INTRODUCTION – PERFORMANCE AND BENEFITS

MediWaterSafe 4.0 is an irrigation control unit developed by Harpo for the creation of home automation green roofs. Its unique feature is the ability to interpret the energy state of water in Harpo substrates and to modulate irrigation to stabilize hydration conditions at a state of moderate water availability. The Harpo home automation green roof system has been tested at the University of Trieste. The study identified multiple benefits of the system as follows.

RESEARCH AT THE UNIVERSITY OF TRIESTE

The two graphs on the left show the irrigation volumes and the water content in the substrate of two Harpo green roof modules, identical in construction and vegetation but irrigated with different devices: a classic timer in the CTR module and with MediWaterSafe 4.0 in the MWS module.

In the control module (CTR), irrigation started every day for a fixed time, during which 7 mm of water was supplied through drippers. The control irrigation is represented by the continuous black horizontal line in the upper graph and is recorded by the peaks at regular intervals visible in the water content graph below. The larger peaks correspond instead to rainfall events, which have been highlighted by the blue arrows. It can be noted that in the control module (CTR) the volume of water remained at a fairly high value and often reached (and exceeded) the maximum water retention, equal to about 40%.

The MediWaterSafe unit, on the other hand, maintained the water status at a much lower level and the substrate never reached maximum retention in the period represented. This graph allows us to make important considerations:

WATER SAVING: USE OF RAINWATER

The precipitation intercepted by the control module found a often high water content, consequently almost always bringing the substrate to maximum retention and the excess volume of rain was lost. The MWS module, on the other hand, always retained all precipitation. The MediWaterSafe unit therefore allowed a better use of free inputs (as evidenced by the periods in which it did not irrigate because it was supported by the water accumulated in the last rainfall), allowing for significant savings. During the three summer months monitored, the Harpo home automation green roof system saved 68% of water.

HYDRAULIC INVARIANCE

The previous point can also be seen from the opposite perspective, that is, that of the generated runoff: the CTR module, in reaching the maximum retention, generated runoff on several occasions, while MWS on the other hand was able to completely retain the precipitation that characterized that study period, reaching the surprising performance of “zero runoff”.

WATER SAVING: LESS WATER LOSS DUE TO EVAPOTRANSPIRATION

A moderate water deficit induces in many plants physiological responses oriented towards an efficient and parsimonious management of the water resource. The mechanisms can be of various types, such as the control of stoma opening and the development of a smaller and more compact leaf apparatus. These measures lead to a reduction in evapotranspiration and water requirements. For example, observe the days around August 17 (those between the two dashed vertical lines in the following graph): in those days the volume of irrigation supplied in the control module was higher than in the MWS module. The volume was also almost constant in both modules. Despite receiving the same amount of water, the water content in the CTR module declined, while the MWS module maintained a constant level. This is because the plants in the module irrigated with the normal timer consumed more water, despite being equal in number and species to the twin module irrigated with MediWaterSafe 4.0.

ADAPTIVE SYSTEM

The irrigation duration in the CTR module had been defined by the university following in-depth evaluations of the plants’ water needs under those conditions. Nevertheless, the graphs show how constant irrigation is always subject to both the risk of over-irrigating (as evidenced by the frequent reaching of maximum retention with consequent loss due to drainage) and the risk of incurring water stress: if the rains had been less frequent, the evapotranspiration trend of the CTR module would have led to severe water stress (see the red arrow).

On the contrary, the MediWaterSafe 4.0 control unit showed an adaptive behavior: it modulated the irrigation by interrupting or reducing it when the water status of the substrate was very favorable and increasing it progressively as the water status approached the desired value, in order to stabilize it, as evidenced by the trend indicated by the green arrow.

STRESS RESISTANCE

The ability to maintain a moderately deficient water status stimulates plants to develop a structure and physiology to stress tolerance. The study revealed that plants irrigated using the MediWaterSafe system exhibited lower stress levels compared to those watered with a traditional timer during summer months. Stress was determined both on the basis of the maximum quantum yield of photosystem II (Fv/Fm) and on the basis of the damage suffered by the roots at increasing temperatures, as illustrated in the image alongside, where on the vertical axis you can see the damage suffered by the plants (REL) irrigated by MediWaterSafe 4.0 (gray indicators) and those irrigated with a normal timer (white dots). It is evident how irrigation controlled by MediWaterSafe induced Hypericum plants to better resist high temperatures.

HOME AUTOMATION 4.0

MediWaterSafe integrates the physical environment of the green roof with the virtual environment on the web: thanks to custom-designed software, the user can continuously monitor the water status and temperature of their green roof, make changes to the programmed irrigation and monitor water consumption.