## 4 Results and Discussion
The temperature in the proximity of the BHE (10 m downgradient) is around 11 \({}^{\circ}\)C because the aquifer has been cooled by the thermal plumes of the previous seasons (to be noted that the heating period, i.e., extraction of heat from subsurface, is greater than the cooling one). Over the distance, a trace of the succession of all the plumes of the previous seasons is present. For instance, the warm plume induced by the cooling period can be seen in layer 1 at 320, 750, and 1400 m; similarly, the warm plumes can be seen in layer 5 at 420, 1000 m. After 3 years, the warm and cold peaks of each year decrease in intensity, so the maximum groundwater temperature value can be measured at a specific distance from the borefield for each aquifer. The temperature distribution in Aquifer A (continuous line in Figure 8) shows an important variation (greater than 1 \({}^{\circ}\)C compared to the unperturbed value) up to 250 m. From 210 m onward, the groundwater temperature variation around the unperturbed value is lower than 1 \({}^{\circ}\)C. In Aquifer B (similarly to Aquifer A), the greatest groundwater temperature variation is found within 230 m from the borefield, and then it shows values lower than 1 \({}^{\circ}\)C. In Aquifer C, because of the lower hydraulic conductivity values, the biggest effects on temperature variation are recorded within 60 m, showing a more radial thermal perturbation around the borefield. This result shows how any future GSHP systems installed in a radius area of 200 m around the building MIA will need to take this temperature variation into account for their design. To account for the thermal perturbation at the Armi pumping well locations, which is the main focus of this study, the temperatures at wells number 3, 5, 8, 18, and 19 were monitored through the numerical model. This was not possible in the real wells because of their continuous operation or the impossibility of placing measuring instruments in the wells. Wells n. 8 and n. 19 are screened in Aquifer Groups B and C but are not currently in operation. Wells n. 5 and n. 19 are screened in Aquifer Group B (model layers from 5 to 7), while well n. 3 is screened in Aquifer Groups A and B (i.e., from layer 2 to layer 7). Figure 9 shows the groundwater temperature variation for each aquifer (Aquifer A--layer 1, Aquifer B--layer 5, Aquifer C--layer 9) over 3 years of GHSP system operation. Figure 8: Groundwater temperature distribution inside 90 observation points in Aquifer Groups A, B, and C after the last heating period of the 3 rd year simulation. In wells n. 3, 18, and 19 (Figure 9), no groundwater temperature variation is observed, since these wells fall outside the thermal perturbation area induced by the GSHP system. Indeed, the groundwater temperature values observed are equal to the unperturbed value of the aquifer. In wells n. 5 and n. 8 (Figure 9), the groundwater temperature oscillates around the unperturbed value according to the operational season. After the heating period, the temperature increases, whereas after the cooling period, a decreasing groundwater temperature is observed. However, the thermal variation is always less than 1.2 \({}^{\circ}\)C in both Aquifer Groups A and B, while no thermal effect was predicted for Aquifer Group C. Tables 4 and 5 show the computed thermal variation from the undisturbed aquifer values (15.2 \({}^{\circ}\)C in layer 1 and 14.5 \({}^{\circ}\)C in layer 5) at the maximum and minimum peaks of the curves presented in Figure 9.  
Figure 9: Groundwater temperature distribution inside Armi station wells: (**a**) well n.3, (**b**) well n.5, (**c**) well n. 8, (**d**) well n. 18, and (**e**) well n. 19. A maximum decrease of \(-1.17\)\({}^{\circ}\)C (day 328) and \(-0.78\)\({}^{\circ}\)C (day 744) and a maximum increase of +0.96 \({}^{\circ}\)C (day 504) and +0.35 \({}^{\circ}\)C (day 557) were predicted in well n. 5 and well n. 8, respectively. In other periods, a similar increase or decrease was achieved.