OCR Text |
Show 3.70 -= » 60 - I 50 40 30 20 10 00 90 80 70 60 50 40 30 20 10 00 90 80 70 60 50 40 30 20 10 LU LU Z 2.80 ^ - J < Z HI LU UL U. Q Q < LU X 1.00 - 5 0.90 - 1 0.80 HEAD DIFFERENTIALS DURING DATE RANGES INDICATED WHEN THE LAKE'S RANGE WAS WITHIN THE 4,197.5 TO 4,200- FOOT ELEVATION RANGE. nOTICE THAT THE PRE- FLOODING, PRE- SPRR CAUSEWAY BUILDUP HEAD DIFFERENTIALS ( PRE- 1983) ARE SIMILAR, BUT THE POST- FLOODING HEAD DIFFERENTIALS ARE GREATER AT THE SAME LAKE ELEVATIONS, SUGGESTING A LOWER TRANSMIS- SIVITY RATE AND THUS A LOWER PERMEABILITY. THE 1972 GROUP REPRESENT A RISING LAKE, THE 1977 GROUP A SOMEWHAT STABLE LAKE, AND THE 1992 GROUP THE LOW POINT AFTER THE HISTORIC HIGH, AND JUST BEFORE THE LAKE'S PRESENT UPWARD TREND. IAKE ELEVATIONS ARE CORRECTED AS PER WOLD/ WADDELL'S RECENT MODEL CORRECTIONS. . AVERAGE MEAN 1970 1975 1980 1985 TIME IN YEARS 1990 1995 2000 Figure A. Plot of head differential versus time- in- years showing two pre- breach head- differential groups and one post- breach group which illustrate possible changes in the permeability of the SPRR causeway. |