Water resources: long-term annual average

The minimum period taken into account for the calculation of long term annual averages is 20 years. - Actual evapotranspiration is the volume of water transported from the ground (including inland water surfaces) into the atmosphere by evaporation and by transpiration of plants. - Internal flow is the total volume of river run-off and groundwater renewal generated, in natural conditions, exclusively by precipitation into a territory. The internal flow is equal to precipitation less actual evapotranspiration. - Actual external inflow is the total volume of actual inflow of rivers and groundwater coming from neighbouring territories. - Total fresh water resources is the total volume of water that is additionally available due to internal flow and external inflow. - Total actual outflow is the total actual outflow of rivers and groundwater into the sea and into neighbouring territories.

计算长期年平均值时需纳入考量的最短周期为20年。 - 实际蒸散发（Actual evapotranspiration）：指通过蒸发作用及植物蒸腾作用，从地表（包括内陆水域）输送至大气中的水量。 - 境内产流（Internal flow）：指自然条件下，某一区域内仅由降水产生的河流径流与地下水补给总量，境内产流量等于降水量减去实际蒸散发量。 - 实际外来入境水量（Actual external inflow）：指从周边区域汇入的河流与地下水实际总入境水量。 - 淡水总水资源量（Total fresh water resources）：指由境内产流与外来入境水量共同提供的额外可用水资源总量。 - 实际总出境水量（Total actual outflow）：指河流与地下水实际注入海洋及周边区域的总水量。