GEOSTATS: rainfall estimation for agriculture potential

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• Bonjour, We work on a pedological database called Donesol that cover France ( not yet all!). Sory for my bad english. This database describes all the
Message 1 of 1 , Feb 11, 1999
Bonjour,

We work on a pedological database called Donesol that cover France ( not
yet all!). Sory for my bad english. This database describes all the
pedological landscape at the 1/100000 scale. All the types of soil
discovered in those 'pedopaysage' (pedological landscape) are described
(not geometricaly) and analysed.
This databse give us a spatial value for the usefull reserve of water.
I would like to estimate an hydric state of the soils during the year. We
work on a simple region where the rainfall are distributed West-East
relatively regularly. To calculate the quantity of water in the soil I
need to sum Precipitations every ten days period. Usualy, experts make
this at each point location and interpolate after.
But I would like to use spatial data to improve ( I hope !) the results. I
would like to produce rainfall surface for each ten days period and I will
probably do it on a 30 years period.
The simple aspect of the boundary we are going to study let me think that
a simple method that use elevation-orientation and wind could be enough.
I'd like to implement it in an Arc-Info AML programm to produce a lot of
comparison whith my soil database.

My Algorythme could look like this :

RU1 = RU0 + P0 - K0.ETP0
if RU1 > RU0, RU1=RU0 (when water exeed soil capabilty to store it )
RU2 = RU1 + P1 - K1.ETP1
.... -> the end of the year (October for cultures)

where
- RU0 is the initial value in March for usefull water storage. It is a
grid. 0 is an index for each ten days period.
- Px is a grid of rainfall during the ten-days period.
- ETPx is a grid of Evapotranspiration Potentielle ( water eject by
vegetal in the atmosphere)
- Kx is a scalar that depends on the vegetal and the date.

For each iteration I need to calculate 2 grid ( P and ETP ) and there are
3 iteration by month during 6 month and I have to do it for 30 years. The
interest of this is to introduce the RU factor that depends on the soils.
So this method is heavy but computers are here to work for me. But I just
would like to know if someone has a simple formule to estimate rainfall.
This could, in a first time, reduce my calculs and perhaps it could be
enough for the boundary we study.

Cordialement,

Lionel Bargeot

http://www.cnerta.educagri.fr/infogeo/contact.htm

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