河岸带地下水理化指标变化及与洪水的响应关系研究

Relationship Between Groundwater Quality Index of Physics and Chemistry in Riparian Zone and Water Quality in River

河岸带地下水和河水存在复杂的交互作用,地下水和地表水存在明显的补排关系,洪水事件是影响河岸带地下水水质波动的重要水文过程.以黄河湿地国家级自然保护区孟津湿地为对象,通过河岸带地下理化指标(特别是小浪底水库调水调沙期间)野外定位观测,深入分析了河岸带地下水水质与洪水的响应关系.结果表明,受河流与荷塘蓄水的影响,地下水温度最高点春季靠近荷塘,冬季靠近河流;小浪底调水也对湿地地下水水温产生影响,在离河岸100 m处达到最大.河岸带在沿岸50 m内,存在一个硝化作用强烈的区域带,其地下水pH较滩区其它区域偏低0.2～0.4,且年度变化幅度大.河岸带地下水的浊度受农业灌溉的影响较其它指标更为明显;在洪水退却初期,由于水力携带作用会导致地下水及河水浊度的迅速上升.河岸边坡的稳定性成为影响洪水退却初期土壤侵蚀程度的主要因素之一.电导率、氯化物和硫酸根的检测结果表明,位于沿岸50～200 m的范围内,是河岸区重要的积盐带,其宽度会随着季节的变化而变化,同时这一区域也是重要的硫元素还原发生带.距离河道200 m左右的区域内地下水水质受洪水影响显著,水质理化指标变化强烈,表明其水力联系非常密切,为典型的滩区地下水-河流的水陆交错带.该区域的合理保护,对于保护河流水质和地下水水质十分重要.

Riparian zone hydrology is dominated by shallow groundwater with complex interactions between groundwater and surface water.There are obvious relations of discharge and recharge between groundwater and surface water.Flood is an important hydrological incident that affects groundwater quality in riparian zone.By observing variations of physical and chemical groundwater indicators in riparian zone at the Kouma section of the Yellow River Wetland,especially those took place in the period of regulation for water and sediment at the Xiaolangdi Reservoir,relationship between the groundwater quality in riparian zone and the flood water quality in the river is studied.Results show that,affected by the river and pond water,the highest point of groundwater temperature is near the pond in spring,and near the river in winter;and regulation for water and sediment at the Xiaolangdi Reservoir also affects groundwater temperature in riparian zone,which reaches its maximum at 100 m far from the river bank.There exists a strong zone of nitrification area at 50 m from the river bank,and in this area,the groundwater pH value is lower by 0.2 to 0.4 unit than that of the other regions,with great annual varieties.The turbidity of groundwater is affected by irrigation,which is more obvious than other indicators of groundwater.The turbidity of groundwater and river water increase rapidly during the early phase of flood retreat,and slope stability of river bank is the initial impact of the soil erosion of river bank.Conductivity,chloride and sulfate data show that the range of 50-200 m in riparian wetland is a very important salt accumulation zone,and the width of salt accumulation zone changes with seasons,and this area is also a very important zone of sulfur reduction.The quality of groundwater at 200 m from the river bank is also significantly affected by floods.Physical and chemical indicators of water change strongly in this area.The result indicates that there is a very close relationship between groundwater and surface water,and it is the typical land and water ecotone between groundwater of riparian zone and the river.Rational protection for this region is critical for the conservation of water quality both in the river and groundwater.