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period 1924 to date. The vertical Beale on the left hand series of graphs represents the contents of Wngon Wheel Gap Reservoir an~ the Colorado accrued debits or credits, in units of 100,000 acre-feet. The series of graphs on the right hand side of the drawing shows the correspond- ing operation of Elephant Butte Reservoir. , An inspeetion of the oper"Uon of lQp.gon Wheel Gap Reser- voir as disclosed on Graph "C", indiet'.tes thnt for the period 1925 to 1930 inclusive, the reservoir would have been practically full n.nd would have spilled ~.uring ench of the yenrs. From 1930 to the end of the :rrigation season in 1937, the reservoir would have been drawn down materially. It is apparent from Grnph "C" that abeut 750,000 ncre-foet of "new water" would be rele/\Sed during such a low-water period. It might be assumed offhand and somewhat logically that if the criticnl period were en- tered ~Ii th a full reservoir 0 ~mter th".t was captured and held over from periods of large water supply and which wns then released during the period of low~wnter supply would cause a greater discharge at the State line due to in- creased return flow. At the present time about 16 per cent of the totnl diver- sions between Del Nerte and Alrumosa return to the streon. In the report on the Upper Rio Grande Joint Investigation' two assuoptiens were made as to return-flow between Del Norte a.~d Alnnosn: One based upon a return of eight per cent and the other on a return of 16 per cent of the to- tal diversions. The conclusions of the engineers making the study seened to be that it was reasonable to assume 16 per cent of the total diversions will return to the strean in the future. If this were true during the period 1925-1939 inclusive, the roservoir could operate to pro- vide a diveroion of 670,000 acre-feet per annum between Del Norte and Alanosa without violating the terns of the Conpact. However, the najor part of the 750,000 acre- feet of new water that would be released during such a critical period as 1925-1937, would be diverted to the Closed Basin and no increased return to the river from these diversions could be expected except by :..dditional drainage construction. Ta~ing a rather pessinistie view ef the nnount of water which would return to the river during the 1925- 1939 operation, it was found that if annual diver- sions of 670,000 acre-feet were made, by 1934 all the water in the reservoir would belong to Elephant Butte Reservoir and under the terms of the Compact, would hElVe to be relen.sed to that reservoir. Under 11 1763