REPORT OF INVESTIGATIONS No. 41


Weather Panama showing


Bureau. During the past 29 years the annual rainfall at City has varied from 37.6 inches to 85.0 inches. Graphs variations in rainfall are given in figure 4. Short periods


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Figure 4. Bar graphs of maximum, minimum, and average monthly rainfall,
          and annual rainfall, at Panama City from 1935 to 1963.

of low rainfall and short periods of high rainfall have little- direct effect on the water resources; that is,.the amount of water in storage. Extended periods of below-average rainfall, or droughts, cause reduction in storage. The most severe drought of record ended in 1956 with a 7-year deficiency in rainfall of 50.2 inches. Within 'this 7-year period, 1953 was a single year of above-average rainfall but did not bring about a complete recovery of water lost from storage duri ng the preceding years of low rainfall. The 6-year period from 1944 to 1949 was the wettest of record. Records of water levels indicate that storage was near an all-time high during this wet period.


            WATER QUALITY CHARACTERISTICS
    The water in the lakes and streams of the area has about -the same mineral concentration as rain water. Samples of rain water contained as much as 13 ppm of dissolved mineral matter; the water in the streams and lakes ranged from about 6 to 25 ppm. The mineral concentration of the surface water differs little from rainwater because of the r,4ative insolubility of the surface materials. During periods of low flow, high mineral concentrations are normally expected in stream water because a large part of the flow is seepage from the


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