![](bg3.png)
G = Soil flux density (MJ/m
2
)
T = Mean daily air temperature at 2m height (° C)
u
2
= Wind speed at 2m hieghr (m/sec)
e
s
= Saturation vapour pressure (kPa)
e
a
= Actual vapour pressure (kPa)
The FAO Penman-monteith (Savva and Frenken,
2002) is used to determine the ET
c
and then the IR,
Irrigation requirement equation 2.
IR = ET
c
− (Pe − Ge +Wb) + LR (2)
IR= Irrigation Requirement (mm)
ET
c
= Crop Evapotranspiration (mm)
Pe= effective dependable rainfall (mm)
Ge= Groundwater contribution from water table
(mm)
W b = Water stored in the soil at the beginning of each
period (mm)
LR = Leaching Requirement (mm)
It is important to distinct CWR and IR. In fact, for
an effective irrigation, more parameters like the cli-
mate, the crop type and the growth stage of the crops,
need to be taken into consideration to attain plant wa-
ter need.
2.3 Computer Simulation Model for
Natural Water Resources
Computer science helps to model efficient water use
in crop field. Powerful evaluation and simulation
tools are made to help water usage planning. To re-
flect actual values of field parameters, these models
have to fit in real time system to avoid ineffective
performance of irrigation schedule. In addition, crop
growth, depend closely to irrigation frequency and
amount of water supplied to the plants. So, it is cru-
cial to have a model to produce a good watering plan.
There are many tools used to model water use in crop
field, for example (Chen et al., 2018):
• The Soil Water Assessment Tool (SWAT) for wa-
tershed scale model, used to simulate the quality
and quantity of surface and ground water and pre-
dict the environmental impact of land use, land
management practices, and climate change.
• MODFLOW wich is a program used by hydro-
geologists to simulate the flow of groundwater
through aquifers.
• Decision Support System for Agrotechnology
Transfer (DSSAT) is software application pro-
gram that comprises dynamic crop growth simu-
lation models for over 40 crops.
SWAT model is widely used for managing water re-
sources.
2.4 Internet of Things - IoT
ICTs has a significant impact on the concept of smart
agriculture. Smart-agriculture is the use of computer
devices, in the farming process to optimize usage of
natural resources, limit human labor and have a good
profitability.
The Internet of Things (IoT), in particular Wire-
less Sensor Networks (WSN) is commonly used in
Smart-agriculture. WSN is a collection of physical
modules called sensors to capture, process and trans-
mit information in the environment in which they are
deployed. Sensors are deployed at different soil depth
to sense water flow and help to determine proper time
for water supply. Based on IoT, SMART-Irrigation
can help for water wastage problems, over-irrigation
that can lead to the leaching of nutrients and slowing
down crop growth (George, 2017). Precise irrigation
is a concept of saving water supply to use exactly the
exact amount of water for the plant to develop cor-
rectly. Many parameters are taken in account to define
a precise irrigation. Some of them are meteorological
data like temperature, humidity, the wind, etc. Some
of those can be obtained by using sensing elements
like soil moisture sensors.
3 RELATED WORK
SMART-Irrigation is the use of technology in the
farming process to automatize certain procedures and
increase yields. Sensor devices are linked by wireless
communication technology to monitor data from the
agricultural field. Many studies are focused on using
soil moisture sensors to determinate water supply or
to determine when to irrigate. In the following we
will see some work on Smart-irrigation.
CROPWAT(Savva and Frenken, 2002) is a soft-
ware that can calculate CWR and IR from climatic
and crop data in a particular area. Various tables are
given to estimate the exact value of each parameter of
the Penman-Monteith equation. Meteorological sta-
tions are distributed all through a given country mak-
ing it possible to prepare reference crop evapotran-
spiration maps for a country. Those meteorological
stations are contained in CLIMWAT wich is a soft-
ware that help to obtain value of each parameter of
the Penman-Monteith equation. I
In (Chen et al., 2018), authors created a SWAT
based algorithm. The algorithm simulates manage-
ment allowed depletion (MAD) irrigation schedul-
Approach using the Internet of Things in the Sahel for Smart Irrigation
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