WSP04845 - Laserfiche WebLink

Home Browse Search

...... c..J c.a .., W 8 concentrations associated with rill flow, and higher SMC values. Furthermore, she observed that rill flow has a much higher rate of erosion than that of sheet flow, therefore it introduces more sediment and salt to the runoff. Investigations on SMC of surficial materials have been conducted by Laronne (1977), the Bureau of Land Management (1978), and others. Samples tested by Laronne show: 1) the dominant mineral in Mancos Shale is gypsum, while calcite, dolomite, and gypsum are dominant in all uvium; 2) soil crust salinity increases as the permeability decreases and the SMC of the underlying material ,increases; 3) SMC increases with depth in shallow alluvium overlying Mancos Shale; 4) a uniform SMC with depth characterizes deep and leached bed materials and terrace deposits; and 5) Mancos Shale hillslopes contain an appreciably higher content of soluble minerals than do alluvial samples. The Bureau of Land Management has made' the following salinity classification: 1) soils developed on gravel pediment surfaces are non saline (EC <4000 ]Jmho/cm) in the top 75 CM, but saline at greater depths; 2) soils developed on Mancos Shale are nonsaline in the top 30 cm, but saline at greater depths; and 3) soils on alluvial deposits are saline throughout the profile. Carter (1980) studied pediment gravels and the gravel-bedrock interface and related his findings to salinity. Although no samples were collected, he proposed that where ground water could migrate through pediment gravel, it would become highly saline from the calcite cement in the gravels and from leached salts concentrated at the gravel-bedrock interface ..