ESTIMATION OF REGIONAL EVAPOTRANSPIRATION FROM ARID AND SEMI‐ARID SURFACES¹

Abstract

Evapotranspiration (ET) from oasis and Gobi surfaces in the Heihe River region of China was estimated by Kotoda (1986) and Advection‐Aridity (Brutsaert and Stricker, 1979) models. The ET estimates were compared with eddy‐correlation ET estimates. The ET estimated by both models are in good agreement with ET obtained by means of eddy‐correlation method for the oasis surface while underestimating ET as compared to the eddy‐correlation method. For the Gobi surface, the models yielded obviously overestimates of evapotranspiration. In order to estimate evapotranspiration from arid surfaces, the Kotoda model was modified by introducing the surface moisture availability parameter a from Barton (1979). The modified Kotoda model yielded ET estimates that were very close to that from the eddy‐correlation method for the Gobi surface. The modified Kotoda model was used to estimate evapotranspiration from the Heihe River watershed, an area with complicated topography and land use, and the results compared with those from a water balance method. A sensitivity analysis of the modified model was performed. The results show that the modified Kotoda model can reflect the relationship between the actual evapotranspiration and the main controlling factors on it for both wet and arid surfaces reasonably. From this study, it can be concluded that the modified Kotoda model is applicable fro the estimation of regional evapotranspiration from areas with complicated topography and land use.

A complementary relationship evaporation model referring to the Granger model and the advection–aridity model

“…The typical annual rainfall is as less as 100 mm, and the land surfaces are covered primarily with sand and Gobi desert with some dotted oases and irrigated farm lands (Sugita et al, 2001). This region is characterized by low-air absolute moisture content, especially on the surface of Gobi where absolute moisture content is far from being saturated (Liu and Kotoda, 1998). The Gobi site is located at a latitude of 100°06 0 E, longitude of 39°09 0 N, and altitude of about 1480 m above grit and gravel surface.…”

Evaluation of three complementary relationship approaches for evapotranspiration over the Yellow River basin

“…Hobbins et al (2001b) adopted a value of a D 1Ð28 to estimate regional evapotranspiration across the conterminous USA. Lemeur and Zhang (1990) and Liu and Kotoda (1998) used a value of a D 1Ð26 to estimate regional evapotranspiration over the Urumqi river catchment and the Heihe river basin in western China respectively. Zhang et al (2004) found that the seasonal average a is 1Ð17 and 1Ð26 for winter wheat and 1Ð06 and 1Ð09 for maize in the North China Plain.…”

“…In the past 20 years, several studies have been conducted to estimate regional evapotranspiration with these models (Morton, 1983;Kovacs, 1987). Also, based on observation and/or other model results, some careful comparisons and model improvements have been made (Lemeur and Zhang, 1990;Katul and Parlange, 1992;Parlange and Katul, 1992;Kim and Entekhabi, 1997;Liu and Kotoda, 1998;Hobbins et al, 1999Hobbins et al, , 2001aSugita et al, 2001). However, there are still few studies on the evaluation of these complementary relationship models over different temporal scales and over a wide range of climatologically varying conditions.…”

Construction, installation, and performance of two repacked weighing lysimeters

“…Micrometeorological techniques such as the Bowen ratio and Eddy covariance methods have become popular in recent times for directly measuring ET (Payero et al 2003;Todd et al 2000a;Verhoef et al 1999;Liu and Kotoda 1998;Laubach et al 1994). However, lysimeters are still considered as the standard method to directly measure ET.…”