Uncovering Phytocaps at the WMRR conference

By conference attendee and co-paper presenter Ruben Andersen, HydroTerra Field Technician.

I was lucky enough to attend and present at the 2023 Australian Landfill & Transfer Stations Conference (ALTSC) in June and help showcase HydroTerra’s suite of landfill monitoring equipment and turnkey solutions. It was invaluable listening to the breadth of expert presenters on myriad landfill topics and getting to know the attendees, many of whom visited the HydroTerra booth for a chat.

Our Managing Director, Richard Campbell and I presented our experiences and insights into the benefits and design considerations of phytocaps, as well as some techniques for monitoring their performance.

Many have since requested a copy of our presentation, so here is a quick summary:

Phytocaps: Design considerations, pros & cons

Phytocaps are innovative covers used to minimize rain infiltration and promote the conversion of gases within the root zone. Plants regulate soil moisture through transpiring water captured within the soil layers. Compared to conventional covers, they are easier to construct, cost less, and offer ecological advantages.

To ensure the long-term success of phytocaps, performance monitoring is essential. Various techniques are employed, including lysimeters, weather stations, soil moisture probes, cap vegetation assessments, and gas monitoring. Lysimeters, which measure water losses and gains, provide comprehensive information on the water balance within the cap. They are constructed in the field with drainage outlets for measuring water infiltrating through the cap.

Minimizing leachate production is a key goal of phytocaps. Key processes governing leachate production, such as precipitation, evapotranspiration, runoff, soil moisture storage, lateral flow, and drainage, are measured. On-site weather stations with tipping bucket rain gauges measure precipitation, while surface pit tipping bucket flow gauges monitor runoff. Soil moisture storage is calculated based on directly measured water processes, with lateral flow typically being negligible.

Monitoring ecological processes is crucial in assessing phytocap performance. Effective root depth, vegetation coverage, regulation of water influx, and overall ecological health are important considerations. Soil moisture trends can provide insights into these processes, aiding the evaluation of phytocap efficiency.

Soil moisture probes are valuable tools for monitoring trends in soil moisture. Trigger levels can be set to detect plant stress or full point conditions when the soil profile is fully saturated. HydroTerra has used soil moisture probes to map soil moisture patterns across the phytocap, in turn teasing out key parameters for assessing the efficacy of the cap vegetation.

Phytocaps offer a sustainable approach to waste management, and their design and performance can be effectively assessed through comprehensive monitoring techniques. By considering factors such as vegetation selection, water balance, plant processes, and utilizing soil moisture probes, stakeholders can ensure the optimal functioning of phytocaps.

If you would like to discuss phytocaps, please reach out to Ruben Andersen.