Research Article: Simulating Crop Evapotranspiration Response under Different Planting Scenarios by Modified SWAT Model in an Irrigation District, Northwest China

Date Published: October 6, 2015

Publisher: Public Library of Science

Author(s): Xin Liu, Sufen Wang, Han Xue, Vijay P. Singh, Wujun Ma.


Modelling crop evapotranspiration (ET) response to different planting scenarios in an irrigation district plays a significant role in optimizing crop planting patterns, resolving agricultural water scarcity and facilitating the sustainable use of water resources. In this study, the SWAT model was improved by transforming the evapotranspiration module. Then, the improved model was applied in Qingyuan Irrigation District of northwest China as a case study. Land use, soil, meteorology, irrigation scheduling and crop coefficient were considered as input data, and the irrigation district was divided into subdivisions based on the DEM and local canal systems. On the basis of model calibration and verification, the improved model showed better simulation efficiency than did the original model. Therefore, the improved model was used to simulate the crop evapotranspiration response under different planting scenarios in the irrigation district. Results indicated that crop evapotranspiration decreased by 2.94% and 6.01% under the scenarios of reducing the planting proportion of spring wheat (scenario 1) and summer maize (scenario 2) by keeping the total cultivated area unchanged. However, the total net output values presented an opposite trend under different scenarios. The values decreased by 3.28% under scenario 1, while it increased by 7.79% under scenario 2, compared with the current situation. This study presents a novel method to estimate crop evapotranspiration response under different planting scenarios using the SWAT model, and makes recommendations for strategic agricultural water management planning for the rational utilization of water resources and development of local economy by studying the impact of planting scenario changes on crop evapotranspiration and output values in the irrigation district of northwest China.

Partial Text

The irrigation district in the arid area of northwest China has low precipitation and high evaporation, and runoff is not the main hydrological cycle process of this arid region. Artificial irrigation-evapotranspiration is the most important hydrological process, which forms the distinctive hydrological system in the arid irrigation district. However, because of the influence of human activities, the ecosystem there is quite fragile and a series of ecological problems have resulted, such as groundwater decline, grassland degradation, and soil desertification. Shortage of water resources has become a major obstacle to agricultural production and social and economic development in the arid region of northwest China [1]. Generally, crop evapotranspiration (ET) directly influences the hydrological cycle and the effective utilization of agricultural water resources, which plays a significant role in local food security and ecosystem conservation. Accurate measurement or estimation of crop evapotranspiration is important to develop exact irrigation scheduling and reasonably use water resources and optimize crop water management in irrigation district [2–5]. Crop evapotranspiration is also a major process influencing crop yield in water-limited environments [6, 7]. Therefore, study of crop evapotranspiration response to environmental changes is significant for developing agricultural water resources management strategies [8].

The SWAT model incorporating the improved evapotranspiration module (FAO–56 dual crop coefficient method) was developed for studying the hydrological processes in an irrigation district of evapotranspiration-dominant arid area. Then, the original and improved models were used for model calibration and verification. As the improved model showed better simulation efficiency, it was applied to simulate crop evapotranspiration response to different planting scenarios in Qingyuan Irrigation District of northwest China.