## 2 Materials and Methods
### Preliminary Field Test, Full Gate Installation and Monitoring Approach  
Preliminary cartridge design was tested from 1 July 2019 to 7 August 2019 with just one cartridge filled with Al-WTR placed in Eckert's Dutch (Supplemental Figure S1). A temporary gate made from two angle irons (3.81 cm \(\times\) 0.32 cm), one u-gauge signpost (1.27 cm \(\times\) 182.8 cm \(\times\) 0.16 cm) and one steel bar (2.54 cm \(\times\) 182.8 cm) to secure the cartridge. A second cartridge was tested from 26 September 2019 to 25 October 2019.  
No physical damage occurred to the test cartridge during the preliminary testing. Despite this, the research team decided that long term in-field use and the need for a more 'rugged' installation/removal dictated additional support needs. This was addressed by thickening the corners of the star shape walls where they connect to the sides, top and bottom of the cartridge.  
Full-sized gates were installed in Eckert Ditch in April 2020 and May 2020. Gates were installed in a zig-zag pattern, staggered to allow water to flow both through and around the gates. Gate 1 is located on the west bank of Eckert Ditch at Dawley Road. Gate 2 is located on the east bank, several feet down stream of Gate 1. Continuing downstream, all sequential odd number gates are on the west bank and even number gates on the east bank. A simplified sketch of the gate and sample locations are provided in Figure 2.  
Eckert Ditch is a shallow, flashy ditched stream, prone to flooding and changing water speed/height during storm events. Figure 2(a) demonstrates 'normal' water levels, as well as significantly changing water levels during such events. This was tracked across sampling dates and different gates during the same sampling event. An independent depth marker was used to provide more accurate measurements of the water level (Figure 2(b)) to assess how much of each of cartridge was in contact with water. Tracking the water level is  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Advantages** & **Disadvantages** \\ \hline ABS [31; 32] & Cost, temperature resistant & Potential styrene leaching, warping, UV exposure, heated bed requirement for printing process \\ \hline PLA [32; 33] & Cost & UV exposure, water exposure, temperature, biodegradable \\ \hline Nylon 12 [32; 34] & Flexibility, durability & Hydroscope, adhesion sheets and ventilation required for printing process \\ \hline PETG [33; 35] & Layer adhesion during printing process, humidity resistance & Higher density, heat resistance, glycol functionality \\ \hline ASA [36; 37] & Impact strength, UV exposure & Potential styrene leaching, cost, heated bed and ventilation required for printing process \\ \hline Polycarbonate [33; 35] & Durability, high impact strength, mechanical properties & High extruder temperature during printing process \\ \hline UltemTM 1010 [38] & High impact strength, NSF 51 certification, mechanical properties & Cost \\ \hline \hline \end{tabular}
\end{table}
Table 2: Advantages and disadvantages of various 3D print materials.  
important as effectiveness of the gates are a function of the WTR capacity, but only when they are submerged in water.