近50年来三江平原水循环过程对人类活动和气候变化的响应

Response of Water Cycle Processes in Sanjiang Plain to Human Activities and Climate Change in Recent 50 Years

人类活动对三江平原水循环过程的影响主要表现在：①大型水利枢纽工程显著削弱了黑龙江、乌苏里江和松花江流经三江平原江段的洪泛过程，减少了三江平原获得过境水资源的天然补给机会与补给量；②大量排水沟的修建，提高区域排水水文梯度，加速了地表径流的集散过程；③旱田改成水稻田，提高了有效降水的利用效率，减少了区域地表径流深，增大了区域蒸散量；④井灌水稻田大面积发展驱动了地下水的大量开采，导致地下水采补平衡打破，地下水位持续下降，地下水贮存量减少；⑤流域源头森林植被破坏，冬季降雪量转变成地表径流量的比例在减少，森林土壤涵养水源能力下降。人类活动作用在三江平原水循环过程的结果是导致水输入项减少。而水的输出项在增大。气候变化对水循环影响主要体现在：①区域降水总量呈减少趋势，但变化趋势不显著；②区域温度上升，蒸发潜力增大；③三江平原地温上升最为显著，冻土层变薄，冻土融通时间提前并缩短55-62d左右，且冻土层融通后土壤水分的含水量较50年前有明显降低的趋势。耕地土壤含水量明显减少；这些变化均不利于地表径流的形成以及降水入渗补充地下水；基于水循环过程分析，三江平原正在朝旱化趋势发展。加强农业保护性耕作措施的开发与应用，以及加快湿地水资源的恢复，提高区域蓄水能力和农业节水水平是确保未来三江平原水安全的重要努力方向。

Impacts of human activities on water cycle process in Sanjiang plain mainly include： ①large-scale hydro-junction project dramatically weakened the flood processes of Heilongjiang, Wusuli and Songhua Rivers flowing through Sanjiang plain sections, and reduced natural groundw- ater and surface water recharges opportunities and amount for Sanjiang plain; ②construction of large number of drainage canals enhanced the hydrological gradient of regional drainage,and accelerated the generation and distribution processes of surface runoff; ③conversion from glebe into paddy field enhanced the utilization efficiency of effective precipitation, reduced the regional surface runoff depth,and enlarged the regional evapotranspiration;④area enlargement of well irrigated rice field drives large-scale groundwater exploitation, which leads to the imbalance of ex- ploitation and recharge of groundwater, the continuous decline of the groundwater table, and the reduction of groundwater storage volume; Ode- forestation in the headstream region,which causes the reduction of the proportion of snowfall converting into surface runoff and the decline of water conservation capabilities of forest soil. The resulting influences human activities have on water cycle processes in Sanjiang plain are that water input is decreasing and water output is increasing. Major impacts from climate change on water cycle process mainly inelude：①total area precipitation shows a declining trend, but not obvious; ②regional temperature and potential evaporation are rising;③the rise of land temperature is the most obvious,the permafrost layer is becoming thinner,duration of permafrost fusion is shortened by 55 to 62 days,and the soil moisture of permafrost layer is apparently lower than that 50 years ago. Cultivated soil water moisture visibly declines. These changes will not benefit the surface runoff generation and precipitation infiltration to recharge groundwater, Based on the water cycle processes analysis, it is concluded that Sanjiang plain is getting drought. Therefore, strengthening the development and application of agricultural conservation tillage measures, as well as speeding up the restoration of degraded wetland water resources, enhancing the regional water storage capacity and water saving level in agri cultural aspect will be important directions to ensure Sanjiang plain water security.