Study On Groundwater Recharge Of Agricultural Activity Area Based On Soil Water Balance

Groundwater is one of important water resources.With the characteristics of stable quantity and good quality,groundwater has become one of the important water source for agricultural irrigation,industry and urban water supply.In some drought areas,groundwater is regarded as the main water source.The groundwater recharge is a fundamental part in groundwater system.The quality and long term supply of the groundwater rely on the quantity and quality of groundwater recharge.It is of great theoretical and practical significance to obtain accurate groundwater recharge information for the rational development and utilization of groundwater resources.Soil is a link between atmospheric water,surface' water and groundwater.There is a close relationship between soil and groundwater recharge.This study built the groundwater recharge model based on the movement of water in the vadose zone and soil water balance principle;then designed and developed a groundwater recharge software using the MATLAB-GUI interface.We studied the crop evapotranspication and groundwater recharge in the agricultural area in Chengdu plain.the Penman-Monteith formula and Hargreaves formula were used to calculate the crop evapotranspiration,then improving the results of Hargreaves by comparing the results of Penman-Monteith calculation.Correction parameters were obtained:a=0.7294 and b=0.2653,with the relative error of crop evapotranspiration dropping from 33.16%to 6.06%.The high crop evapotranspiration rate appeared from April to September with the maximum value of 4.725 mm/day,;the low crop evapotranspiration rate appeared from December to February with the minimum value of 0.926 mm/day.The groundwater recharge model was built by studying the movement and balance of soil water,establishing the relationship between groundwater recharge and evapotranspiration,soil water movement,rainfall and other factors.The result of model calculation shows that the groundwater recharge is uneven throughout a year.The groundwater recharge mainly occurs in July,August and September in the study area.The sum of groundwater recharge in July,August and September accounts for 58.7%(WenJiang-2006),60.7%(WenJiang-2003)and 32.97%(PiXian)of annual groundwater recharge,respectively.Annual rainfall infiltration coefficient is 5%-8%for WenJiang,18.5%for PiXian and 21.4%for DeYmig,respectively.The correlation coefficient between rainfall and groundwater recharge is larger than 0.9.The sensitivity coefficient of groundwater recharge to rainfall is more than 1.Analysis shows that rainfall is a main factor of groundwater recharge.The dynamic distribution of groundwater recharge was calculated on the basis of the soil water balance principle.The calculation results are highly accurate,flexible and strongly applicable,providing a scientific basis for the dynamic groundwater recharge.It is suggested to carry out the further study on model parameters optimization and model validation with field experiment in future.