基于水热耦合平衡理论的嫩江流域蒸散发估算

由于区域蒸散发时空变异性较大,难以采用点位监测方法来测定,因此,流域蒸散发估算是目前水文学领域的难点和重点问题。从水热耦合平衡理论入手,采用傅抱璞公式估算嫩江流域及典型汇水区的实际蒸散发。结果表明,傅抱璞公式的逐年蒸散发估算结果具有较高精度,且干燥度较大的汇水区的估算结果精度较高。然后,对嫩江流域蒸散发进行时空演化分析。结果表明:在1956—2000年,年实际蒸散发和潜在蒸散发均无趋势性变化;在2000—2013年,多年平均实际蒸散发与潜在蒸散发在空间上呈相反分布,整体上从上游至下游递减(递增)。最后,分析了下垫面参数w的分布规律,其表现为由上游至下游随植被覆盖率的减小而减小的特征。研究表明,傅抱璞公式为流域的蒸散发估算提供了可靠的方法,对于流域水资源预测和生态需水推求等具有十分重要的意义。

Evapotranspiration Estimation Study Based on Coupled Water-energy Balance Theory in Nenjiang River Basin

As the spatiotemporal variability is large in the regional evapotranspiration, it is difficult to determine through spot monito-ring methods. Therefore, the evapotranspiration estimation of river basin is an important but difficult problem in the field of hydrology. The paper starts with Budyko coupled water-energy balance theory, then utilizes Fu′s equation to estimate the actual evapotranspiration yearly in Nenjiang River Basin and typical collection areas. The result shows that Fu′s equation has high precision for estimating evapo-transpiration yearly in Nenjiang River Basin, and the estimation result has higher precision in the area with high dryness. Furthermore, the paper analyzes the laws of spatio-temporal evolution of evapotranspiration in Nenjiang River Basin. The results show that there are no trend changes in the actual evapotranspiration and the potential evapotranspiration from 1956 to 2000, and the average annual actual evapotranspiration and potential evapotranspiration from 2000 to 2013 are opposite on the spatial distribution, which the former is de-creasing but the later is increasing from upstream to downstream on the whole. Finally, the paper analyzes the distribution rule of un-derlying surface parameter, which diminishes with the decrease of vegetation coverage from upstream to downstream. The study indi-cates that Fu′s equation provides a reliable method for evapotranspiration estimation in river basin, which has great significance for fore-casting river basin water resources and inquiring into ecological water requirement.