大沽河下游农田土壤水分含量动态变化特征

Dynamic Characteristics of Soil Moisture in Downstream Farmland of Dagu River

土壤水分作为土壤的组成部分以及"四水"转化的重要环节,其储存情况严重影响土壤中其他环境因子,因此,研究含水量动态变化特征具有重要的意义。回归等值线图能够较为直接地反映出土壤水分的时空分布。通过田间采样监测,获得了大沽河下游地区6个代表性农田剖面2017年4月21日至12月2日5～150 cm深度的土壤含水量数据,并采用回归等值线法分析其动态变化特征。结果表明:除研究区中部的毛子埠监测点外,其余5个监测点所求回归方程均能较好再现实际含水量;在时间尺度上,研究区南部、中部及北部沙梁监测点的土壤含水量随时间推移先减少,而后增加,最后再减少;位于研究区最北部的南村监测点,其土壤含水量随时间呈"增加–减少"趋势;在空间尺度上,北部两个监测点存在差异,其中南村监测点随研究深度增加,土壤含水量也逐渐增加;而沙梁与南部监测点相同,土壤含水量随深度先增加后减少;中部六里监测点的土壤含水量随深度先减少后增加。另外,可根据土壤含水量的剖面分布判断零通量面位置,并据此推测水分在空间上的运动方向。土壤含水量的变化随降雨量增加表现出一定的滞后效应,研究区降雨主要集中在7、8月份,除北部的南村监测点外,各监测点各深度土层含水量一般在9月达到最大值。该研究结果可以为合理制定区域土壤水–地下水联合调控方案提供科学依据。

Soil water is an integral part of soil and an important part of “four-water” transformation. Water storage affects other environmental factors in the soil, so studying its dynamic characteristics is of paramount importance. The regression isogram can reflect the spatio-temporal distribution of water more directly. Through sampling and monitoring in the field, soil moistures of 6 representative farmland sections with depth from 5cm to 150cm had been obtained in the downstream area of Dagu River from April 21 to December 2 in 2017 and their dynamic changes were analyzed by regression isogram. The results showed that except for Maozibu point in the middle part of study area, the regression equations obtained in the other five monitoring points could reflect well the actual soil moistures. On the temporal scale, soil moistures of points in southern and central parts and Shaliang point in the northern part of study area decreased first, then increased, and decreased finally with time, while soil moisture in Nancun point in the northernmost part increased first then decreased with time. On the spatial scale, there were differences between the two monitoring points in the north part, as the depth increasing, soil moisture in Nancun point also increased gradually, but that of Shaliang point was consistent with the monitoring points in the southern part, increased first then decreased. Soil moisture in Liuli point in the middle part decreased first then increased. In addition, according to the section distribution of soil moisture, the position of the zero flux plane could be judged and the spatial movement direction of water could be inferred. The change of soil moisture showed a certain lag effect with the increase of precipitation. Because the rainfall mainly concentrated in July and August, except Nancun point in the northern part of the study area, soil moisture in each deep layer in other points reached a maximum in September. The above results can provide references for the proposing the reasonable regional joint regulation program of soil water and groundwater.