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<br />7 <br /> <br />.- ungrazed watersheds, whereas later in the year, after the effect of <br />W <br />CJ1 summer storms, runoff was more nearly equal. <br />9J <br /> <br />Other causes of increased runoff and erosion have been attri- <br /> <br />buted to off-road vehicles and natural gas and coal exploration and <br /> <br />extraction. The associated roads, trails, and other disturbances <br /> <br />compact soils, reduce plant cover, and expose fresh shale. The most <br /> <br />obvious erosion effects are rill erosion and gully headcut extension <br /> <br />along vehicle tracks (Bureau of Land Management, 1978). <br /> <br />Investigations of relationships between salt release and runoff <br /> <br />and erosion began in the last decade. Contributions have been made <br /> <br />by Ponce (1975), Laronne (1977), and Sunday (1979). Ponce <br /> <br />examined relationships between salinity and rainfall intensity, runoff <br /> <br />,rate, runoff duration, and suspended solids in runoff. In general, <br /> <br />he concluded the following: 1) salt concentration in runoff is <br /> <br />decreased when a change in rainfall intensity is not accompanied by <br /> <br />a direct change in erosion rate; 2) salt con,centration is increased <br /> <br /> <br />when an increase in rainfall intensity is accompanied by soil erosion; <br /> <br />3) salt concentration is highest at the onset of runoff generation and <br /> <br />soon decreases to a relatively constant value; and 4) salt concentra- <br /> <br />tion is dependent on the dissolution of mineral salts that have been <br /> <br />exposed by erosion and that are contained in the soil matrix and on <br /> <br />soil particles suspended in the runoff. One of Laronne's observations <br /> <br />was that the salinity of storm runoff is influenced primarily by the <br /> <br />availability of soluble minerals on the surface and in salt crusts <br /> <br />derived from evaporation of soil moisture. Tests conducted by Sunday <br /> <br />led to conclusions that the specific conductivity (EC) of runoff in- <br /> <br />creases with increasing slope, increasing suspended sediment <br />