下辽河平原新近系地下水开采的动态变化特征

Exploitation Change of Neogene Groundwater on the Lower Liaohe River Plain

新近系地下淡水是下辽河三角洲地区的盘锦市和辽河油田主要供水水源。地下水处于封闭到半封闭环境,包括明化镇组(Nm)和馆陶组(Ng)两个含水岩组。天然状态下,地下水位接近或高于地表;开采条件下,地下水位逐年下降,形成区域性降落漏斗,地下水流场均发生显著变化,形成汇向开采区的向心流场。开采明化镇组地下水为主的盘东水源地,开采初期水位下降速率为1.61～5.19m/a,至1996年降至0.63～1.03m/a;馆陶组地下水为主的各水源地,开采初期水位下降速率为2.10～4.21m/a,至1996年减至1.49～2.05m/a。这是由于地下水流场变化,导致明化镇咸水体内侵和下移所致,该地地下水中Cl-的不断增高也证明了这一点。至1998年,平面上,咸水体每年增加3.18km2,盘东水源南部,咸水体内侵速率已达每年220m。垂向上咸水体年下移速率一般每年0.5～1.67m。进行新近系地下水动态特征和演化趋势研究,将为合理开发利用宝贵的淡水资源提供科学依据。

The underground fresh water in the Neogene System from the lower Liaohe delta area is the main water resourse for Panjin City and Liaohe Oil field. The underground water is in the closed and semiclosed state, including the Minghuazhen and Guantao water-bearing formations. In the natural condition, the groundwater table is nearly or slightly higher than the land surface. Under the pumping condition, it lowed year by year, forming the cone of exhaustion. The groundwater flow field changed into the central flow field. And the water flew toward the pumping centre. In the Pandong area, where the ground water is being pumped from the Minghuazhen Formation, the water table lowed for 1.61 ～ 5.19 m/a at the beginning, where it reduced to 0.63 ～ 1.03 m/a in 1996. In the water source of Guantao Formation, the ground water level lowed at 2.10 ～ 4.21 m/a at the beginning of pumping, and decresed to 1.49 ～ 2.05 m/a in 1996. That is becauce the salty water body in Minghuazhen formation intruded toward inland and moved downward, which is proved by that the (Cl^-) in the groundwater has been increasing constantly since 1977. Till 1998, the salt water moved toward the inland for 3.18 km^2 every year. In the south to the Pandong water source, it intruded for 220 m horizontally every year. In the vertical direction, the salt water penetrated for 0.5 m ～ 1.67 m downward every year. Study on the water dynamic character and evolution trend will provide a better choice for reasonable exploitation of the valuble fresh water resource.