An improved evaporation dome for forest environments

We describe an improved ‘evaporation dome’ for measuring ground evaporation in forests. We reduced the size of the dome to ease transport through rugged terrain and replaced the data-logger, notebook computer and lead-acid battery with the hand-held data acquisition and analysis tool, the Vernier LabQuest. This evaporation dome is a significant improvement on previous instruments because of its light-weight, ease of transport and deployment and low power consumption. The Vernier LabQuest enables graphing of data in real time and allows the user to perform quality checks and to calculate evaporation rapidly in the field, eliminating the need for further processing of data in the laboratory. The LabQuest is light and rugged, is self-powered with a long-lasting battery, and has four voltage input channels and two digital input channels. The relative humidity and temperature sensor we used occupied two voltage channels but the spare channels on the LabQuest could be used to expand the range of measurements made with the evaporation dome to include global solar radiation and soil temperature. We also redesigned the ventilation system such that air was well mixed to ensure a good response time in the temperature and humidity sensor, but that the boundary layer of the evaporating surface received minimal disturbance. In addition to making ground evaporation measurements practical in forests, the improved dome should also find application in agriculture and rangelands, owing to the greatly reduced health and safety concerns of deploying larger, heavier instruments.