Figure 1: The proposed multi-module smart drainage management approach.
2.1 Meteorological Forecasting
Module
In the first module, the forecasted hydro-climatological data of the
study area are collected and characterized in detail. The 1-10 day
forecasted rainfall and temperature data, provided by regional
authorities and meteorological institutes, are used as initial input.
The forecasted temperature is applied to estimate the daily reference
evapotranspiration (ET0). The crop evapotranspiration
(ETc) will be calculated based on the ET0 and crop
coefficient (Kc) in the different growth stages.
2.2 Hydrological Simulation
Module
Using ETc, current soil water holding, and forecasted rainfall, the
daily soil moisture will be estimated for the next 10 days using the
Water Balance Simulation (WBS) in the hydrological simulation module.
The results of the WBS will propose tentative irrigation or drainage
demand values to farmers (or system operators). This provides the basis
to implement optimal irrigation or drainage management.
In the first step of the implementation module, the water level in the
crop field will be optimized by using the automatic drainage control
system. For instance, if currently (e.g., today) the field has enough
water, but no (or deficit) rainfall is forecasted within the next 10
days, the drainage valve will automatically be closed (or partially
closed) to keep soil moisture near the root zone. Conversely, if an
extreme rainfall event is forecasted, a drainage valve will
automatically be fully opened to facilitate drainage and avoid
waterlogging. WBS simulation takes advantage of the ICT sensors by
considering soil hydraulic properties (e.g. soil water retention curve)
to regulate the drainage outflow.
2.3 Implementation Module using novel ICT based sensor
network
In the final part of the implementation module, the excess drained water
from heavy rainfall events can be stored in a buffer pond or portable
storage tank (Fig. 1). Some parts of the drainage ditch, beside the
field, can be used as a buffer pond by applying a water level
controller. During a summer drought, the stored water can be used for
fertigation. Care needs to be taken in assessing the water quality of
the stored water, thus avoiding excess fertilization and degradation of
soils (i.e. through heavy metals, salinization, etc.). The assessed
irrigation water can be fed back through the existing drainage system
using these as underground irrigation pipes, thus avoiding additional
irrigation infrastructure and using emission-free systems (e.g. solar
pumps). An elevated storage tank can also help overcome the possible
uncertainty in the weather predictions. A solar pump will be applied to
store drained water into a portable storage tankwhich can then be used
for fertigation by gravity flow. Given the climatic conditions of the
Nordic region, the tank can be filled with melted water from snow before
the cropping season. Additionally, the drainage water recycling reduces
nutrient loading to surface water from agriculture.