Calculate Water Storage Calculation - Hydrology?

I am wondering if I got the correct answer for this problem:

A lake has a SA of 1050 acres. Inflow to the lake was 33 cfs (ft^3/s) and the outflow was 27 cfs. A 1.5 inch seepage loss was measured; precipitation was recorded at 4.5 inches and evaporation loss was 6.0 inches. Estimate the storage change in inches over a one month (30 day) period. 

So I did: 

= [water in] - [water out]

= [+33 cfs + (4.5 in*1050 acres)] - [27cfs + (1.5 in * 1050 acres) + (6.0 in * 1050 acres)]*

=+2.685 E 10 in^3/month

Does this seem correct? 

*conversions not shown

1 Answer

  • 1 month ago

    what is missing is time period for many of the numbers: seepage, precipitation, evaporation. Without that, it's just a guess.

    as to your calculation, it is a mess dimensionally. Always compare and check dimensions.

    = [+33 cfs + (4.5 in*1050 acres)] - [27cfs + (1.5 in * 1050 acres) + (6.0 in * 1050 acres)]*

    you are adding ft³/s to inch•acres in two cases, which you cannot do. inch•acres is a volume, you cannot add a volume (even if you converted it to ft³) to a rate, ft³/s

    • ...Show all comments
    • billrussell42
      Lv 7
      1 month agoReport

      and you didn't think that 1 month was important?

      you have 33 cfs in your equation, how is that converted in in^3/mo?

      if you want help, provide the complete problem, not just parts of it.

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