# Difficulty wrapping my head around the units being used and the target values for training, etc

Hi,

I’ve been pondering this issue for a couple of days now, and I can’t seem to come to any resolution on a few show stopping misconceptions of mine. Hopefully the answers will be quick and easy to explain (otherwise I may not be able to score better than ~400 even when 2024 rolls around, hah).

• The USGS streamflow data uses units of cubic feet per second (CFS). What’s the formula for turning this number into KAH – for example, assuming a trivially simple classroom exercise where the streamflow in cubic feet per second is constant and never changes, can it possibly be:
``````600CFS = 600*(seconds per year) / 43559.9 = Y KAF
``````

… where CFS = cubic feet per second, KAF is thousand acre-feet, and Y is the variable of interest? My submissions are scoring erratically no matter what my local tests and validation are saying, and I can’t seem to come up with the same numbers as I see in the train.csv file provided.

• I’m also stumbling a little trying to comprehend the periods of time involved in the relevant data. For example, a cubic foot per second has a time component, so if it’s measured at high noon, I understand 100 CFS as being 100 cubic feet of water over a time period of one second. But thousand acre-feet have no time component. Something just isn’t clicking in my head about how to interpret the various numbers and measurements available and combine them (and if I can’t do it myself, I can’t very well write a program that can do it either).

Any clarifications would be welcome. Thanks for your time, folks.

Hi @mmiron,

You’ve generally got some of the right ideas.

• The USGS streamflow data (cubic feet per second) is a rate of water flow. You can think of the units of volume per unit time.
• The target seasonal water supply variable is a volume of water (in KAF, which is thousand acre-feet).

So you have the right idea that you need to integrate streamflow over some period of time to get from a volumetric flow rate to a volume. If you assume a constant flow rate then your idea of multiplication is correct.

A few key things that you’re missing:

• The target seasonal water supply value is not the total amount of water over the whole year. Each forecast site has a particular forecast season. You can find the forecast season for each site in the `metadata.csv` file. For most of the sites, that season is April through July. Make sure to read the “Forecasting task” section carefully.
• Cubic feet and thousand acre-feet are two different units of volume, so you will need to convert between them as well.

So let’s say we pick a constant streamflow that is 600 CFS and a site that has a water supply forecast season of April through July. The number of days from April 1 through July 31 is 30+31+30+31 = 122 days.

Here’s the calculation. The same units are colored and are crossed out if they cancel out from being on both sides of a fraction.

Hope that helps! Also welcome anyone else to chime in with different approaches to the explanation.

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Just wanted to thank you for taking the time to help me understand, @jayqi – I’m doin’ my best to make sure your time was well spent. Thanks!