# Changing z coefficient does not change water yield output

**URL:** <https://community.naturalcapitalalliance.org/t/changing-z-coefficient-does-not-change-water-yield-output/2991>\
**Category:** Software Support\
**Tags:** annual-water-yield\
**Created:** [August 16, 2022, 2:10pm UTC](https://community.naturalcapitalalliance.org/t/changing-z-coefficient-does-not-change-water-yield-output/2991 "2022-08-16T14:10:11Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dcdenu4](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/dcdenu4/32/544_2.png) [@dcdenu4](https://community.naturalcapitalalliance.org/u/dcdenu4)\
**Post date:** [August 16, 2022, 2:10pm UTC](https://community.naturalcapitalalliance.org/t/changing-z-coefficient-does-not-change-water-yield-output/2991/1 "2022-08-16T14:10:11Z")

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Moving a question from another topic to its own.

> [@Water yield output 0](https://community.naturalcapitalalliance.org/t/water-yield-output-0/2683/9):
>
> Thank you for your reply, this problem was caused by my improper operation and has been solved. But there is a new question: I change the z coefficient, why won’t wyield\_vol change?

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**Author:** ![dcdenu4](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/dcdenu4/32/544_2.png) [@dcdenu4](https://community.naturalcapitalalliance.org/u/dcdenu4)\
**Post date:** [August 16, 2022, 2:18pm UTC](https://community.naturalcapitalalliance.org/t/changing-z-coefficient-does-not-change-water-yield-output/2991/2 "2022-08-16T14:18:41Z")

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Hi @yqyq

It could be that the function in which the z coefficient is being used is being capped at it’s maximum allowed limit. If this is the case, then changing it would not have any effect. See the [Users Guide](https://storage.googleapis.com/releases.naturalcapitalproject.org/invest-userguide/latest/annual_water_yield.html), equation 2.

The max value of `w(x)` is 5. What values of the z coefficient have you tried? You could try setting a value of 1 and seeing if that has any difference than a higher value.

Doug

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**Author:** ![yqyq](https://avatars.discourse-cdn.com/v4/letter/y/eada6e/32.png) [@yqyq](https://community.naturalcapitalalliance.org/u/yqyq)\
**Post date:** [August 16, 2022, 2:55pm UTC](https://community.naturalcapitalalliance.org/t/changing-z-coefficient-does-not-change-water-yield-output/2991/3 "2022-08-16T14:55:49Z")

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> [@dcdenu4](#):
>
> 您尝试过 z 系数的哪些值？您可以尝试将值设置为 1，然后查看该值是否与较高的值有任何差异。`w(x)`

Thank you for your advice. I have used 30 and 10.