黄河中游河口-龙门区间多年平均流域水平衡特征 ——-区域蒸散量估算模型验证与下垫面参数校核

采用黄河中游河口镇至龙门区间1980-2000 年间径流及气象数据, 通过对Zhang 等2001 建立的区域(流域) 多年平均蒸散量估算模型进行验证和下垫面参数校核工作, 探索了干旱半干旱地区水循环要素相应于不同土地覆被类型的结构变化及水平衡特征和规律。结果表明, 由于研究区处于干旱半干旱气候区, 采用原模型及参数对蒸散量的预测能力好于对径流的预测能力。使用优化后的下垫面参数使原模型对河龙区间蒸散量和径流预测能力得以改进, 一致性指标分别从0.89 和0.21 提高到0.94 和0.63。对实际蒸散量进行预测的相对误差和均方误从3.6%和17.2 mm 减小到1.5%和7.9 mm, 对径流进行预测的相对误差从42.7%减小到18.0%。聚类分析和下垫面参数优化结果表明, 河龙区间流域水循环要素变化特征受不同土地 覆被影响可以分为3 个明显不同的区域。由于大面积林地截流蒸发的作用, 南部林地覆被区具有较高蒸发系数, 适用下垫面参数值为1.61。西北部风沙地貌区受粉沙覆盖层和地下径流补给影响, 使该区蒸发系数较小, 适用值为0.1。中部典型黄土丘陵覆盖区适用值为0.45。

The Mean Annual Water Balance in the Hekou- Longmen Section of the Middle Yellow River : Testing of the Regional Scale Water Balance Model and Its Calibr ation

Ecosystem health and sustainability of social and economic development in arid and semi-arid regions depends on water availability.To study the responses of water balance components to the different land cover types on mean annual scale,the data of streamflow,precipitation and Epan from 1980 to 2000 in the He-Long section(briefly for Hekou-Longmen section)of the middle reaches of the Yellow River,were used to test and calibrate the water balance model set up by Zhang in 2001.The results showed that the model was able to accurately simulate mean annual evapotranspiration,but not mean annual streamflow when compared with streamflow measurements from 38 hydrologic stations in the study area.Using the optimized parameters,the index of agreement between modeled and observed evaporation increased from 0.89 to 0.94,and the relative error and root mean square error decreased from 3.6% and 17.2 mm to 1.5% and 7.9 mm.The index of agreement for streamflow increased from 0.21 to 0.63 and the relative error decreased from 42.7% to 18.0%.Hierarchical cluster analysis showed that 3 types of water cycles exist due to the different land cover types.The parameter optimization showed that due to the effects of forest interception,the evaporation coefficient(ET/P)in the southern part of the He-Long section is fairly high so the region is suitable for the parameter w 1.61.For the influence of sandy soil and high groundwater,the evaporation coefficient in the northwestern region is low,so that for this region the parameter value of 0.10 was used.In the middle part of the He-Long section,it is fit for the parameter value of 0.45.