Abstract:

Leizhou peninsula in South China is facing a serious water shortage problem. Because of the special regional geomorphological and geological conditions, it is lacking in surface water, but abundant in groundwater resource. As ground water is the important water source for industrial and agricultural production and domestic use, it is of great significance to study the soil permeability and groundwater recharge potential area in order to maintain the long term sustainability of water resources. In this study, inversed auge-hold and groundwater level dynamic method are used to analyze soil permeability and groundwater recharge, respectively, and we try to delimitate potential areas of groundwater recharge. Soil permeability in the peninsula varies considerably at spatial scale, and soil hydraulic conductivities range from 0.04 to 8.83 m/d. In general, soil permeability in the southern Leizhou peninsula and Northwest Suixi County is good, while that in the central is poor. There are lots of factors making impact on soil permeability, such as land use, soil particle size, and soil organic matter, etc. With the increase of soil particle of median diameter and organic matter content, hydraulic conductivity increases. The average soil hydraulic conductivity under different land use types from high to low is in the order as: uncultivated land, eucalyptus land, sugarcane field, vegetable field, pineapple field, forest land, banana field, nursery garden, rice field. The mean annual precipitation recharge coefficients range from 0.04 to 0.41, and they are high in the North and South, and much lower in the central areas. However, recharge coefficients from rainfall are high in Zhanjiang urban area, which may be associated with groundwater exploitation. It can get more lateral recharge caused by increased hydraulic gradient besides natural rainfall recharge. Except Zhanjiang urban area, infiltration coefficient distribution characteristic is consistent with that of topography and soil permeability coefficient. And recharge coefficient increases with the increase of soil hydraulic conductivity (K< 2 m/d). While soil hydraulic conductivity is greater than 2 m/d, soil permeability makes less impact on recharge, and embedded depth of groundwater and rainfall may be the main limiting factors of rainfall infiltration. Nevertheless, because of the limitation of phreatic well observation data, there is a little deviation for precipitation recharge coefficients, and it’s hard to get a more explicit relationship between recharge coefficients and soil hydraulic conductivity. Influential thematic factors, including geomorphology, soil permeability and groundwater recharge are integrated to identify groundwater recharge potential area. Results of the study reveal that higher groundwater recharge potential areas are in the Southern Leizhou peninsula, where the terrain, hydraulic conductivity, and recharge coefficient are relatively high. In order to improve the soil permeability and groundwater recharge capacity, we suggest that more trees or grasses in the uncultivated land, especially bare land, should be planted, and, in nursery garden area, if possible, fallow and crop rotation might be a better choice.

Key words: the Leizhou Peninsula, hydraulic conductivity, groundwater recharge, groundwater recharge potential area