A dynamic harmonic regression approach to estimating groundwater evapotranspiration based on diurnal groundwater-level fluctuations

• Published in: Hydrogeology journal Vol. 32; no. 1; pp. 253 - 266
• Main Authors: Huang, Jinting, Wang, Jiawei, Zhou, Yangxiao, Fang, Tuo, Ning, Bohan, Song, Ge, Huang, Tian, Li, Linghua, Yang, Zhan, lv, Qiu, Pu, Fang, Li, Zongze, Wang, Wenke
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2024; Springer Nature B.V
• Subjects: Aquatic Pollution; Boussinesq approximation; Boussinesq equations; Diurnal; Earth and Environmental Science; Earth Sciences; Energy balance; Estimation; Evapotranspiration; Evapotranspiration estimates; Exact solutions; Fluctuations; Gels; Geology; Geophysics/Geodesy; Groundwater; Groundwater flow; Groundwater levels; Groundwater recharge; Groundwater table; Hydrogeology; Hydrology/Water Resources; Lidar; Mathematical analysis; Regression analysis; Semi arid environments; Semiarid environments; Shallow water; Sminthopsis psammophila; Vadose water; Waste Water Technology; Water Management; Water Pollution Control; Water Quality/Water Pollution; Water table; China; Arid regions; Dynamic harmonic regression; Boussinesq equation; Diurnal groundwater level fluctuation; Evapotranspiration
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-023-02719-1

Groundwater evapotranspiration (ET g ) is a significant component of water and energy balance analyses in arid and semiarid environments; however, it is also one of the most challenging items to estimate. Estimation of ET g using diurnal groundwater-level fluctuation is considered cost-effective and straightforward, while more accurate estimation technology continues to be developed due to the complex set of factors that influence the variation of groundwater level. This paper proposes a method for calculating ET g that combines the analytical solution of the Boussinesq equation and dynamic harmonic regression analysis, which is a nonstationary approach to groundwater-level signal extraction. The presented approach can calculate ET g values with a high time resolution consistent with the groundwater-level monitoring frequency, and it is robust enough to handle large amounts of measurement data. More importantly, this method eliminates the influence of recharge during the groundwater-level-rise stage. The method is tested in bushland dominated by Sminthopsis psammophila in Mu Us Desert (northern China), which has a shallow water table. The results show that this method is easy to perform and it obtains a reasonable estimate of ET g in the unfrozen seasons, regardless of the disturbance of recharge that results in a sharp rise in groundwater level. However, the method does not work well in the frozen seasons because of the physical mechanisms of change in groundwater movement in the vadose zone and a strong barometric effect. Overall, the method provides a step toward accuracy of ET g estimation using diurnal groundwater-level fluctuation, and this paper provides guidelines for its use.