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oaJ213 42 shouid be charged to the reservoir run. It Is our opinion that only the In- creased diversion caused by a reservoir run should be charged to the reservoir run. The values presented. I n this report are based upon that ilssumption. In order to present a figure from which to begin shaping administration policy., this preliminary report has assumed a constant 4 per cent unauthor- Ized surface diversion charge for reservoir runs from Twin lakes to the Colo- rado Canal. WEll PUMP I NG . ! ~ i ; .The matter of well pumping along the Arkansas River, from tributary wells "drJlled Into the alluvium, cannot be Ignored. However, the well pumping Is expe~ted to be much more highly controlled In the future than It Is now, or has'been In past years. The cone of depression of wells pumping from the alluvium often Inter- sects the stream channel. Sometimes the wells merely Intercept tributary water on the way to the river. There are good indications that wells also lower the ground water table under phreatophytes and under high water table areas, thus reducing the non-benefIcIal consumptIve use. The well pumping, authorized or otherwise, would occur or be control led whether or not reservoir water was being carried In the river. Thus, It would appear that the same "Incremental" loss philosophy applied to evaporation loss- es should be applied to the well pumping losses. A review of the hydraulic nature of. the interception of the cone of de- pression with the rIver channel Indicates that the Incremental losses would relate to the rise In river stage resulting from the additional reservoir water, and the permeability of the river channel bank material. This Is sim- Ilar to the bank storage loss phenomenon. BANK STORAGE During a rise in stage of a river,' groundwater levels may be temporar- Ily raised near the channel by Inflow from the river. This Inflow of water, and Its detention, is known as.bank storage. In general, the ground water table slopes down toward the Arkansas River between Twin lakes and about Pueblo, thus making the Arkansas an effluent stream in this reach. Below Pueblo, the Arkansas River can be either an Influent or effluent stream de- pending on the season, stage of river, and use of wells near the river. It probably takes several days for bank storage water to come out of the banks after a shut off. This small quantity of "reservoir water" that gets to the diverting headgate several days after the shuf off is generally not diverted and can be considered as a loss to the reservoir run. When a reservoir run Is being made on a rising or falling river, the bank storage attributable to the reservoir water may be difficult, if not impossible, to identify. I . When the reservol r run Is shut off, the stage falls, leaving sand bars and part of the bank wet and exposed to the atmosphere. The water In these bars and banks then Is able to evaporate. This evaporation would not have occurred If there was no reservoIr release.