Seasonal variation of shallow groundwater characteristics and their influence factors in karst mountains: A case study of the Houzhai River in Puding County

This study focuses on the shallow groundwater of karst mountain areas in the Houzhai river in Puding county, Guizhou Province. Seasonal variations of characteristics and influence factors of shallow groundwater were analyzed. The results show that the shallow groundwater of this area contains main anion of HCO3-,SO42- and Cl-,accounting for 53%, 15% and 3% of the total ion content, and main cation of Ca2+ and Mg2+, accounting for 19% and 6% of the total ion, respectively. The hydrochemical feature is of HCO3-Ca type water. The pH is between 7.51 and 8.23. The shallow groundwater has obvious seasonal variations in terms of hydro-chemical constituents, of which the contents of HCO3-, Na+, NO3--N, Ca2+and TP have significant seasonal differences (P<0.05), while those of K+, Mg2+, Cl-, TN, NH4+-N and SO42-also seasonally fluctuate with the significant levels less than P<0.05. The chemical properties of the shallow groundwater are affected in a combined way by agricultural activity, human disturbance and rock formation lithology, of which the most typical is agricultural activity, followed by human disturbance. These two impact factors have drastically elevated the N and P concentrations in shallow groundwater in the karst mountainous areas and as a result the water quality declined.