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WSP04095
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Last modified
1/26/2010 12:53:43 PM
Creation date
10/12/2006 12:07:17 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8270.100
Description
Colorado River Basin Water Quality/Salinity -- Misc Water Quality
Basin
Colorado Mainstem
Water Division
5
Date
1/1/1987
Author
USDOI
Title
Quality of Water - Colorado River Basin - Progress Report No. 13 - January 1987
Water Supply Pro - Doc Type
Report/Study
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<br />7. Erosion <br /> <br />Several researchers[15,16,17,l8] have shown that erosion of saline <br />~ shales and dissolution of efflorescence increase salinity during runoff <br />-J events. These and previous studies have primarily focused on conditions <br />~ caused by summer and fall thundershowers. Lower elevation snowmelt on marine <br />~_ (saline) geologic formations may contribute more significantly to salinity. <br />Analyses of the Green River near the Green River station indicate that <br />electrical conductivity (a measure of salinity) remains high or may increase <br />with flow peaks associated with snowmelt runoff events in January through <br />April. <br /> <br />During Reclamation studies on the McElmo Creek Salinity Control <br />Unit, it was found that approximately 32 percent of the total salt load could <br />be related to runoff events. Similarly, recent salinity control <br />investigations by Reclamation show that 21 percent of the Price River salt <br />budget and 14 percent of the San Rafael River salt budget are related to <br />natural runoff. <br /> <br />Studies (19] conducted on Mancos Shale within the upper Basin of the <br />Colorado river drainage have demonstrated a positive relationship between <br />sediment yield and salt production. Sediment yield occurs as a result of <br />either upland erosion, or streambank and gully erosion. Upland erosion is <br />attributed to rill and inter ill. Salt and sediment yields are dependent upon <br />storm period, landf0rm type, and the soluble mineral content of the geologic <br />formation. <br /> <br />Studies (20] conducted in the Price River Basin have demonstrated <br />that the highest salt and sediment concentrations occur in the first <br />streamflow event following a long period of no discharge. The accumulation of <br />salts in the channel may be attributed to efflorescence resulting from the <br />drying of the channel. Salt yields occurring after the initial flushing of <br />the channel are similar to those found in the surrounding watershed soils. <br /> <br />Sediment and the resulting salt yield is highly dependent upon <br />landform type. Three major landform types--badlands, pediments, and alluvial <br />valleys--are associated with the Mancos Shale terrain. <br /> <br />Badlands are the most erosionally unstable, with sediment yields <br />as large as 15 tons per acre [21]. Rilling accounts for approximately 80 <br />percent of the erosion (20]. Because salt production is closely related to <br />sediment yield and the badland soils have not been leached of their soluble <br />minerals, they produce the greatest amount of salt of the landform types. <br /> <br />Pediments are gently inclined planate erosion surface carved in <br />bedrock and generally veneered with fluvial gravels. The surface slopes of <br />pediments are gentle, making them relatively stable. Pediments have deeper <br />soils and higher infiltration rates than badlands, thus they support a greater <br />vegetation cover and are less erosive. <br /> <br />Alluvial valleys are formed by a change in gradient and the <br />deposition of sediment. They are stable except along the channel where <br />headcutting and gullying occur. Most of the salts have been leached from the <br />alluvial deposits, thus erosion of their landform type yields less salts per <br />unit volume of sediment than the other two landform types. However, channels <br /> <br />v-7 <br /> <br />- <br />
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