不同尺度下蒸散量测算方法的应用及展望

在水资源日益稀缺的背景下,蒸散作为陆地水循环的重要组成部分,对水资源管理和农业灌溉方案的制定都起着决定性作用。在全球尺度上,蒸散量整体呈现出了明显的随时间增加趋势,但区域尺度及流域尺度的蒸散变化则呈现出较大的不确定性,并且在一些下垫面比较复杂的地区,如喀斯特小流域,蒸散作为流域水循环的重要组成部分往往难以准确测定,所以更需要因地制宜地选择蒸散量测算方法。基于此,本文以各种方法的研究尺度为切入点,将当前被广泛接受的蒸散研究方法分为小尺度方法,即针对单体植株和适用于田块尺度的蒸散研究方法,包括树干液流法、零通量面法、风调室法、蒸渗仪法以及土壤-植被-大气连续体(SPAC)水分传输综合模拟法;百米尺度方法,包括波文比法和涡动相关法;公里尺度方法,主要包括闪烁仪法;流域及区域尺度方法,包括水量平衡法和空间遥感法。概述了各个方法的应用范围、特点以及局限性,列举了前人工作中各种方法之间的对比验证,着重分析了闪烁仪方法在复杂下垫面的应用前景,以便在不同研究条件和研究尺度下能选择最佳的蒸散量测算方法,并对未来蒸散研究进行了展望。

Application and prospect of evapotranspiration measuring methods under different scales

Background, aim, and scope Evapotranspiration, as an important part of terrestrial water cycle, plays a decisive role in water resource management. On global scale, the evapotranspiration overall presents an obvious increasing trend, but regional scale and watershed scale evapotranspiration has a large uncertainty. And in some area with complex surface condition, evapotranspiration as an important part of the basin water cycle is often difficult to be accurately measured. Therefore, it is necessary to summarize previous studies, analyze the basics, advantages and disadvantages of various evapotranspiration measuring methods in order to choose the better methods at practical works. Materials and methods In this paper, different evapotranspiration measuring methods are divided into point scale methods, including zero-flux plane (ZFP) method, lysimeter method, plant physiology method, soil-vegetation-atmospheric continuum (SPAC) comprehensive simulation method, Bowen ratio-energy balance method, eddy covariance (EC) method; and regional or watershed scale methods, including water balance method, remote sensing method, Penman-Monteith equation method and scintillometer method. Results Flux observation network (FLUXNET), remote sensing method and scintillometer method have promising application prospect. And the results of different evapotranspiration measuring methods are often compared with each other. Discussion All kinds of methods are developed and evolved according to different application scenarios and different scientific research objectives, and all have their basic principles, advantages and disadvantages which means there will be great differences in their practicability. Therefore, the evapotranspiration measuring methods should be selected according to specific researching situation. Conclusions Different evapotranspiration measuring methods are complementary in many research scenarios. When selecting methods with larger observing scale at regional and watershed area, attention should also be paid to the comparison and verification of different methods in order to obtain more accurate evapotranspiration results. Recommendations and perspectives Different researching teams should have more communications, and their results in different surface conditions should also be compared with each other more often.