I am new to using SMATH and could use assistance getting it to work for me. I am not sure what I am doing wrong. Attached is a screenshot of the variables and equations, unfortunately I can never get a result for Q1 and RV. I keep getting "units do not match", but don't know how to fix the problem. The results should be in inches and acre-feet.

Please let me know if you can help? Thanks in advance.

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Runoff Calculations.sm (13 KiB) downloaded 32 time(s).

Hi idelarca1,

hold the mouse pointer over Q.1yrpre, you can see that the sum is not possible, because S.pre is dimensionless while P is a length.

You have used "Ignore units", but this feature works fine only using direct assignments inside the function (look here)

Therefore you have to use the classic approach: modify Q.1yrpre to add a unit to S.pre or made P dimensionless.