Relationship between sand dew and plant leaf dew and its significance in irrigation water supplementation in Guanzhong Basin, China

摘要

Dew can serve as an important source of moisture for plants, biological crusts, insects and small animals in arid and semiarid basin. Dew amount and the relationship between sand dew and plant leaf dew were analyzed to understand dew transformation law under different condensation surfaces and its significance in irrigation water supplementation. During April 1-May 31, and September 1-October 31, 2018, field monitoring was carried out at the groundwater and environment site of Chang'an University, in Guanzhong Basin, China, using weighing method for sand dew measure, as well as leaf wetness sensors for plant leaf dew measure. Results showed that both sand dew and leaf dew manifested high frequency and low amount pattern. Their dew days (69days, 66days) accounted for 80% and 77% of rainless days (86days), but dew amount (6.56mm, 14.75mm) accounted for 3.3% and 7.4% of rainfall (198.2mm) in the same period, respectively. The average daily dew amount for sand was 0.054mm with a daily maximum of 0.22mm, and that for plant leaf was 0.12mm with a daily maximum of 0.78mm. Average daily leaf dew amount was about 2.2 times that of sand dew amount. Sand dew amount (W) was highly and positively correlated to leaf dew amount (D), and the fitting equation was W=0.237xD+0.044 (p0.01), which will provide a reference for the transformation between sand dew amount and leaf dew amount, and provide a theoretical basis for the evaluation of dew resources in a region. Moreover, dew harvesting is passive and mainly occurs in the natural states, which has no energy requirements, such as electrical energy. Dew harvesting system, as an independent system, can minimize the transportation cost of irrigation and entails low initial investment. And dew water quality is better once pretreated. Hence, artificial condensation surfaces and structure designed to maximize dew amount is of great significance in irrigation water supplementation.