these values indicates that along Fish Creek, the allowable change in soil conductivity will
be experienced with [he application of 0.663 feet of irrigation water. The salinity threshold on Trout
• Creek below Middle Creek will be exceeded with the application of 0.986 feet of irrigation water. Along
l~rrnrt Creek below Fish Creek, the threshold will be exceeded at 0.889 feet of water. The above
dcmonsU'a[ion reveals that there is a theoretical potential salinization of irrigated lands using waters from
Fish Creek and along Trout Creek below Middle Creek. This value, however, ignores the fact that
leaching is continuously occurring, as a result of precipitation and irrigation. A significant amount of sah
is removed in the harvested crop and [hat precipitation of salts is naturally occurring in the soil profile.
The leaching requirement as defined in Handbook No. 60 is defined "as the fraction of irrigation water that
must be leached through the root mne to control soil salinity of any specified level". The equation used to
calculate the leaching requirement is given as:
LR = Ddw = ECiw
Diw ECdw
where:
LR = Leaching Requirement;
Ddw = depth of drainage water;
Diw = depth of irrigation water;
Eciw = electrical conductivity of the irrigation water; and
ECdw = electrical conductivity of the drainage water.
For purposes of [Iris evaluation, ECdw equals 2.0 mmhos/cm. The ECiw equals conductivity of 1.22
mittltos/ctn for Fish Creek water and Trout Creek irrigation waters equal 0.82 mmhos/cm at its confluence
with Middle Creek and 0.91 mmhos/ctn below its confluence with Fish Creek. The leaching requirement
for these areas is calculated to equal 61, 41 and 46 percent, respectively.
• The required depth of irrigation water that is necessary to be applied is calculated by the formula:
Diw = ( ECdw_ ).Dcw,
ECdw -ECiw
where:
Diw = Required depth of irrigation water;
ECdw = Electrical Conductivity of the drainage water;
Eciw = Electrical Conductivity of the irrigation water; and
Dcw = depth of consumptive water use which is obtained from studies conducted by
Leonard Rice Water Engineers for the years 1978, 1979 and 1980 and collected by
the Colorado Department of Water Resources for the years 1983, 1984 and 198.
The Itigltest yearly average consumptive use value, for the 6 years studied was
found to equal 21.92 inches of water.
Calculation of the required depths of irrigation water to satisfy both [he consumptive demands of
evapotranspiration and to satisfy the leaching requirement to maintain the soil salinity values belo+v 2.0
nunhoslcm produces a value of iG? inches of water being applied to lands irrigated with Fish Creek
water, 37.2 inches of water being applied to lands irrigated with Trout Creek waters belo+v the Poidel
Creek drainage, and 40? inches of water front Trout Creek being applied to irrigated lands belo++ its
confluence with Fish Creek.
Due to inherent inefficiencies of the existin_ irrigation systems, the actual quantities of +vater beims
. applied are substantially greater than those needed to satisfy [he consumptive water use demands.
According to data from the Colorado Division of Water Resources (CDWR) Office in Steamboat Sprin_s.
MR97-lid 2.06-IS Rcriccd 1'_/09r~?