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24 Chapter 5-Historical Salinity Conditions salinity of production waters varies greatly from location to location and is dependent upon the producing formation. Common disposal techniques include evaporation, injection, and discharge to local drainages. The future development of the oil shale resources in Colorado, Utah, and Wyoming has the potential to increase salt loading to the Colorado River. Salt increases can be attributed to the consumptive use of good quality water, mine dewatering, and, if surface retorting is used, the leaching of spoil materials similar to that of surface coal mining. Some States have enacted drilling and ground-water laws to protect water quality. In the Colorado River Basin, ground-water laws and strict enforcement are essential to prevent further saline aquifer movement and salt loading. Many small saline ground-water springs and/or flowing wells that are probably linked to drilling activities have been identified in the basin and listed in previous progress reports. Drilling activities may be particularly disruptive to shallow ground water systems, and stricter regulation and enforcement should be considered. The Meeker Dome salinity unit is one area where Reclamation has plugged abandoned oil exploration drilling holes anticipating that the aquifers are static and the saline water would not find another path back to the surface. Salinity Control Projects The implementation of salinity control units prevented about 183,500 tons per year of salts from reaching the river in 1990. By 2010, salinity control units will need to prevent about 1.5 million tons per year of salt from entering the Colorado River. To achieve this goal, a variety of salinity control methods is being investigated and constructed. Saline springs and seeps may be collected for disposal by evaporation, industrial use, or deep well injection. See chapter 7, the Paradox Unit, for an example of a deep well injection alternative. Other methods include both onfarm and off-farm delivery system and irrigation improvements which reduce the loss of water and reduce salt pickup by improving irrigation practices and by lining canals, laterals, and ditches. See the Grand Valley Unit as an example of these kinds of improvements. Erosion Several researchers[15,16, 17,18] have shown that erosion of saline shales and dissolution of eftlorescence (surface salts) increase salinity during runoff events. These and previous studies have primarily focused on conditions caused by summer and fall thundershowers. Lower elevation snowmelt on marine (saline) geologic formations may contribute more significantly to salinity. Analyses of the Green River near the Green River station indicate that electrical conductivity (a measure of salinity) remains high or may increase with flow peaks associated with snowmelt runoff events January through April. During Reclamation studies on the McElmo Creek Salinity Control Unit, it was found that approximately 32 percent of the total salt load could be related to runoff events. Similarly, recent salinity control investigations by Reclamation show that 21 percent of the Price River salt budget and 14 percent of the San Rafael River salt budget are related to natural runoff. Studies [19] conducted on Mancos Shale in the Upper Colorado River Basin have demonstrated a positive relationship between sediment yield and salt production. Sediment yield increases as a result of either upland erosion or streambank and gully erosion. Upland erosion is attributed to rill and inter-rill flow. Salt and sediment yields are dependent upon storm period, landform type, and the soluble mineral content of the geologic formation. Studies [20] conducted in the Price River basin have demonstrated that the highest salt and sediment concentrations occur in the first streamflow event following a long period of no discharge. The accumulation of salts in the channel may be attributed to eftlorescence resulting from the drying of the channel. Salt yields occurring after the initial flushing of the ~