WSP11669

• File Number: 8149.100
• Description: Miscellaneous Small Projects and Project Studies - NRCS-Ft Lyon Canal Co Limestone Graveyard Creeks
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 9/1/1996
• Author: Bent Soil Conservati
• Title: Limestone-Graveyard Creeks Watershed Bent County Colorado Prowers County Colorado Watershed Plan and Environmental Assessment
• Water Supply Pro - Doc Type: EIS

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05~1

affected by deep percolation of irrigation waters and were ~arkedly
higher than the mean. The current proposed EPA drinking water
regulation for uranium is 20 micro grams/liter. This 19.4 ~icro
grams/liter concentration is 2-4 times as high as other qua=rangles
tested in wester~ U.S. Future levels are anticipated to cc~tinue to be
high if irrigation practices remain the same.

Uranium concentrations in the drains and creeks flowing int~ the
Arkansas River from the watershed area have readings at times from 20-
50 micro grams/liter. The extensive irrigation in this rea=h of the
Arkansas River significantly elevates the dissolved concentrations of
uranium. This combination of natural and man made effects could
compromise the water quality for domestic use {farms, commu~ities,} and
agricultural use (irrigation, livestock) that derive water :rom the
alluvial aquifer as well as the high concentrations in the river
itself. Excessive levels may also be dangerous to wildlife including
endangered species. Downstream water quality is also decreased to
irrigators who reuse the Arkansas River water.

There are a number of shallow wells in the area that are also high in
nitrates. EPA Storet Data indicates there are six wells in the
watershed found to exceed the EPA standards (10 mg/lppm) N03-N. The
Arkansas Rivers' water approaches the nitrate level standar= at times.
The sources of t~e nitrates are a combination of naturally occurring
and applied. The top two feet of soil were generally found to have
very high concentrations of nitrates. The higher nitrate well
concentrations generally occur in the lower portions of the watershed.
There are about 25 wells that were found to have nitrate levels
approaching or exceeding standards in the watershed area.

Salinity
Valley.
pick up,

is anot~er serious water quality problem in the Arkansas
There are 3 important factors in the salinity problem: salt
concentration, and the management of water, soils, and crops.

Although it is desirable to control salt loading, high salt levels will
remain as long as the water is used. Therefore, the greatest potential
for reducing salinity is through more effectively using water
throughout the valley. Irrigation water diverted into the Fort Lyon
Canal, upstream 53 channel miles from the project, has a mean TDS of
807 milligrams/liter (obtained from USGS records). The mean TDS in the
Arkansas River at Las Animas which is just above the project area is
1041 milligrams/liter. Just downstream from the project at the Lamar
gaging station the mean total dissolved solids (TDS) is 1694
milligrams/liter for the Arkansas River. The TDS levels are therefore
increasing downstream due to concentrations of salt in the remaining
water. No TDS standards have been set for Colorado, however, TDS
levels of 500 is deemed desirable and below 1000 is acceptable for
agricultural purposes. It is anticipated that total TDS will be
lowered through project action.

Eight organochlorine pesticides were detected in some samples of bird
livers and eggs and in fish from the reservoirs. All concentrations
were well within the ranges of reported backgroun~/concentrations
and were less than levels of biological concern.

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