人类活动对白洋淀干旱的影响

Impacts of Human Activities on Drought of Baiyangdian Lake

从白洋淀流域水循环角度出发,通过比较分析白洋淀实际入淀年径流量和还原的天然入淀年径流量,定量评价人类活动对白洋淀干旱的影响。研究结果表明,人类活动导致入淀年径流量减少,干旱发生频率增大,干旱重现期缩短,人类活动对白洋淀干旱产生了较大影响;还原的天然状况下的白洋淀最小入淀年径流量为2.13×108m3,在该入淀年径流量下,白洋淀不会出现持续干淀现象。

As an important unit in the watershed, freshwater lake is one of the ecosystems which are mostly in- fluenced by human activities. Under the cumulative impact of climate change and human activities, the severi- ty, duration and frequency of droughts occurred in freshwater lake are increasing at present, especially in the semi-arid region. This paper made a quantification of human activities on the drought of Baiyangdian Lake through the analysis of actual and natural inflow of Baiyangdian Lake, from the view of water cycle in river basin. The main cause of drought of freshwater lake lines in the reduced inflow, which is mostly used as do- mestic, industrial and agricultural water to support the development of social economy. So in this paper, we simply regarded the effect of human activities on freshwater lake drought as the influence on the inflow of freshwater lake. Firstly, hydrological characteristics of the watershed were analyzed, such as precipitation and inflow, with Mann-Kendall nonparametric statistical test method to realize the evolving features from 1956 to 2000. Secondly, for lacking of the runoff data of some inflow rivers, the natural runoff data of reservoirs were used in the south watershed. In this way, on the basis of the connotation of distributed hydrological model, riv- er network and sub-watershed were got through the digital elevation model, and merged sub-watershed into sub-region according to the inflow river and reservoirs; then using the precipitation data to obtain the natural runoff coefficient of each sub-region. Depended on these runoff coefficients, the inflow coefficient of Baiyang- dian Lake was acquired, and finally natural inflow was got. At last, the frequency of actual and natural inflow of Baiyangdian Lake by Pearson III Curve were analyzed. The results showed that firstly, human activities had a strong impact on the inflow of Baiyangdian Lake, the breakpoint of the inflow was in 1971, after year of 1971 the inflow decreased rapidly, and its variation was bigger than that of precipitation annually; secondly, under the effects of human activities, the mean annual inflow from 1956 to 2000 reduced 8.12× 108 m3; thirdly, the frequency of drought in Baiyangdian Lake increased and the return period decreased, while in the natural condition, the minimum na^tral inflow of Baiyangdian is 2.13 × 10s m3, which would not dry up Baiyangdian Lake for a long period.