# River routing time scale

**URL:** <https://forum.access-hive.org.au/t/river-routing-time-scale/2235>\
**Category:** Earth System Model\
**Created:** [17 July 2024 06:30 UTC](https://forum.access-hive.org.au/t/river-routing-time-scale/2235 "2024-07-17T06:30:16Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![bduboc](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@bduboc](https://forum.access-hive.org.au/u/bduboc)\
**Post date:** [17 July 2024 06:30 UTC](https://forum.access-hive.org.au/t/river-routing-time-scale/2235/1 "2024-07-17T06:30:16Z")

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Hi all,  
I am Bartholome, a practicum student working with Katrin Meissner on the deoxygenation of the oceans.  
I have to clarify the river routing on the ACCESS-ESM model.  
Is the surface runoff instantaneous in this model?  
If not, how long does it take for a rain drop to travel for example down the Nile to the Mediterranean Sea?

Thank you in advance, Bart

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**Author:** ![clairecarouge](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/clairecarouge/32/380_2.png) [@clairecarouge](https://forum.access-hive.org.au/u/clairecarouge)\
**Post date:** [18 July 2024 06:13 UTC](https://forum.access-hive.org.au/t/river-routing-time-scale/2235/2 "2024-07-18T06:13:30Z")

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@bduboc I believe the river routing is instantaneous in all ACCESS coupled models. But I’m tagging some people who know better so they can correct me if I’m wrong. @inh599 @MartinDix @Jhan

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**Author:** ![inh599](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/inh599/32/3400_2.png) [@inh599](https://forum.access-hive.org.au/u/inh599)\
**Post date:** [18 July 2024 06:41 UTC](https://forum.access-hive.org.au/t/river-routing-time-scale/2235/3 "2024-07-18T06:41:10Z")

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@bduboc @clairecarouge @MartinDix @Jhan

I believe that ESM uses the TRIP river routing model - in which case there is a delay between runoff and river outflow to the ocean.

The relevant literature (from comments in JULES code) is Oki et al, 1999, J.Met.Soc.Japan, 77, 235-255. In effect the model specifies a river grid (which is different to atmospheric grid cell), each cell has a river storage, a river length, river meander and a connecting river network. Storage evolves over time depending on inflow (from the upstream network and runoff) and a decay timescale which gets applied to the existing storage. The decay time scale depends on the length and meander (and river routing time step - which is 1 day from memory)

The net result is that it would be very difficult to state how long a particular drop of water takes to pass down any river system.

All runoff (surface and subsurface) passes into the river network instantaneously during that atmospheric time step (20 minutes) - this is accumulated in time to match the river model’s time step.