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<br />The results of this exercise showed a good correlation with the <br />di scharge of salt estimated by Bookman-Edmonston for each subarea, <br />with two exceptions. Notably, the results for the East Side Subarea <br />matched those of the Bookman-Edmonston report. The exceptions were <br />two subareas for which ground water sampling points apparently gave an <br />erroneous indication of average quality, as evidenced by the quality <br />of subsurface drainage discharging into drains. It was concluded that <br />the variations among subareas estimated by Bookman-Edmonston are <br />realistic estimates reflecting differences in ground-water quality. <br />Because the Palo Verde Subarea was shown to be causing most of <br />the District's salt discharge, the preliminary project evaluation in <br />this report has been confined to that Subarea. <br /> <br />Analysis of Palo Verde Subarea <br />The Palo Verde Subarea 1 i es in the southwest corner of the <br />District, adjacent to the mesa. It is approximately 11~ miles long <br />and 3~ miles wide at its widest point, and contains a gross area of <br />approximately 12,550 acres. The Palo Verde Outfall Drain forms half <br />of its eastern boundary, separating much of the Subarea from adjacent <br />subareas. <br /> <br />Agricultural Development. The growth of irrigation in the Palo <br />Verde Subarea is shown on Figure 4, which was compiled through inspec- <br />tion of aerial photos of the District. During the late 1930's and the <br />1940's some land in the Subarea was not farmed for a number of years, <br />reportedly because of poor drai nage that resul ted in a hi gh water <br />table and salt accumulations in the irrigated soils, and also because <br />of economic conditions. During the 1950's an extensive drainage <br />project was undertaken by the District, which included deepening and <br />straightening the Palo Verde Outfall Drain and various other drains. <br />These improvements remedied the drainage problems and a steady agri- <br />cultural growth in the Subarea and adjacent lands followed. The <br />Subarea is now virtually fully developed and, for practical purposes, <br />has been since 1970. The irrigated area is about 10,300 acres. <br />002856 <br /> <br />14 <br />