1. A weighing lysimeter is great for determining the amount of evapotranspiration. It is a pot placed outside, positioned over a sensitive scale, that holds plants, soil, and whatever precipitation that falls into it. The pot’s weight is recorded constantly, and the differences in weight are predominantly due to a gain and loss of water through precipitation absorption/infiltration and evapotranspiration.
2. Soil moisture sensors do not function by weighing anything. They measure water content in soils by giving a voltage related to something called the dielectric permittivity of water. I believe this is similar to the electrical conductivity. The sensors probably shoot an electrical current into their surrounding sphere of influence to measure how water reacts.
3. Why do you think there are soil moisture sensors at multiple locations and depths around the site, isn’t one good enough? These sensors are small. They can only sense water within a 2-cm radius, I believe. Multiple sensors can measure the amount of water infiltration at different depths in the soil as well as the change in water content through evaporation and plant uptake.
4. Why is there a flume on your site and why is it so important to keep it clean?* A flume collects and channels water by capitalizing on the natural gravitational course of water flow. Water should be directed into planted soil to allow organic growth, recharge of groundwater storage, natural filtration, and to avoid its accumulation on roadways and sewers. It’s a low-cost, highly beneficial method of stormwater management. If the flume gets clogged with debris, then stormwater doesn’t reach the soil. It gets backed up and runs onto the street.
5. What is evapotranspiration, anyway? A combined loss of water molecules into the air from the processes of evaporation and transpiration. Water evaporation is the process where water is vaporized into a gas from the surface of condensed liquid (on objects and in soil) because of heat, wind, and other environmental conditions. Transpiration is the process where water moves up through a plant and is released as a gas through the stomata (cells that open to gather CO2 for photosynthesis). Water escapes from these cells indirectly but benefits the plant overall.