2.2.2 Testing System
The experimental setup mainly consists of a bioretention facility system, water supply system, and test system. The site layout is shown in Fig. 4. As shown in Fig. 4(a), the bioretention facility system consists of a 14-m long bioretention facility belt with three typical bioretention facilities and a 14 m × 3.5 m simulated municipal road with compacted loess as the subgrade. The water supply system consists of a reservoir (5 m × 3 m × 1 m), ② a measuring weir, and ③ a return channel. The water in the reservoir was pumped to the measuring weir as necessary during the experiment. An open channel was set at the end of the bioretention facility belt to form a flow loop with the reservoir.
The test system is mainly composed of ① a test I moisture sensor section, ② a test II moisture sensor section, ③ a test III moisture sensor section, and ④ a data collector. The moisture sensor is a CS635 (Campbell Co., USA), and its measurement accuracy is ± 1%. The sensor was embedded by digging an exploratory well. The influence of water infiltration on the vertical water content of the site is usually less than 2 m (Hou et al., 2019b), so a total of 12 soil moisture sensors were arranged at depths of 1.5 m, 2 m, 2.5 m, and 3 m. The sensor positions in the test 1 section are shown as an example in Fig. 4(b). The data collector model is TDS-602 and its fastest sampling speed is 0.02 s.
[Insert Figure 4]