Exhibit A

TENTATIVE AND PRELIMINARY STUDY ESTIMATED MONTHLY DISTRIBUTION OF PUMPED DRAINAGE FROM WELLTON-MOHAWK DISTRICT, WATERS BY-PASSED AND SALINITIES IN COLORADO RIVER AT NORTHERLY BOUNDARY Assuming: 181,000 Acre-Feet Drainage Returns, 1.5 Salt Balance in Deliveries to Mexico, Minimum Treaty Deliveries 90 Days during Winter. EXHIBIT A to accompany letter to Mr. Leonhardy, dated September 12, 1964 TOTAL BY-PASSED TO MEXICO OTHER FLOWS TOTAL FLOWS Month CFS PPM TONS CFS PPM TONS CFS PPM TONS Releases at Gila & Other Drains Imperial Dam CFS PPM CFS PPM Colorado River Northerly Boundary CFS PPM Jan 150 4,000 50,000 0 0 0 150 4,000 50,000 200 1,500 860 900 1,210 1,380 Feb 150 4,000 45,000 0 0 0 150 4,000 45,000 200 1,500 860 900 1,210 1,380 Mar 300 4,900 123,000 0 0 0 300 4,900 123,000 200 1,500 2,000 900 2,500 1,430 Apr 300 4,900 119,000 0 0 0 300 4,900 119,000 200 1,500 2,100 900 2,600 1,410 May 150 4,900 62,000 0 0 0 150 4,900 62,000 200 1,500 1,050 900 1,400 1,410 Jun 300 4,900 119,000 0 0 0 300 4,900 119,000 200 1,500 2,300 900 2,800 1,370 July 300 4,900 123,000 0 0 0 300 4,900 123,000 200 1,500 2,800 900 3,300 1,300 Aug 300 4,900 123,000 0 0 0 300 4,900 123,000 200 1,500 3,100 900 3,600 1,270 Sept 150 4,900 60,000 0 0 0 150 4,900 60,000 200 1,500 1,250 900 1,600 1,350 Oct 300 6,000 150,000 300 6,000 150,000 0 0 0 200 1,500 500 900 700 1,070 Nov 300 6,000 145,000 300 6,000 145,000 0 0 0 200 1,500 500 900 700 1,070 Dec 300 6,000 150,000 300 6,000 150,000 0 0 0 200 1,500 500 900 700 1,070 TOTAL 131,000 5,160 1,269,000 54,000 6,000 445,000 127,000 4,770 824,000 145,000 1,500 1,068,000 900 1,340,000 A.F. A.F. A.F. A.F. A.F. Total By-Pass 54,000 A.F. Waters By-Passed during Excess Flows 54,000 A.F. Waters By-Passed over and above Excess Flows O Total Drainage Pumped 181,000 A.F. Total Salt 1,269,000 Tons Project Salt Balance = 2.3:1 Salt Balance to Mexico = 1.5:1Epson Perfection 4870 Photo, 400 dpi, 8 bit, 13,868,544 byte