Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : The Mechanisms of Groundwater Recharge Originating from Rainfall in Semi-arid Regions

Auteur : 宫程程

Grade : Doctoral Dissertation 2022

Université : Chang’an University

Résumé partiel
In semi-arid and arid regions,evaporation is high,while rainfall is little.Groundwater is the main source of water supplies,including drinking water and irrigation water.Rainfall is the most important contribution to groundwater recharge.Understanding the mechanism of groundwater recharge clearly,and estimating the recharge accurately thus are critical for sustainable groundwater resources management.However,the infiltration process is affected by many factors,such as the thickness of the vadose zone,soil types,and climatic conditions,to mention but a few.Moreover,recharge varies greatly in both space and time and is difficult to observe directly.Recharge,therefore,remains a poorly understood hydrological process.In this thesis,recharge was explored through numerous field-and modeling approaches.We carried out a field experiment in the Guanzhong Basin,China which is a semi-arid region.The soil water content,water level,percolation,and weather data were measured continuously.We systematically analyzed the process of infiltration originating from rainfall,and the factors influencing the infiltration process,evaluated methods to estimate recharge,as well as quantified the uncertainty of predictive recharge by the ways of numerical modeling and statistical analysis.Several important conclusions can be drawn below :（1）The patterns of rainfall infiltration for groundwater recharge through aeolian sand,coarse sand,and fine sand under different water table conditions were systematically studied.We analyzed the influence of rainfall intensity,duration of rainfall,thickness of the vadose zone,soil type,and initial soil water content on the infiltration process.The extinction depth of aeolian sand is 78 cm,and the observed minimum amount of precipitation that can recharge the groundwater is 10.4 mm.We analyzed the recharge characteristic curves in response to rainfall through fine sand and coarse sand under different water table depths systematically.Impulse response functions,including Poisson distribution and Rayleigh distribution functions,were used to simulate the recharge rates.The results show that the Poisson distribution function can be better used to characterize the recharge replenishment process for the coarse sand.The depth interval coefficient of the Poisson distribution decreases as the thickness of the vadose zone increases.In addition,the depth interval coefficient related to the Poisson distribution function of coarse sand is larger than fine sand.The Rayleigh distribution function has the characteristics of positive skew distribution.It thus can better characterize the groundwater recharge process.The Rayleigh distribution function can be better used to characterize the recharge replenishment process through fine sand

Mots clés : Vadose zone ;Groundwater recharge ;Infiltration;Bare soil evaporation ;Saturated and unsaturated flow model ;Semi-arid and arid region ;

Présentation (CNKI)