Plate 6.6 Water Balance of River Basins in the 20th Century

The climatic changes observed since the middle of the 19th century include a rise in temperature which has led to greater melting of glaciers and higher levels of evaporation. Precipitation patterns can also change. Changes in land-use such as more intensive farming or increased afforestation also result in increased evaporation.Long measurement series for the elements that make up the water balance thus show on the one hand the water resources available in a catchment and, on the other, how the water balance has possibly changed owing to the influences mentioned above.自19世纪中叶以来观测到的气候变化包含气温升高，这一现象引发冰川消融加剧与蒸发量攀升。降水格局亦可发生改变。诸如集约化农业规模扩张、造林面积扩大等土地利用变化，同样会导致蒸发量上升。针对构成水平衡（water balance）的各类水文要素的长时序监测序列，一方面可反映某一流域内可利用的水资源状况，另一方面则能揭示在上述各类影响因素作用下，水平衡可能发生的变化。