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<br />.,.1 <br /> <br />There are certain areas, stich as Hexicali Valley. which are <br />experiencing ,,'a tel' level decline. and other areas where the <br />water level has risen. In the consideration of the overall <br />aquifer system in the Colorado delta area, the hydrologic systeI!l <br />had a small imbalance; that is, internal abstraction exceeded <br />internal water sources. The effects from this imbalance are not <br />readily discernible over a short period of time (several years); <br />thus, the regional system might be considered to have been in <br />a near "steady-state condition" in 1970. <br /> <br />East !>lesa Area. California <br /> <br />A groundlfater mound "as established beneath the southern part <br />of East Hesa by leakage of lVater from the unlined All-American <br />and Coachella Canals. Water was transported in these eanals for <br />irrigation purposes since the middle-lateI940's. It has been <br />estimated that through 1967, the leakage amounted to 2.7 million <br />aere-feet from the Coaehella Canal and 4.5 million acre-feet from <br />the All-American Canal (Pilot-Knob to East IIighline Canal) or a <br />total of about 7 million acre-feet. In the middle 1960's, the <br />leakage was about 130,000 acre-feet per year from the Coachella <br />Canal and about 110,000 acre-feet per )'ear from the All-American <br />Canal (Pilot-Knob to East Highline Canal) or a total of 2i;0,OOO <br />acre-feet per year. <br /> <br />The change in water levels in the East Mesa has resulted in <br />a rise, ranging from 10 feet to more than 60 feet by 1967. <br />The pl'incil'al directions of groundlfater flow from the I~ound <br />arc soutln,areI into ~lexico and ,,'est'''Bl'd tOll'aTd Imperial Valley. <br />Tile gradient of the southern cOl!lponent flmf ranges from 0.001 <br />to 0.0025. ,cllereas the westward gradient is about 0.0009; eon- <br />sequently, the maj or part 0:C the 1 eakage from the All-fulleri can <br />Canal flo,...s soutll1';ard. A eOillputation on the magni tude of fIo" <br />incLicates that about 100,000 acre-feet per year of groundlmter <br />crosses the international boundary into clexicali Valley. <br />