白洋淀流域水文条件变化和面临的生态环境问题

Changes in Hydrological Conditions and the Eco-environmental Problems in Baiyangdian Watershed

白洋淀是华北平原最大的平原湖泊,具有缓洪滞沥、蓄水兴利、保护生态平衡等诸多生态功能。近几十年来,气候向暖干方向发展,流域气温逐年升高,降水和径流呈现明显的减少趋势。在气候变化和人类活动的双重影响下,白洋淀流域生态环境问题日益突出,上游山区水土流失严重,平原区地下水水位快速下降,下游水质恶化、湿地锐减。尤其是下游的白洋淀,正面临水体污染,湖面萎缩,湿地锐减,干淀频繁,生物多样性减少等生态环境问题。本文分析了自上世纪50年代以来白洋淀流域水文条件的变化情况,讨论了白洋淀流域当前面临的主要生态环境问题,并指出提高流域水资源综合管理水平,统筹分配流域水资源,提高水资源利用率,建立节水型社会是白洋淀流域生态环境问题综合整治的重要途径。

Baiyangdian Lake is the largest lake on the North China Plain and it serves various ecological functions, such as retaining water and flood and sustaining ecological integrity of the region. In the past five decades, local climate has become warmer, because the air temperature has been increasing, while precipitation and surface runoff have shown a significant declining trend. Global warming and intensified human activities have aggravated the eco-environmental problems in Baiyangdian watershed, such as serious soil erosion in the mountainous area of the upper reaches, fast drop in groundwater table in the plain area of the middle reaches, and serious water pollution and rapid disappearance of wetland on the lower reaches. Especially for Baiyangdian Lake, the outlet of the Baiyangdian watershed, has been suffering series eco-environmental problems, such as drying up of wetland, lake shrinking, water pollution, decreased biodiversity and others. It is suggested that immediate remedial actions should be taken to curb these problems. The changing patterns of the hydrological conditions of Baiyangdian watershed since 1950s can be conclude as following： the annual average temperature increases by about 0.41.2℃/10a, while annual temperature extremes have higher absolute value; annual precipitation reduces by 22.91 mm/10a; annual average runoff decreases at a speed of 3.50m^3s-1/10a, and groundwater table drops about one meter every year. There are no significant changes in annual pan evaporation in the whole area. The eco-environmental problems are analyzed, and water is believed to be the controlling factor of the ecosystem integrity of Baiyangdian watershed. The reasonable use and sound management of water resources are very important for the sustainable development of Baiyangdian watershed. Therefore, in the last part of the paper, some countermeasures for eco-environmental control and protection, such as integrated management of water resources, rational allocation, improving water use efficiency and establishing water-saving society are recommended.